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Index: b/cipher/ecc-ecdsa.c
===================================================================
--- b/cipher/ecc-ecdsa.c
+++ b/cipher/ecc-ecdsa.c
@@ -67,7 +67,16 @@
mpi_rshift (hash, hash, abits - qbits);
}
else
- hash = input;
+ {
+ abits = mpi_get_nbits (input);
+ if (abits > qbits)
+ {
+ hash = _gcry_mpi_copy (input);
+ mpi_rshift (hash, hash, mpi_get_nbits (input) - qbits);
+ }
+ else
+ hash = input;
+ }
k = NULL;
@@ -164,6 +173,7 @@
gcry_mpi_t h, h1, h2, x;
mpi_point_struct Q, Q1, Q2;
mpi_ec_t ctx;
+ unsigned int abits, nbits;
if( !(mpi_cmp_ui (r, 0) > 0 && mpi_cmp (r, pkey->E.n) < 0) )
return GPG_ERR_BAD_SIGNATURE; /* Assertion 0 < r < n failed. */
@@ -183,8 +193,16 @@
/* h = s^(-1) (mod n) */
mpi_invm (h, s, pkey->E.n);
+ abits = mpi_get_nbits (input);
+ nbits = mpi_get_nbits (pkey->E.n);
/* h1 = hash * s^(-1) (mod n) */
- mpi_mulm (h1, input, h, pkey->E.n);
+ if (abits > nbits)
+ {
+ mpi_rshift (h1, input, abits - nbits);
+ mpi_mulm (h1, h1, h, pkey->E.n);
+ }
+ else
+ mpi_mulm (h1, input, h, pkey->E.n);
/* Q1 = [ hash * s^(-1) ]G */
_gcry_mpi_ec_mul_point (&Q1, h1, &pkey->E.G, ctx);
/* h2 = r * s^(-1) (mod n) */
Index: b/tests/pubkey.c
===================================================================
--- b/tests/pubkey.c
+++ b/tests/pubkey.c
@@ -980,9 +980,23 @@
"(data (flags raw)\n"
" (value #00112233445566778899AABBCCDDEEFF"
/* */ "000102030405060708090A0B0C0D0E0F#))";
+ static const char hash2_string[] =
+ "(data (flags raw)\n"
+ " (value #00112233445566778899AABBCCDDEEFF"
+ /* */ "000102030405060708090A0B0C0D0E0F"
+ /* */ "000102030405060708090A0B0C0D0E0F"
+ /* */ "00112233445566778899AABBCCDDEEFF#))";
+ /* hash2, but longer than curve length, so it will be truncated */
+ static const char hash3_string[] =
+ "(data (flags raw)\n"
+ " (value #00112233445566778899AABBCCDDEEFF"
+ /* */ "000102030405060708090A0B0C0D0E0F"
+ /* */ "000102030405060708090A0B0C0D0E0F"
+ /* */ "00112233445566778899AABBCCDDEEFF"
+ /* */ "000102030405060708090A0B0C0D0E0F#))";
gpg_error_t err;
- gcry_sexp_t key, hash, sig;
+ gcry_sexp_t key, hash, hash2, hash3, sig, sig2;
if (verbose)
fprintf (stderr, "Checking sample ECC key.\n");
@@ -990,6 +1004,12 @@
if ((err = gcry_sexp_new (&hash, hash_string, 0, 1)))
die ("line %d: %s", __LINE__, gpg_strerror (err));
+ if ((err = gcry_sexp_new (&hash2, hash2_string, 0, 1)))
+ die ("line %d: %s", __LINE__, gpg_strerror (err));
+
+ if ((err = gcry_sexp_new (&hash3, hash3_string, 0, 1)))
+ die ("line %d: %s", __LINE__, gpg_strerror (err));
+
if ((err = gcry_sexp_new (&key, ecc_private_key, 0, 1)))
die ("line %d: %s", __LINE__, gpg_strerror (err));
@@ -1003,6 +1023,27 @@
if ((err = gcry_pk_verify (sig, hash, key)))
die ("gcry_pk_verify failed: %s", gpg_strerror (err));
+ /* Verify hash truncation */
+ gcry_sexp_release (key);
+ if ((err = gcry_sexp_new (&key, ecc_private_key, 0, 1)))
+ die ("line %d: %s", __LINE__, gpg_strerror (err));
+
+ if ((err = gcry_pk_sign (&sig2, hash2, key)))
+ die ("gcry_pk_sign failed: %s", gpg_strerror (err));
+
+ if ((err = gcry_pk_sign (&sig, hash3, key)))
+ die ("gcry_pk_sign failed: %s", gpg_strerror (err));
+
+ gcry_sexp_release (key);
+ if ((err = gcry_sexp_new (&key, ecc_public_key, 0, 1)))
+ die ("line %d: %s", __LINE__, gpg_strerror (err));
+
+ if ((err = gcry_pk_verify (sig, hash2, key)))
+ die ("gcry_pk_verify failed 2: %s", gpg_strerror (err));
+
+ if ((err = gcry_pk_verify (sig2, hash3, key)))
+ die ("gcry_pk_verify failed 3: %s", gpg_strerror (err));
+
/* Now try signing without the Q parameter. */
gcry_sexp_release (key);
@@ -1021,8 +1062,10 @@
die ("gcry_pk_verify signed without Q failed: %s", gpg_strerror (err));
gcry_sexp_release (sig);
+ gcry_sexp_release (sig2);
gcry_sexp_release (key);
gcry_sexp_release (hash);
+ gcry_sexp_release (hash2);
}

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