Make md_info_t an opaque structure

- more freedom for us to change it in the future
- enforces hygiene
- performance impact of making accessors no longer inline should really be
  negligible

library/ecdsa.c

@@ -60,8 +60,9 @@ static const md_info_t *md_info_by_size( size_t min_size )
     for( md_alg = md_list(); *md_alg != 0; md_alg++ )
     {
         if( ( md_cur = md_info_from_type( (md_type_t) *md_alg ) ) == NULL ||
-            (size_t) md_cur->size < min_size ||
-            ( md_picked != NULL && md_cur->size > md_picked->size ) )
+            (size_t) md_get_size( md_cur ) < min_size ||
+            ( md_picked != NULL &&
+              md_get_size( md_cur ) > md_get_size( md_picked ) ) )
             continue;
 
         md_picked = md_cur;

library/hmac_drbg.c

@@ -62,7 +62,7 @@ static void polarssl_zeroize( void *v, size_t n ) {
 void hmac_drbg_update( hmac_drbg_context *ctx,
                        const unsigned char *additional, size_t add_len )
 {
-    size_t md_len = ctx->md_ctx.md_info->size;
+    size_t md_len = md_get_size( ctx->md_ctx.md_info );
     unsigned char rounds = ( additional != NULL && add_len != 0 ) ? 2 : 1;
     unsigned char sep[1];
     unsigned char K[POLARSSL_MD_MAX_SIZE];
@@ -105,8 +105,8 @@ int hmac_drbg_init_buf( hmac_drbg_context *ctx,
      * Use the V memory location, which is currently all 0, to initialize the
      * MD context with an all-zero key. Then set V to its initial value.
      */
-    md_hmac_starts( &ctx->md_ctx, ctx->V, md_info->size );
-    memset( ctx->V, 0x01, md_info->size );
+    md_hmac_starts( &ctx->md_ctx, ctx->V, md_get_size( md_info ) );
+    memset( ctx->V, 0x01, md_get_size( md_info ) );
 
     hmac_drbg_update( ctx, data, data_len );
 
@@ -165,7 +165,7 @@ int hmac_drbg_init( hmac_drbg_context *ctx,
                     size_t len )
 {
     int ret;
-    size_t entropy_len;
+    size_t entropy_len, md_size;
 
     memset( ctx, 0, sizeof( hmac_drbg_context ) );
 
@@ -174,13 +174,15 @@ int hmac_drbg_init( hmac_drbg_context *ctx,
     if( ( ret = md_init_ctx( &ctx->md_ctx, md_info ) ) != 0 )
         return( ret );
 
+    md_size = md_get_size( md_info );
+
     /*
      * Set initial working state.
      * Use the V memory location, which is currently all 0, to initialize the
      * MD context with an all-zero key. Then set V to its initial value.
      */
-    md_hmac_starts( &ctx->md_ctx, ctx->V, md_info->size );
-    memset( ctx->V, 0x01, md_info->size );
+    md_hmac_starts( &ctx->md_ctx, ctx->V, md_size );
+    memset( ctx->V, 0x01, md_size );
 
     ctx->f_entropy = f_entropy;
     ctx->p_entropy = p_entropy;
@@ -194,9 +196,9 @@ int hmac_drbg_init( hmac_drbg_context *ctx,
      *
      * (This also matches the sizes used in the NIST test vectors.)
      */
-    entropy_len = md_info->size <= 20 ? 16 : /* 160-bits hash -> 128 bits */
-                  md_info->size <= 28 ? 24 : /* 224-bits hash -> 192 bits */
-                                        32;  /* better (256+) -> 256 bits */
+    entropy_len = md_size <= 20 ? 16 : /* 160-bits hash -> 128 bits */
+                  md_size <= 28 ? 24 : /* 224-bits hash -> 192 bits */
+                                  32;  /* better (256+) -> 256 bits */
 
     /*
      * For initialisation, use more entropy to emulate a nonce

library/md.c

@@ -329,4 +329,28 @@ int md_process( md_context_t *ctx, const unsigned char *data )
     return( 0 );
 }
 
