ecc: Fix keygrip computation for compressed points.

* cipher/ecc-misc.c (_gcry_ecc_ec2os): Factor most code out to ...
(_gcry_ecc_ec2os_buf): new.
* cipher/ecc.c (compute_keygrip): Handle compressed keys.
* tests/keygrip.c: Add new tests.
--

It is important to get the keygrips right even if we do not have full
support for compressed points.  Case in point is that I god a
smartcard which returns the key in compressed format.  We need to
early compute the keygrip and use it before doing any computation.

The code has been lifted from _gcry_ecc_sec_decodepoint.  We should
factors parts of the code out to a new function.

GnuPG-bug-id: 4961
Signed-off-by: Werner Koch <wk@gnupg.org>

1 files changed, 44 insertions, 0 deletions

diff --git a/tests/keygrip.c b/tests/keygrip.c
index 56fbba80..cfccc06e 100644
--- a/tests/keygrip.c
+++ b/tests/keygrip.c
@@ -145,6 +145,50 @@ static struct
       " (q #04C8A4CEC2E9A9BC8E173531A67B0840DF345C32E261ADD780E6D83D56EFADFD5DE872F8B854819B59543CE0B7F822330464FBC4E6324DADDCD9D059554F63B344#)))",
       "\xE6\xDF\x94\x2D\xBD\x8C\x77\x05\xA3\xDD\x41\x6E\xFC\x04\x01\xDB\x31\x0E\x99\xB6"
     },
+    {
+      GCRY_PK_ECC,
+      "(public-key"
+      " (ecc"
+      " (curve brainpoolP256r1)"
+      " (q #042ECD8679930BE2DB4AD42B8600BA3F80"
+      /*   */"2D4D539BFF2F69B83EC9B7BBAA7F3406"
+      /*   */"436DD11A1756AFE56CD93408410FCDA9"
+      /*   */"BA95024EB613BD481A14FCFEC27A448A#)))",
+      "\x52\xBA\xD4\xB4\xA3\x2D\x32\xA1\xDD\x06"
+      "\x5E\x99\x0B\xF1\xAB\xC1\x13\x3D\x84\xD4"
+    },
+    { /* Compressed form of above.  */
+      GCRY_PK_ECC,
+      "(public-key"
+      " (ecc"
+      " (curve brainpoolP256r1)"
+      " (q #022ECD8679930BE2DB4AD42B8600BA3F80"
+      /*   */"2D4D539BFF2F69B83EC9B7BBAA7F3406#)))",
+      "\x52\xBA\xD4\xB4\xA3\x2D\x32\xA1\xDD\x06"
+      "\x5E\x99\x0B\xF1\xAB\xC1\x13\x3D\x84\xD4"
+    },
+    {
+      GCRY_PK_ECC,
+      "(public-key"
+      " (ecc"
+      " (curve brainpoolP256r1)"
+      " (q #045B784CA008EE64AB3D85017EE0D2BE87"
+      /*   */"558762C7300E0C8E06B1F9AF7C031458"
+      /*   */"9EBBA41915313417BA54218EB0569C59"
+      /*   */"0B156C76DBCAB6E84575E6EF68CE7B87#)))",
+      "\x99\x38\x6A\x82\x41\x96\x29\x9C\x89\x74"
+      "\xD6\xE1\xBF\x43\xAC\x9B\x9A\x12\xE7\x3F"
+    },
+    { /* Compressed form of above.  */
+      GCRY_PK_ECC,
+      "(public-key"
+      " (ecc"
+      " (curve brainpoolP256r1)"
+      " (q #035B784CA008EE64AB3D85017EE0D2BE87"
+      /*   */"558762C7300E0C8E06B1F9AF7C031458#)))",
+      "\x99\x38\x6A\x82\x41\x96\x29\x9C\x89\x74"
+      "\xD6\xE1\xBF\x43\xAC\x9B\x9A\x12\xE7\x3F"
+    },
     { /* Ed25519 standard */
       GCRY_PK_ECC,
       "(public-key"