├── .github ├── pass └── dnsvalidator.png ├── dnsvalidator ├── __init__.py ├── lib │ ├── __init__.py │ └── core │ │ ├── __init__.py │ │ ├── __version__.py │ │ ├── output.py │ │ └── input.py └── dnsvalidator.py ├── .dockerignore ├── test-requirements.txt ├── requirements.txt ├── CREDITS.md ├── Dockerfile ├── .gitignore ├── setup.py ├── README.md └── LICENSE /.github/pass: -------------------------------------------------------------------------------- 1 | 2 | -------------------------------------------------------------------------------- /dnsvalidator/__init__.py: -------------------------------------------------------------------------------- 1 | -------------------------------------------------------------------------------- /dnsvalidator/lib/__init__.py: -------------------------------------------------------------------------------- 1 | -------------------------------------------------------------------------------- /dnsvalidator/lib/core/__init__.py: -------------------------------------------------------------------------------- 1 | -------------------------------------------------------------------------------- /.dockerignore: -------------------------------------------------------------------------------- 1 | .git 2 | .github 3 | Dockerfile 4 | -------------------------------------------------------------------------------- /dnsvalidator/lib/core/__version__.py: -------------------------------------------------------------------------------- 1 | __version__ = '0.1' 2 | 3 | -------------------------------------------------------------------------------- /test-requirements.txt: -------------------------------------------------------------------------------- 1 | requests 2 | dnspython 3 | colorclass 4 | 5 | -------------------------------------------------------------------------------- /requirements.txt: -------------------------------------------------------------------------------- 1 | requests 2 | dnspython 3 | colorclass 4 | netaddr 5 | ipaddress 6 | -------------------------------------------------------------------------------- /.github/dnsvalidator.png: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/objects/dnsvalidator/master/.github/dnsvalidator.png -------------------------------------------------------------------------------- /CREDITS.md: -------------------------------------------------------------------------------- 1 | # Credits 2 | 3 | ## Positive checking and anti-hijack detection. 4 | Functionality for positively checking for known-good domains and validating domains that are often poisoned by resolvers was suggested by [@eur0pa_](https://twitter.com/eur0pa_). Thanks! 5 | -------------------------------------------------------------------------------- /Dockerfile: -------------------------------------------------------------------------------- 1 | FROM python:3.7.3-alpine3.9 2 | 3 | RUN apk add --no-cache shadow bash && \ 4 | mkdir /dnsvalidator && \ 5 | useradd --create-home --shell /sbin/nologin dnsvalidator 6 | 7 | COPY . /dnsvalidator/ 8 | 9 | WORKDIR /dnsvalidator/ 10 | 11 | RUN chown -R dnsvalidator:dnsvalidator /dnsvalidator && \ 12 | python3 setup.py install 13 | 14 | USER dnsvalidator 15 | 16 | ENTRYPOINT ["/usr/local/bin/dnsvalidator"] 17 | -------------------------------------------------------------------------------- /.gitignore: -------------------------------------------------------------------------------- 1 | # VIM temporary files 2 | *.pyc 3 | 4 | # Distribution / packaging 5 | .Python 6 | env/ 7 | build/ 8 | develop-eggs/ 9 | dist/ 10 | downloads/ 11 | eggs/ 12 | .eggs/ 13 | lib64/ 14 | parts/ 15 | sdist/ 16 | var/ 17 | wheels/ 18 | *.egg-info/ 19 | .installed.cfg 20 | *.egg 21 | 22 | # PyInstaller 23 | # Usually these files are written by a python script from a template 24 | # before PyInstaller builds the exe, so as to inject date/other infos into it. 25 | *.manifest 26 | *.spec 27 | 28 | # Installer logs 29 | pip-log.txt 30 | pip-delete-this-directory.txt 31 | 32 | # Unit test / coverage reports 33 | htmlcov/ 34 | .tox/ 35 | .coverage 36 | .coverage.