scdaemon changes

[NIIBE Yutaka]

Hello,

I haven't yet decided how to change key attribute from ECC to RSA
(scdaemon doesn't know about the card format of key attribute for
RSA), RSA key attribute change for different key size and RSA to ECC
should be supported.

Here is a change forcing key attribute change at KEYTOCARD.
I'm going to commit this change together with minor clean up
of scdaemon.


diff --git a/scd/app-openpgp.c b/scd/app-openpgp.c
index f7ad274..8f7c8b0 100644
--- a/scd/app-openpgp.c
+++ b/scd/app-openpgp.c
@@ -2729,6 +2729,43 @@ change_keyattr (app_t app, int keyno, const unsigned char *buf, size_t buflen,
 }


+static gpg_error_t
+change_rsa_keyattr (app_t app, int keyno, unsigned int nbits,
+                    gpg_error_t (*pincb)(void*, const char *, char **),
+                    void *pincb_arg)
+{
+  gpg_error_t err = 0;
+  unsigned char *buf;
+  size_t buflen;
+  void *relptr;
+
+  /* Read the current attributes into a buffer.  */
+  relptr = get_one_do (app, 0xC1+keyno, &buf, &buflen, NULL);
+  if (!relptr)
+    err = gpg_error (GPG_ERR_CARD);
+  else if (buflen < 6 || buf[0] != PUBKEY_ALGO_RSA)
+    {
+      /* Attriutes too short or not an RSA key.  */
+      xfree (relptr);
+      err = gpg_error (GPG_ERR_CARD);
+    }
+  else
+    {
+      /* We only change n_bits and don't touch anything else.  Before we
+         do so, we round up NBITS to a sensible way in the same way as
+         gpg's key generation does it.  This may help to sort out problems
+         with a few bits too short keys.  */
+      nbits = ((nbits + 31) / 32) * 32;
+      buf[1] = (nbits >> 8);
+      buf[2] = nbits;
+      err = change_keyattr (app, keyno, buf, buflen, pincb, pincb_arg);
+      xfree (relptr);
+    }
+
+  return err;
+}
+
+
 /* Helper to process an setattr command for name KEY-ATTR.
    In (VALUE,VALUELEN), it expects following string:
         RSA: "--force <key> <algo> rsa<nbits>"
@@ -2779,36 +2816,7 @@ change_keyattr_from_string (app_t app,
       else if (nbits > 4096)
         err = gpg_error (GPG_ERR_TOO_LARGE);
       else
-        {
-          unsigned char *buf;
-          size_t buflen;
-          void *relptr;
-
-          /* Read the current attributes into a buffer.  */
-          relptr = get_one_do (app, 0xC1+keyno, &buf, &buflen, NULL);
-          if (!relptr)
-            {
-              err = gpg_error (GPG_ERR_CARD);
-              goto leave;
-            }
-          if (buflen < 6 || buf[0] != PUBKEY_ALGO_RSA)
-            {
-              /* Attriutes too short or not an RSA key.  */
-              xfree (relptr);
-              err = gpg_error (GPG_ERR_CARD);
-              goto leave;
-            }
-
-          /* We only change n_bits and don't touch anything else.  Before we
-             do so, we round up NBITS to a sensible way in the same way as
-             gpg's key generation does it.  This may help to sort out problems
-             with a few bits too short keys.  */
-          nbits = ((nbits + 31) / 32) * 32;
-          buf[1] = (nbits >> 8);
-          buf[2] = nbits;
-          err = change_keyattr (app, keyno, buf, buflen, pincb, pincb_arg);
-          xfree (relptr);
-        }
+        err = change_rsa_keyattr (app, keyno, nbits, pincb, pincb_arg);
     }
   else if (algo == PUBKEY_ALGO_ECDH || algo == PUBKEY_ALGO_ECDSA
            || algo == PUBKEY_ALGO_EDDSA)
@@ -2971,6 +2979,14 @@ rsa_writekey (app_t app, gpg_error_t (*pincb)(void*, const char *, char **),
   if (opt.verbose)
     log_info ("RSA modulus size is %u bits (%u bytes)\n",
               nbits, (unsigned int)rsa_n_len);
+  if (nbits && nbits != maxbits
+      && app->app_local->extcap.algo_attr_change)
+    {
+      /* Try to switch the key to a new length.  */
+      err = change_rsa_keyattr (app, keyno, nbits, pincb, pincb_arg);
+      if (!err)
+        maxbits = app->app_local->keyattr[keyno].rsa.n_bits;
+    }
   if (nbits != maxbits)
     {
       log_error (_("RSA modulus missing or not of size %d bits\n"),
@@ -3327,9 +3343,22 @@ ecc_writekey (app_t app, gpg_error_t (*pincb)(void*, const char *, char **),
       || app->app_local->keyattr[keyno].ecc.oid != oidstr
       || app->app_local->keyattr[keyno].ecc.flags != flag_djb_tweak)
     {
-      log_error ("key attribute on card doesn't match\n");
-      err = gpg_error (GPG_ERR_INV_VALUE);
-      goto leave;
+      if (app->app_local->extcap.algo_attr_change)
+        {
+          unsigned char keyattr[oid_len];
+
+          keyattr[0] = algo;
+          memcpy (keyattr+1, oidbuf+1, oid_len-1);
+          err = change_keyattr (app, keyno, keyattr, oid_len, pincb, pincb_arg);
+          if (err)
+            goto leave;
+        }
+      else
+        {
+          log_error ("key attribute on card doesn't match\n");
+          err = gpg_error (GPG_ERR_INV_VALUE);
+          goto leave;
+        }
     }

   if (opt.verbose)
--