source: lib/sha1.c @ 8fdeaa5

#include "sha1.h"
#include <string.h>
#include <stdio.h>


void sha1_init(sha1_state_t *ctx)
{
        *ctx = g_checksum_new(G_CHECKSUM_SHA1);
}

void sha1_append(sha1_state_t *ctx, const guint8 * message_array, guint len)
{
        g_checksum_update(*ctx, message_array, len);
}

void sha1_finish(sha1_state_t *ctx, guint8 digest[SHA1_HASH_SIZE])
{
        gsize digest_len = SHA1_HASH_SIZE;

        g_checksum_get_digest(*ctx, digest, &digest_len);
        g_checksum_free(*ctx);
}

#define HMAC_BLOCK_SIZE 64

/* BitlBee addition: */
void sha1_hmac(const char *key_, size_t key_len, const char *payload, size_t payload_len, guint8 digest[SHA1_HASH_SIZE])
{
        sha1_state_t sha1;
        guint8 hash[SHA1_HASH_SIZE];
        guint8 key[HMAC_BLOCK_SIZE + 1];
        int i;

        if (key_len == 0) {
                key_len = strlen(key_);
        }
        if (payload_len == 0) {
                payload_len = strlen(payload);
        }

        /* Create K. If our current key is >64 chars we have to hash it,
           otherwise just pad. */
        memset(key, 0, HMAC_BLOCK_SIZE + 1);
        if (key_len > HMAC_BLOCK_SIZE) {
                sha1_init(&sha1);
                sha1_append(&sha1, (guint8 *) key_, key_len);
                sha1_finish(&sha1, key);
        } else {
                memcpy(key, key_, key_len);
        }

        /* Inner part: H(K XOR 0x36, text) */
        sha1_init(&sha1);
        for (i = 0; i < HMAC_BLOCK_SIZE; i++) {
                key[i] ^= 0x36;
        }
        sha1_append(&sha1, key, HMAC_BLOCK_SIZE);
        sha1_append(&sha1, (const guint8 *) payload, payload_len);
        sha1_finish(&sha1, hash);

        /* Final result: H(K XOR 0x5C, inner stuff) */
        sha1_init(&sha1);
        for (i = 0; i < HMAC_BLOCK_SIZE; i++) {
                key[i] ^= 0x36 ^ 0x5c;
        }
        sha1_append(&sha1, key, HMAC_BLOCK_SIZE);
        sha1_append(&sha1, hash, SHA1_HASH_SIZE);
        sha1_finish(&sha1, digest);
}

/* I think this follows the scheme described on:
   http://en.wikipedia.org/wiki/Universally_unique_identifier#Version_4_.28random.29
   My random data comes from a SHA1 generator but hey, it's random enough for
   me, and RFC 4122 looks way more complicated than I need this to be.

   Returns a value that must be free()d. */
char *sha1_random_uuid(sha1_state_t * context)
{
        guint8 dig[SHA1_HASH_SIZE];
        char *ret = g_new0(char, 40);   /* 36 chars + \0 */
        int i, p;

        sha1_finish(context, dig);
        for (p = i = 0; i < 16; i++) {
                if (i == 4 || i == 6 || i == 8 || i == 10) {
                        ret[p++] = '-';
                }
                if (i == 6) {
                        dig[i] = (dig[i] & 0x0f) | 0x40;
                }
                if (i == 8) {
                        dig[i] = (dig[i] & 0x30) | 0x80;
                }

                sprintf(ret + p, "%02x", dig[i]);
                p += 2;
        }
        ret[p] = '\0';

        return ret;
}