agent: Enumerate only the supported signature schemes for RSA keys

SHA-384 is not supported but is selected by signature_schemes_for_key()
for keys between 3072 and 7680 bits.

Since this is only called for IKEv2 signature authentication we don't
even provide SHA-1 anymore.  We always provide both schemes, though,
which is what pubkey-authenticator does too for RSA.

Older agents apparently just ignore the flags and always return a SHA-1
signature.  If that's the case, charon.signature_authentication has to
be disabled.

diff --git a/src/libstrongswan/plugins/agent/agent_private_key.c b/src/libstrongswan/plugins/agent/agent_private_key.c
index 70bee69817a885a90a2d290ffa1a7ce5bf03df78..961b30a044bc78936c40038810402fdd6f8d6c54 100644 (file)
--- a/src/libstrongswan/plugins/agent/agent_private_key.c
+++ b/src/libstrongswan/plugins/agent/agent_private_key.c
@@ -371,6 +371,76 @@ METHOD(private_key_t, get_keysize, int,
        return this->pubkey->get_keysize(this->pubkey);
 }
 
+/**
+ * Private data for RSA scheme enumerator
+ */
+typedef struct {
+       enumerator_t public;
+       int index;
+       bool reverse;
+} scheme_enumerator_t;
+
+static signature_params_t rsa_schemes[] = {
+       { .scheme = SIGN_RSA_EMSA_PKCS1_SHA2_256 },
+       { .scheme = SIGN_RSA_EMSA_PKCS1_SHA2_512 },
+};
+
+METHOD(enumerator_t, enumerate_rsa_scheme, bool,
+       scheme_enumerator_t *this, va_list args)
+{
+       signature_params_t **params;
+
+       VA_ARGS_VGET(args, params);
+
+       if ((this->reverse && --this->index >= 0) ||
+          (!this->reverse && ++this->index < countof(rsa_schemes)))
+       {
+               *params = &rsa_schemes[this->index];
+               return TRUE;
+       }
+       return FALSE;
+}
+
+/**
+ * Create an enumerator for the supported RSA signature schemes
+ */
+static enumerator_t *create_rsa_enumerator(private_agent_private_key_t *this)
+{
+       scheme_enumerator_t *enumerator;
+
+       INIT(enumerator,
+               .public = {
+                       .enumerate = enumerator_enumerate_default,
+                       .venumerate = _enumerate_rsa_scheme,
+                       .destroy = (void*)free,
+               },
+               .index = -1,
+               .reverse = FALSE,
+       );
+       /* propose SHA-512 first for larger keys */
+       if (get_keysize(this) > 3072)
+       {
+               enumerator->index = countof(rsa_schemes);
+               enumerator->reverse = TRUE;
+       }
+       return &enumerator->public;
+}
+
+METHOD(private_key_t, supported_signature_schemes, enumerator_t*,
+       private_agent_private_key_t *this)
+{
+       switch (get_type(this))
+       {
+               case KEY_RSA:
+                       return create_rsa_enumerator(this);
+               case KEY_ECDSA:
+                       return signature_schemes_for_key(KEY_ECDSA, get_keysize(this));
+               default:
+                       break;
+       }
+       return enumerator_create_empty();
+}
+
 METHOD(private_key_t, get_public_key, public_key_t*,
        private_agent_private_key_t *this)
 {
@@ -444,6 +514,7 @@ agent_private_key_t *agent_private_key_open(key_type_t type, va_list args)
                .public = {
                        .key = {
                                .get_type = _get_type,
+                               .supported_signature_schemes = _supported_signature_schemes,
                                .sign = _sign,
                                .decrypt = _decrypt,
                                .get_keysize = _get_keysize,