├── .pylintrc
├── images
    └── csp_bypass.png
├── csp_known_bypasses.py
├── .gitignore
├── README.md
├── tests.py
├── csp_parser.py
├── burp_scanner_issues.py
├── burp_csp_bypass.py
└── LICENSE


/.pylintrc:
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1 | [MASTER]
2 | 
3 | disable=F0401,W0232,W0613,W0401,W0614
4 | 


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/images/csp_bypass.png:
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https://raw.githubusercontent.com/moloch--/CSP-Bypass/HEAD/images/csp_bypass.png


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/csp_known_bypasses.py:
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 1 | """
 2 | Common domains that contain known CSP bypasses
 3 | """
 4 | # pylint: disable=C0301
 5 | 
 6 | 
 7 | CSP_KNOWN_BYPASSES = {
 8 |     "script-src": [
 9 |         # (DOMAIN, DESCRIPTION/EXAMPLE,)
10 |         ("ajax.googleapis.com", '''
11 | Additional information is available here:  https://github.com/cure53/XSSChallengeWiki/wiki/H5SC-Minichallenge-3:-%22Sh*t,-it%27s-CSP!%22
12 | 
13 | Example Payload:
14 | "><script src=//ajax.googleapis.com/ajax/services/feed/find?v=1.0%26callback=alert%26context=1337></script>
15 | '''),
16 |     ]
17 | }
18 | 


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/.gitignore:
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 1 | csp-bypass-plugin.py
 2 | 
 3 | 
 4 | *.py[co]
 5 | 
 6 | # Data files
 7 | *.csv
 8 | *.zip
 9 | *.cfg
10 | 
11 | *.egg
12 | *.egg-info
13 | dist
14 | build
15 | eggs
16 | parts
17 | bin
18 | var
19 | sdist
20 | develop-eggs
21 | .installed.cfg
22 | 
23 | # SSL Stuff
24 | *.crt
25 | *.key
26 | 
27 | # SSH Keys
28 | id_*
29 | *.pub
30 | 
31 | # XML exports
32 | *.xml
33 | 
34 | # SQLite3 databases
35 | *.db
36 | 
37 | # Screen files
38 | *.0
39 | 
40 | # Log files
41 | *.log
42 | 
43 | # Installer logs
44 | pip-log.txt
45 | 
46 | # Eclipse
47 | .project
48 | .pydevproject
49 | 
50 | # PyCharm
51 | .idea/*
52 | 
53 | # OSX
54 | .DS_Store
55 | 


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/README.md:
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 1 | CSP Bypass
 2 | ============
 3 | 
 4 | This is a Burp plugin that is designed to passively scan for CSP headers that contain known bypasses as well as other potential weaknesses.
 5 | 
 6 | ![CSP Bypass](/images/csp_bypass.png?raw=true)
 7 | 
 8 | ## Installation
 9 | 
10 | #### Jython Setup
11 |  1. Download the latest standalone [Jython 2.7.x](http://www.jython.org/downloads.html) .jar file
12 |  1. In Burp select `Extender` and then the `Options` tab, under the _Python Environment_ heading click `Select File ...` and browse to the Jython .jar file
13 | 
14 | #### CSP Bypass Plugin Setup
15 |  1. Execute the `build-plugin.sh` script, you should see a `csp-bypass-plugin.py` file appear
16 |  1. In Burp select `Extender` and then the `Extensions` tab
17 |  1. Click `Add` in the window that appears, select `Python` from the `Extension Type` dropdown menu
18 |  1. Click `Select File ...` next to `Extension File` and select the generated `csp-bypass-plugin.py` file
19 |  1. Click `Next` and you're done!
20 | 
21 | ## Report Bypasses in Common Domains
22 | 
23 | To add bypasses simply edit [csp_known_bypasses.py](https://github.com/moloch--/CSP-Bypass/blob/master/csp_known_bypasses.py) with a domain, and an example payload or description of the bypass. Be sure to use the full domain, the plugin will match wildcards (e.g. if a policy allows `*.googleapis.com` it will match against `ajax.googleapis.com`). Submit a pull request to get your bypass in the main repository!
24 | 


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/tests.py:
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 1 | #!/usr/bin/env python
 2 | """
 3 | @author: moloch
 4 | 
 5 | Unit tests for the CSP parser, the parser is written in "pure" Python so we
 6 | don't need Jython to run the unit tests.
 7 | """
 8 | # pylint: disable=C0111,C0301
 9 | 
10 | 
11 | import unittest
12 | 
13 | from csp_parser import *
14 | 
15 | # Constants
16 | CSP_HEADER_NAME = "Content-Security-Policy"
17 | 
18 | # Test cases
19 | CSP_TEST_PARSER_1 = (
20 |     CSP_HEADER_NAME,
21 |     "default-src 'self' https://cdn.example.net; child-src 'none'; object-src 'none'")
22 | 
23 | CSP_TEST_PARSER_2 = (
24 |     CSP_HEADER_NAME,
25 |     "default-src 'self' https:; connect-src 'self' https: http:; font-src 'self' https:; frame-src *; img-src 'self' https: http: data:; media-src 'self' https:; object-src 'self' https:; script-src 'self' https: 'unsafe-eval' 'unsafe-inline' http:; style-src 'self' https: 'unsafe-inline' http:; report-uri /tracking/csp;")
26 | 
27 | CSP_TEST_INVALID_TYPES = (
28 |     CSP_HEADER_NAME,
29 |     "default-src 'self' https://cdn.example.net; foobar-src 'none';")
30 | 
31 | 
32 | class TestContentSecurityPolicy(unittest.TestCase):
33 | 
34 |     def test_parser_1(self):
35 |         csp = ContentSecurityPolicy(*CSP_TEST_PARSER_1)
36 |         self.assertTrue(SCRIPT_SRC in csp)
37 |         self.assertTrue(SELF in csp[SCRIPT_SRC])
38 | 
39 |     def test_parser_2(self):
40 |         csp = ContentSecurityPolicy(*CSP_TEST_PARSER_2)
41 |         self.assertTrue(SCRIPT_SRC in csp)
42 |         self.assertTrue(SELF in csp[SCRIPT_SRC])
43 |         self.assertTrue(UNSAFE_EVAL in csp[SCRIPT_SRC])
44 | 
45 |     def test_invalid_types(self):
46 |         with self.assertRaises(ValueError):
47 |             ContentSecurityPolicy(*CSP_TEST_INVALID_TYPES)
48 | 
49 | 
50 | class TestCSPMatchDomains(unittest.TestCase):
51 | 
52 |     def test_simple_domain_match(self):
53 |         self.assertTrue(csp_match_domains("foo.bar.com", "foo.bar.com"))
54 | 
55 |     def test_wildcard_main(self):
56 |         self.assertTrue(csp_match_domains("*.bar.com", "foo.bar.com"))
57 | 
58 |     def test_simple_mismatch(self):
59 |         self.assertFalse(csp_match_domains("foobar.com", "foobar.net"))
60 |         self.assertFalse(csp_match_domains("foobar.com", "foo.bar.com"))
61 | 
62 |     def test_scheme_match(self):
63 |         self.assertTrue(csp_match_domains("ws://*.bar.com", "foo.bar.com"))
64 | 
65 |     def test_scheme_mismatch(self):
66 |         self.assertFalse(csp_match_domains("ws://*.foo.com", "foo.bar.com"))
67 | 
68 |     def test_realworld_match(self):
69 |         self.assertTrue(csp_match_domains("*.googleapis.com", "ajax.googleapis.com"))
70 |         self.assertTrue(csp_match_domains("ajax.googleapis.com", "ajax.googleapis.com"))
71 | 
72 | 
73 | if __name__ == '__main__':
74 |     unittest.main()
75 | 


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/csp_parser.py:
--------------------------------------------------------------------------------
  1 | """
  2 | @author: moloch
  3 | 
  4 | A basic Content Security Policy parser.