* 37 | .cache 38 | nosetests.xml 39 | coverage.xml 40 | *.cover 41 | .hypothesis/ 42 | 43 | # Translations 44 | *.mo 45 | *.pot 46 | 47 | # JetBrains Rider 48 | .idea/ 49 | *.sln.iml 50 | -------------------------------------------------------------------------------- /setup.py: -------------------------------------------------------------------------------- 1 | """ __Doc__ File handle class """ 2 | from setuptools import find_packages, setup 3 | from dnsvalidator.lib.core.__version__ import __version__ 4 | 5 | 6 | def dependencies(imported_file): 7 | """ __Doc__ Handles dependencies """ 8 | with open(imported_file) as file: 9 | return file.read().splitlines() 10 | 11 | 12 | with open("README.md") as file: 13 | setup( 14 | name="DNSValidator", 15 | license="GPLv3", 16 | description="Maintains a list of DNS servers useful for brute forcing.", 17 | long_description=file.read(), 18 | author="vortexau and codingo", 19 | version=__version__, 20 | author_email="", 21 | url="https://github.com/vortexau/dnsvalidator", 22 | packages=find_packages(exclude=('tests')), 23 | package_data={'dnsvalidator': ['*.txt']}, 24 | entry_points={ 25 | 'console_scripts': [ 26 | 'dnsvalidator = dnsvalidator.dnsvalidator:main' 27 | ] 28 | }, 29 | install_requires=dependencies('requirements.txt'), 30 | setup_requires=['pytest-runner'], 31 | tests_require=dependencies('test-requirements.txt'), 32 | include_package_data=True) 33 | -------------------------------------------------------------------------------- /dnsvalidator/lib/core/output.py: -------------------------------------------------------------------------------- 1 | from colorclass import Color 2 | from colorclass import disable_all_colors, enable_all_colors, is_enabled 3 | from time import localtime, strftime 4 | from enum import IntEnum 5 | 6 | from dnsvalidator.lib.core.__version__ import __version__ 7 | 8 | 9 | class OutputHelper(object): 10 | def __init__(self, arguments): 11 | if arguments.nocolor: 12 | disable_all_colors() 13 | 14 | self.verbose = arguments.verbose 15 | self.silent = arguments.silent 16 | self.seperator = "=======================================================" 17 | self.silent = arguments.silent 18 | self.output = arguments.output 19 | 20 | def print_banner(self): 21 | if self.silent: 22 | return 23 | 24 | print(self.seperator, flush=True) 25 | print("dnsvalidator v%s\tby James McLean (@vortexau) " 26 | "\n \t& Michael Skelton (@codingo_)" % __version__, flush = True) 27 | print(self.seperator, flush=True) 28 | 29 | def terminal(self, level, target, message=""): 30 | if level == 0 and not self.verbose: 31 | return 32 | 33 | # print accepted hosts in silent mode and ignore all other content 34 | if self.silent: 35 | if level == 2: 36 | print(target, flush = True) 37 | return 38 | 39 | formatting = { 40 | 0: Color('{autoblue}[VERBOSE]{/autoblue}'), 41 | 1: Color('{autoyellow}[INFO]{/autoyellow}'), 42 | 2: Color('{autogreen}[ACCEPTED]{/autogreen}'), 43 | 3: Color('{autored}[REJECTED]{/autored}'), 44 | 4: Color('{autobgyellow}{autored}[ERROR]{/autored}{/autobgyellow}') 45 | } 46 | 47 | leader = formatting.get(level, '[#]') 48 | 49 | format_args = { 50 | 'time': strftime("%H:%M:%S", localtime()), 51 | 'target': target, 52 | 'message': message, 53 | 'leader': leader 54 | } 55 | 56 | # allows for leader/message printing in verbose mode without a target 57 | if target == 0: 58 | template = '[{time}] {leader} {message}' 59 | else: 60 | template = '[{time}] {leader} [{target}] {message}' 61 | 62 | print(template.format(**format_args), flush = True) 63 | 64 | if self.output and level == 2: 65 | f = open(self.output, 'a+') 66 | f.writelines(target+"\n") 67 | f.close() 68 | 69 | 70 | class Level(IntEnum): 71 | VERBOSE = 0 72 | INFO = 1 73 | ACCEPTED = 2 74 | REJECTED = 3 75 | ERROR = 4 76 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # DNS Validator 2 | Maintains a list of IPv4 DNS servers by verifying them against baseline servers, and ensuring accurate responses. 