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Add additional DigestInfo checks.

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Reencode DigestInto in DER and check against the original: this
will reject any improperly encoded DigestInfo structures.

Note: this is a precautionary measure, there is no known attack
which can exploit this.

Thanks to Brian Smith for reporting this issue.
Reviewed-by: Tim Hudson <tjh@openssl.org>
This commit is contained in:
Dr. Stephen Henson 2014-09-25 23:28:48 +01:00
parent 3d81ec5b92
commit 1cfd255c91
2 changed files with 30 additions and 1 deletions
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10
CHANGES
View File

@ -627,6 +627,16 @@
Changes between 1.0.1g and 1.0.1h [5 Jun 2014]
*) Add additional DigestInfo checks.
Reencode DigestInto in DER and check against the original: this
will reject any improperly encoded DigestInfo structures.
Note: this is a precautionary measure OpenSSL and no attacks
are currently known.
[Steve Henson]
*) Fix for SSL/TLS MITM flaw. An attacker using a carefully crafted
handshake can force the use of weak keying material in OpenSSL
SSL/TLS clients and servers.

21
crypto/rsa/rsa_sign.c
View File

@ -143,6 +143,25 @@ int RSA_sign(int type, const unsigned char *m, unsigned int m_len,
return(ret);
}
/*
* Check DigestInfo structure does not contain extraneous data by reencoding
* using DER and checking encoding against original.
*/
static int rsa_check_digestinfo(X509_SIG *sig, const unsigned char *dinfo, int dinfolen)
{
unsigned char *der = NULL;
int derlen;
int ret = 0;
derlen = i2d_X509_SIG(sig, &der);
if (derlen <= 0)
return 0;
if (derlen == dinfolen && !memcmp(dinfo, der, derlen))
ret = 1;
OPENSSL_cleanse(der, derlen);
OPENSSL_free(der);
return ret;
}
int int_rsa_verify(int dtype, const unsigned char *m,
unsigned int m_len,
unsigned char *rm, size_t *prm_len,
@ -211,7 +230,7 @@ int int_rsa_verify(int dtype, const unsigned char *m,
if (sig == NULL) goto err;
/* Excess data can be used to create forgeries */
if(p != s+i)
if(p != s+i || !rsa_check_digestinfo(sig, s, i))
{
RSAerr(RSA_F_INT_RSA_VERIFY,RSA_R_BAD_SIGNATURE);
goto err;