  5 | """
  6 | # pylint: disable=C0103,C0111,R0201
  7 | 
  8 | from collections import defaultdict
  9 | from urlparse import urlparse
 10 | 
 11 | ### Constants
 12 | BASE_URI = "base-uri"
 13 | FORM_ACTION = "form-action"
 14 | FRAME_ANCESTORS = "frame-ancestors"
 15 | PLUGIN_TYPES = "plugin-types"
 16 | REPORT_URI = "report-uri"
 17 | SANDBOX = "sandbox"
 18 | UPGRADE_INSECURE_REQUESTS = "upgrade-insecure-requests"
 19 | REFLECTIVE_XSS = "reflected-xss"
 20 | REFERRER = "referrer"
 21 | 
 22 | DEFAULT_SRC = "default-src"
 23 | SCRIPT_SRC = "script-src"
 24 | CHILD_SRC = "child-src"
 25 | FRAME_SRC = "frame-src"
 26 | CONNECT_SRC = "connect-src"
 27 | FONT_SRC = "font-src"
 28 | IMG_SRC = "img-src"
 29 | MEDIA_SRC = "media-src"
 30 | OBJECT_SRC = "object-src"
 31 | STYLE_SRC = "style-src"
 32 | MANIFEST_SRC = "manifest-src"
 33 | 
 34 | SELF = "'self'"
 35 | NONE = "'none'"
 36 | UNSAFE_INLINE = "'unsafe-inline'"
 37 | UNSAFE_EVAL = "'unsafe-eval'"
 38 | HTTP = "http:"
 39 | HTTPS = "https:"
 40 | BLOB = "blob:"
 41 | DATA = "data:"
 42 | FILESYSTEM = "filesystem:"
 43 | MEDIASTREAM = "mediastream:"
 44 | 
 45 | 
 46 | def csp_match_domains(content_src, domain):
 47 |     """ Does a `content_src' allow a `domain' """
 48 |     # Isolate just the domain incase there is a scheme/etc.
 49 |     content_src = content_src.lower()
 50 |     domain = domain.lower()
 51 |     if urlparse(content_src).netloc != '':
 52 |         content_src = urlparse(content_src).netloc
 53 | 
 54 |     src_parts = content_src.split(".")[::-1]  # Reverse the domains
 55 |     domain_parts = domain.split(".")[::-1]
 56 |     for index, src_part in enumerate(src_parts):
 57 |         if src_part == "*":
 58 |             return True
 59 |         if src_part == domain_parts[index]:
 60 |             continue
 61 |         else:
 62 |             return False
 63 |     return len(src_parts) == len(domain_parts)
 64 | 
 65 | 
 66 | class ContentSecurityPolicy(object):
 67 | 
 68 |     """
 69 |     A simple Content-Security-Policy object, it resembles a dictionary but has
 70 |     logic to return `default-src' when approiate, etc.
 71 |     """
 72 | 
 73 |     HEADERS = ["content-security-policy",
 74 |                "content-security-policy-report-only",
 75 |                "x-content-security-policy",
 76 |                "x-webkit-csp"]
 77 | 
 78 |     # All content directives
 79 |     CONTENT_DIRECTIVES = [
 80 |         DEFAULT_SRC, SCRIPT_SRC, CHILD_SRC, FRAME_SRC, CONNECT_SRC, FONT_SRC,
 81 |         IMG_SRC, MEDIA_SRC, OBJECT_SRC, STYLE_SRC, MANIFEST_SRC,
 82 | 
 83 |         BASE_URI, FORM_ACTION, FRAME_ANCESTORS, PLUGIN_TYPES,
 84 |         REPORT_URI, SANDBOX, REFLECTIVE_XSS, REFERRER]
 85 | 
 86 |     # These directives do not fallback to default-src
 87 |     NO_FALLBACK = [BASE_URI, FORM_ACTION, FRAME_ANCESTORS, PLUGIN_TYPES,
 88 |                    REPORT_URI, SANDBOX, REFLECTIVE_XSS, REFERRER]
 89 | 
 90 |     def __init__(self, header_name, header_value):
 91 |         self._content_policies = defaultdict(list)
 92 |         self._header_name = None
 93 |         self._header_value = None
 94 |         self.header_name = header_name
 95 |         self.header_value = header_value
 96 | 
 97 |     @property
 98 |     def header_name(self):
 99 |         return self._header_name
100 | 
101 |     @header_name.setter
102 |     def header_name(self, value):
103 |         """ Setter for the header name """
104 |         if value.lower() not in self.HEADERS:
105 |             raise ValueError("Unknown header name: '%s'" % value)
106 |         else:
107 |             self._header_name = value.lower()
108 | 
109 |     @property
110 |     def header_value(self):
111 |         return self._header_value
112 | 
113 |     @header_value.setter
114 |     def header_value(self, value):
115 |         """ Sets the header value and parses it """
116 |         self._header_value = value.lower()
117 |         self._parse_header()
118 | 
119 |     def _parse_header(self):
120 |         """ Splits the header on ';' then subsequently on whitespace """
121 |         for policy in self._header_value.split(";"):
122 |             if not len(policy):
123 |                 continue  # Skip blanks
124 |             directive, sources = self._unpack_policy(*policy.strip().split(" "))
125 |             self[directive] = sources
126 | 
127 |     def _unpack_policy(self, directive, *content_sources):
128 |         """ Used to unpack the directive name and directives """
129 |         return directive, [src.strip() for src in content_sources]
130 | 
131 |     def is_deprecated_header(self):
132 |         """ Check for X-WebKit-CSP or X-Content-Security-Policy """
133 |         return self.header_name.startswith('x')
134 | 
135 |     def is_report_only_mode(self):
136 |         return self.header_name.endswith("report-only")
137 | 
138 |     def iteritems(self):
139 |         """ Similar to a dictionary, iterates tuples of key/value pairs """
140 |         for key in self.CONTENT_DIRECTIVES:
141 |             yield (key, self[key],)
142 | 
143 |     def __setitem__(self, key, value):
144 |         if key not in self.CONTENT_DIRECTIVES:
145 |             raise ValueError("Unknown directive '%s'" % key)
146 |         if isinstance(value, list):
147 |             self._content_policies[key].extend(value)
148 |         elif isinstance(value, basestring):
149 |             self._content_policies[key].append(value)
150 |         else:
151 |             raise ValueError("Expected list or basestring")
152 | 
153 |     def __getitem__(self, key):
154 |         """
155 |         Get the policy or return default-src if the policy isn't in NO_FALLBACK
156 |         """
157 |         if key not in self.CONTENT_DIRECTIVES:
158 |             raise ValueError("Unknown directive '%s'" % key)
159 |         if key in self._content_policies:
160 |             return self._content_policies[key]
161 |         elif key not in self.NO_FALLBACK:
162 |             return self._content_policies[DEFAULT_SRC]
163 | 
164 |     def __contains__(self, item):
165 |         if item not in self.NO_FALLBACK and item in self.CONTENT_DIRECTIVES:
166 |             return True
167 |         else:
168 |             return item in self._content_policies
169 | 
170 |     def __iter__(self):
171 |         for key in self.CONTENT_DIRECTIVES:
172 |             yield key
173 | 


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/burp_scanner_issues.py:
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  1 | """
  2 | @author: moloch
  3 | 
  4 | Scanner issues reported by the plugin.
