Commit f3a7e57c authored by Andy Polyakov's avatar Andy Polyakov Committed by Matt Caswell
Browse files

crypto/evp: harden RC4_MD5 cipher. 



Originally a crash in 32-bit build was reported CHACHA20-POLY1305
cipher. The crash is triggered by truncated packet and is result
of excessive hashing to the edge of accessible memory (or bogus
MAC value is produced if x86 MD5 assembly module is involved). Since
hash operation is read-only it is not considered to be exploitable
beyond a DoS condition.

Thanks to Robert Święcki for report.

CVE-2017-3731

Reviewed-by: default avatarRich Salz <rsalz@openssl.org>
parent b8552dc8

crypto/evp/e_rc4_hmac_md5.c

+2 −0
Original line number Diff line number Diff line
@@ -219,6 +219,8 @@ static int rc4_hmac_md5_ctrl(EVP_CIPHER_CTX *ctx, int type, int arg, 
            len = p[arg - 2] << 8 | p[arg - 1];



            if (!EVP_CIPHER_CTX_encrypting(ctx)) {

                if (len < MD5_DIGEST_LENGTH)

                    return -1;

                len -= MD5_DIGEST_LENGTH;

                p[arg - 2] = len >> 8;

                p[arg - 1] = len;