ikev2: Don't use SHA-1 for RFC 7427 signature authentication

RFC 8247 demoted it to MUST NOT.

References #2427.

src/libcharon/sa/ikev2/authenticators/pubkey_authenticator.c

@@ -156,14 +156,12 @@ static array_t *select_signature_schemes(keymat_v2_t *keymat,
 		}
 		enumerator->destroy(enumerator);
 
-		/* for RSA we tried at least SHA-512, also try other schemes down to
+		/* for RSA we tried at least SHA-512, also try other schemes */
-		 * what we'd use with classic authentication */
 		if (key_type == KEY_RSA)
 		{
 			signature_scheme_t schemes[] = {
 				SIGN_RSA_EMSA_PKCS1_SHA2_384,
 				SIGN_RSA_EMSA_PKCS1_SHA2_256,
-				SIGN_RSA_EMSA_PKCS1_SHA1,
 			}, contained;
 			bool found;
 			int i, j;

src/libstrongswan/crypto/hashers/hasher.c

@@ -287,7 +287,6 @@ bool hasher_algorithm_for_ikev2(hash_algorithm_t alg)
 	switch (alg)
 	{
 		case HASH_IDENTITY:
-		case HASH_SHA1:
 		case HASH_SHA256:
 		case HASH_SHA384:
 		case HASH_SHA512:
@@ -296,6 +295,7 @@ bool hasher_algorithm_for_ikev2(hash_algorithm_t alg)
 		case HASH_MD2:
 		case HASH_MD4:
 		case HASH_MD5:
+		case HASH_SHA1:
 		case HASH_SHA224:
 		case HASH_SHA3_224:
 		case HASH_SHA3_256:

src/libstrongswan/tests/suites/test_hasher.c

@@ -226,7 +226,7 @@ typedef struct {
 
 static hasher_ikev2_t ikev2[] = {
 	{ HASH_IDENTITY, TRUE  },
-	{ HASH_SHA1,     TRUE  },
+	{ HASH_SHA1,     FALSE },
 	{ HASH_SHA256,   TRUE  },
 	{ HASH_SHA384,   TRUE  },
 	{ HASH_SHA512,   TRUE  },