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add a special case to the X509 code that deals with RDP certificates.

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Basically, at least some rdp certificates specify a completely invalid
and nonsensical value for theyr key type. OpenSSL does not like this and
refuses to parse the key in this case. With this change, we detect this
case and special-case it, hinting to OpenSSL what kind of key we have.
This gives us additional information that we would not have otherwhise
in the log file (like key length and the exponent).
This commit is contained in:
Johanna Amann 2015-03-05 12:59:03 -08:00
parent 276e072e6e
commit 9441dc68ec
2 changed files with 21 additions and 3 deletions
Download patch file Download diff file Expand all files Collapse all files

18
src/file_analysis/analyzer/x509/X509.cc
View file

@ -120,6 +120,19 @@ RecordVal* file_analysis::X509::ParseCertificate(X509Val* cert_val)
pX509Cert->Assign(6, new StringVal(buf));
// Special case for RDP server certificates. For some reason some (all?) RDP server
// certificates like to specify their key algorithm as md5WithRSAEncryption, which
// is wrong on so many levels. We catch this special case here and set it to what is
// actually should be (namely - rsaEncryption), so that OpenSSL will parse out the
// key later. Otherwise it will just fail to parse the certificate key.
ASN1_OBJECT* old_algorithm = 0;
if ( OBJ_obj2nid(ssl_cert->cert_info->key->algor->algorithm) == NID_md5WithRSAEncryption )
{
old_algorithm = ssl_cert->cert_info->key->algor->algorithm;
ssl_cert->cert_info->key->algor->algorithm = OBJ_nid2obj(NID_rsaEncryption);
}
if ( ! i2t_ASN1_OBJECT(buf, 255, ssl_cert->sig_alg->algorithm) )
buf[0] = 0;
@ -152,6 +165,11 @@ RecordVal* file_analysis::X509::ParseCertificate(X509Val* cert_val)
}
#endif
// set key algorithm back. We do not have to free the value that we created because (I think) it
// comes out of a static array from OpenSSL memory.
if ( old_algorithm )
ssl_cert->cert_info->key->algor->algorithm = old_algorithm;
unsigned int length = KeyLength(pkey);
if ( length > 0 )
pX509Cert->Assign(9, new Val(length, TYPE_COUNT));

6
testing/btest/Baseline/scripts.base.protocols.rdp.rdp-x509/x509.log
View file

@ -3,9 +3,9 @@
#empty_field (empty)
#unset_field -
#path x509
#open 2015-03-05-05-26-13
#open 2015-03-05-20-58-46
#fields ts id certificate.version certificate.serial certificate.subject certificate.issuer certificate.not_valid_before certificate.not_valid_after certificate.key_alg certificate.sig_alg certificate.key_type certificate.key_length certificate.exponent certificate.curve san.dns san.uri san.email san.ip basic_constraints.ca basic_constraints.path_len
#types time string count string string string time time string string string count string string vector[string] vector[string] vector[string] vector[addr] bool count
1423755602.103140 F71ADVSn3rOqVhNh1 3 59EB28CB02B1A0D4 L=TURNBKL+CN=SERVR L=TURNBKL+CN=SERVR 1423664106.000000 1431388800.000000 rsaEncryption sha1WithRSA rsa 512 65537 - - - - - T 0
1423755602.103140 F71ADVSn3rOqVhNh1 3 0100000001 serialNumber=1BcKefYSF97EvkaiCqahPY8uPd0=\0D\0A+L=ncalrpc:SERVR+CN=ncalrpc:SERVR L=TURNBKL+CN=SERVR 1365174955.000000 1483228799.000000 md5WithRSAEncryption sha1WithRSA - - - - - - - - - -
#close 2015-03-05-05-26-13
1423755602.103140 F71ADVSn3rOqVhNh1 3 0100000001 serialNumber=1BcKefYSF97EvkaiCqahPY8uPd0=\0D\0A+L=ncalrpc:SERVR+CN=ncalrpc:SERVR L=TURNBKL+CN=SERVR 1365174955.000000 1483228799.000000 md5WithRSAEncryption sha1WithRSA rsa 512 65537 - - - - - - -
#close 2015-03-05-20-58-46