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curl / Docs / Security Problems / not verifying certs for TLS to IP address / Darwinssl
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not verifying certs for TLS to IP address / Darwinssl

Project curl Security Advisory, March 26th 2014 permalink

VULNERABILITY

When asked to do a TLS connection (HTTPS, FTPS, IMAPS, etc) to a URL specified with an IP address instead of a name, libcurl would wrongly not verify the server's name in the certificate. The signature (whether it was signed by a trusted CA) and validity (whether the date was within the certificate's lifetime and it was not revoked) verifications were still performed.

This is a problem in libcurl built to use the SecureTransport/Darwinssl backend. SecureTransport/Darwinssl is the TLS library present and used on Mac OS X and iOS.

Only users on Mac OS X or iOS can be affected by this. And only if libcurl was built to use the native TLS backend library.

This problem was initially used as an example of the Apple SSL bug that hit the news in late February 2014 but that was not correct.

The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2014-1263 to this issue.

CWE-297: Improper Validation of Certificate with Host Mismatch

AFFECTED VERSIONS

This flaw has existed ever since libcurl started to support the SecureTransport/Darwinssl backend.

libcurl is used by many applications, but not always advertised as such!

THE SOLUTION

libcurl 7.36.0 makes sure that all TLS using requests verify the host name even if specified as an IP address in the URL.

A patch for this problem is available.

The fix was committed to the public source code repository because the full security impact wasn't properly realized until after the fact.

RECOMMENDATIONS

We suggest you take one of the following actions immediately, in order of preference:

A - Upgrade to curl and libcurl 7.36.0

B - Apply the patch and rebuild libcurl

C - Rebuild libcurl to use another TLS backend

TIME LINE

It was discovered by the curl project during late February 2014.

libcurl 7.36.0 was released on March 26th 2014, coordinated with the publication of this advisory.

CREDITS

This was indirectly reported by numerous people and it was also clarified by Adam Langley that it wasn't the problem Apple themselves fixed. Roland Moriz is credited in Apple's security note.

David Ryskalczyk wrote the patch.

Nick Zitzmann helped coordinate the bug fix.

Apple claims to have fixed this problem in an update of their own. That was done independently from and without informing the curl project.

Thanks a lot!