Handle max_fragment_length overflow for DTLS
Allow for encryption overhead in early DTLS size check
and send overflow if validated record is too long
@@ -1630,6 +1630,7 @@ int dtls1_process_record(SSL *s, DTLS1_BITMAP *bitmap)
int imac_size;
size_t mac_size;
unsigned char md[EVP_MAX_MD_SIZE];
+ size_t max_plain_length = SSL3_RT_MAX_PLAIN_LENGTH;
rr = RECORD_LAYER_get_rrec(&s->rlayer);
sess = s->session;
@@ -1797,7 +1798,12 @@ int dtls1_process_record(SSL *s, DTLS1_BITMAP *bitmap)
}
}
- if (rr->length > SSL3_RT_MAX_PLAIN_LENGTH) {
+ /* use current Max Fragment Length setting if applicable */
+ if (s->session != NULL && USE_MAX_FRAGMENT_LENGTH_EXT(s->session))
+ max_plain_length = GET_MAX_FRAGMENT_LENGTH(s->session);
+
+ /* send overflow if the plaintext is too long now it has passed MAC */
+ if (rr->length > max_plain_length) {
SSLfatal(s, SSL_AD_RECORD_OVERFLOW, SSL_F_DTLS1_PROCESS_RECORD,
SSL_R_DATA_LENGTH_TOO_LONG);
return 0;
@@ -1941,7 +1947,7 @@ int dtls1_get_record(SSL *s)
/* If received packet overflows own-client Max Fragment Length setting */
if (s->session != NULL && USE_MAX_FRAGMENT_LENGTH_EXT(s->session)
- && rr->length > GET_MAX_FRAGMENT_LENGTH(s->session)) {
+ && rr->length > GET_MAX_FRAGMENT_LENGTH(s->session) + SSL3_RT_MAX_ENCRYPTED_OVERHEAD) {
/* record too long, silently discard it */
rr->length = 0;
rr->read = 1;
