| /* 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@gmail.com, http://libtomcrypt.com |
| */ |
| #include "tomcrypt.h" |
| |
| /** |
| @file der_decode_bit_string.c |
| ASN.1 DER, encode a BIT STRING, Tom St Denis |
| */ |
| |
| |
| #ifdef LTC_DER |
| |
| /** |
| Store a BIT STRING |
| @param in The DER encoded BIT STRING |
| @param inlen The size of the DER BIT STRING |
| @param out [out] The array of bits stored (one per char) |
| @param outlen [in/out] The number of bits stored |
| @return CRYPT_OK if successful |
| */ |
| int der_decode_bit_string(const unsigned char *in, unsigned long inlen, |
| unsigned char *out, unsigned long *outlen) |
| { |
| unsigned long dlen, blen, x, y; |
| |
| LTC_ARGCHK(in != NULL); |
| LTC_ARGCHK(out != NULL); |
| LTC_ARGCHK(outlen != NULL); |
| |
| /* packet must be at least 4 bytes */ |
| if (inlen < 4) { |
| return CRYPT_INVALID_ARG; |
| } |
| |
| /* check for 0x03 */ |
| if ((in[0]&0x1F) != 0x03) { |
| return CRYPT_INVALID_PACKET; |
| } |
| |
| /* offset in the data */ |
| x = 1; |
| |
| /* get the length of the data */ |
| if (in[x] & 0x80) { |
| /* long format get number of length bytes */ |
| y = in[x++] & 0x7F; |
| |
| /* invalid if 0 or > 2 */ |
| if (y == 0 || y > 2) { |
| return CRYPT_INVALID_PACKET; |
| } |
| |
| /* read the data len */ |
| dlen = 0; |
| while (y--) { |
| dlen = (dlen << 8) | (unsigned long)in[x++]; |
| } |
| } else { |
| /* short format */ |
| dlen = in[x++] & 0x7F; |
| } |
| |
| /* is the data len too long or too short? */ |
| if ((dlen == 0) || (dlen + x > inlen)) { |
| return CRYPT_INVALID_PACKET; |
| } |
| |
| /* get padding count */ |
| blen = ((dlen - 1) << 3) - (in[x++] & 7); |
| |
| /* too many bits? */ |
| if (blen > *outlen) { |
| *outlen = blen; |
| return CRYPT_BUFFER_OVERFLOW; |
| } |
| |
| /* decode/store the bits */ |
| for (y = 0; y < blen; y++) { |
| out[y] = (in[x] & (1 << (7 - (y & 7)))) ? 1 : 0; |
| if ((y & 7) == 7) { |
| ++x; |
| } |
| } |
| |
| /* we done */ |
| *outlen = blen; |
| return CRYPT_OK; |
| } |
| |
| #endif |
| |
| /* $Source: /cvs/libtom/libtomcrypt/src/pk/asn1/der/bit/der_decode_bit_string.c,v $ */ |
| /* $Revision: 1.4 $ */ |
| /* $Date: 2006/06/16 21:53:41 $ */ |