Fix for DTLS DoS issue introduced by fix for CVE-2011-4109.

[openssl.git] / ssl / d1_pkt.c

diff --git a/ssl/d1_pkt.c b/ssl/d1_pkt.c
index fdeaac88049134a5f274ee5f31f365606383f844..4dc091a20ec8ca114454bdb2df8d10886ae98189 100644 (file)
--- a/ssl/d1_pkt.c
+++ b/ssl/d1_pkt.c
@@ -384,6 +384,7 @@ dtls1_process_record(SSL *s)
        unsigned int mac_size;
        unsigned char md[EVP_MAX_MD_SIZE];
        int decryption_failed_or_bad_record_mac = 0;
+       unsigned char *mac = NULL;
 
 
        rr= &(s->s3->rrec);
@@ -455,19 +456,15 @@ printf("\n");
 #endif                 
                        }
                /* check the MAC for rr->input (it's in mac_size bytes at the tail) */
-               if (rr->length < mac_size)
+               if (rr->length >= mac_size)
                        {
-#if 0 /* OK only for stream ciphers */
-                       al=SSL_AD_DECODE_ERROR;
-                       SSLerr(SSL_F_DTLS1_PROCESS_RECORD,SSL_R_LENGTH_TOO_SHORT);
-                       goto f_err;
-#else
-                       decryption_failed_or_bad_record_mac = 1;
-#endif
+                       rr->length -= mac_size;
+                       mac = &rr->data[rr->length];
                        }
-               rr->length-=mac_size;
+               else
+                       rr->length = 0;
                i=s->method->ssl3_enc->mac(s,md,0);
-               if (i < 0 || memcmp(md,&(rr->data[rr->length]),mac_size) != 0)
+               if (i < 0 || mac == NULL || memcmp(md, mac, mac_size) != 0)
                        {
                        decryption_failed_or_bad_record_mac = 1;
                        }