1 files changed, 44 insertions, 0 deletions
diff --git a/common/openpgp-misc.c b/common/openpgp-misc.c
index 178a4938e..4d057e5ed 100644
--- a/common/openpgp-misc.c
+++ b/common/openpgp-misc.c
@@ -50,3 +50,47 @@ openpgp_ecc_parse_key (pubkey_algo_t pkalgo, const char *curve,
   else
     return gcry_mpi_set_opaque_copy (NULL, buf+1, 448);
 }
+
+
+/*
+ * Fix up public key for OpenPGP adding the prefix.
+ */
+gpg_error_t
+openpgp_fixup_pubkey_448 (int algo, gcry_mpi_t *p_pubkey)
+{
+  gcry_mpi_t pubkey_mpi;
+  gcry_mpi_t a;
+  unsigned char *p;
+  const unsigned char *p_key;
+  unsigned int nbits;
+  unsigned int len;
+
+  pubkey_mpi = *p_pubkey;
+  *p_pubkey = NULL;
+  p_key = gcry_mpi_get_opaque (pubkey_mpi, &nbits);
+  len = (nbits+7)/8;
+  if ((algo == PUBKEY_ALGO_ECDH && len != 56)
+      || (algo == PUBKEY_ALGO_EDDSA && len != 57)
+      || (algo != PUBKEY_ALGO_ECDH && algo != PUBKEY_ALGO_EDDSA))
+    {
+      gcry_mpi_release (pubkey_mpi);
+      return gpg_error (GPG_ERR_BAD_PUBKEY);
+    }
+
+  p = xtrymalloc (1 + len);
+  if (!p)
+    {
+      gcry_mpi_release (pubkey_mpi);
+      return gpg_error_from_syserror ();
+    }
+
+  p[0] = 0x40;
+  memcpy (p+1, p_key, len);
+
+  a = gcry_mpi_set_opaque (NULL, p, 0);
+  gcry_mpi_set_flag (a, GCRYMPI_FLAG_USER2);
+  *p_pubkey = a;
+  gcry_mpi_release (pubkey_mpi);
+
+  return 0;
+}