3 | 4 | [![Python 3.2|3.6](https://img.shields.io/badge/python-3.2|3.6-green.svg)](https://www.python.org/) [![License](https://img.shields.io/badge/license-GPL3-_red.svg)](https://www.gnu.org/licenses/gpl-3.0.en.html) 5 | [![Twitter](https://img.shields.io/badge/twitter-@vortexau-blue.svg)](https://twitter.com/vortexau) 6 | [![Twitter](https://img.shields.io/badge/twitter-@codingo__-blue.svg)](https://twitter.com/codingo_) 7 | 8 | ![DNSValidator](https://github.com/vortexau/dnsvalidator/blob/master/.github/dnsvalidator.png) 9 | 10 | DNS Validator's approach is different to other DNS query validation tools. This tool performs multiple validation steps on each resolver: 11 | 12 | * Baselines non-geolocated domain names against "trusted" public DNS resolvers, `1.1.1.1`, `8.8.8.8` and `9.9.9.9` 13 | * For each resolver being tested DNS Validator ensures that each baselined domain name resolves to the same IP Address. 14 | * Servers that return an answer that differs from the baseline are immediately skipped 15 | * Performs DNS lookup of known commonly spoofed DNS addresses to ensure NXDOMAIN is returned when expected. 16 | * Resolvers that do not return NXDOMAIN for random subdomains of known target domains are immediately skipped. 17 | 18 | # Usage 19 | 20 | | Argument | Description | 21 | |------------|--------------------------------------------------------------------------------------------------------------| 22 | | (stdin) | Pipe target lists from another application to verify. | 23 | | -t | Specify a target DNS server to verify. | 24 | | -tL | Specify a list of targets or a URL to a list of targets | 25 | | -e | Specify a target exclusion. | 26 | | -eL | Specify a list of targets or a URL to a list of targets to exclude. | 27 | | -r | Specify a root domain to compare to. Must be non-geolocated or most resolvers will fail. | 28 | | -q | Specify a resolver query to use (default:dnsvalidator) | 29 | | -threads | Specify the maximum number of threads to run at any one time (DEFAULT:5) | 30 | | -timeout | Specify a timeout value in seconds for any single thread (DEFAULT:600) | 31 | | -o | Specify an output file to write successful output to. | 32 | | --no-color | If set then any foreground or background colours will be stripped out | 33 | | --silent | If set then only successfully resolved servers will be displayed and banners and other information will be redacted. | 34 | | -v | If set then verbose output will be displayed in the terminal. | 35 | 36 | # Setup 37 | Install using: 38 | ``` 39 | $ python3 setup.py install 40 | ``` 41 | Dependencies will then be installed and DNS Validator will be added to your path as `dnsvalidator`. 42 | 43 | # Examples: 44 | 45 | ## CLI: 46 | 47 | ```bash 48 | $ dnsvalidator -tL https://public-dns.info/nameservers.txt -threads 20 -o resolvers.txt 49 | ``` 50 | 51 | ## Docker: 52 | 53 | Build 54 | 55 | ```bash 56 | $ docker build -t dnsvalidator . 57 | ``` 58 | 59 | Run: 60 | 61 | ```bash 62 | $ docker run -v $(pwd):/dnsvalidator/output -t dnsvalidator -tL https://public-dns.info/nameservers.txt -threads 20 -o /dnsvalidator/output/resolvers.txt 63 | ``` 64 | 65 | # Caveats 66 | 67 | * **WARNING** Keep the thread count to a reasonable level and/or use a VPS/VPN appropriately. Pushing the thread count too high can make it look like you are attempting to attack DNS servers, resulting in network level DNS blocks from your ISP. _Ask us how we know..._ 68 | * Root domains used for baseline tests must not be geolocated; specifically they must return the same IP address regardless of the location on the planet they are resolved from. Domains such as `google.com` or `facebook.com` (and many others) are not suitable for baselines, as they return a geo-located IP address when resolved. 69 | * Using a root domain that is geo-located will result in only resolvers local to the user being returned as valid. 70 | -------------------------------------------------------------------------------- /dnsvalidator/dnsvalidator.py: -------------------------------------------------------------------------------- 1 | #!