commit f00f15244428a917503182c16d1c2a5cd738f91a
author Gilles Peskine <Gilles.Peskine@arm.com> Tue Jun 22 00:09:00 2021 +0200
committer Gilles Peskine <Gilles.Peskine@arm.com> Fri Jun 25 00:46:22 2021 +0200
tree 5f772ca9e07e23a296f7641530eca1f2643ce982
parent 1fed4b8324f640802e281504bfa4c8f1c0b276bb

Add output size parameter to signature functions

The functions mbedtls_pk_sign(), mbedtls_pk_sign_restartable(),
mbedtls_ecdsa_write_signature() and mbedtls_ecdsa_write_signature_restartable()
now take an extra parameter indicating the size of the output buffer for the
signature.

No change to RSA because for RSA, the output size is trivial to calculate.

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

library/pk.c

diff --git a/library/pk.c b/library/pk.c
index 275d34b..ea4869c 100644
--- a/library/pk.c
+++ b/library/pk.c
@@ -396,7 +396,7 @@
 int mbedtls_pk_sign_restartable( mbedtls_pk_context *ctx,
              mbedtls_md_type_t md_alg,
              const unsigned char *hash, size_t hash_len,
-             unsigned char *sig, size_t *sig_len,
+             unsigned char *sig, size_t sig_size, size_t *sig_len,
              int (*f_rng)(void *, unsigned char *, size_t), void *p_rng,
              mbedtls_pk_restart_ctx *rs_ctx )
 {
@@ -421,7 +421,9 @@
             return( ret );
 
         ret = ctx->pk_info->sign_rs_func( ctx->pk_ctx, md_alg,
-                hash, hash_len, sig, sig_len, f_rng, p_rng, rs_ctx->rs_ctx );
+                                          hash, hash_len,
+                                          sig, sig_size, sig_len,
+                                          f_rng, p_rng, rs_ctx->rs_ctx );
 
         if( ret != MBEDTLS_ERR_ECP_IN_PROGRESS )
             mbedtls_pk_restart_free( rs_ctx );
@@ -435,8 +437,10 @@
     if( ctx->pk_info->sign_func == NULL )
         return( MBEDTLS_ERR_PK_TYPE_MISMATCH );
 
-    return( ctx->pk_info->sign_func( ctx->pk_ctx, md_alg, hash, hash_len,
-                                     sig, sig_len, f_rng, p_rng ) );
+    return( ctx->pk_info->sign_func( ctx->pk_ctx, md_alg,
+                                     hash, hash_len,
+                                     sig, sig_size, sig_len,
+                                     f_rng, p_rng ) );
 }
 
 /*
@@ -444,11 +448,12 @@
  */
 int mbedtls_pk_sign( mbedtls_pk_context *ctx, mbedtls_md_type_t md_alg,
              const unsigned char *hash, size_t hash_len,
-             unsigned char *sig, size_t *sig_len,
+             unsigned char *sig, size_t sig_size, size_t *sig_len,
              int (*f_rng)(void *, unsigned char *, size_t), void *p_rng )
 {
     return( mbedtls_pk_sign_restartable( ctx, md_alg, hash, hash_len,
-                                         sig, sig_len, f_rng, p_rng, NULL ) );
+                                         sig, sig_size, sig_len,
+                                         f_rng, p_rng, NULL ) );
 }
 
 /*