[UNIX] OpenSSL Multiple Vulnerabilities (Malformed ASN.1, Malformed Public Key)
From: SecuriTeam (support_at_securiteam.com)
Date: 10/01/03
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To: list@securiteam.com Date: 1 Oct 2003 10:27:37 +0200
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OpenSSL Multiple Vulnerabilities (Malformed ASN.1, Malformed Public Key)
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SUMMARY
NISCC (www.niscc.gov.uk) prepared a test suite to check the operation of
SSL/TLS software when presented with a wide range of malformed client
certificates.
Dr Stephen Henson (steve@openssl.org) of the OpenSSL core team identified
and prepared fixes for a number of vulnerabilities in the OpenSSL ASN1
code when running the test suite.
A bug in OpenSSLs SSL/TLS protocol was also identified which causes
OpenSSL to parse a client certificate from an SSL/TLS client when it
should reject it as a protocol error.
DETAILS
1. Certain ASN.1 encodings that are rejected as invalid by the parser can
trigger a bug in the deallocation of the corresponding data structure,
corrupting the stack. This can be used as a denial of service attack. It
is currently unknown whether this can be exploited to run malicious code.
This issue does not affect OpenSSL 0.9.6.
2. Unusual ASN.1 tag values can cause an out of bounds read under certain
circumstances, resulting in a denial of service vulnerability.
3. A malformed public key in a certificate will crash the verify code if
it is set to ignore public key decoding errors. Public key decode errors
are not normally ignored, except for debugging purposes, so this is
unlikely to affect production code. Exploitation of an affected
application would result in a denial of service vulnerability.
4. Due to an error in the SSL/TLS protocol handling, a server will parse a
client certificate when one is not specifically requested. This by itself
is not strictly speaking a vulnerability but it does mean that *all*
SSL/TLS servers that use OpenSSL can be attacked using vulnerabilities 1,
2 and 3 even if they don't enable client authentication.
Who is affected?
All versions of OpenSSL up to and including 0.9.6j and 0.9.7b and all
versions of SSLeay are affected.
Any application that makes use of OpenSSL's ASN1 library to parse
untrusted data. This includes all SSL or TLS applications, those using
S/MIME (PKCS#7) or certificate generation routines.
Recommendations:
Upgrade to OpenSSL 0.9.7c or 0.9.6k. Recompile any OpenSSL applications
statically linked to OpenSSL libraries.
ADDITIONAL INFORMATION
The information has been provided by <mailto:steve@openssl.org> Dr
Stephen Henson of OpenSSL.
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