This commit was manufactured by cvs2svn to create branch 'vserver'.

[linux-2.6.git] / crypto / signature / dsa.c

diff --git a/crypto/signature/dsa.c b/crypto/signature/dsa.c
new file mode 100644 (file)
index 0000000..5b5c736
--- /dev/null
+++ b/crypto/signature/dsa.c
@@ -0,0 +1,98 @@
+/* dsa.c  -  DSA signature algorithm
+ *     Copyright (C) 1998, 1999, 2000 Free Software Foundation, Inc.
+ *
+ * This file is part of GnuPG.
+ *
+ * GnuPG is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * GnuPG is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
+ */
+
+#include <linux/kernel.h>
+#include <linux/crypto/mpi.h>
+#include <asm/errno.h>
+#include "local.h"
+
+/*****************************************************************************/
+/*
+ * perform DSA algorithm signature verification
+ */
+int DSA_verify(const MPI datahash, const MPI sig[], const MPI pkey[])
+{
+       MPI p, q, g, y, r, s;
+       MPI w = NULL, u1 = NULL, u2 = NULL, v = NULL;
+       MPI base[3];
+       MPI exp[3];
+       int rc;
+
+       if (!datahash ||
+           !sig[0] || !sig[1] ||
+           !pkey[0] || !pkey[1] || !pkey[2] || !pkey[3]
+           )
+               return -EINVAL;
+
+       p = pkey[0];    /* prime */
+       q = pkey[1];    /* group order */
+       g = pkey[2];    /* group generator */
+       y = pkey[3];    /* g^x mod p */
+       r = sig[0];
+       s = sig[1];
+
+       if (!(mpi_cmp_ui(r, 0) > 0 && mpi_cmp(r, q) < 0)) {
+               printk("DSA_verify assertion failed [0 < r < q]\n");
+               return -EPERM;
+       }
+
+       if (!(mpi_cmp_ui(s, 0) > 0 && mpi_cmp(s, q) < 0)) {
+               printk("DSA_verify assertion failed [0 < s < q]\n");
+               return -EPERM;
+       }
+
+       rc = -ENOMEM;
+       w  = mpi_alloc(mpi_get_nlimbs(q)); if (!w ) goto cleanup;
+       u1 = mpi_alloc(mpi_get_nlimbs(q)); if (!u1) goto cleanup;
+       u2 = mpi_alloc(mpi_get_nlimbs(q)); if (!u2) goto cleanup;
+       v  = mpi_alloc(mpi_get_nlimbs(p)); if (!v ) goto cleanup;
+
+       /* w = s^(-1) mod q */
+       if (mpi_invm(w, s, q) < 0)
+               goto cleanup;
+
+       /* u1 = (datahash * w) mod q */
+       if (mpi_mulm(u1, datahash, w, q) < 0)
+               goto cleanup;
+
+       /* u2 = r * w mod q  */
+       if (mpi_mulm(u2, r, w, q) < 0)
+               goto cleanup;
+
+       /* v =  g^u1 * y^u2 mod p mod q */
+       base[0] = g;    exp[0] = u1;
+       base[1] = y;    exp[1] = u2;
+       base[2] = NULL; exp[2] = NULL;
+
+       if (mpi_mulpowm(v, base, exp, p) < 0)
+               goto cleanup;
+
+       if (mpi_fdiv_r(v, v, q) < 0)
+               goto cleanup;
+
+       rc = mpi_cmp(v, r) == 0 ? 0 : -EPERM;
+
+ cleanup:
+       mpi_free(w);
+       mpi_free(u1);
+       mpi_free(u2);
+       mpi_free(v);
+       return rc;
+} /* end DSA_verify() */