pki: Support RSA verification using different hash algorithms

This changes the private API by adding one more argument to function

  pki_signature_from_blob()

Signed-off-by: Jakub Jelen <jjelen@redhat.com>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
(cherry picked from commit fa60827840)

include/libssh/pki.h

@@ -69,6 +69,7 @@ struct ssh_key_struct {
 
 struct ssh_signature_struct {
     enum ssh_keytypes_e type;
+    enum ssh_digest_e hash_type;
     const char *type_c;
 #ifdef HAVE_LIBGCRYPT
     gcry_sexp_t dsa_sig;

include/libssh/pki_priv.h

@@ -45,6 +45,8 @@ int bcrypt_pbkdf(const char *pass,
 
 int pki_key_ecdsa_nid_from_name(const char *name);
 const char *pki_key_ecdsa_nid_to_name(int nid);
+const char *ssh_key_signature_to_char(enum ssh_keytypes_e type,
+                                      enum ssh_digest_e hash_type);
 
 /* SSH Key Functions */
 ssh_key pki_key_dup(const ssh_key key, int demote);
@@ -85,7 +87,8 @@ ssh_string pki_publickey_to_blob(const ssh_key key);
 ssh_string pki_signature_to_blob(const ssh_signature sign);
 ssh_signature pki_signature_from_blob(const ssh_key pubkey,
                                       const ssh_string sig_blob,
-                                      enum ssh_keytypes_e type);
+                                      enum ssh_keytypes_e type,
+                                      enum ssh_digest_e hash_type);
 int pki_signature_verify(ssh_session session,
                          const ssh_signature sig,
                          const ssh_key key,

include/libssh/wrapper.h

@@ -27,6 +27,13 @@
 #include "libssh/libgcrypt.h"
 #include "libssh/libmbedcrypto.h"
 
+enum ssh_digest_e {
+    SSH_DIGEST_AUTO=0,
+    SSH_DIGEST_SHA1=1,
+    SSH_DIGEST_SHA256,
+    SSH_DIGEST_SHA512
+};
+
 enum ssh_mac_e {
   SSH_MAC_SHA1=1,
   SSH_MAC_SHA256,