commit 799e57612abd3f587206f2034ba04b9dc7c57ba2
author Gilles Peskine <Gilles.Peskine@arm.com> Fri Sep 14 17:34:00 2018 +0200
committer Gilles Peskine <Gilles.Peskine@arm.com> Wed Jul 22 02:48:31 2020 +0200
tree bbd70a2a902c0d12ab490734d8d484bc573d7102
parent 8f4f9a8dafc3ecf0c36d4b6588a8d9edf05720e5

ECDSA requires a short Weierstrass curve

Document in config.h, and enforce in check_config.h, that
MBEDTLS_ECDSA_C requires at least one short Weierstrass curve to be
enabled. A Montgomery curve is not enough.

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

include/mbedtls/check_config.h

diff --git a/include/mbedtls/check_config.h b/include/mbedtls/check_config.h
index f2148a8..3596597 100644
--- a/include/mbedtls/check_config.h
+++ b/include/mbedtls/check_config.h
@@ -103,6 +103,17 @@
 
 #if defined(MBEDTLS_ECDSA_C) &&            \
     ( !defined(MBEDTLS_ECP_C) ||           \
+      !( defined(MBEDTLS_ECP_DP_SECP192R1_ENABLED) || \
+         defined(MBEDTLS_ECP_DP_SECP224R1_ENABLED) || \
+         defined(MBEDTLS_ECP_DP_SECP256R1_ENABLED) || \
+         defined(MBEDTLS_ECP_DP_SECP384R1_ENABLED) || \
+         defined(MBEDTLS_ECP_DP_SECP521R1_ENABLED) || \
+         defined(MBEDTLS_ECP_DP_SECP192K1_ENABLED) || \
+         defined(MBEDTLS_ECP_DP_SECP224K1_ENABLED) || \
+         defined(MBEDTLS_ECP_DP_SECP256K1_ENABLED) || \
+         defined(MBEDTLS_ECP_DP_BP256R1_ENABLED) ||   \
+         defined(MBEDTLS_ECP_DP_BP384R1_ENABLED) ||   \
+         defined(MBEDTLS_ECP_DP_BP512R1_ENABLED) ) || \
       !defined(MBEDTLS_ASN1_PARSE_C) ||    \
       !defined(MBEDTLS_ASN1_WRITE_C) )
 #error "MBEDTLS_ECDSA_C defined, but not all prerequisites"

include/mbedtls/config.h

diff --git a/include/mbedtls/config.h b/include/mbedtls/config.h
index e00c546..0bab0c0 100644
--- a/include/mbedtls/config.h
+++ b/include/mbedtls/config.h
@@ -756,6 +756,7 @@
  *
  * Comment macros to disable the curve and functions for it
  */
+/* Short Weierstrass curves (supporting ECP, ECDH, ECDSA) */
 #define MBEDTLS_ECP_DP_SECP192R1_ENABLED
 #define MBEDTLS_ECP_DP_SECP224R1_ENABLED
 #define MBEDTLS_ECP_DP_SECP256R1_ENABLED
@@ -767,6 +768,7 @@
 #define MBEDTLS_ECP_DP_BP256R1_ENABLED
 #define MBEDTLS_ECP_DP_BP384R1_ENABLED
 #define MBEDTLS_ECP_DP_BP512R1_ENABLED
+/* Montgomery curves (supporting ECP) */
 #define MBEDTLS_ECP_DP_CURVE25519_ENABLED
 #define MBEDTLS_ECP_DP_CURVE448_ENABLED
 
@@ -2571,7 +2573,9 @@
  * This module is used by the following key exchanges:
  *      ECDHE-ECDSA
  *
- * Requires: MBEDTLS_ECP_C, MBEDTLS_ASN1_WRITE_C, MBEDTLS_ASN1_PARSE_C
+ * Requires: MBEDTLS_ECP_C, MBEDTLS_ASN1_WRITE_C, MBEDTLS_ASN1_PARSE_C,
+ *           and at least one MBEDTLS_ECP_DP_XXX_ENABLED for a
+ *           short Weierstrass curve.
  */
 #define MBEDTLS_ECDSA_C