Empty record limit.
Limit the number of empty records that will be processed consecutively
in order to prevent ssl3_get_record from never returning.
Reported by "oftc_must_be_destroyed" and George Kadianakis.
diff --git a/ssl/s3_pkt.c b/ssl/s3_pkt.c
index b66f15f..172573f 100644
--- a/ssl/s3_pkt.c
+++ b/ssl/s3_pkt.c
@@ -273,6 +273,12 @@
return(n);
}
+/* MAX_EMPTY_RECORDS defines the number of consecutive, empty records that will
+ * be processed per call to ssl3_get_record. Without this limit an attacker
+ * could send empty records at a faster rate than we can process and cause
+ * ssl3_get_record to loop forever. */
+#define MAX_EMPTY_RECORDS 32
+
/* Call this to get a new input record.
* It will return <= 0 if more data is needed, normally due to an error
* or non-blocking IO.
@@ -293,6 +299,7 @@
short version;
unsigned mac_size, orig_len;
size_t extra;
+ unsigned empty_record_count = 0;
rr= &(s->s3->rrec);
sess=s->session;
@@ -525,7 +532,17 @@
s->packet_length=0;
/* just read a 0 length packet */
- if (rr->length == 0) goto again;
+ if (rr->length == 0)
+ {
+ empty_record_count++;
+ if (empty_record_count > MAX_EMPTY_RECORDS)
+ {
+ al=SSL_AD_UNEXPECTED_MESSAGE;
+ OPENSSL_PUT_ERROR(SSL, ssl3_get_record, SSL_R_TOO_MANY_EMPTY_FRAGMENTS);
+ goto f_err;
+ }
+ goto again;
+ }
#if 0
fprintf(stderr, "Ultimate Record type=%d, Length=%d\n", rr->type, rr->length);
diff --git a/ssl/ssl.h b/ssl/ssl.h
index dac4c3e..bae6a35 100644
--- a/ssl/ssl.h
+++ b/ssl/ssl.h
@@ -2974,5 +2974,6 @@
#define SSL_R_CERT_CB_ERROR 428
#define SSL_R_DTLS_MESSAGE_TOO_BIG 429
#define SSL_R_INVALID_SRP_USERNAME 430
+#define SSL_R_TOO_MANY_EMPTY_FRAGMENTS 431
#endif
diff --git a/ssl/ssl_error.c b/ssl/ssl_error.c
index 1d84012..1c0c93b 100644
--- a/ssl/ssl_error.c
+++ b/ssl/ssl_error.c
@@ -475,6 +475,7 @@
{ERR_PACK(ERR_LIB_SSL, 0, SSL_R_TLS_INVALID_ECPOINTFORMAT_LIST), "TLS_INVALID_ECPOINTFORMAT_LIST"},
{ERR_PACK(ERR_LIB_SSL, 0, SSL_R_TLS_PEER_DID_NOT_RESPOND_WITH_CERTIFICATE_LIST), "TLS_PEER_DID_NOT_RESPOND_WITH_CERTIFICATE_LIST"},
{ERR_PACK(ERR_LIB_SSL, 0, SSL_R_TLS_RSA_ENCRYPTED_VALUE_LENGTH_IS_WRONG), "TLS_RSA_ENCRYPTED_VALUE_LENGTH_IS_WRONG"},
+ {ERR_PACK(ERR_LIB_SSL, 0, SSL_R_TOO_MANY_EMPTY_FRAGMENTS), "TOO_MANY_EMPTY_FRAGMENTS"},
{ERR_PACK(ERR_LIB_SSL, 0, SSL_R_TRIED_TO_USE_UNSUPPORTED_CIPHER), "TRIED_TO_USE_UNSUPPORTED_CIPHER"},
{ERR_PACK(ERR_LIB_SSL, 0, SSL_R_UNABLE_TO_DECODE_DH_CERTS), "UNABLE_TO_DECODE_DH_CERTS"},
{ERR_PACK(ERR_LIB_SSL, 0, SSL_R_UNABLE_TO_DECODE_ECDH_CERTS), "UNABLE_TO_DECODE_ECDH_CERTS"},
