| /* 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_encode_object_identifier.c |
| ASN.1 DER, Encode Object Identifier, Tom St Denis |
| */ |
| |
| #ifdef LTC_DER |
| /** |
| Encode an OID |
| @param words The words to encode (upto 32-bits each) |
| @param nwords The number of words in the OID |
| @param out [out] Destination of OID data |
| @param outlen [in/out] The max and resulting size of the OID |
| @return CRYPT_OK if successful |
| */ |
| int der_encode_object_identifier(unsigned long *words, unsigned long nwords, |
| unsigned char *out, unsigned long *outlen) |
| { |
| unsigned long i, x, y, z, t, mask, wordbuf; |
| int err; |
| |
| LTC_ARGCHK(words != NULL); |
| LTC_ARGCHK(out != NULL); |
| LTC_ARGCHK(outlen != NULL); |
| |
| /* check length */ |
| if ((err = der_length_object_identifier(words, nwords, &x)) != CRYPT_OK) { |
| return err; |
| } |
| if (x > *outlen) { |
| *outlen = x; |
| return CRYPT_BUFFER_OVERFLOW; |
| } |
| |
| /* compute length to store OID data */ |
| z = 0; |
| wordbuf = words[0] * 40 + words[1]; |
| for (y = 1; y < nwords; y++) { |
| t = der_object_identifier_bits(wordbuf); |
| z += t/7 + ((t%7) ? 1 : 0) + (wordbuf == 0 ? 1 : 0); |
| if (y < nwords - 1) { |
| wordbuf = words[y + 1]; |
| } |
| } |
| |
| /* store header + length */ |
| x = 0; |
| out[x++] = 0x06; |
| if (z < 128) { |
| out[x++] = (unsigned char)z; |
| } else if (z < 256) { |
| out[x++] = 0x81; |
| out[x++] = (unsigned char)z; |
| } else if (z < 65536UL) { |
| out[x++] = 0x82; |
| out[x++] = (unsigned char)((z>>8)&255); |
| out[x++] = (unsigned char)(z&255); |
| } else { |
| return CRYPT_INVALID_ARG; |
| } |
| |
| /* store first byte */ |
| wordbuf = words[0] * 40 + words[1]; |
| for (i = 1; i < nwords; i++) { |
| /* store 7 bit words in little endian */ |
| t = wordbuf & 0xFFFFFFFF; |
| if (t) { |
| y = x; |
| mask = 0; |
| while (t) { |
| out[x++] = (unsigned char)((t & 0x7F) | mask); |
| t >>= 7; |
| mask |= 0x80; /* upper bit is set on all but the last byte */ |
| } |
| /* now swap bytes y...x-1 */ |
| z = x - 1; |
| while (y < z) { |
| t = out[y]; out[y] = out[z]; out[z] = (unsigned char)t; |
| ++y; |
| --z; |
| } |
| } else { |
| /* zero word */ |
| out[x++] = 0x00; |
| } |
| |
| if (i < nwords - 1) { |
| wordbuf = words[i + 1]; |
| } |
| } |
| |
| *outlen = x; |
| return CRYPT_OK; |
| } |
| |
| #endif |
| |
| /* $Source: /cvs/libtom/libtomcrypt/src/pk/asn1/der/object_identifier/der_encode_object_identifier.c,v $ */ |
| /* $Revision: 1.6 $ */ |
| /* $Date: 2006/12/04 21:34:03 $ */ |