  5 | """
  6 | # pylint: disable=E0602,C0103,W0621,R0201
  7 | 
  8 | 
  9 | from burp import IScanIssue
 10 | 
 11 | 
 12 | class BaseCSPIssue(IScanIssue):
 13 | 
 14 |     """
 15 |     Just a base class with some helpful docstrings and a slightly modified
 16 |     constructor so we can track what directive we're reporting about.
 17 |     """
 18 | 
 19 |     # pylint: disable=R0913
 20 |     def __init__(self, httpService, url, httpMessages, severity, confidence,
 21 |                  directive=None):
 22 |         """
 23 |         Setters for all the getters, `directive' is optional
 24 |         """
 25 |         self._httpService = httpService
 26 |         self._url = url
 27 |         self._httpMessages = httpMessages
 28 |         self._severity = severity
 29 |         self._confidence = confidence
 30 |         self._directive = directive
 31 | 
 32 |     def getUrl(self):
 33 |         """
 34 |         This method returns the URL for which the issue was generated.
 35 |         @return The URL for which the issue was generated.
 36 |         """
 37 |         return self._url
 38 | 
 39 |     def getIssueName(self):
 40 |         """
 41 |         This method returns the name of the issue type.
 42 |         @return The name of the issue type (e.g. "SQL injection").
 43 |         """
 44 |         raise NotImplementedError()
 45 | 
 46 |     def getIssueType(self):
 47 |         """
 48 |         This method returns a numeric identifier of the issue type. See the Burp
 49 |         Scanner help documentation for a listing of all the issue types.
 50 |         @return A numeric identifier of the issue type.
 51 |         """
 52 |         return 0  # https://portswigger.net/burp/help/scanner_issuetypes.html
 53 | 
 54 |     def getSeverity(self):
 55 |         """
 56 |         This method returns the issue severity level.
 57 |         @return The issue severity level. Expected values are "High", "Medium",
 58 |         "Low", "Information" or "False positive".
 59 |         """
 60 |         return self._severity
 61 | 
 62 |     def getConfidence(self):
 63 |         """
 64 |         This method returns the issue confidence level.
 65 |         @return The issue confidence level. Expected values are "Certain", "Firm"
 66 |         or "Tentative".
 67 |         """
 68 |         return self._confidence
 69 | 
 70 |     def getIssueBackground(self):
 71 |         """
 72 |         This method returns a background description for this type of issue.
 73 |         @return A background description for this type of issue, or
 74 |         <code>null</code> if none applies.
 75 |         """
 76 |         return """
 77 | Content security policy (CSP) is an HTML5 standard primarily designed to mitigate
 78 | the issue of cross-site scripting (XSS) and other content injection vulnerabilities
 79 | within web applications. Weak content security policies stem from overly permissive
 80 | or ineffective content source directives.
 81 | """
 82 | 
 83 |     def getRemediationBackground(self):
 84 |         """
 85 |         This method returns a background description of the remediation for this
 86 |         type of issue.
 87 |         @return A background description of the remediation for this type of
 88 |         issue, or
 89 |         <code>null</code> if none applies.
 90 |         """
 91 |         return """
 92 | While non-trivial to implement, modern browser headers such
 93 | as Content-Security-Policy (CSP) can provide extremely robust protection against
 94 | XSS and related content injection issues. To fix weak policies enforce as much
 95 | restriction on the content sources as possible, strive to disable unsafe, insecure,
 96 | and wildcard sources, and where possible limit 3rd party domains.
 97 | """
 98 | 
 99 |     def getIssueDetail(self):
100 |         """
101 |         This method returns detailed information about this specific instance of
102 |         the issue.
103 |         @return Detailed information about this specific instance of the issue,
104 |         or
105 |         <code>null</code> if none applies.
106 |         """
107 |         raise NotImplementedError()
108 | 
109 |     def getRemediationDetail(self):
110 |         """
111 |         This method returns detailed information about the remediation for this
112 |         specific instance of the issue.
113 |         @return Detailed information about the remediation for this specific
114 |         instance of the issue, or
115 |         <code>null</code> if none applies.
116 |         """
117 |         raise NotImplementedError()
118 | 
119 |     def getHttpMessages(self):
120 |         """
121 |         This method returns the HTTP messages on the basis of which the issue was
122 |         generated.
123 |         @return The HTTP messages on the basis of which the issue was generated.
124 |         Note: The items in this array should be instances of
125 |         <code>IHttpRequestResponseWithMarkers</code> if applicable, so that
126 |         details of the relevant portions of the request and response messages are
127 |         available.
128 |         """
129 |         if isinstance(self._httpMessages, list):
130 |             return self._httpMessages
131 |         else:
132 |             return [self._httpMessages]
133 | 
134 |     def getHttpService(self):
135 |         """
136 |         This method returns the HTTP service for which the issue was generated.
137 |         @return The HTTP service for which the issue was generated.
138 |         """
139 |         return self._httpService
140 | 
141 | 
142 | class WildcardContentSource(BaseCSPIssue):
143 | 
144 |     """
145 |     Wildcard content sources. Note: this does not flag wildcard subdomains
146 |     """
147 | 
148 |     def getIssueName(self):
149 |         return "Wildcard Content Source: %s" % self._directive
150 | 
151 |     def getIssueDetail(self):
152 |         return "The %s CSP directive does not enforce any restrictions on what \
153 |         origins content can be loaded from." % self._directive
154 | 
155 |     def getRemediationDetail(self):
156 |         return "Remove all wildcards from the content security policy."
157 | 
158 | 
159 | class WildcardSubdomainContentSource(BaseCSPIssue):
160 | 
161 |     """
162 |     Wildcard subdomain content sources.
163 |     """
164 | 
165 |     def getIssueName(self):
166 |         return "Wildcard Subdomain Content Source: %s" % self._directive
167 | 
168 |     def getIssueDetail(self):
169 |         return "Wildcard subdomains expose additional attack surface, since an \
170 |         attacker can potentially leverage a vulnerability in any subdomain to \
171 |         to bypass the CSP."
172 | 
173 |     def getRemediationDetail(self):
174 |         return "Avoid use of wildcard subdomains in CSP directives."
175 | 
176 | 
177 | class UnsafeContentSource(BaseCSPIssue):
178 | 
179 |     """ Any directive that allows unsafe content (e.g. 'unsafe-eval') """
180 | 
181 |     def getIssueName(self):
182 |         return "Unsafe Content Source: %s" % self._directive
183 | 
184 |     def getIssueDetail(self):
185 |         return "This content security policy allows for unsafe content sources"
186 | 
187 |     def getRemediationDetail(self):
188 |         return "Refactor the website to remove inline JavaScript and CSS"
189 | 
190 | 
191 | class InsecureContentDirective(BaseCSPIssue):
192 | 
193 |     """
194 |     Any directive that allows insecure network protocols (e.g. ws: or http:)
195 |     """
196 | 
197 |     def getIssueName(self):
198 |         return "Insecure Content Source: %s" % self._directive
199 | 
200 |     def getIssueDetail(self):
201 |         return "The content directive %s allows resources to be loaded over \
202 |         insecure network protocols." % self._directive
203 | 
204 |     def getRemediationDetail(self):
205 |         return "Restrict content sources to only use secure protocols such as \
206 |         https:// and wss://."