+unsigned char md_get_size( const md_info_t *md_info )
+{
+    if( md_info == NULL )
+        return( 0 );
+
+    return md_info->size;
+}
+
+md_type_t md_get_type( const md_info_t *md_info )
+{
+    if( md_info == NULL )
+        return( POLARSSL_MD_NONE );
+
+    return md_info->type;
+}
+
+const char *md_get_name( const md_info_t *md_info )
+{
+    if( md_info == NULL )
+        return( NULL );
+
+    return md_info->name;
+}
+
 #endif /* POLARSSL_MD_C */

library/pk.c

@@ -166,7 +166,7 @@ static inline int pk_hashlen_helper( md_type_t md_alg, size_t *hash_len )
     if( ( md_info = md_info_from_type( md_alg ) ) == NULL )
         return( -1 );
 
-    *hash_len = md_info->size;
+    *hash_len = md_get_size( md_info );
     return( 0 );
 }
 

library/rsa.c

@@ -473,7 +473,7 @@ static void mgf_mask( unsigned char *dst, size_t dlen, unsigned char *src,
     memset( mask, 0, POLARSSL_MD_MAX_SIZE );
     memset( counter, 0, 4 );
 
-    hlen = md_ctx->md_info->size;
+    hlen = md_get_size( md_ctx->md_info );
 
     // Generate and apply dbMask
     //

library/ssl_cli.c

@@ -2194,7 +2194,7 @@ static int ssl_parse_server_key_exchange( ssl_context *ssl )
         }
 
         SSL_DEBUG_BUF( 3, "parameters hash", hash, hashlen != 0 ? hashlen :
-                (unsigned int) ( md_info_from_type( md_alg ) )->size );
+            (unsigned int) ( md_get_size( md_info_from_type( md_alg ) ) ) );
 
         /*
          * Verify signature

library/ssl_srv.c

@@ -3085,7 +3085,7 @@ curve_matching_done:
         }
 
         SSL_DEBUG_BUF( 3, "parameters hash", hash, hashlen != 0 ? hashlen :
-                (unsigned int) ( md_info_from_type( md_alg ) )->size );
+            (unsigned int) ( md_get_size( md_info_from_type( md_alg ) ) ) );
 
         /*
          * Make the signature

library/x509.c

@@ -845,8 +845,8 @@ int x509_sig_alg_gets( char *buf, size_t size, const x509_buf *sig_oid,
         mgf_md_info = md_info_from_type( pss_opts->mgf1_hash_id );
 
         ret = polarssl_snprintf( p, n, " (%s, MGF1-%s, 0x%02X)",
-                              md_info ? md_info->name : "???",
-                              mgf_md_info ? mgf_md_info->name : "???",
+                              md_info ? md_get_name( md_info ) : "???",
+                              mgf_md_info ? md_get_name( mgf_md_info ) : "???",
                               pss_opts->expected_salt_len );
         SAFE_SNPRINTF();
     }

library/x509_crt.c

@@ -1505,7 +1505,7 @@ static int x509_crt_verifycrl( x509_crt *crt, x509_crt *ca,
         md( md_info, crl_list->tbs.p, crl_list->tbs.len, hash );
 
         if( pk_verify_ext( crl_list->sig_pk, crl_list->sig_opts, &ca->pk,
-                           crl_list->sig_md, hash, md_info->size,
+                           crl_list->sig_md, hash, md_get_size( md_info ),
                            crl_list->sig.p, crl_list->sig.len ) != 0 )
         {
             flags |= BADCRL_NOT_TRUSTED;
@@ -1768,7 +1768,7 @@ static int x509_crt_verify_top(
         }
 
         if( pk_verify_ext( child->sig_pk, child->sig_opts, &trust_ca->pk,
-                           child->sig_md, hash, md_info->size,
+                           child->sig_md, hash, md_get_size( md_info ),
                            child->sig.p, child->sig.len ) != 0 )
         {
             continue;
@@ -1864,7 +1864,7 @@ static int x509_crt_verify_child(
         md( md_info, child->tbs.p, child->tbs.len, hash );
 
         if( pk_verify_ext( child->sig_pk, child->sig_opts, &parent->pk,
-                           child->sig_md, hash, md_info->size,
+                           child->sig_md, hash, md_get_size( md_info ),
                            child->sig.p, child->sig.len ) != 0 )
         {
             *flags |= BADCERT_NOT_TRUSTED;