/**
Gets length of DER encoding of Object Identifier
@param nwords The number of OID words
@param words The actual OID words to get the size of
@param outlen [out] The length of the DER encoding for the given string
@return CRYPT_OK if successful
*/
int der_length_object_identifier(unsigned long *words, unsigned long nwords, unsigned long *outlen)
{
unsigned long y, z, t, wordbuf;
LTC_ARGCHK(words != NULL);
LTC_ARGCHK(outlen != NULL);
/* must be >= 2 words */
if (nwords < 2) {
return CRYPT_INVALID_ARG;
}
/* word1 = 0,1,2,3 and word2 0..39 */
if (words[0] > 3 || (words[0] < 2 && words[1] > 39)) {
return CRYPT_INVALID_ARG;
}
/* leading word is the first two */
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) {
/* grab next word */
wordbuf = words[y+1];
}
}
/* now depending on the length our length encoding changes */
if (z < 128) {
z += 2;
} else if (z < 256) {
z += 3;
} else if (z < 65536UL) {
z += 4;
} else {
return CRYPT_INVALID_ARG;
}
*outlen = z;
return CRYPT_OK;
}
/**
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(const 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;
y = *outlen - x;
if ((err = der_encode_asn1_length(z, out + x, &y)) != CRYPT_OK) {
return err;
}
x += y;
/* 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];
}
}