207 | 
208 | 
209 | class MissingDirective(BaseCSPIssue):
210 | 
211 |     """
212 |     Directives that 'fail open', that is to say they are not restricted by the
213 |     CSP and do not fallback to `default-src'.
214 |     """
215 | 
216 |     def getIssueName(self):
217 |         return "Missing CSP Directive: %s" % self._directive
218 | 
219 |     def getIssueDetail(self):
220 |         return "The %s content directive does not fallback to default-src, if \
221 |         no content sources are explicitly set it will default to completely \
222 |         open." % self._directive
223 | 
224 |     def getRemediationDetail(self):
225 |         return "Explicitly set a %s directive in your content policy." % self._directive
226 | 
227 | 
228 | class WeakDefaultSource(BaseCSPIssue):
229 | 
230 |     """ Any `default-src' that is not 'none' 'self' or 'https:' """
231 | 
232 |     def getIssueName(self):
233 |         return "Weak default-src Directive"
234 | 
235 |     def getIssueDetail(self):
236 |         return "The default content source should be as restrictive as possible \
237 |         the content policy for this website does not restrict the default source \
238 |         to either 'none' 'self' (and 'https:')."
239 | 
240 |     def getRemediationDetail(self):
241 |         return "Set the default-src to either 'self' or preferrably 'none'. If \
242 |         the default source is set to 'self' also consider adding 'https:' to \
243 |         ensure resources are loaded over a secure network connection."
244 | 
245 | 
246 | 
247 | class DeprecatedHeader(BaseCSPIssue):
248 | 
249 |     """ Flags use of `X-WebKit-CSP' and `X-Content-Security-Policy' """
250 | 
251 |     def getIssueName(self):
252 |         return "Deprecated Header"
253 | 
254 |     def getIssueDetail(self):
255 |         return "The site uses a deprecated CSP header"
256 | 
257 |     def getRemediationDetail(self):
258 |         return "Change the server response header to `Content-Security-Policy'"
259 | 
260 | 
261 | class ReportOnlyHeader(BaseCSPIssue):
262 | 
263 |     """ Flags use of `Content-Security-Policy-Report-Only' """
264 | 
265 |     def getIssueName(self):
266 |         return "Report Only Header"
267 | 
268 |     def getIssueDetail(self):
269 |         return "The site uses a CSP in report-only mode"
270 | 
271 |     def getRemediationDetail(self):
272 |         return "Change the server response header to `Content-Security-Policy'"
273 | 
274 | 
275 | class NonceContentSource(BaseCSPIssue):
276 | 
277 |     """ Alerts the user that a `nonce-' source was found """
278 | 
279 |     def getIssueName(self):
280 |         return "Nonce Content Source"
281 | 
282 |     def getIssueDetail(self):
283 |         return "This site uses nonces to secure inline content"
284 | 
285 |     def getRemediationDetail(self):
286 |         return "Refactor the website to disallow all inline content, and remove \
287 |         nonce content sources from the CSP."
288 | 
289 | 
290 | class KnownCSPBypass(BaseCSPIssue):
291 | 
292 |     """ Reports a known bypass in a domain whitelisted by a CSP """
293 | 
294 |     # pylint: disable=W0231,R0913
295 |     def __init__(self, httpService, url, httpMessages, severity, confidence,
296 |                  directive=None, bypass=None):
297 |         """
298 |         Burp uses old style classes so we can't use super()
299 |         """
300 |         self._httpService = httpService
301 |         self._url = url
302 |         self._httpMessages = httpMessages
303 |         self._severity = severity
304 |         self._confidence = confidence
305 |         self._directive = directive
306 |         self._bypass = bypass
307 | 
308 |     def getIssueName(self):
309 |         return "Known CSP Bypass: %s" % self._directive
310 | 
311 |     def getIssueDetail(self):
312 |         return "A known bypass exists in the '%s' directive for the domain \
313 |         '%s'. %s" % (self._directive, self._bypass[0], self._bypass[1])
314 | 
315 |     def getRemediationDetail(self):
316 |         return "Remove the content source '%s' domain from your '%s' CSP \
317 |         directive." % (self._bypass[0], self._directive)
318 | 


--------------------------------------------------------------------------------
/burp_csp_bypass.py:
--------------------------------------------------------------------------------
  1 | """
  2 | @author: moloch
  3 | 
  4 | This is a Burp plugin to parse Content-Security-Policy headers and detect
  5 | weaknesses and possibly bypasses in the policy.
  6 | """
  7 | # pylint: disable=E0602,C0103,W0621,R0903,R0201
  8 | 
  9 | 
 10 | from httplib import HTTPResponse
 11 | from StringIO import StringIO
 12 | from urlparse import urlparse
 13 | 
 14 | from burp import IBurpExtender, IScannerCheck
 15 | 
 16 | 
 17 | class HttpDummySocket(object):
 18 | 
 19 |     """
 20 |     A dummy socket object so we can use httplib to parse the response bytearray
 21 |     """
 22 | 
 23 |     def __init__(self, byteResponse):
 24 |         self._file = StringIO(byteResponse)
 25 | 
 26 |     def makefile(self, *args, **kwargs):
 27 |         """ API compatability with `socket' """
 28 |         return self._file
 29 | 
 30 | 
 31 | class ContentSecurityPolicyScan(IScannerCheck):
 32 | 
 33 |     """ Implements the actual passive scan """
 34 | 
 35 |     def __init__(self, callbacks):
 36 |         """
 37 |         WARNING: Only one IScannerCheck object is ever created, because of this
 38 |         you effectively cannot use Python's `self' have to pass around any
 39 |         variables as method args if you want access to them, fml.
 40 |         """
 41 |         self._helpers = callbacks.getHelpers()
 42 | 
 43 |         # Checks must return a list of IScanIssue objects
 44 |         self._checks = [
 45 |             self.deprecatedHeaderCheck,
 46 |             self.reportOnlyHeaderCheck,
 47 |             self.unsafeContentSourceCheck,
 48 |             self.wildcardContentSourceCheck,
 49 |             self.wildcardSubdomainContentSourceCheck,
 50 |             self.insecureContentSourceCheck,
 51 |             self.nonceSourceCheck,
 52 |             self.missingDirectiveCheck,
 53 |             self.weakDefaultSourceCheck,
 54 |             self.knownBypassCheck,
 55 |         ]
 56 | 
 57 |     def _getUrl(self, burpHttpReqResp):
 58 |         """
 59 |         Uses the Burp helper APIs to get the URL from the HttpReqResp object
 60 |         """
 61 |         return self._helpers.analyzeRequest(burpHttpReqResp).getUrl()
 62 | 
 63 |     def doPassiveScan(self, burpHttpReqResp):
 64 |         """
 65 |         This is a callback method for Burp, its called for each HTTP req/resp.
