gpg: Fix SOS handling with libgcrypt version <= 1.8.

* g10/misc.c (checksum_mpi): Don't depend new feature
of gcry_mpi_print which supports opaque MPI.

--

GnuPG-bug-id: 5116
Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>

1 files changed, 19 insertions, 0 deletions

diff --git a/g10/misc.c b/g10/misc.c
index 111a916e8..0d457365b 100644
--- a/g10/misc.c
+++ b/g10/misc.c
@@ -257,6 +257,25 @@ checksum_mpi (gcry_mpi_t a)
   byte *buffer;
   size_t nbytes;
 
+  /*
+   * This code can be skipped when gcry_mpi_print
+   * supports opaque MPI.
+   */
+  if (gcry_mpi_get_flag (a, GCRYMPI_FLAG_OPAQUE))
+    {
+      const byte *p;
+      unsigned int nbits;
+
+      p = gcry_mpi_get_opaque (a, &nbits);
+      if (!p)
+        return 0;
+
+      csum = nbits >> 8;
+      csum += (nbits & 0xff);
+      csum += checksum (p, (nbits+7)/8);
+      return csum;
+    }
+
   if ( gcry_mpi_print (GCRYMPI_FMT_PGP, NULL, 0, &nbytes, a) )
     BUG ();
   /* Fixme: For numbers not in secure memory we should use a stack