[Bug 1380229] [NEW] Potential Vulnerability for X509 Certificate Verification

[Jerry Zhang]

*** This bug is a security vulnerability ***

Public security bug reported:

Hostname verification is an important step when verifying X509
certificates, however, people tend to miss the step when using SSL/TLS,
which might cause severe man in the middle attack and break the entire
TLS mechanism.

We believe that nagios-nrpe-plugin didn't check whether the hostname
matches the name in the ssl certificate and the expired date of the
certificate.

We found the vulnerability by static analysis, typically, a process of verification involves calling a chain of API, and we can deduce whether the communication process is vulnerable by detecting whether the process satisfies a certain relation.
The result format is like this:
notice: Line Number at Method Name, Source File

We provide this result to help developers to locate the problem faster.

This is the result for nagios-nrpe-plugin:
[PDG]main'3
	[Found]SSL_connect()
	[HASH] 2600616823 [LineNo]@ 157[Kind]call-site[Char] SSL_connect()[Src] /home/roca/workspace/codebase/code/ubuntu_pkg/nagios-nrpe-plugin/nagios-nrpe-2.12/src/check_nrpe.c
	[INFO] API SSL_new() Found! --> [HASH] 4103224634 [LineNo]@ 154[Kind]call-site[Char] SSL_new()[Src] /home/roca/workspace/codebase/code/ubuntu_pkg/nagios-nrpe-plugin/nagios-nrpe-2.12/src/check_nrpe.c
	[INFO] API SSL_CTX_new() Found! --> [HASH] 4083349714 [LineNo]@ 235[Kind]call-site[Char] SSL_CTX_new()[Src] /home/roca/workspace/codebase/code/ubuntu_pkg/nagios-nrpe-plugin/nagios-nrpe-2.12/src/nrpe.c
	[Warning] No secure SSL_Method API found! Potentially vulnerable!!!

The result means that we found that nagios-nrpe-plugin uses ssl and it
didn't invoke the method pertaining to the certificate, thus it is
vulnearable if the certificate is tampered.

We don't have a POC because we didn't succeed in configuring this
software or don't know the way to verify the vulnerability. But through
the analysis of the source code, we believe it breaks the ssl
certificate verfication protocol.

for more information about the importance of checking hostname:
see http://people.stfx.ca/x2011/x2011ucj/SSL/p38-georgiev.pdf

Thanks.

** Affects: nagios-nrpe (Ubuntu)
     Importance: Undecided
         Status: New

** Information type changed from Private Security to Public

** Information type changed from Public to Public Security

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https://bugs.launchpad.net/bugs/1380229

Title:
  Potential Vulnerability for X509 Certificate Verification

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