 66 |         Returns a list of IScanIssue(s)
 67 |         """
 68 |         if len(burpHttpReqResp.getResponse()):
 69 |             return self.proccessHttpResponse(burpHttpReqResp)
 70 |         else:
 71 |             return []
 72 | 
 73 |     def consolidateDuplicateIssues(self, existingIssue, newIssue):
 74 |         """
 75 |         This is a callback method for Burp, and is used to cleanup duplicate
 76 |         findings.
 77 |         @return An indication of which issue(s) should be reported in the main
 78 |         Scanner results.
 79 |         <code>-1</code> to report the existing issue only
 80 |         <code>0</code> to report both issues
 81 |         <code>1</code> to report the new issue only
 82 |         """
 83 |         if existingIssue.getIssueName() == newIssue.getIssueName():
 84 |             return -1
 85 |         else:
 86 |             return 0
 87 | 
 88 |     def proccessHttpResponse(self, burpHttpReqResp):
 89 |         """ Processes only the HTTP repsonses with a CSP header """
 90 |         byteResponse = burpHttpReqResp.getResponse()
 91 |         httpSocket = HttpDummySocket(bytearray(byteResponse))
 92 |         response = HTTPResponse(httpSocket)
 93 |         response.begin()
 94 |         issues = []
 95 |         for header in response.getheaders():
 96 |             if header[0].lower() in ContentSecurityPolicy.HEADERS:
 97 |                 findings = self.parseContentSecurityPolicy(header, burpHttpReqResp)
 98 |                 issues.extend(findings)
 99 |         return issues
100 | 
101 |     def parseContentSecurityPolicy(self, cspHeader, burpHttpReqResp):
102 |         """ Parses the CSP response header and searches for issues """
103 |         csp = ContentSecurityPolicy(cspHeader[0], cspHeader[1])
104 |         issues = []
105 |         for check in self._checks:
106 |             issues.extend(check(csp, burpHttpReqResp))
107 |         return issues
108 | 
109 |     def deprecatedHeaderCheck(self, csp, burpHttpReqResp):
110 |         """
111 |         Checks for the use of a deprecated header such as `X-WebKit-CSP'
112 |         """
113 |         issues = []
114 |         if csp.is_deprecated_header():
115 |             deprecatedHeader = DeprecatedHeader(
116 |                 httpService=burpHttpReqResp.getHttpService(),
117 |                 url=self._getUrl(burpHttpReqResp),
118 |                 httpMessages=burpHttpReqResp,
119 |                 severity="Medium",
120 |                 confidence="Certain")
121 |             issues.append(deprecatedHeader)
122 |         return issues
123 | 
124 |     def reportOnlyHeaderCheck(self, csp, burpHttpReqResp):
125 |         """
126 |         Checks for the use of a report-only CSP header
127 |         """
128 |         issues = []
129 |         if csp.is_report_only_mode():
130 |             reportOnly = ReportOnlyHeader(
131 |                 httpService=burpHttpReqResp.getHttpService(),
132 |                 url=self._getUrl(burpHttpReqResp),
133 |                 httpMessages=burpHttpReqResp,
134 |                 severity="High",
135 |                 confidence="Certain")
136 |             issues.append(reportOnly)
137 |         return issues
138 | 
139 |     def unsafeContentSourceCheck(self, csp, burpHttpReqResp):
140 |         """ Checks the current CSP header for unsafe content sources """
141 |         issues = []
142 |         for directive in [SCRIPT_SRC, STYLE_SRC]:
143 |             if UNSAFE_EVAL in csp[directive] or UNSAFE_INLINE in csp[directive]:
144 |                 unsafeContent = UnsafeContentSource(
145 |                     httpService=burpHttpReqResp.getHttpService(),
146 |                     url=self._getUrl(burpHttpReqResp),
147 |                     httpMessages=burpHttpReqResp,
148 |                     severity="High",
149 |                     confidence="Certain",
150 |                     directive=directive)
151 |                 issues.append(unsafeContent)
152 |         return issues
153 | 
154 |     def wildcardContentSourceCheck(self, csp, burpHttpReqResp):
155 |         """
156 |         Check content sources for wildcards '*' note that wilcard subdomains
157 |         are checked by `wildcardSubdomainContentSourceCheck'
158 |         """
159 |         issues = []
160 |         for directive, sources in csp.iteritems():
161 |             if sources is None:
162 |                 continue  # Skip unspecified directives in NO_FALLBACK
163 |             if any(src == "*" for src in sources):
164 |                 wildcardContent = WildcardContentSource(
165 |                     httpService=burpHttpReqResp.getHttpService(),
166 |                     url=self._getUrl(burpHttpReqResp),
167 |                     httpMessages=burpHttpReqResp,
168 |                     severity="Medium",
169 |                     confidence="Certain",
170 |                     directive=directive)
171 |                 issues.append(wildcardContent)
172 |         return issues
173 | 
174 |     def wildcardSubdomainContentSourceCheck(self, csp, burpHttpReqResp):
175 |         """ Check content sources for wildcards subdomains '*.foo.com' """
176 |         issues = []
177 |         for directive, sources in csp.iteritems():
178 |             if sources is None:
179 |                 continue
180 |             # This check is a little hacky but should work well
181 |             # the shortest subdomain string should be like *.a.bc
182 |             if any("*" in src and 5 <= len(src) for src in sources):
183 |                 wilcardSubdomain = WildcardSubdomainContentSource(
184 |                     httpService=burpHttpReqResp.getHttpService(),
185 |                     url=self._getUrl(burpHttpReqResp),
186 |                     httpMessages=burpHttpReqResp,
187 |                     severity="Low",
188 |                     confidence="Certain",
189 |                     directive=directive)
190 |                 issues.append(wilcardSubdomain)
191 |         return issues
192 | 
193 |     def nonceSourceCheck(self, csp, burpHttpReqResp):
194 |         """
195 |         Check content sources for wildcards '*' note that wilcard subdomains
196 |         are checked by `wildcardSubdomainContentSourceCheck'
197 |         """
198 |         issues = []
199 |         for directive, sources in csp.iteritems():
200 |             if sources is None:
201 |                 continue
202 |             if any(src.startswith("'nonce-") for src in sources):
203 |                 nonceContent = NonceContentSource(
204 |                     httpService=burpHttpReqResp.getHttpService(),
205 |                     url=self._getUrl(burpHttpReqResp),
206 |                     httpMessages=burpHttpReqResp,
207 |                     severity="Informational",
208 |                     confidence="Certain",
209 |                     directive=directive)
210 |                 issues.append(nonceContent)
211 |         return issues
212 | 
213 |     def insecureContentSourceCheck(self, csp, burpHttpReqResp):
214 |         """ Check content sources that allow insecure network protocols """
215 |         issues = []
216 |         for directive, sources in csp.iteritems():
217 |             if sources is None:
218 |                 continue
219 |             for src in sources:
220 |                 if src == HTTP or urlparse(src).scheme in ["http", "ws"]:
221 |                     insecureContent = InsecureContentDirective(
222 |                         httpService=burpHttpReqResp.getHttpService(),
223 |                         url=self._getUrl(burpHttpReqResp),
224 |                         httpMessages=burpHttpReqResp,
225 |                         severity="High",
226 |                         confidence="Certain",
227 |                         directive=directive)
228 |                     issues.append(insecureContent)
229 |         return issues
230 | 
231 |     def missingDirectiveCheck(self, csp, burpHttpReqResp):
232 |         """
233 |         Check for missing directives that do not inherit from `default-src'
234 |         """
235 |         issues = []
236 |         for directive in ContentSecurityPolicy.NO_FALLBACK:
237 |             if directive not in csp:
238 |                 missingDirective = MissingDirective(
239 |                     httpService=burpHttpReqResp.getHttpService(),
240 |                     url=self._getUrl(burpHttpReqResp),
241 |                     httpMessages=burpHttpReqResp,
242 |                     severity="Medium",
243 |                     confidence="Certain",
244 |                     directive=directive)
245 |                 issues.append(missingDirective)
246 |         return issues
247 | 
248 |     def weakDefaultSourceCheck(self, csp, burpHttpReqResp):
249 |         """
250 |         Any `default-src' that is not 'none'/'self'/https: is considered weak
251 |         """
252 |         issues = []
253 |         for contentSource in csp[DEFAULT_SRC]:
254 |             if contentSource not in [SELF, NONE, HTTPS]:
255 |                 weakDefault = WeakDefaultSource(
256 |                     httpService=burpHttpReqResp.getHttpService(),
257 |                     url=self._getUrl(burpHttpReqResp),
258 |                     httpMessages=burpHttpReqResp,
259 |                     severity="Medium",
260 |                     confidence="Certain")
261 |                 issues.append(weakDefault)
262 |                 break
263 |         return issues
264 | 
265 |     def knownBypassCheck(self, csp, burpHttpReqResp):
266 |         """
267 |         Parses the CSP for known bypasses, this check is a little more
268 |         complicated, and calls into other subroutines.
