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CVE-2016-2126: auth/kerberos: only allow known checksum types in check_pac_checksum()

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aes based checksums can only be checked with the
corresponding aes based keytype.

Otherwise we may trigger an undefined code path
deep in the kerberos libraries, which can leed to
segmentation faults.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=12446

Signed-off-by: Stefan Metzmacher <metze@samba.org>
This commit is contained in:
Stefan Metzmacher 2016-11-22 17:08:46 +01:00
parent 6459543b5a
commit ab25cdfa9d
1 changed files with 22 additions and 0 deletions
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22
auth/kerberos/kerberos_pac.c
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@ -39,6 +39,28 @@ krb5_error_code check_pac_checksum(DATA_BLOB pac_data,
krb5_boolean checksum_valid = false; krb5_boolean checksum_valid = false;
krb5_data input; krb5_data input;
switch (sig->type) {
case CKSUMTYPE_HMAC_MD5:
/* ignores the key type */
break;
case CKSUMTYPE_HMAC_SHA1_96_AES_256:
if (KRB5_KEY_TYPE(keyblock) != ENCTYPE_AES256_CTS_HMAC_SHA1_96) {
return EINVAL;
}
/* ok */
break;
case CKSUMTYPE_HMAC_SHA1_96_AES_128:
if (KRB5_KEY_TYPE(keyblock) != ENCTYPE_AES128_CTS_HMAC_SHA1_96) {
return EINVAL;
}
/* ok */
break;
default:
DEBUG(2,("check_pac_checksum: Checksum Type %d is not supported\n",
(int)sig->type));
return EINVAL;
}
#ifdef HAVE_CHECKSUM_IN_KRB5_CHECKSUM /* Heimdal */ #ifdef HAVE_CHECKSUM_IN_KRB5_CHECKSUM /* Heimdal */
cksum.cksumtype = (krb5_cksumtype)sig->type; cksum.cksumtype = (krb5_cksumtype)sig->type;
cksum.checksum.length = sig->signature.length; cksum.checksum.length = sig->signature.length;