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-rw-r--r--lib/mpi/mpicoder.c365
1 files changed, 365 insertions, 0 deletions
diff --git a/lib/mpi/mpicoder.c b/lib/mpi/mpicoder.c
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+/* mpicoder.c - Coder for the external representation of MPIs
+ * Copyright (C) 1998, 1999 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 "mpi-internal.h"
+
+#define DIM(v) (sizeof(v)/sizeof((v)[0]))
+#define MAX_EXTERN_MPI_BITS 16384
+
+static uint8_t asn[15] = /* Object ID is 1.3.14.3.2.26 */
+{ 0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 0x2b, 0x0e, 0x03,
+ 0x02, 0x1a, 0x05, 0x00, 0x04, 0x14
+};
+
+MPI do_encode_md(const void *sha_buffer, unsigned nbits)
+{
+ int nframe = (nbits + 7) / 8;
+ uint8_t *frame, *fr_pt;
+ int i = 0, n;
+ size_t asnlen = DIM(asn);
+ MPI a = MPI_NULL;
+
+ if (SHA1_DIGEST_LENGTH + asnlen + 4 > nframe)
+ pr_info("MPI: can't encode a %d bit MD into a %d bits frame\n",
+ (int)(SHA1_DIGEST_LENGTH * 8), (int)nbits);
+
+ /* We encode the MD in this way:
+ *
+ * 0 A PAD(n bytes) 0 ASN(asnlen bytes) MD(len bytes)
+ *
+ * PAD consists of FF bytes.
+ */
+ frame = kmalloc(nframe, GFP_KERNEL);
+ if (!frame)
+ return MPI_NULL;
+ n = 0;
+ frame[n++] = 0;
+ frame[n++] = 1; /* block type */
+ i = nframe - SHA1_DIGEST_LENGTH - asnlen - 3;
+
+ if (i <= 1) {
+ pr_info("MPI: message digest encoding failed\n");
+ kfree(frame);
+ return a;
+ }
+
+ memset(frame + n, 0xff, i);
+ n += i;
+ frame[n++] = 0;
+ memcpy(frame + n, &asn, asnlen);
+ n += asnlen;
+ memcpy(frame + n, sha_buffer, SHA1_DIGEST_LENGTH);
+ n += SHA1_DIGEST_LENGTH;
+
+ i = nframe;
+ fr_pt = frame;
+
+ if (n != nframe) {
+ printk
+ ("MPI: message digest encoding failed, frame length is wrong\n");
+ kfree(frame);
+ return a;
+ }
+
+ a = mpi_alloc((nframe + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB);
+ mpi_set_buffer(a, frame, nframe, 0);
+ kfree(frame);
+
+ return a;
+}
+
+MPI mpi_read_from_buffer(const void *xbuffer, unsigned *ret_nread)
+{
+ const uint8_t *buffer = xbuffer;
+ int i, j;
+ unsigned nbits, nbytes, nlimbs, nread = 0;
+ mpi_limb_t a;
+ MPI val = MPI_NULL;
+
+ if (*ret_nread < 2)
+ goto leave;
+ nbits = buffer[0] << 8 | buffer[1];
+
+ if (nbits > MAX_EXTERN_MPI_BITS) {
+ pr_info("MPI: mpi too large (%u bits)\n", nbits);
+ goto leave;
+ }
+ buffer += 2;
+ nread = 2;
+
+ nbytes = (nbits + 7) / 8;
+ nlimbs = (nbytes + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB;
+ val = mpi_alloc(nlimbs);
+ if (!val)
+ return MPI_NULL;
+ i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
+ i %= BYTES_PER_MPI_LIMB;
+ val->nbits = nbits;
+ j = val->nlimbs = nlimbs;
+ val->sign = 0;
+ for (; j > 0; j--) {
+ a = 0;
+ for (; i < BYTES_PER_MPI_LIMB; i++) {
+ if (++nread > *ret_nread) {
+ printk
+ ("MPI: mpi larger than buffer nread=%d ret_nread=%d\n",
+ nread, *ret_nread);
+ goto leave;
+ }
+ a <<= 8;
+ a |= *buffer++;
+ }
+ i = 0;
+ val->d[j - 1] = a;
+ }
+
+leave:
+ *ret_nread = nread;
+ return val;
+}
+EXPORT_SYMBOL_GPL(mpi_read_from_buffer);
+
+/****************
+ * Make an mpi from a character string.
