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Compliant Solution (Heartbleed)
OpenSSL version 1.0.1g contains the following patch, which guarantees that payload
is within a valid range. The range is limited by the size of the input record.
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int dtls1_process_heartbeat(SSL *s) { unsigned char *p = &s->s3->rrec.data[0], *pl; unsigned short hbtype; unsigned int payload; unsigned int padding = 16; /* Use minimum padding */ /* ... More code ... */ /* Read type and payload length first */ if (1 + 2 + 16 > s->s3->rrec.length) return 0; /* Silently discard */ hbtype = *p++; n2s(p, payload); if (1 + 2 + payload + 16 > s->s3->rrec.length) return 0; /* Silently discard per RFC 6520 */ pl = p; /* ... More code ... */ if (hbtype == TLS1_HB_REQUEST) { unsigned char *buffer, *bp; int r; /* * Allocate memory for the response; size is 1 byte * message type, plus 2 bytes payload length, plus * payload, plus padding. */ buffer = OPENSSL_malloc(1 + 2 + payload + padding); bp = buffer; /* Enter response type, length, and copy payload */ *bp++ = TLS1_HB_RESPONSE; s2n(payload, bp); memcpy(bp, pl, payload); /* ... More code ... */ } /* ... More code ... */ } |
Risk Assessment
Depending on the library function called, an attacker may be able to use a heap or stack overflow vulnerability to run arbitrary code.
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