/usr/bin/env python3 2 | 3 | import dns.resolver 4 | import re 5 | import sys 6 | import os 7 | import signal 8 | import random 9 | import string 10 | import threading 11 | import time 12 | import concurrent.futures 13 | from ipaddress import ip_address, IPv4Address, IPv6Address 14 | 15 | 16 | from .lib.core.input import InputParser, InputHelper 17 | from .lib.core.output import OutputHelper, Level 18 | 19 | 20 | def rand(): 21 | return ''.join(random.choice(string.ascii_lowercase) for i in range(10)) 22 | 23 | 24 | def resolve(): 25 | pass 26 | 27 | 28 | parser = InputParser() 29 | arguments = parser.parse(sys.argv[1:]) 30 | 31 | output = OutputHelper(arguments) 32 | output.print_banner() 33 | baselines = ["1.1.1.1", "8.8.8.8"] 34 | 35 | positivebaselines = ["bet365.com", "telegram.com"] 36 | nxdomainchecks = ["facebook.com", "paypal.com", "google.com", 37 | "bet365.com", "wikileaks.com"] 38 | 39 | goodip = "" 40 | valid_servers = [] 41 | responses = {} 42 | 43 | def validIPAddress(IP): 44 | try: 45 | ipType = type(ip_address(IP)) 46 | if ipType is IPv4Address or ipType is IPv6Address: 47 | return ipType 48 | else: 49 | return False 50 | except ValueError: 51 | return False 52 | 53 | def resolve_address(server): 54 | # Skip if not IPv4 55 | valid = validIPAddress(server) 56 | if not valid: 57 | output.terminal(Level.VERBOSE, server, "skipping as not valid IP") 58 | return 59 | 60 | output.terminal(Level.INFO, server, "Checking...") 61 | 62 | resolver = dns.resolver.Resolver(configure=False) 63 | resolver.nameservers = [server] 64 | 65 | # Try to resolve our positive baselines before going any further 66 | for nxdomaincheck in nxdomainchecks: 67 | # make sure random subdomains are NXDOMAIN 68 | try: 69 | positivehn = "{rand}.{domain}".format( 70 | rand=rand(), 71 | domain=nxdomaincheck 72 | ) 73 | posanswer = resolver.query(positivehn, 'A') 74 | 75 | # nxdomain exception was not thrown, we got records when we shouldn't have. 76 | # Skip the server. 77 | output.terminal(Level.ERROR, server, 78 | "DNS poisoning detected, for " + positivehn + " passing") 79 | return 80 | except dns.resolver.NXDOMAIN: 81 | pass 82 | except Exception as e: 83 | output.terminal(Level.ERROR, server, 84 | "Error when checking for DNS poisoning, passing") 85 | 86 | # Check for nxdomain on the rootdomain we're checking 87 | try: 88 | nxquery = "{rand}.{rootdomain}".format( 89 | rand=rand(), 90 | rootdomain=arguments.rootdomain 91 | ) 92 | nxanswer = resolver.query(nxquery, 'A') 93 | except dns.resolver.NXDOMAIN: 94 | gotnxdomain = True 95 | except: 96 | output.terminal(Level.ERROR, server, 97 | "Error when checking NXDOMAIN, passing") 98 | return 99 | 100 | resolvematches = 0 101 | nxdommatches = 0 102 | 103 | for goodresponse in responses: 104 | if responses[goodresponse]["goodip"] == goodip: 105 | resolvematches += 1 106 | if responses[goodresponse]["nxdomain"] == gotnxdomain: 107 | nxdommatches += 1 108 | 109 | if resolvematches == 2 and nxdommatches == 2: 110 | output.terminal(Level.ACCEPTED, server, "provided valid response") 111 | valid_servers.append(server) 112 | else: 113 | output.terminal(Level.REJECTED, server, 114 | "invalid response received") 115 | 116 | 117 | def main(): 118 | global goodip 119 | # Perform resolution on each of the 'baselines' 120 | for baseline in baselines: 121 | output.terminal(Level.INFO, baseline, "resolving baseline") 122 | baseline_server = {} 123 | 124 | resolver = dns.resolver.Resolver(configure=False) 125 | resolver.nameservers = [baseline] 126 | 127 | # Check our baseline against this server 128 | try: 129 | goodanswer = resolver.query(arguments.rootdomain, 'A') 130 | except dns.exception.Timeout: 131 | output.terminal(Level.ERROR, baseline, 132 | "DNS Timeout for baseline server. Fatal") 133 | sys.exit(1) 134 | 135 | for rr in goodanswer: 136 | baseline_server["goodip"] = str(rr) 137 | goodip = str(rr) 138 | 139 | # checks for often poisoned domains 140 | baseline_server["pos"] = {} 