src/lib/pkcs5.c

/* Copyright (c) 2016-2018 Dovecot authors, see the included COPYING file */

#include "lib.h"
#include "buffer.h"
#include "hash-method.h"
#include "hmac.h"
#include "pkcs5.h"

#include <stdint.h>
#include <arpa/inet.h>

static
int pkcs5_pbkdf1(const struct hash_method *hash,
    const unsigned char *password, size_t password_len,
    const unsigned char *salt, size_t salt_len,
    unsigned int iter, uint32_t length,
    buffer_t *result)
{
    if (length < 1 ||
        length > hash->digest_size) return -1;
    if (iter < 1) return -1;

    unsigned char dk[hash->digest_size];
    unsigned char ctx[hash->context_size];

    hash->init(ctx);
    hash->loop(ctx, password, password_len);
    hash->loop(ctx, salt, salt_len);
    hash->result(ctx, dk);
    length--;

    for(;length>0;length--) {
        hash->init(ctx);
        hash->loop(ctx, dk, hash->digest_size);
        hash->result(ctx, dk);
    }

    buffer_append(result, dk, hash->digest_size);

    return 0;
}

static
int pkcs5_pbkdf2(const struct hash_method *hash,
    const unsigned char *password, size_t password_len,
    const unsigned char *salt, size_t salt_len,
    unsigned int iter, uint32_t length,
    buffer_t *result)
{
    if (length < 1 || iter < 1) return -1;

    size_t l = (length + hash->digest_size - 1)/hash->digest_size; /* same as ceil(length/hash->digest_size) */
    unsigned char dk[l * hash->digest_size];
    unsigned char *block;
    struct hmac_context hctx;
    unsigned int c,i,t;
    unsigned char U_c[hash->digest_size];

    for(t = 0; t < l; t++) {
        block = &(dk[t*hash->digest_size]);
        /* U_1 = PRF(Password, Salt|| INT_BE32(Block_Number)) */
        c = htonl(t+1);
        hmac_init(&hctx, password, password_len, hash);
        hmac_update(&hctx, salt, salt_len);
        hmac_update(&hctx, &c, sizeof(c));
        hmac_final(&hctx, U_c);
        /* block = U_1 ^ .. ^ U_iter */
        memcpy(block, U_c, hash->digest_size);
        /* U_c = PRF(Password, U_c-1) */
        for(c = 1; c < iter; c++) {
            hmac_init(&hctx, password, password_len, hash);
            hmac_update(&hctx, U_c, hash->digest_size);
            hmac_final(&hctx, U_c);
            for(i = 0; i < hash->digest_size; i++)
                block[i] ^= U_c[i];
        }
    }

    buffer_append(result, dk, length);

    return 0;
}

int pkcs5_pbkdf(enum pkcs5_pbkdf_mode mode, const struct hash_method *hash,
    const unsigned char *password, size_t password_len,
    const unsigned char *salt, size_t salt_len,
    unsigned int iterations, uint32_t dk_len,
    buffer_t *result)
{
    if (mode == PKCS5_PBKDF1)
        return pkcs5_pbkdf1(hash,password,password_len,
            salt,salt_len,iterations,dk_len,result);
    else if (mode == PKCS5_PBKDF2)
        return pkcs5_pbkdf2(hash,password,password_len,
            salt,salt_len,iterations,dk_len,result);
    i_unreached();
}