mirror of
https://github.com/clearml/dropbear
synced 2025-06-26 18:17:32 +00:00
0c10d50a69
--HG-- branch : libtomcrypt-orig extra : convert_revision : 7122128aa22564d1a53eebfac79c0393c4d0c011
84 lines
2.1 KiB
C
84 lines
2.1 KiB
C
/* LibTomCrypt, modular cryptographic library -- Tom St Denis
|
|
*
|
|
* LibTomCrypt is a library that provides various cryptographic
|
|
* algorithms in a highly modular and flexible manner.
|
|
*
|
|
* The library is free for all purposes without any express
|
|
* guarantee it works.
|
|
*
|
|
* Tom St Denis, tomstdenis@iahu.ca, http://libtomcrypt.org
|
|
*/
|
|
|
|
#include "mycrypt.h"
|
|
|
|
|
|
/* decodes a DER INTEGER in [in]. You have to tell this function
|
|
* how many bytes are available [inlen]. It will then attempt to
|
|
* read the INTEGER. If all goes well it stores the number of bytes
|
|
* read in [inlen] and the number in [num].
|
|
*/
|
|
int der_decode_integer(const unsigned char *in, unsigned long *inlen, mp_int *num)
|
|
{
|
|
unsigned long tmplen, y, z;
|
|
|
|
_ARGCHK(num != NULL);
|
|
_ARGCHK(in != NULL);
|
|
_ARGCHK(inlen != NULL);
|
|
|
|
/* save copy of max output size */
|
|
tmplen = *inlen;
|
|
*inlen = 0;
|
|
|
|
/* min DER INTEGER is 0x02 01 00 == 0 */
|
|
if (tmplen < (1 + 1 + 1)) {
|
|
return CRYPT_INVALID_PACKET;
|
|
}
|
|
|
|
/* ok expect 0x02 when we AND with 0011 1111 [3F] */
|
|
if ((*in++ & 0x3F) != 0x02) {
|
|
return CRYPT_INVALID_PACKET;
|
|
}
|
|
++(*inlen);
|
|
|
|
/* now decode the len stuff */
|
|
z = *in++;
|
|
++(*inlen);
|
|
|
|
if ((z & 0x80) == 0x00) {
|
|
/* short form */
|
|
|
|
/* will it overflow? */
|
|
if (*inlen + z > tmplen) {
|
|
return CRYPT_INVALID_PACKET;
|
|
}
|
|
|
|
/* no so read it */
|
|
(*inlen) += z;
|
|
return mpi_to_ltc_error(mp_read_unsigned_bin(num, (unsigned char *)in, z));
|
|
} else {
|
|
/* long form */
|
|
z &= 0x7F;
|
|
|
|
/* will number of length bytes overflow? (or > 4) */
|
|
if (((*inlen + z) > tmplen) || (z > 4)) {
|
|
return CRYPT_INVALID_PACKET;
|
|
}
|
|
|
|
/* now read it in */
|
|
y = 0;
|
|
while (z--) {
|
|
y = ((unsigned long)(*in++)) | (y << 8);
|
|
++(*inlen);
|
|
}
|
|
|
|
/* now will reading y bytes overrun? */
|
|
if ((*inlen + y) > tmplen) {
|
|
return CRYPT_INVALID_PACKET;
|
|
}
|
|
|
|
/* no so read it */
|
|
(*inlen) += y;
|
|
return mpi_to_ltc_error(mp_read_unsigned_bin(num, (unsigned char *)in, y));
|
|
}
|
|
}
|