[krbdev.mit.edu #6774] pkinit client cert matching can be disrupted by one of the candidate certs
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Tue Sep 14 14:58:51 EDT 2010
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Date: Mon, 13 Sep 2010 13:39:31 -0400
Message-Id: <201009131739.o8DHdV3c028015 at blade.bos.redhat.com>
To: krb5-bugs at mit.edu
Subject: pkinit client cert matching can be disrupted by one of the candidate
certs
From: nalin at redhat.com
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>Submitter-Id: net
>Originator:
>Organization:
>Confidential: no
>Synopsis: pkinit client cert matching can be disrupted by one of the candidate certs
>Severity: non-critical
>Priority: medium
>Category: krb5-libs
>Class: sw-bug
>Release: 1.8.2
>Environment:
System: Linux blade.bos.redhat.com 2.6.34-43.fc14.x86_64 #1 SMP Thu Jun 17 10:32:12 UTC 2010 x86_64 x86_64 x86_64 GNU/Linux
Architecture: x86_64
>Description:
In crypto_retrieve_X509_sans(), the "i" used to hold the result of
X509_get_ext_by_NID() is unsigned, so without a cast or changing its
type, the comparison to -1 will always succeed.
If the attempt to parse the SAN value then fails because the extension
is not present, then crypto_retrieve_X509_sans(),
crypto_cert_get_matching_data(), and obtain_all_cert_matching_data()
will all return EINVAL, pkinit_cert_matching() will fail, and
pkinit_identity_initialize() will fail. As a result, the presence one
candidate certificate which doesn't contain any SAN values will cause
the client to fail to locate its certificate.
>How-To-Repeat:
We're testing with a PKCS11 smart card here, but I expect it can be
reproduced using multiple certificates in files, so long as at least one
of the certificates being considered is lacking a subjectAltName
extension.
>Fix:
Here's one possible patch:
Index: src/plugins/preauth/pkinit/pkinit_crypto_openssl.c
===================================================================
--- src/plugins/preauth/pkinit/pkinit_crypto_openssl.c (revision 24305)
+++ src/plugins/preauth/pkinit/pkinit_crypto_openssl.c (working copy)
@@ -1787,7 +1787,7 @@
buf, sizeof(buf));
pkiDebug("%s: looking for SANs in cert = %s\n", __FUNCTION__, buf);
- if ((i = X509_get_ext_by_NID(cert, NID_subject_alt_name, -1)) >= 0) {
+ if (((int)(i = X509_get_ext_by_NID(cert, NID_subject_alt_name, -1))) >= 0) {
X509_EXTENSION *ext = NULL;
GENERAL_NAMES *ialt = NULL;
GENERAL_NAME *gen = NULL;
@@ -1896,6 +1896,8 @@
}
}
sk_GENERAL_NAME_pop_free(ialt, GENERAL_NAME_free);
+ } else {
+ pkiDebug("%s: found no subject alt name extensions\n", __FUNCTION__);
}
retval = 0;
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