269 |         """
270 |         issues = []
271 |         for directive, knownBypasses in CSP_KNOWN_BYPASSES.iteritems():
272 |             bypasses = self._bypassCheckDirective(csp, directive, knownBypasses)
273 |             for bypass in bypasses:
274 |                 bypassIssue = self._createBypassIssue(directive, bypass, burpHttpReqResp)
275 |                 issues.append(bypassIssue)
276 |         return issues
277 | 
278 |     def _createBypassIssue(self, directive, bypass, burpHttpReqResp):
279 |         """ Creates the KnownCSPBypass issue object """
280 |         knownBypass = KnownCSPBypass(
281 |             httpService=burpHttpReqResp.getHttpService(),
282 |             url=self._getUrl(burpHttpReqResp),
283 |             httpMessages=burpHttpReqResp,
284 |             severity="High",
285 |             confidence="Certain",
286 |             directive=directive,
287 |             bypass=bypass)
288 |         return knownBypass
289 | 
290 |     def _bypassCheckDirective(self, csp, directive, knownBypasses):
291 |         """
292 |         Check an individual directive (e.g. `script-src') to see if it contains
293 |         any domains that host known CSP bypasses.
294 |         """
295 |         bypasses = []
296 |         for src in csp[directive]:
297 |             if src.startswith("'") or src in [HTTP, HTTPS, DATA, BLOB]:
298 |                 continue  # We only care about domains
299 | 
300 |             # Iterate over all bypasses and check if `src' allows loading
301 |             # content from `domain' if so, we have a bypass!
302 |             for domain, payload in knownBypasses:
303 |                 if csp_match_domains(src, domain):
304 |                     bypasses.append((domain, payload,))
305 |         return bypasses
306 | 
307 | 
308 | class BurpExtender(IBurpExtender):
309 | 
310 |     """ Burp extension object """
311 | 
312 |     NAME = "CSP Bypass"
313 | 
314 |     def	registerExtenderCallbacks(self, callbacks):
315 |         """ Entrypoint and setup """
316 |         callbacks.setExtensionName(self.NAME)
317 |         callbacks.registerScannerCheck(ContentSecurityPolicyScan(callbacks))
318 |         print '[*] CSP-Bypass extension loaded successfully.'
319 | 


--------------------------------------------------------------------------------
/LICENSE:
--------------------------------------------------------------------------------
  1 |                     GNU GENERAL PUBLIC LICENSE
  2 |                        Version 3, 29 June 2007
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276 |     place (gratis or for a charge), and offer equivalent access to the
277 |     Corresponding Source in the same way through the same place at no
278 |     further charge.  You need not require recipients to copy the
279 |     Corresponding Source along with the object code.  If the place to
280 |     copy the object code is a network server, the Corresponding Source
281 |     may be on a different server (operated by you or a third party)
282 |     that supports equivalent copying facilities, provided you maintain
283 |     clear directions next to the object code saying where to find the
284 |     Corresponding Source.  Regardless of what server hosts the
285 |     Corresponding Source, you remain obligated to ensure that it is
286 |     available for as long as needed to satisfy these requirements.
287 | 
288 |     e) Convey the object code using peer-to-peer transmission, provided
289 |     you inform other peers where the object code and Corresponding
290 |     Source of the work are being offered to the general public at no
291 |     charge under subsection 6d.
292 | 
293 |   A separable portion of the object code, whose source code is excluded
294 | from the Corresponding Source as a System Library, need not be
295 | included in conveying the object code work.
296 | 
297 |   A "User Product" is either (1) a "consumer product", which means any
298 | tangible personal property which is normally used for personal, family,
299 | or household purposes, or (2) anything designed or sold for incorporation
300 | into a dwelling.  In determining whether a product is a consumer product,
301 | doubtful cases shall be resolved in favor of coverage.  For a particular
302 | product received by a particular user, "normally used" refers to a
303 | typical or common use of that class of product, regardless of the status
304 | of the particular user or of the way in which the particular user
305 | actually uses, or expects or is expected to use, the product.  A product
306 | is a consumer product regardless of whether the product has substantial
307 | commercial, industrial or non-consumer uses, unless such uses represent
308 | the only significant mode of use of the product.
309 | 
310 |   "Installation Information" for a User Product means any methods,
311 | procedures, authorization keys, or other information required to install
312 | and execute modified versions of a covered work in that User Product from
313 | a modified version of its Corresponding Source.  The information must
314 | suffice to ensure that the continued functioning of the modified object
315 | code is in no case prevented or interfered with solely because
316 | modification has been made.
317 | 
318 |   If you convey an object code work under this section in, or with, or
319 | specifically for use in, a User Product, and the conveying occurs as
320 | part of a transaction in which the right of possession and use of the
321 | User Product is transferred to the recipient in perpetuity or for a
322 | fixed term (regardless of how the transaction is characterized), the
323 | Corresponding Source conveyed under this section must be accompanied
324 | by the Installation Information.  But this requirement does not apply
325 | if neither you nor any third party retains the ability to install
326 | modified object code on the User Product (for example, the work has
327 | been installed in ROM).
328 | 
329 |   The requirement to provide Installation Information does not include a
330 | requirement to continue to provide support service, warranty, or updates
331 | for a work that has been modified or installed by the recipient, or for
332 | the User Product in which it has been modified or installed.  Access to a
333 | network may be denied when the modification itself materially and
334 | adversely affects the operation of the network or violates the rules and
335 | protocols for communication across the network.
336 | 
337 |   Corresponding Source conveyed, and Installation Information provided,
338 | in accord with this section must be in a format that is publicly
339 | documented (and with an implementation available to the public in
340 | source code form), and must require no special password or key for
341 | unpacking, reading or copying.
342 | 
343 |   7. Additional Terms.
344 | 
345 |   "Additional permissions" are terms that supplement the terms of this
346 | License by making exceptions from one or more of its conditions.