141 | for positivebaseline in positivebaselines: 142 | posanswer = resolver.query(positivebaseline, 'A') 143 | for rr in posanswer: 144 | baseline_server["pos"][positivebaseline] = str(rr) 145 | 146 | try: 147 | nxdomanswer = resolver.query( 148 | arguments.query + arguments.rootdomain, 'A') 149 | baseline_server["nxdomain"] = False 150 | except dns.resolver.NXDOMAIN: 151 | baseline_server["nxdomain"] = True 152 | except dns.exception.Timeout: 153 | output.terminal(Level.ERROR, baseline, 154 | "DNS Timeout for baseline server. Fatal") 155 | sys.exit(1) 156 | 157 | responses[baseline] = baseline_server 158 | 159 | # loop through the list 160 | with concurrent.futures.ThreadPoolExecutor(max_workers=int(arguments.threads)) as executor: 161 | thread = {executor.submit( 162 | resolve_address, server): server for server in InputHelper.return_targets(arguments)} 163 | output.terminal(Level.INFO, 0, "Finished. Discovered {size} servers".format( 164 | size=len(valid_servers))) 165 | 166 | # Declare signal handler to immediately exit on KeyboardInterrupt 167 | 168 | 169 | def signal_handler(signal, frame): 170 | os._exit(0) 171 | 172 | 173 | signal.signal(signal.SIGINT, signal_handler) 174 | 175 | 176 | if __name__ == "__main__": 177 | main() 178 | -------------------------------------------------------------------------------- /dnsvalidator/lib/core/input.py: -------------------------------------------------------------------------------- 1 | #!/usr/bin/env python3 2 | 3 | import sys 4 | import requests 5 | from urllib.parse import urlparse 6 | from argparse import ArgumentParser 7 | from pathlib import Path 8 | 9 | class InputHelper(object): 10 | @staticmethod 11 | def process_targets(parser, arg): 12 | if InputHelper.validate_url(arg): 13 | targets = InputHelper.process_url(parser, arg) 14 | else: 15 | filename = InputHelper.validate_filename(parser, arg) 16 | if filename: 17 | targets = InputHelper.process_file(filename) 18 | 19 | if len(targets) == 0: 20 | raise Exception("No target provided, or empty target list") 21 | 22 | return targets 23 | 24 | @staticmethod 25 | def validate_url(string): 26 | try: 27 | result = urlparse(string) 28 | # if there isn't a scheme, its probably not a URL we can reliably use 29 | return result.scheme 30 | except: 31 | # assume its a file and let the os decide 32 | return False 33 | 34 | @staticmethod 35 | def validate_filename(parser, arg): 36 | filename_arg = Path(arg) 37 | # sometimes we'll encounter ~ and .. 38 | filename_resolved = filename_arg.expanduser().resolve() 39 | if not filename_resolved.is_file(): 40 | parser.error("The file %s does not exist or is not a valid URL!" % arg) 41 | else: 42 | return str(filename_resolved) 43 | 44 | @staticmethod 45 | def process_url(parser, arg): 46 | try: 47 | items = requests.get(arg) 48 | except: 49 | e = sys.exc_info()[0] 50 | parser.error(f"Tried to fetch {arg} but got {e} are you sure this is a valid URL?") 51 | 52 | if items.status_code != 200: 53 | parser.error(f"Tried to fetch {arg} but got HTTP {items.status_code} {items.reason}.") 54 | 55 | return items.text.split() 56 | 57 | @staticmethod 58 | def process_file(arg): 59 | with open(arg, 'r') as file: 60 | return [line.rstrip('\n') for line in file] 61 | 62 | @staticmethod 63 | def check_positive(parser, arg): 64 | i = int(arg) 65 | if i <= 0: 66 | raise parser.ArgumentTypeError( 67 | "%s is not a valid positive integer!" % arg) 68 | 69 | return arg 70 | 71 | @staticmethod 72 | def return_targets(arguments): 73 | targets = set() 74 | exclusions = set() 75 | if arguments.target: 76 | targets.add(arguments.target) 77 | else: 78 | for item in arguments.target_list: 79 | targets.add(item) 80 | 81 | if arguments.exclusion: 82 | exclusions.add(arguments.exclusion) 83 | elif arguments.exclusions_list: 84 | for item in arguments.exclusions_list: 85 | exclusions.add(item) 86 | 87 | # difference operation 88 | targets -= exclusions 89 | 90 | if len(targets) == 0: 91 | raise Exception( 92 | "No target remaining after removing all exceptions.") 