gpg: Fix export of NIST ECC keys.

* common/openpgp-oid.c (struct oidtable): New.
(openpgp_curve_to_oid): Rewrite and allow OID as input.
(openpgp_oid_to_curve): Make use of the new table.
--

Due to the previous change we now usually store the OID with the
private key and not the name.  Thus during import we do not anymore
need to map the name to an oid but can use the oid directly.  We fix
that by extending openpgp_curve_to_oid to allow an oidstr as input.

common/openpgp-oid.c

@@ -37,6 +37,30 @@
 #include "util.h"
 
 
+/* A table with all our supported OpenPGP curves.  */
+static struct {
+  const char *name;   /* Standard name.  */
+  const char *oidstr; /* IETF formatted OID.  */
+  unsigned int nbits; /* Nominla bit length of the curve.  */
+  const char *alias;  /* NULL or alternative name of the curve.  */
+} oidtable[] = {
+
+  { "Ed25519",         "1.3.6.1.4.1.11591.15.1", 255, "ed25519" },
+
+  { "NIST P-256",      "1.2.840.10045.3.1.7",    256, "nistp256" },
+  { "NIST P-384",      "1.3.132.0.34",           384, "nistp384" },
+  { "NIST P-521",      "1.3.132.0.35",           521, "nistp521" },
+
+  { "brainpoolP256r1", "1.3.36.3.3.2.8.1.1.7",   256 },
+  { "brainpoolP384r1", "1.3.36.3.3.2.8.1.1.11",  384 },
+  { "brainpoolP512r1", "1.3.36.3.3.2.8.1.1.13",  512 },
+
+  { "secp256k1",       "1.3.132.0.10",           256 },
+
+  { NULL, NULL, 0}
+};
+
+
 /* The OID for Curve Ed25519 in OpenPGP format.  */
 static const char oid_ed25519[] =
   { 0x09, 0x2b, 0x06, 0x01, 0x04, 0x01, 0xda, 0x47, 0x0f, 0x01 };
@@ -270,56 +294,33 @@ openpgp_oid_is_ed25519 (gcry_mpi_t a)
 const char *
 openpgp_curve_to_oid (const char *name, unsigned int *r_nbits)
 {
+  int i;
   unsigned int nbits = 0;
-  const char *oidstr;
+  const char *oidstr = NULL;
 
-  if (!name)
+  if (name)
-    oidstr = NULL;
-  else if (!strcmp (name, "Ed25519") || !strcmp (name, "ed25519"))
     {
-      oidstr = "1.3.6.1.4.1.11591.15.1";
+      for (i=0; oidtable[i].name; i++)
-      nbits = 255;
+        if (!strcmp (oidtable[i].name, name)
-    }
+            || (oidtable[i].alias && !strcmp (oidtable[i].alias, name)))
-  else if (!strcmp (name, "nistp256") || !strcmp (name, "NIST P-256"))
           {
-      /* Libgcrypt uses "NIST P-256" as standard name for this curve
+            oidstr = oidtable[i].oidstr;
-         and thus the key generation returns this value.  Thus we
+            nbits  = oidtable[i].nbits;
-         allow both strings.  */
+            break;
-      oidstr = "1.2.840.10045.3.1.7";
-      nbits = 256;
           }
-  else if (!strcmp (name, "nistp384") || !strcmp (name, "NIST P-384"))
+      if (!oidtable[i].name)
         {
-      oidstr = "1.3.132.0.34";
+          /* If not found assume the input is already an OID and check
-      nbits = 384;
+             whether we support it.  */
-    }
+          for (i=0; oidtable[i].name; i++)
-  else if (!strcmp (name, "nistp521") || !strcmp (name, "NIST P-521"))
+            if (!strcmp (name, oidtable[i].oidstr))
               {
-      oidstr = "1.3.132.0.35";
+                oidstr = oidtable[i].oidstr;
-      nbits = 521;
+                nbits  = oidtable[i].nbits;
+                break;
               }
-  else if (!strcmp (name,"brainpoolP256r1"))
-    {
-      oidstr = "1.3.36.3.3.2.8.1.1.7";
-      nbits = 256;
         }
-  else if (!strcmp (name, "brainpoolP384r1"))
-    {
-      oidstr = "1.3.36.3.3.2.8.1.1.11";
-      nbits = 384;
     }
-  else if (!strcmp (name, "brainpoolP512r1"))
-    {
-      oidstr =  "1.3.36.3.3.2.8.1.1.13";
-      nbits = 512;
-    }
-  else if (!strcmp (name, "secp256k1"))
-    {
-      oidstr =  "1.3.132.0.10";
-      nbits = 256;
-    }
-  else
-    oidstr = NULL;
 
   if (r_nbits)
     *r_nbits = nbits;
@@ -328,32 +329,19 @@ openpgp_curve_to_oid (const char *name, unsigned int *r_nbits)
 
 
 /* Map an OpenPGP OID to the Libgcrypt curve NAME.  Returns "?" for
-   unknown curve names.  */
+   unknown curve names.  We prefer an alias name here which is more
+   suitable for printing.  */
 const char *
-openpgp_oid_to_curve (const char *oid)
+openpgp_oid_to_curve (const char *oidstr)
 {
-  const char *name;
+  int i;
 
-  if (!oid)
+  if (!oidstr)
-    name = "";
+    return "";
-  else if (!strcmp (oid, "1.3.6.1.4.1.11591.15.1"))
-    name = "ed25519";
-  else if (!strcmp (oid, "1.2.840.10045.3.1.7"))
-    name = "nistp256";
-  else if (!strcmp (oid, "1.3.132.0.10"))
-    name = "secp256k1";
-  else if (!strcmp (oid, "1.3.132.0.34"))
-    name = "nistp384";
-  else if (!strcmp (oid, "1.3.132.0.35"))
-    name = "nistp521";
-  else if (!strcmp (oid, "1.3.36.3.3.2.8.1.1.7"))
-    name = "brainpoolP256r1";
-  else if (!strcmp (oid, "1.3.36.3.3.2.8.1.1.11"))
-    name = "brainpoolP384r1";
-  else if (!strcmp (oid, "1.3.36.3.3.2.8.1.1.13"))
-    name = "brainpoolP512r1";
-  else
-    name = "?";
 
-  return name;
+  for (i=0; oidtable[i].name; i++)
+    if (!strcmp (oidtable[i].oidstr, oidstr))
+      return oidtable[i].alias? oidtable[i].alias : oidtable[i].name;
+
+  return "?";
 }