347 | Additional permissions that are applicable to the entire Program shall
348 | be treated as though they were included in this License, to the extent
349 | that they are valid under applicable law.  If additional permissions
350 | apply only to part of the Program, that part may be used separately
351 | under those permissions, but the entire Program remains governed by
352 | this License without regard to the additional permissions.
353 | 
354 |   When you convey a copy of a covered work, you may at your option
355 | remove any additional permissions from that copy, or from any part of
356 | it.  (Additional permissions may be written to require their own
357 | removal in certain cases when you modify the work.)  You may place
358 | additional permissions on material, added by you to a covered work,
359 | for which you have or can give appropriate copyright permission.
360 | 
361 |   Notwithstanding any other provision of this License, for material you
362 | add to a covered work, you may (if authorized by the copyright holders of
363 | that material) supplement the terms of this License with terms:
364 | 
365 |     a) Disclaiming warranty or limiting liability differently from the
366 |     terms of sections 15 and 16 of this License; or
367 | 
368 |     b) Requiring preservation of specified reasonable legal notices or
369 |     author attributions in that material or in the Appropriate Legal
370 |     Notices displayed by works containing it; or
371 | 
372 |     c) Prohibiting misrepresentation of the origin of that material, or
373 |     requiring that modified versions of such material be marked in
374 |     reasonable ways as different from the original version; or
375 | 
376 |     d) Limiting the use for publicity purposes of names of licensors or
377 |     authors of the material; or
378 | 
379 |     e) Declining to grant rights under trademark law for use of some
380 |     trade names, trademarks, or service marks; or
381 | 
382 |     f) Requiring indemnification of licensors and authors of that
383 |     material by anyone who conveys the material (or modified versions of
384 |     it) with contractual assumptions of liability to the recipient, for
385 |     any liability that these contractual assumptions directly impose on
386 |     those licensors and authors.
387 | 
388 |   All other non-permissive additional terms are considered "further
389 | restrictions" within the meaning of section 10.  If the Program as you
390 | received it, or any part of it, contains a notice stating that it is
391 | governed by this License along with a term that is a further
392 | restriction, you may remove that term.  If a license document contains
393 | a further restriction but permits relicensing or conveying under this
394 | License, you may add to a covered work material governed by the terms
395 | of that license document, provided that the further restriction does
396 | not survive such relicensing or conveying.
397 | 
398 |   If you add terms to a covered work in accord with this section, you
399 | must place, in the relevant source files, a statement of the
400 | additional terms that apply to those files, or a notice indicating
401 | where to find the applicable terms.
402 | 
403 |   Additional terms, permissive or non-permissive, may be stated in the
404 | form of a separately written license, or stated as exceptions;
405 | the above requirements apply either way.
406 | 
407 |   8. Termination.
408 | 
409 |   You may not propagate or modify a covered work except as expressly
410 | provided under this License.  Any attempt otherwise to propagate or
411 | modify it is void, and will automatically terminate your rights under
412 | this License (including any patent licenses granted under the third
413 | paragraph of section 11).
414 | 
415 |   However, if you cease all violation of this License, then your
416 | license from a particular copyright holder is reinstated (a)
417 | provisionally, unless and until the copyright holder explicitly and
418 | finally terminates your license, and (b) permanently, if the copyright
419 | holder fails to notify you of the violation by some reasonable means
420 | prior to 60 days after the cessation.
421 | 
422 |   Moreover, your license from a particular copyright holder is
423 | reinstated permanently if the copyright holder notifies you of the
424 | violation by some reasonable means, this is the first time you have
425 | received notice of violation of this License (for any work) from that
426 | copyright holder, and you cure the violation prior to 30 days after
427 | your receipt of the notice.
428 | 
429 |   Termination of your rights under this section does not terminate the
430 | licenses of parties who have received copies or rights from you under
431 | this License.  If your rights have been terminated and not permanently
432 | reinstated, you do not qualify to receive new licenses for the same
433 | material under section 10.
434 | 
435 |   9. Acceptance Not Required for Having Copies.
436 | 
437 |   You are not required to accept this License in order to receive or
438 | run a copy of the Program.  Ancillary propagation of a covered work
439 | occurring solely as a consequence of using peer-to-peer transmission
440 | to receive a copy likewise does not require acceptance.  However,
441 | nothing other than this License grants you permission to propagate or
442 | modify any covered work.  These actions infringe copyright if you do
443 | not accept this License.  Therefore, by modifying or propagating a
444 | covered work, you indicate your acceptance of this License to do so.
445 | 
446 |   10. Automatic Licensing of Downstream Recipients.
447 | 
448 |   Each time you convey a covered work, the recipient automatically
449 | receives a license from the original licensors, to run, modify and
450 | propagate that work, subject to this License.  You are not responsible
451 | for enforcing compliance by third parties with this License.
452 | 
453 |   An "entity transaction" is a transaction transferring control of an
454 | organization, or substantially all assets of one, or subdividing an
455 | organization, or merging organizations.  If propagation of a covered
456 | work results from an entity transaction, each party to that
457 | transaction who receives a copy of the work also receives whatever
458 | licenses to the work the party's predecessor in interest had or could
459 | give under the previous paragraph, plus a right to possession of the
460 | Corresponding Source of the work from the predecessor in interest, if
461 | the predecessor has it or can get it with reasonable efforts.
462 | 
463 |   You may not impose any further restrictions on the exercise of the
464 | rights granted or affirmed under this License.  For example, you may
465 | not impose a license fee, royalty, or other charge for exercise of
466 | rights granted under this License, and you may not initiate litigation
467 | (including a cross-claim or counterclaim in a lawsuit) alleging that
468 | any patent claim is infringed by making, using, selling, offering for
469 | sale, or importing the Program or any portion of it.
470 | 
471 |   11. Patents.
472 | 
473 |   A "contributor" is a copyright holder who authorizes use under this
474 | License of the Program or a work on which the Program is based.  The
475 | work thus licensed is called the contributor's "contributor version".
476 | 
477 |   A contributor's "essential patent claims" are all patent claims
478 | owned or controlled by the contributor, whether already acquired or
479 | hereafter acquired, that would be infringed by some manner, permitted
480 | by this License, of making, using, or selling its contributor version,
481 | but do not include claims that would be infringed only as a
482 | consequence of further modification of the contributor version.  For
483 | purposes of this definition, "control" includes the right to grant
484 | patent sublicenses in a manner consistent with the requirements of
485 | this License.
486 | 
487 |   Each contributor grants you a non-exclusive, worldwide, royalty-free
488 | patent license under the contributor's essential patent claims, to
489 | make, use, sell, offer for sale, import and otherwise run, modify and
490 | propagate the contents of its contributor version.
491 | 
492 |   In the following three paragraphs, a "patent license" is any express
493 | agreement or commitment, however denominated, not to enforce a patent
494 | (such as an express permission to practice a patent or covenant not to
495 | sue for patent infringement).  To "grant" such a patent license to a
496 | party means to make such an agreement or commitment not to enforce a
497 | patent against the party.
498 | 
499 |   If you convey a covered work, knowingly relying on a patent license,
500 | and the Corresponding Source of the work is not available for anyone
501 | to copy, free of charge and under the terms of this License, through a
502 | publicly available network server or other readily accessible means,
503 | then you must either (1) cause the Corresponding Source to be so
504 | available, or (2) arrange to deprive yourself of the benefit of the
505 | patent license for this particular work, or (3) arrange, in a manner
506 | consistent with the requirements of this License, to extend the patent
507 | license to downstream recipients.  "Knowingly relying" means you have
508 | actual knowledge that, but for the patent license, your conveying the
509 | covered work in a country, or your recipient's use of the covered work
510 | in a country, would infringe one or more identifiable patents in that
511 | country that you have reason to believe are valid.
