72 lines
3.3 KiB
Markdown
72 lines
3.3 KiB
Markdown
---
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type: reference
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---
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# How we manage the TLS protocol CRIME vulnerability
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[CRIME](https://en.wikipedia.org/w/index.php?title=CRIME&oldid=692423806) is a security exploit against
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secret web cookies over connections using the HTTPS and SPDY protocols that also
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use data compression. When used to recover the content of secret
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authentication cookies, it allows an attacker to perform session hijacking on an
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authenticated web session, allowing the launching of further attacks.
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## Description
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The TLS Protocol CRIME Vulnerability affects systems that use data compression
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over HTTPS. Your system might be vulnerable to the CRIME vulnerability if you use
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SSL Compression (for example, Gzip) or SPDY (which optionally uses compression).
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GitLab supports both Gzip and [SPDY](http://nginx.org/en/docs/http/ngx_http_spdy_module.html) and mitigates the CRIME
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vulnerability by deactivating Gzip when HTTPS is enabled. The sources of the
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files are here:
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- [Source installation NGINX file](https://gitlab.com/gitlab-org/gitlab/blob/master/lib/support/nginx/gitlab-ssl)
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- [Omnibus installation NGINX file](https://gitlab.com/gitlab-org/omnibus-gitlab/blob/master/files/gitlab-cookbooks/gitlab/templates/default/nginx-gitlab-http.conf.erb)
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Although SPDY is enabled in Omnibus installations, CRIME relies on compression
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(the 'C') and the default compression level in NGINX's SPDY module is 0
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(no compression).
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## Nessus
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The Nessus scanner, [reports a possible CRIME vulnerability](https://www.tenable.com/plugins/index.php?view=single&id=62565) in GitLab
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similar to the following format:
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```plaintext
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Description
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This remote service has one of two configurations that are known to be required for the CRIME attack:
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SSL/TLS compression is enabled.
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TLS advertises the SPDY protocol earlier than version 4.
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...
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Output
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The following configuration indicates that the remote service may be vulnerable to the CRIME attack:
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SPDY support earlier than version 4 is advertised.
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```
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From the report above it is important to note that Nessus is only checking if
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TLS advertises the SPDY protocol earlier than version 4. It does not perform an
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attack nor does it check if compression is enabled. The Nessus scanner alone
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cannot tell that SPDY's compression is disabled and not subject to the CRIME
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vulnerability.
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## References
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- NGINX ["Module ngx_http_spdy_module"](http://nginx.org/en/docs/http/ngx_http_spdy_module.html)
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- Tenable Network Security, Inc. ["Transport Layer Security (TLS) Protocol CRIME Vulnerability"](https://www.tenable.com/plugins/index.php?view=single&id=62565)
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- Wikipedia contributors, ["CRIME"](https://en.wikipedia.org/wiki/CRIME) Wikipedia, The Free Encyclopedia
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<!-- ## Troubleshooting
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