From a1684f42d33343435e8229db578ed245c79b08fd Mon Sep 17 00:00:00 2001
From: Gilles Peskine <Gilles.Peskine@arm.com>
Date: Tue, 23 Mar 2021 13:12:34 +0100
Subject: [PATCH] PSA: Reject curves that are not enabled in the PSA
 configuration

If an elliptic curve was enabled in the Mbed TLS classic API (#define
MBEDTLS_ECP_DP_xxx), but not enabled in the PSA configuration (#define
PSA_WANT_ECC_xxx), it would still work if you tried to use it through
PSA.

This is generally benign, but could be a security issue if you want to
disable a curve in PSA for some security reason (such as a known bug
in its implementation, which may not matter in the classic API if Mbed
TLS is running in a secure enclave and is only reachable from
untrusted callers through the PSA API). More urgently, this broke
test_suite_psa_crypto_not_supported.generated.

So if a curve is not enabled in the PSA configuration, ensure that
it's treated as unsupported through the PSA software implementation.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
---
 library/psa_crypto.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index 8c61cb968..a4ca1d0bf 100644
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -423,58 +423,84 @@ mbedtls_ecp_group_id mbedtls_ecc_group_of_psa( psa_ecc_family_t curve,
         case PSA_ECC_FAMILY_SECP_R1:
             switch( bits )
             {
+#if defined(PSA_WANT_ECC_SECP_R1_192)
                 case 192:
                     return( MBEDTLS_ECP_DP_SECP192R1 );
+#endif
+#if defined(PSA_WANT_ECC_SECP_R1_224)
                 case 224:
                     return( MBEDTLS_ECP_DP_SECP224R1 );
+#endif
+#if defined(PSA_WANT_ECC_SECP_R1_256)
                 case 256:
                     return( MBEDTLS_ECP_DP_SECP256R1 );
+#endif
+#if defined(PSA_WANT_ECC_SECP_R1_384)
                 case 384:
                     return( MBEDTLS_ECP_DP_SECP384R1 );
+#endif
+#if defined(PSA_WANT_ECC_SECP_R1_521)
                 case 521:
                     return( MBEDTLS_ECP_DP_SECP521R1 );
                 case 528:
                     if( bits_is_sloppy )
                         return( MBEDTLS_ECP_DP_SECP521R1 );
                     break;
+#endif
             }
             break;
 
         case PSA_ECC_FAMILY_BRAINPOOL_P_R1:
             switch( bits )
             {
+#if defined(PSA_WANT_ECC_BRAINPOOL_P_R1_256)
                 case 256:
                     return( MBEDTLS_ECP_DP_BP256R1 );
+#endif
+#if defined(PSA_WANT_ECC_BRAINPOOL_P_R1_384)
                 case 384:
                     return( MBEDTLS_ECP_DP_BP384R1 );
+#endif
+#if defined(PSA_WANT_ECC_BRAINPOOL_P_R1_512)
                 case 512:
                     return( MBEDTLS_ECP_DP_BP512R1 );
+#endif
             }
             break;
 
         case PSA_ECC_FAMILY_MONTGOMERY:
             switch( bits )
             {
+#if defined(PSA_WANT_ECC_MONTGOMERY_255)
                 case 255:
                     return( MBEDTLS_ECP_DP_CURVE25519 );
                 case 256:
                     if( bits_is_sloppy )
                         return( MBEDTLS_ECP_DP_CURVE25519 );
                     break;
+#endif
+#if defined(PSA_WANT_ECC_MONTGOMERY_448)
                 case 448:
                     return( MBEDTLS_ECP_DP_CURVE448 );
+#endif
             }
             break;
 
         case PSA_ECC_FAMILY_SECP_K1:
             switch( bits )
             {
+#if defined(PSA_WANT_ECC_SECP_K1_192)
                 case 192:
                     return( MBEDTLS_ECP_DP_SECP192K1 );
+#endif
+#if defined(PSA_WANT_ECC_SECP_K1_224)
                 case 224:
                     return( MBEDTLS_ECP_DP_SECP224K1 );
+#endif
+#if defined(PSA_WANT_ECC_SECP_K1_256)
                 case 256:
                     return( MBEDTLS_ECP_DP_SECP256K1 );
+#endif
             }
             break;
     }