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An incompatibility has always existed between the format used for RSA

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signatures and MDC2 using EVP or RSA_sign. This has become more apparent
when the dgst utility in OpenSSL 1.0.0 and later switched to using the
EVP_DigestSign functions which call RSA_sign.

This means that the signature format OpenSSL 1.0.0 and later used with
dgst -sign and MDC2 is incompatible with previous versions.

Add detection in RSA_verify so either format works.

Note: MDC2 is disabled by default in OpenSSL and very rarely used in practice.
This commit is contained in:
Dr. Stephen Henson 2012-02-15 14:00:09 +00:00
parent 424ba8b588
commit 16b7c81d55
2 changed files with 23 additions and 0 deletions
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7
CHANGES
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@ -4,6 +4,13 @@
Changes between 1.0.0f and 1.0.1 [xx XXX xxxx]
*) The format used for MDC2 RSA signatures is inconsistent between EVP
and the RSA_sign/RSA_verify functions. This was made more apparent when
OpenSSL used RSA_sign/RSA_verify for some RSA signatures in particular
those which went through EVP_PKEY_METHOD in 1.0.0 and later. Detect
the correct format in RSA_verify so both forms transparently work.
[Steve Henson]
*) Some servers which support TLS 1.0 can choke if we initially indicate
support for TLS 1.2 and later renegotiate using TLS 1.0 in the RSA
encrypted premaster secret. As a workaround use the maximum pemitted

16
crypto/rsa/rsa_sign.c
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@ -199,6 +199,22 @@ int int_rsa_verify(int dtype, const unsigned char *m,
i=RSA_public_decrypt((int)siglen,sigbuf,s,rsa,RSA_PKCS1_PADDING);
if (i <= 0) goto err;
/* Oddball MDC2 case: signature can be OCTET STRING.
* check for correct tag and length octets.
*/
if (dtype == NID_mdc2 && i == 18 && s[0] == 0x04 && s[1] == 0x10)
{
if (rm)
{
memcpy(rm, s + 2, 16);
*prm_len = 16;
ret = 1;
}
else if(memcmp(m, s + 2, 16))
RSAerr(RSA_F_INT_RSA_VERIFY,RSA_R_BAD_SIGNATURE);
else
ret = 1;
}
/* Special case: SSL signature */
if(dtype == NID_md5_sha1) {