/*
* Generate a bignum of a specified length, with the given
* high and low 8 bits. "High" is merged into the high 8 bits of the
* number. For example, set it to 0x80 to ensure that the number is
* exactly "bits" bits long (i.e. 2^(bits-1) <= bn < 2^bits).
* "Low" is merged into the low 8 bits. For example, set it to
* 1 to ensure that you generate an odd number.
*
* The bignum is generated using the given seed string. The
* technique is from David Kravitz (of the NSA)'s "kosherizer".
* The string is hashed, and that (with the low bit forced to 1)
* is used for the low 160 bits of the number. Then the string,
* considered as a big-endian array of bytes, is incremented
* and the incremented value is hashed to produce the next most
* significant 160 bits, and so on. The increment is performed
* modulo the size of the seed string.
*
* The most significant *two* bits are forced to 1, the first to
* ensure that the number is long enough, and the second just to
* place the prime in the high half of the range to make breaking
* it slightly more difficult, since it makes essentially no
* difference to the use of the number.
*/
static int
genRandBn(struct BigNum *bn, unsigned bits, unsigned char high,
unsigned char low, unsigned char *seed, unsigned len)
{
unsigned char buf[SHA_DIGESTSIZE];
unsigned bytes;
unsigned l = 0; /* Current position */
unsigned i;
struct SHAContext sha;
bnSetQ(bn, 0);
bytes = (bits+7) / 8; /* Number of bytes to use */
shaInit(&sha);
shaUpdate(&sha, seed, len);
shaFinal(&sha, buf);
buf[SHA_DIGESTSIZE-1] |= low;
while (bytes > SHA_DIGESTSIZE) {
bytes -= SHA_DIGESTSIZE;
/* Merge in low half of high bits, if necessary */
if (bytes == 1 && (bits & 7))
buf[0] |= high << (bits & 7);
if (bnInsertBigBytes(bn, buf, l, SHA_DIGESTSIZE) < 0)
return -1;
l += SHA_DIGESTSIZE;
/* Increment the seed, ignoring carry out. */
i = len;
while (i--) {
if (++seed[i] & 255)
break; /* Didn't wrap; done */
}
shaInit(&sha);
shaUpdate(&sha, seed, len);
shaFinal(&sha, buf);
}
/* Do the final "bytes"-long section, using the tail bytes in buf */
/* Mask off excess high bits */
buf[SHA_DIGESTSIZE-bytes] &= 255 >> (-bits & 7);
/* Merge in specified high bits */
buf[SHA_DIGESTSIZE-bytes] |= high >> (-bits & 7);
if (bytes > 1 && (bits & 7))
buf[SHA_DIGESTSIZE-bytes+1] |= high << (bits & 7);
/* Merge in the appropriate bytes of the buffer */
if (bnInsertBigBytes(bn, buf+SHA_DIGESTSIZE-bytes, l, bytes) < 0)
return -1;
return 0;
}
void
msn_user_set_buddy_icon(MsnUser *user, const char *filename)
{
struct stat st;
FILE *fp;
MsnObject *msnobj = msn_user_get_object(user);
g_return_if_fail(user != NULL);
if (filename == NULL || g_stat(filename, &st) == -1)
{
msn_user_set_object(user, NULL);
}
else if ((fp = g_fopen(filename, "rb")) != NULL)
{
unsigned char *buf;
SHA_CTX ctx;
gsize len;
char *base64;
unsigned char digest[20];
if (msnobj == NULL)
{
msnobj = msn_object_new(TRUE);
msn_object_set_local(msnobj);
msn_object_set_type(msnobj, MSN_OBJECT_USERTILE);
msn_object_set_location(msnobj, "TFR2C2.tmp");
msn_object_set_creator(msnobj, msn_user_get_passport(user));
msn_user_set_object(user, msnobj);
}
msn_object_set_real_location(msnobj, filename);
buf = g_malloc(st.st_size);
len = fread(buf, 1, st.st_size, fp);
fclose(fp);
/* Compute the SHA1D field. */
memset(digest, 0, sizeof(digest));
shaInit(&ctx);
shaUpdate(&ctx, buf, st.st_size);
shaFinal(&ctx, digest);
g_free(buf);
base64 = gaim_base64_encode(digest, sizeof(digest));
msn_object_set_sha1d(msnobj, base64);
g_free(base64);
msn_object_set_size(msnobj, st.st_size);
/* Compute the SHA1C field. */
buf = g_strdup_printf(
"Creator%sSize%dType%dLocation%sFriendly%sSHA1D%s",
msn_object_get_creator(msnobj),
msn_object_get_size(msnobj),
msn_object_get_type(msnobj),
msn_object_get_location(msnobj),
msn_object_get_friendly(msnobj),
msn_object_get_sha1d(msnobj));
memset(digest, 0, sizeof(digest));
shaInit(&ctx);
shaUpdate(&ctx, buf, strlen(buf));
shaFinal(&ctx, digest);
g_free(buf);
base64 = gaim_base64_encode(digest, sizeof(digest));
msn_object_set_sha1c(msnobj, base64);
g_free(base64);
}
else
{
gaim_debug_error("msn", "Unable to open buddy icon %s!\n", filename);
msn_user_set_object(user, NULL);
}
}