+ */
+int mpi_fromstr(MPI val, const char *str)
+{
+ int hexmode = 0, sign = 0, prepend_zero = 0, i, j, c, c1, c2;
+ unsigned nbits, nbytes, nlimbs;
+ mpi_limb_t a;
+
+ if (*str == '-') {
+ sign = 1;
+ str++;
+ }
+ if (*str == '0' && str[1] == 'x')
+ hexmode = 1;
+ else
+ return -EINVAL; /* other bases are not yet supported */
+ str += 2;
+
+ nbits = strlen(str) * 4;
+ if (nbits % 8)
+ prepend_zero = 1;
+ nbytes = (nbits + 7) / 8;
+ nlimbs = (nbytes + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB;
+ if (val->alloced < nlimbs)
+ if (!mpi_resize(val, nlimbs))
+ return -ENOMEM;
+ i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
+ i %= BYTES_PER_MPI_LIMB;
+ j = val->nlimbs = nlimbs;
+ val->sign = sign;
+ for (; j > 0; j--) {
+ a = 0;
+ for (; i < BYTES_PER_MPI_LIMB; i++) {
+ if (prepend_zero) {
+ c1 = '0';
+ prepend_zero = 0;
+ } else
+ c1 = *str++;
+ assert(c1);
+ c2 = *str++;
+ assert(c2);
+ if (c1 >= '0' && c1 <= '9')
+ c = c1 - '0';
+ else if (c1 >= 'a' && c1 <= 'f')
+ c = c1 - 'a' + 10;
+ else if (c1 >= 'A' && c1 <= 'F')
+ c = c1 - 'A' + 10;
+ else {
+ mpi_clear(val);
+ return 1;
+ }
+ c <<= 4;
+ if (c2 >= '0' && c2 <= '9')
+ c |= c2 - '0';
+ else if (c2 >= 'a' && c2 <= 'f')
+ c |= c2 - 'a' + 10;
+ else if (c2 >= 'A' && c2 <= 'F')
+ c |= c2 - 'A' + 10;
+ else {
+ mpi_clear(val);
+ return 1;
+ }
+ a <<= 8;
+ a |= c;
+ }
+ i = 0;
+
+ val->d[j - 1] = a;
+ }
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(mpi_fromstr);
+
+/****************
+ * Special function to get the low 8 bytes from an mpi.
+ * This can be used as a keyid; KEYID is an 2 element array.
+ * Return the low 4 bytes.
+ */
+u32 mpi_get_keyid(const MPI a, u32 *keyid)
+{
+#if BYTES_PER_MPI_LIMB == 4
+ if (keyid) {
+ keyid[0] = a->nlimbs >= 2 ? a->d[1] : 0;
+ keyid[1] = a->nlimbs >= 1 ? a->d[0] : 0;
+ }
+ return a->nlimbs >= 1 ? a->d[0] : 0;
+#elif BYTES_PER_MPI_LIMB == 8
+ if (keyid) {
+ keyid[0] = a->nlimbs ? (u32) (a->d[0] >> 32) : 0;
+ keyid[1] = a->nlimbs ? (u32) (a->d[0] & 0xffffffff) : 0;
+ }
+ return a->nlimbs ? (u32) (a->d[0] & 0xffffffff) : 0;
+#else
+#error Make this function work with other LIMB sizes
+#endif
+}
+
+/****************
+ * Return an allocated buffer with the MPI (msb first).
+ * NBYTES receives the length of this buffer. Caller must free the
+ * return string (This function does return a 0 byte buffer with NBYTES
+ * set to zero if the value of A is zero. If sign is not NULL, it will
+ * be set to the sign of the A.