93 | return targets 94 | 95 | class InputParser(object): 96 | def __init__(self): 97 | self._parser = self.setup_parser() 98 | 99 | def parse(self, argv): 100 | return self._parser.parse_args(argv) 101 | 102 | @staticmethod 103 | def setup_parser(): 104 | parser = ArgumentParser() 105 | 106 | targets = parser.add_mutually_exclusive_group(required=False) 107 | 108 | targets.add_argument( 109 | '-t', dest='target', required=False, 110 | help='Specify a target DNS server to try resolving.' 111 | ) 112 | 113 | targets.add_argument( 114 | '-tL', dest='target_list', required=False, 115 | help='Specify a list of target DNS servers to try to resolve. ' 116 | 'May be a file, or URL to listing', 117 | default="https://public-dns.info/nameservers.txt", 118 | type=lambda x: InputHelper.process_targets(parser, x) 119 | ) 120 | 121 | # exclusions group 122 | exclusions = parser.add_mutually_exclusive_group() 123 | 124 | exclusions.add_argument( 125 | '-e', dest='exclusion', required=False, 126 | help='Specify an exclusion to remove from any target lists.' 127 | ) 128 | 129 | exclusions.add_argument( 130 | '-eL', dest='exclusions_list', required=False, 131 | help='Specify a list of exclusions to avoid resolving. ' 132 | 'May be a file or URL to listing', 133 | type=lambda x: InputHelper.process_targets(parser, x) 134 | ) 135 | 136 | parser.add_argument('-o', '--output', 137 | dest='output', 138 | help='Destination file to write successful DNS validations to.') 139 | 140 | parser.add_argument( 141 | '-r', dest='rootdomain', required=False, 142 | help="Specify a root domain to compare to (default:", 143 | default="bet365.com" 144 | ) 145 | 146 | parser.add_argument( 147 | '-q', dest='query', required=False, 148 | help="Specify a resolver query to use (default:dnsvalidator)", 149 | default="dnsvalidator" 150 | ) 151 | 152 | parser.add_argument( 153 | '-threads', dest='threads', required=False, 154 | help="Specify the maximum number of threads to run (DEFAULT:5)", 155 | default=5, 156 | type=lambda x: InputHelper.check_positive(parser, x) 157 | ) 158 | 159 | parser.add_argument( 160 | '-timeout', dest='timeout', required=False, 161 | help="Command timeout in seconds (DEFAULT:600)", 162 | default=600, 163 | type=lambda x: InputHelper.check_positive(parser, x) 164 | ) 165 | 166 | parser.add_argument( 167 | '--no-color', dest='nocolor', action='store_true', default=False, 168 | help='If set then any foreground or background colours will be ' 169 | 'stripped out.' 170 | ) 171 | 172 | output_types = parser.add_mutually_exclusive_group() 173 | output_types.add_argument( 174 | '-v', '--verbose', dest='verbose', action='store_true', default=False, 175 | help='If set then verbose output will be displayed in the terminal.' 176 | ) 177 | output_types.add_argument( 178 | '--silent', dest='silent', action='store_true', default=False, 179 | help='If set only findings will be displayed and banners ' 180 | 'and other information will be redacted.' 181 | ) 182 | 183 | return parser 184 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | GNU GENERAL PUBLIC LICENSE 2 | Version 3, 29 June 2007 3 | 4 | Copyright (C) 2007 Free Software Foundation, Inc. 5 | Everyone is permitted to copy and distribute verbatim copies 6 | of this license document, but changing it is not allowed. 7 | 8 | Preamble 9 | 10 | The GNU General Public License is a free, copyleft license for 11 | software and other kinds of works. 12 | 13 | The licenses for most software and other practical works are designed 14 | to take away your freedom to share and change the works. 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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 | 635 | Copyright (C) 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 . 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 | Copyright (C) 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 | . 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 | . 675 | --------------------------------------------------------------------------------