agent: Add option --pss to pksign to be used by smartcards.

* agent/command.c (cmd_sethash): Add option --pss and allow for
--hash=null.
* agent/agent.h (struct server_control_s): Add digest.is_pss and
zero where needed.
* agent/pksign.c (agent_pksign_do): Allow for PSS with cards.
* scd/command.c (cmd_pksign): Add for --hash=none.
--

This is not a full implementaion of PSS but allows scdaemon card
drivers to detect already PSS formatted data.

Signed-off-by: Werner Koch <wk@gnupg.org>

agent/agent.h

@@ -254,12 +254,14 @@ struct server_control_s
   /* Information on the currently used digest (for signing commands).  */
   struct {
     char *data;    /* NULL or malloced data of length VALUELEN.  If
-                      this is set The other fields are ignored.  Used
-                      for PureEdDSA. */
+                      this is set the other fields are ignored.  Used
+                      for PureEdDSA and RSA with PSS (in which case
+                      data_is_pss is also set).  */
     int valuelen;
     int algo;
     unsigned char value[MAX_DIGEST_LEN];
-    int raw_value: 1;
+    unsigned int raw_value: 1;
+    unsigned int is_pss: 1;    /* DATA holds PSS formated data.  */
   } digest;
   unsigned char keygrip[20];
   int have_keygrip;

agent/command-ssh.c

@@ -2790,6 +2790,7 @@ ssh_handler_sign_request (ctrl_t ctrl, estream_t request, estream_t response)
   ctrl->digest.algo = hash_algo;
   xfree (ctrl->digest.data);
   ctrl->digest.data = NULL;
+  ctrl->digest.is_pss = 0;
   if ((spec.flags & SPEC_FLAG_USE_PKCS1V2))
     ctrl->digest.raw_value = 0;
   else

agent/command.c

@@ -707,11 +707,12 @@ cmd_setkeydesc (assuan_context_t ctx, char *line)
 
 static const char hlp_sethash[] =
   "SETHASH (--hash=<name>)|(<algonumber>) <hexstring>]\n"
-  "SETHASH --inquire\n"
+  "SETHASH [--pss] --inquire\n"
   "\n"
   "The client can use this command to tell the server about the data\n"
   "(which usually is a hash) to be signed.  The option --inquire is\n"
-  "used to ask back for to-be-signed data in case of PureEdDSA";
+  "used to ask back for to-be-signed data in case of PureEdDSA or\n"
+  "with --pss for pre-formatted rsaPSS.";
 static gpg_error_t
 cmd_sethash (assuan_context_t ctx, char *line)
 {
@@ -722,7 +723,7 @@ cmd_sethash (assuan_context_t ctx, char *line)
   unsigned char *buf;
   char *endp;
   int algo;
-  int opt_inquire;
+  int opt_inquire, opt_pss;
 
   /* Parse the alternative hash options which may be used instead of
      the algo number.  */
@@ -744,6 +745,8 @@ cmd_sethash (assuan_context_t ctx, char *line)
         algo = GCRY_MD_MD5;
       else if (has_option (line, "--hash=tls-md5sha1"))
         algo = MD_USER_TLS_MD5SHA1;
+      else if (has_option (line, "--hash=none"))
+        algo = 0;
       else
         {
           err = set_error (GPG_ERR_ASS_PARAMETER, "invalid hash algorithm");
@@ -753,6 +756,7 @@ cmd_sethash (assuan_context_t ctx, char *line)
   else
     algo = 0;
 
+  opt_pss = has_option (line, "--pss");
   opt_inquire = has_option (line, "--inquire");
   line = skip_options (line);
 
@@ -772,6 +776,7 @@ cmd_sethash (assuan_context_t ctx, char *line)
   ctrl->digest.data = NULL;
   ctrl->digest.algo = algo;
   ctrl->digest.raw_value = 0;
+  ctrl->digest.is_pss = opt_pss;
 
   if (opt_inquire)
     {
@@ -3807,6 +3812,7 @@ start_command_handler (ctrl_t ctrl, gnupg_fd_t listen_fd, gnupg_fd_t fd)
 
   ctrl->digest.data = NULL;
   ctrl->digest.raw_value = 0;
+  ctrl->digest.is_pss = 0;
 
   assuan_set_io_monitor (ctx, io_monitor, NULL);
   agent_set_progress_cb (progress_cb, ctrl);

agent/pksign.c

@@ -497,6 +497,12 @@ agent_pksign_do (ctrl_t ctrl, const char *cache_nonce,
         err = do_encode_dsa (data, datalen,
                              algo, s_skey,
                              &s_hash);
+      else if (ctrl->digest.is_pss)
+        {
+          log_info ("signing with rsaPSS is currently only supported"
+                    " for (some) smartcards\n");
+          err = gpg_error (GPG_ERR_NOT_SUPPORTED);
+        }
       else
         err = do_encode_md (data, datalen,
                             ctrl->digest.algo,
@@ -540,7 +546,13 @@ agent_pksign_do (ctrl_t ctrl, const char *cache_nonce,
 
       if (s_hash == NULL)
         {
-          if (ctrl->digest.algo == MD_USER_TLS_MD5SHA1)
+          if (ctrl->digest.is_pss)
+            {
+              err = gcry_sexp_build (&s_hash, NULL,
+                                     "(data (flags raw) (value %b))",
+                                     (int)datalen, data);
+            }
+          else if (ctrl->digest.algo == MD_USER_TLS_MD5SHA1)
             err = do_encode_raw_pkcs1 (data, datalen,
                                        gcry_pk_get_nbits (sexp_key), &s_hash);
           else

scd/command.c

@@ -891,7 +891,7 @@ pin_cb (void *opaque, const char *info, char **retstr)
 
 
 static const char hlp_pksign[] =
-  "PKSIGN [--hash=[rmd160|sha{1,224,256,384,512}|md5]] <hexified_id>\n"
+  "PKSIGN [--hash=[rmd160|sha{1,224,256,384,512}|md5|none]] <hexified_id>\n"
   "\n"
   "The --hash option is optional; the default is SHA1.";
 static gpg_error_t
@@ -920,6 +920,8 @@ cmd_pksign (assuan_context_t ctx, char *line)
     hash_algo = GCRY_MD_SHA512;
   else if (has_option (line, "--hash=md5"))
     hash_algo = GCRY_MD_MD5;
+  else if (has_option (line, "--hash=none"))  /* For raw RSA.  */
+    hash_algo = 0;
   else if (!strstr (line, "--"))
     hash_algo = GCRY_MD_SHA1;
   else