+ */
+void *mpi_get_buffer(MPI a, unsigned *nbytes, int *sign)
+{
+ uint8_t *p, *buffer;
+ mpi_limb_t alimb;
+ int i;
+ unsigned int n;
+
+ if (sign)
+ *sign = a->sign;
+ *nbytes = n = a->nlimbs * BYTES_PER_MPI_LIMB;
+ if (!n)
+ n++; /* avoid zero length allocation */
+ p = buffer = kmalloc(n, GFP_KERNEL);
+
+ for (i = a->nlimbs - 1; i >= 0; i--) {
+ alimb = a->d[i];
+#if BYTES_PER_MPI_LIMB == 4
+ *p++ = alimb >> 24;
+ *p++ = alimb >> 16;
+ *p++ = alimb >> 8;
+ *p++ = alimb;
+#elif BYTES_PER_MPI_LIMB == 8
+ *p++ = alimb >> 56;
+ *p++ = alimb >> 48;
+ *p++ = alimb >> 40;
+ *p++ = alimb >> 32;
+ *p++ = alimb >> 24;
+ *p++ = alimb >> 16;
+ *p++ = alimb >> 8;
+ *p++ = alimb;
+#else
+#error please implement for this limb size.
+#endif
+ }
+
+ /* this is sub-optimal but we need to do the shift operation
+ * because the caller has to free the returned buffer */
+ for (p = buffer; !*p && *nbytes; p++, --*nbytes)
+ ;
+ if (p != buffer)
+ memmove(buffer, p, *nbytes);
+
+ return buffer;
+}
+EXPORT_SYMBOL_GPL(mpi_get_buffer);
+
+/****************
+ * Use BUFFER to update MPI.
+ */
+int mpi_set_buffer(MPI a, const void *xbuffer, unsigned nbytes, int sign)
+{
+ const uint8_t *buffer = xbuffer, *p;
+ mpi_limb_t alimb;
+ int nlimbs;
+ int i;
+
+ nlimbs = (nbytes + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB;
+ if (RESIZE_IF_NEEDED(a, nlimbs) < 0)
+ return -ENOMEM;
+ a->sign = sign;
+
+ for (i = 0, p = buffer + nbytes - 1; p >= buffer + BYTES_PER_MPI_LIMB;) {
+#if BYTES_PER_MPI_LIMB == 4
+ alimb = (mpi_limb_t) *p--;
+ alimb |= (mpi_limb_t) *p-- << 8;
+ alimb |= (mpi_limb_t) *p-- << 16;
+ alimb |= (mpi_limb_t) *p-- << 24;
+#elif BYTES_PER_MPI_LIMB == 8
+ alimb = (mpi_limb_t) *p--;
+ alimb |= (mpi_limb_t) *p-- << 8;
+ alimb |= (mpi_limb_t) *p-- << 16;
+ alimb |= (mpi_limb_t) *p-- << 24;
+ alimb |= (mpi_limb_t) *p-- << 32;
+ alimb |= (mpi_limb_t) *p-- << 40;
+ alimb |= (mpi_limb_t) *p-- << 48;
+ alimb |= (mpi_limb_t) *p-- << 56;
+#else
+#error please implement for this limb size.
+#endif
+ a->d[i++] = alimb;
+ }
+ if (p >= buffer) {
+#if BYTES_PER_MPI_LIMB == 4
+ alimb = *p--;
+ if (p >= buffer)
+ alimb |= (mpi_limb_t) *p-- << 8;
+ if (p >= buffer)
+ alimb |= (mpi_limb_t) *p-- << 16;
+ if (p >= buffer)
+ alimb |= (mpi_limb_t) *p-- << 24;
+#elif BYTES_PER_MPI_LIMB == 8
+ alimb = (mpi_limb_t) *p--;
+ if (p >= buffer)
+ alimb |= (mpi_limb_t) *p-- << 8;
+ if (p >= buffer)
+ alimb |= (mpi_limb_t) *p-- << 16;
+ if (p >= buffer)
+ alimb |= (mpi_limb_t) *p-- << 24;
+ if (p >= buffer)
+ alimb |= (mpi_limb_t) *p-- << 32;
+ if (p >= buffer)
+ alimb |= (mpi_limb_t) *p-- << 40;
+ if (p >= buffer)
+ alimb |= (mpi_limb_t) *p-- << 48;
+ if (p >= buffer)
+ alimb |= (mpi_limb_t) *p-- << 56;
+#else
+#error please implement for this limb size.
+#endif
+ a->d[i++] = alimb;
+ }
+ a->nlimbs = i;
+
+ if (i != nlimbs) {
+ pr_emerg("MPI: mpi_set_buffer: Assertion failed (%d != %d)", i,
+ nlimbs);
+ BUG();
+ }
+ return 0;
+}
+EXPORT_SYMBOL_GPL(mpi_set_buffer);
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