512 | 
513 |   If, pursuant to or in connection with a single transaction or
514 | arrangement, you convey, or propagate by procuring conveyance of, a
515 | covered work, and grant a patent license to some of the parties
516 | receiving the covered work authorizing them to use, propagate, modify
517 | or convey a specific copy of the covered work, then the patent license
518 | you grant is automatically extended to all recipients of the covered
519 | work and works based on it.
520 | 
521 |   A patent license is "discriminatory" if it does not include within
522 | the scope of its coverage, prohibits the exercise of, or is
523 | conditioned on the non-exercise of one or more of the rights that are
524 | specifically granted under this License.  You may not convey a covered
525 | work if you are a party to an arrangement with a third party that is
526 | in the business of distributing software, under which you make payment
527 | to the third party based on the extent of your activity of conveying
528 | the work, and under which the third party grants, to any of the
529 | parties who would receive the covered work from you, a discriminatory
530 | patent license (a) in connection with copies of the covered work
531 | conveyed by you (or copies made from those copies), or (b) primarily
532 | for and in connection with specific products or compilations that
533 | contain the covered work, unless you entered into that arrangement,
534 | or that patent license was granted, prior to 28 March 2007.
535 | 
536 |   Nothing in this License shall be construed as excluding or limiting
537 | any implied license or other defenses to infringement that may
538 | otherwise be available to you under applicable patent law.
539 | 
540 |   12. No Surrender of Others' Freedom.
541 | 
542 |   If conditions are imposed on you (whether by court order, agreement or
543 | otherwise) that contradict the conditions of this License, they do not
544 | excuse you from the conditions of this License.  If you cannot convey a
545 | covered work so as to satisfy simultaneously your obligations under this
546 | License and any other pertinent obligations, then as a consequence you may
547 | not convey it at all.  For example, if you agree to terms that obligate you
548 | to collect a royalty for further conveying from those to whom you convey
549 | the Program, the only way you could satisfy both those terms and this
550 | License would be to refrain entirely from conveying the Program.
551 | 
552 |   13. Use with the GNU Affero General Public License.
553 | 
554 |   Notwithstanding any other provision of this License, you have
555 | permission to link or combine any covered work with a work licensed
556 | under version 3 of the GNU Affero General Public License into a single
557 | combined work, and to convey the resulting work.  The terms of this
558 | License will continue to apply to the part which is the covered work,
559 | but the special requirements of the GNU Affero General Public License,
560 | section 13, concerning interaction through a network will apply to the
561 | combination as such.
562 | 
563 |   14. Revised Versions of this License.
564 | 
565 |   The Free Software Foundation may publish revised and/or new versions of
566 | the GNU General Public License from time to time.  Such new versions will
567 | be similar in spirit to the present version, but may differ in detail to
568 | address new problems or concerns.
569 | 
570 |   Each version is given a distinguishing version number.  If the
571 | Program specifies that a certain numbered version of the GNU General
572 | Public License "or any later version" applies to it, you have the
573 | option of following the terms and conditions either of that numbered
574 | version or of any later version published by the Free Software
575 | Foundation.  If the Program does not specify a version number of the
576 | GNU General Public License, you may choose any version ever published
577 | by the Free Software Foundation.
578 | 
579 |   If the Program specifies that a proxy can decide which future
580 | versions of the GNU General Public License can be used, that proxy's
581 | public statement of acceptance of a version permanently authorizes you
582 | to choose that version for the Program.
583 | 
584 |   Later license versions may give you additional or different
585 | permissions.  However, no additional obligations are imposed on any
586 | author or copyright holder as a result of your choosing to follow a
587 | later version.
588 | 
589 |   15. Disclaimer of Warranty.
590 | 
591 |   THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
592 | APPLICABLE LAW.  EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT
593 | HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY
594 | OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO,
595 | THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
596 | PURPOSE.  THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM
597 | IS WITH YOU.  SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF
598 | ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
599 | 
600 |   16. Limitation of Liability.
601 | 
602 |   IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
603 | WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS
604 | THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY
605 | GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE
606 | USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF
607 | DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD
608 | PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS),
609 | EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
610 | SUCH DAMAGES.
611 | 
612 |   17. Interpretation of Sections 15 and 16.
613 | 
614 |   If the disclaimer of warranty and limitation of liability provided
615 | above cannot be given local legal effect according to their terms,
616 | reviewing courts shall apply local law that most closely approximates
617 | an absolute waiver of all civil liability in connection with the
618 | Program, unless a warranty or assumption of liability accompanies a
619 | copy of the Program in return for a fee.
620 | 
621 |                      END OF TERMS AND CONDITIONS
622 | 
623 |             How to Apply These Terms to Your New Programs
624 | 
625 |   If you develop a new program, and you want it to be of the greatest
626 | possible use to the public, the best way to achieve this is to make it
627 | free software which everyone can redistribute and change under these terms.
628 | 
629 |   To do so, attach the following notices to the program.  It is safest
630 | to attach them to the start of each source file to most effectively
631 | state the exclusion of warranty; and each file should have at least
632 | the "copyright" line and a pointer to where the full notice is found.
633 | 
634 |     <one line to give the program's name and a brief idea of what it does.>
635 |     Copyright (C) <year>  <name of author>
636 | 
637 |     This program is free software: you can redistribute it and/or modify
638 |     it under the terms of the GNU General Public License as published by
639 |     the Free Software Foundation, either version 3 of the License, or
640 |     (at your option) any later version.
641 | 
642 |     This program is distributed in the hope that it will be useful,
643 |     but WITHOUT ANY WARRANTY; without even the implied warranty of
644 |     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
645 |     GNU General Public License for more details.
646 | 
647 |     You should have received a copy of the GNU General Public License
648 |     along with this program.  If not, see <https://www.gnu.org/licenses/>.
649 | 
650 | Also add information on how to contact you by electronic and paper mail.
651 | 
652 |   If the program does terminal interaction, make it output a short
653 | notice like this when it starts in an interactive mode:
654 | 
655 |     <program>  Copyright (C) <year>  <name of author>
656 |     This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
657 |     This is free software, and you are welcome to redistribute it
658 |     under certain conditions; type `show c' for details.
659 | 
660 | The hypothetical commands `show w' and `show c' should show the appropriate
661 | parts of the General Public License.  Of course, your program's commands
662 | might be different; for a GUI interface, you would use an "about box".
663 | 
664 |   You should also get your employer (if you work as a programmer) or school,
665 | if any, to sign a "copyright disclaimer" for the program, if necessary.
666 | For more information on this, and how to apply and follow the GNU GPL, see
667 | <https://www.gnu.org/licenses/>.
668 | 
669 |   The GNU General Public License does not permit incorporating your program
670 | into proprietary programs.  If your program is a subroutine library, you
671 | may consider it more useful to permit linking proprietary applications with
672 | the library.  If this is what you want to do, use the GNU Lesser General
673 | Public License instead of this License.  But first, please read
674 | <https://www.gnu.org/licenses/why-not-lgpl.html>.


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