Commit 64a786a2 authored by Adam Langley's avatar Adam Langley Committed by Ben Laurie
Browse files

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.
parent a54a61e7

ssl/s3_pkt.c

+18 −1
Original line number Diff line number Diff line
@@ -272,6 +272,12 @@ int ssl3_read_n(SSL *s, int n, int max, int extend) 
	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.
@@ -292,6 +298,7 @@ static int ssl3_get_record(SSL *s) 
	short version;

	unsigned mac_size;

	size_t extra;

	unsigned empty_record_count = 0;



	rr= &(s->s3->rrec);

	sess=s->session;
@@ -522,7 +529,17 @@ printf("\n"); 
	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;

			SSLerr(SSL_F_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);

ssl/ssl.h

+1 −0
Original line number Diff line number Diff line
@@ -2914,6 +2914,7 @@ void ERR_load_SSL_strings(void); 
#define SSL_R_TLS_INVALID_ECPOINTFORMAT_LIST		 157

#define SSL_R_TLS_PEER_DID_NOT_RESPOND_WITH_CERTIFICATE_LIST 233

#define SSL_R_TLS_RSA_ENCRYPTED_VALUE_LENGTH_IS_WRONG	 234

#define SSL_R_TOO_MANY_EMPTY_FRAGMENTS			 388

#define SSL_R_TRIED_TO_USE_UNSUPPORTED_CIPHER		 235

#define SSL_R_UNABLE_TO_DECODE_DH_CERTS			 236

#define SSL_R_UNABLE_TO_DECODE_ECDH_CERTS		 313

ssl/ssl_err.c

+1 −0
Original line number Diff line number Diff line
@@ -578,6 +578,7 @@ static ERR_STRING_DATA SSL_str_reasons[]= 
{ERR_REASON(SSL_R_TLS_INVALID_ECPOINTFORMAT_LIST),"tls invalid ecpointformat list"},

{ERR_REASON(SSL_R_TLS_PEER_DID_NOT_RESPOND_WITH_CERTIFICATE_LIST),"tls peer did not respond with certificate list"},

{ERR_REASON(SSL_R_TLS_RSA_ENCRYPTED_VALUE_LENGTH_IS_WRONG),"tls rsa encrypted value length is wrong"},

{ERR_REASON(SSL_R_TOO_MANY_EMPTY_FRAGMENTS),"too many empty fragments"},

{ERR_REASON(SSL_R_TRIED_TO_USE_UNSUPPORTED_CIPHER),"tried to use unsupported cipher"},

{ERR_REASON(SSL_R_UNABLE_TO_DECODE_DH_CERTS),"unable to decode dh certs"},

{ERR_REASON(SSL_R_UNABLE_TO_DECODE_ECDH_CERTS),"unable to decode ecdh certs"},