Fix various certificate fingerprint issues.

By using non-DER or invalid encodings outside the signed portion of a
certificate the fingerprint can be changed without breaking the signature.
Although no details of the signed portion of the certificate can be changed
this can cause problems with some applications: e.g. those using the
certificate fingerprint for blacklists.

1. Reject signatures with non zero unused bits.

If the BIT STRING containing the signature has non zero unused bits reject
the signature. All current signature algorithms require zero unused bits.

2. Check certificate algorithm consistency.

Check the AlgorithmIdentifier inside TBS matches the one in the
certificate signature. NB: this will result in signature failure
errors for some broken certificates.

3. Check DSA/ECDSA signatures use DER.

Reencode DSA/ECDSA signatures and compare with the original received
signature. Return an error if there is a mismatch.

This will reject various cases including garbage after signature
(thanks to Antti Karjalainen and Tuomo Untinen from the Codenomicon CROSS
program for discovering this case) and use of BER or invalid ASN.1 INTEGERs
(negative or with leading zeroes).

CVE-2014-8275
Reviewed-by: Emilia Käsper <emilia@openssl.org>
(cherry picked from commit 684400ce192dac51df3d3e92b61830a6ef90be3e)

diff --git a/CHANGES b/CHANGES
index c3bb94052d764e57b52b6fac2614f6677d86f2c4..c91552ca12897b462829a845b7cc77457cc2510b 100644 (file)
--- a/CHANGES
+++ b/CHANGES
@@ -4,6 +4,43 @@
 
  Changes between 1.0.1j and 1.0.1k [xx XXX xxxx]
 
+  *) Fix various certificate fingerprint issues.
+
+     By using non-DER or invalid encodings outside the signed portion of a
+     certificate the fingerprint can be changed without breaking the signature.
+     Although no details of the signed portion of the certificate can be changed
+     this can cause problems with some applications: e.g. those using the
+     certificate fingerprint for blacklists.
+
+     1. Reject signatures with non zero unused bits.
+
+     If the BIT STRING containing the signature has non zero unused bits reject
+     the signature. All current signature algorithms require zero unused bits.
+
+     2. Check certificate algorithm consistency.
+
+     Check the AlgorithmIdentifier inside TBS matches the one in the
+     certificate signature. NB: this will result in signature failure
+     errors for some broken certificates.
+
+     Thanks to Konrad Kraszewski from Google for reporting this issue.
+
+     3. Check DSA/ECDSA signatures use DER.
+
+     Reencode DSA/ECDSA signatures and compare with the original received
+     signature. Return an error if there is a mismatch.
+
+     This will reject various cases including garbage after signature
+     (thanks to Antti Karjalainen and Tuomo Untinen from the Codenomicon CROSS
+     program for discovering this case) and use of BER or invalid ASN.1 INTEGERs
+     (negative or with leading zeroes).
+
+     Further analysis was conducted and fixes were developed by Stephen Henson
+     of the OpenSSL core team.
+
+     (CVE-2014-8275)
+     [Steve Henson]
+
    *) Do not resume sessions on the server if the negotiated protocol
       version does not match the session's version. Resuming with a different
       version, while not strictly forbidden by the RFC, is of questionable

diff --git a/crypto/asn1/a_verify.c b/crypto/asn1/a_verify.c
index fc84cd3d191bcec17bc4553eaeb0ef963cc540b4..a571009ab9d0b9212de79a30d6a694ca8b83e10b 100644 (file)
--- a/crypto/asn1/a_verify.c
+++ b/crypto/asn1/a_verify.c
@@ -90,6 +90,12 @@ int ASN1_verify(i2d_of_void *i2d, X509_ALGOR *a, ASN1_BIT_STRING *signature,
                ASN1err(ASN1_F_ASN1_VERIFY,ASN1_R_UNKNOWN_MESSAGE_DIGEST_ALGORITHM);
                goto err;
                }
+
+       if (signature->type == V_ASN1_BIT_STRING && signature->flags & 0x7)
+               {
+               ASN1err(ASN1_F_ASN1_VERIFY, ASN1_R_INVALID_BIT_STRING_BITS_LEFT);
+               goto err;
+               }
        
        inl=i2d(data,NULL);
        buf_in=OPENSSL_malloc((unsigned int)inl);
@@ -146,6 +152,12 @@ int ASN1_item_verify(const ASN1_ITEM *it, X509_ALGOR *a,
                return -1;
                }
 
