ssl/statem: Don't compare size_t with less than zero

Reviewed-by: NPaul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/7194)

(cherry picked from commit 60690b5b8396d7d5234cd067206190fb8aca78d2)

ssl/statem/extensions.c

@@ -1530,10 +1530,12 @@ int tls_psk_do_binder(SSL *s, const EVP_MD *md, const unsigned char *msgstart,
      */
     if (s->hello_retry_request == SSL_HRR_PENDING) {
         size_t hdatalen;
+        long hdatalen_l;
         void *hdata;
 
-        hdatalen = BIO_get_mem_data(s->s3->handshake_buffer, &hdata);
-        if (hdatalen <= 0) {
+        hdatalen = hdatalen_l =
+            BIO_get_mem_data(s->s3->handshake_buffer, &hdata);
+        if (hdatalen_l <= 0) {
             SSLfatal(s, SSL_AD_INTERNAL_ERROR, SSL_F_TLS_PSK_DO_BINDER,
                      SSL_R_BAD_HANDSHAKE_LENGTH);
             goto err;

ssl/statem/statem_lib.c

@@ -203,9 +203,10 @@ static int get_cert_verify_tbs_data(SSL *s, unsigned char *tls13tbs,
         *hdatalen = TLS13_TBS_PREAMBLE_SIZE + hashlen;
     } else {
         size_t retlen;
+        long retlen_l;
 
-        retlen = BIO_get_mem_data(s->s3->handshake_buffer, hdata);
-        if (retlen <= 0) {
+        retlen = retlen_l = BIO_get_mem_data(s->s3->handshake_buffer, hdata);
+        if (retlen_l <= 0) {
             SSLfatal(s, SSL_AD_INTERNAL_ERROR, SSL_F_GET_CERT_VERIFY_TBS_DATA,
                      ERR_R_INTERNAL_ERROR);
             return 0;