commit 487bbf68053143cdcb27cc60a91caf7738d86b68
author Gilles Peskine <Gilles.Peskine@arm.com> Thu May 27 22:17:07 2021 +0200
committer Gilles Peskine <Gilles.Peskine@arm.com> Tue Jun 15 00:12:37 2021 +0200
tree ecad368d220314fbe6134c3bf3cfc6664096a7bd
parent 85b1bc65a0f84aa6e453f316ce73e778b2cf8717

DHM: new functions to query the length of the modulus

Add two functions mbedtls_dhm_get_len() and mbedtls_dhm_get_bitlen() to
query the length of the modulus in bytes or bits.

Remove the len field: the cost of calling mbedtls_dhm_get_len() each time
it's needed is negligible, and this improves the abstraction of the DHM
module.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>

library/ssl_cli.c

diff --git a/library/ssl_cli.c b/library/ssl_cli.c
index 12ed0fb..1bacd64 100644
--- a/library/ssl_cli.c
+++ b/library/ssl_cli.c
@@ -2553,7 +2553,7 @@
         return( ret );
     }
 
-    dhm_actual_bitlen = mbedtls_mpi_bitlen( &ssl->handshake->dhm_ctx.P );
+    dhm_actual_bitlen = mbedtls_dhm_get_bitlen( &ssl->handshake->dhm_ctx );
     if( dhm_actual_bitlen < ssl->conf->dhm_min_bitlen )
     {
         MBEDTLS_SSL_DEBUG_MSG( 1, ( "DHM prime too short: %" MBEDTLS_PRINTF_SIZET " < %u",
@@ -3588,14 +3588,14 @@
         /*
          * DHM key exchange -- send G^X mod P
          */
-        content_len = ssl->handshake->dhm_ctx.len;
+        content_len = mbedtls_dhm_get_len( &ssl->handshake->dhm_ctx );
 
         ssl->out_msg[4] = (unsigned char)( content_len >> 8 );
         ssl->out_msg[5] = (unsigned char)( content_len      );
         header_len = 6;
 
         ret = mbedtls_dhm_make_public( &ssl->handshake->dhm_ctx,
-                          (int) mbedtls_mpi_size( &ssl->handshake->dhm_ctx.P ),
+                          (int) mbedtls_dhm_get_len( &ssl->handshake->dhm_ctx ),
                           &ssl->out_msg[header_len], content_len,
                           ssl->conf->f_rng, ssl->conf->p_rng );
         if( ret != 0 )
@@ -3848,7 +3848,7 @@
             /*
              * ClientDiffieHellmanPublic public (DHM send G^X mod P)
              */
-            content_len = ssl->handshake->dhm_ctx.len;
+            content_len = mbedtls_dhm_get_len( &ssl->handshake->dhm_ctx );
 
             if( header_len + 2 + content_len >
                 MBEDTLS_SSL_OUT_CONTENT_LEN )
@@ -3862,7 +3862,7 @@
             ssl->out_msg[header_len++] = (unsigned char)( content_len      );
 
             ret = mbedtls_dhm_make_public( &ssl->handshake->dhm_ctx,
-                    (int) mbedtls_mpi_size( &ssl->handshake->dhm_ctx.P ),
+                    (int) mbedtls_dhm_get_len( &ssl->handshake->dhm_ctx ),
                     &ssl->out_msg[header_len], content_len,
                     ssl->conf->f_rng, ssl->conf->p_rng );
             if( ret != 0 )