+       if (signature->type == V_ASN1_BIT_STRING && signature->flags & 0x7)
+               {
+               ASN1err(ASN1_F_ASN1_VERIFY, ASN1_R_INVALID_BIT_STRING_BITS_LEFT);
+               return -1;
+               }
+
        EVP_MD_CTX_init(&ctx);
 
        /* Convert signature OID into digest and public key OIDs */

diff --git a/crypto/dsa/dsa_asn1.c b/crypto/dsa/dsa_asn1.c
index 60585343746d97d64c0d2e26dea335b69c763f0f..473af873e02beffe2cb638153ddc2d993b930591 100644 (file)
--- a/crypto/dsa/dsa_asn1.c
+++ b/crypto/dsa/dsa_asn1.c
@@ -176,13 +176,25 @@ int DSA_verify(int type, const unsigned char *dgst, int dgst_len,
             const unsigned char *sigbuf, int siglen, DSA *dsa)
        {
        DSA_SIG *s;
+       const unsigned char *p = sigbuf;
+       unsigned char *der = NULL;
+       int derlen = -1;
        int ret=-1;
 
        s = DSA_SIG_new();
        if (s == NULL) return(ret);
-       if (d2i_DSA_SIG(&s,&sigbuf,siglen) == NULL) goto err;
+       if (d2i_DSA_SIG(&s,&p,siglen) == NULL) goto err;
+       /* Ensure signature uses DER and doesn't have trailing garbage */
+       derlen = i2d_DSA_SIG(s, &der);
+       if (derlen != siglen || memcmp(sigbuf, der, derlen))
+               goto err;
        ret=DSA_do_verify(dgst,dgst_len,s,dsa);
 err:
+       if (derlen > 0)
+               {
+               OPENSSL_cleanse(der, derlen);
+               OPENSSL_free(der);
+               }
        DSA_SIG_free(s);
        return(ret);
        }

diff --git a/crypto/ecdsa/ecs_vrf.c b/crypto/ecdsa/ecs_vrf.c
index ef9acf7b610284d697bcea815061ef29a67fce0e..2836efe5eff228bf9ef0e707f723f1b6e8ba937e 100644 (file)
--- a/crypto/ecdsa/ecs_vrf.c
+++ b/crypto/ecdsa/ecs_vrf.c
@@ -57,6 +57,7 @@
  */
 
 #include "ecs_locl.h"
+#include "cryptlib.h"
 #ifndef OPENSSL_NO_ENGINE
 #include <openssl/engine.h>
 #endif
@@ -84,13 +85,25 @@ int ECDSA_verify(int type, const unsigned char *dgst, int dgst_len,
                const unsigned char *sigbuf, int sig_len, EC_KEY *eckey)
        {
        ECDSA_SIG *s;
+       const unsigned char *p = sigbuf;
+       unsigned char *der = NULL;
+       int derlen = -1;
        int ret=-1;
 
        s = ECDSA_SIG_new();
        if (s == NULL) return(ret);
-       if (d2i_ECDSA_SIG(&s, &sigbuf, sig_len) == NULL) goto err;
+       if (d2i_ECDSA_SIG(&s, &p, sig_len) == NULL) goto err;
+       /* Ensure signature uses DER and doesn't have trailing garbage */
+       derlen = i2d_ECDSA_SIG(s, &der);
+       if (derlen != sig_len || memcmp(sigbuf, der, derlen))
+               goto err;
        ret=ECDSA_do_verify(dgst, dgst_len, s, eckey);
 err:
+       if (derlen > 0)
+               {
+               OPENSSL_cleanse(der, derlen);
+               OPENSSL_free(der);
+               }
        ECDSA_SIG_free(s);
        return(ret);
        }

diff --git a/crypto/x509/x_all.c b/crypto/x509/x_all.c
index e06602d65abcc05825cb9461eb31fc5f3dc4d103..fef55f89d9a076cfe576ba0405d015fae03b15a8 100644 (file)
--- a/crypto/x509/x_all.c
+++ b/crypto/x509/x_all.c
@@ -72,6 +72,8 @@
 
 int X509_verify(X509 *a, EVP_PKEY *r)
        {
+       if (X509_ALGOR_cmp(a->sig_alg, a->cert_info->signature))
+               return 0;
        return(ASN1_item_verify(ASN1_ITEM_rptr(X509_CINF),a->sig_alg,
                a->signature,a->cert_info,r));
        }