providers/implementations/kdfs/pbkdf2.c

/*
 * Copyright 2018-2025 The OpenSSL Project Authors. All Rights Reserved.
 *
 * Licensed under the Apache License 2.0 (the "License").  You may not use
 * this file except in compliance with the License.  You can obtain a copy
 * in the file LICENSE in the source distribution or at
 * https://www.openssl.org/source/license.html
 */

/*
 * HMAC low level APIs are deprecated for public use, but still ok for internal
 * use.
 */
#include "internal/deprecated.h"

#include <stdlib.h>
#include <stdarg.h>
#include <string.h>
#include <openssl/hmac.h>
#include <openssl/evp.h>
#include <openssl/kdf.h>
#include <openssl/core_names.h>
#include <openssl/proverr.h>
#include "internal/cryptlib.h"
#include "internal/fips.h"
#include "internal/numbers.h"
#include "crypto/evp.h"
#include "prov/provider_ctx.h"
#include "prov/providercommon.h"
#include "prov/implementations.h"
#include "prov/provider_util.h"
#include "prov/securitycheck.h"
#include "providers/implementations/kdfs/pbkdf2.inc"

/* Constants specified in SP800-132 */
#define KDF_PBKDF2_MIN_KEY_LEN_BITS 112
#define KDF_PBKDF2_MAX_KEY_LEN_DIGEST_RATIO 0xFFFFFFFF
#define KDF_PBKDF2_MIN_ITERATIONS 1000
#define KDF_PBKDF2_MIN_SALT_LEN (128 / 8)
/*
 * The Implementation Guidance for FIPS 140-3 says in section D.N
 * "Password-Based Key Derivation for Storage Applications" that "the vendor
 * shall document in the module's Security Policy the length of
 * a password/passphrase used in key derivation and establish an upper bound
 * for the probability of having this parameter guessed at random. This
 * probability shall take into account not only the length of the
 * password/passphrase, but also the difficulty of guessing it. The decision on
 * the minimum length of a password used for key derivation is the vendor's,
 * but the vendor shall at a minimum informally justify the decision."
 *
 * ACVP may assume 8, most FIPS modules choose 8, BC-FJA chose 14.
 *
 * Allow setting this for default provider too, in case consistency is
 * desired for FIPS and Default providers. Because password being
 * accepted on one system, but not the other, is very confusing.
 */
#ifndef KDF_PBKDF2_MIN_PASSWORD_LEN
#ifdef FIPS_MODULE
#define KDF_PBKDF2_MIN_PASSWORD_LEN (8)
#define KDF_PBKDF2_FIPS_SELF_TEST_ITERATIONS 2
#else
#define KDF_PBKDF2_MIN_PASSWORD_LEN (1)
#endif
#endif

static OSSL_FUNC_kdf_newctx_fn kdf_pbkdf2_new;
static OSSL_FUNC_kdf_dupctx_fn kdf_pbkdf2_dup;
static OSSL_FUNC_kdf_freectx_fn kdf_pbkdf2_free;
static OSSL_FUNC_kdf_reset_fn kdf_pbkdf2_reset;
static OSSL_FUNC_kdf_derive_fn kdf_pbkdf2_derive;
static OSSL_FUNC_kdf_settable_ctx_params_fn kdf_pbkdf2_settable_ctx_params;
static OSSL_FUNC_kdf_set_ctx_params_fn kdf_pbkdf2_set_ctx_params;
static OSSL_FUNC_kdf_gettable_ctx_params_fn kdf_pbkdf2_gettable_ctx_params;
static OSSL_FUNC_kdf_get_ctx_params_fn kdf_pbkdf2_get_ctx_params;

typedef struct {
    void *provctx;
    unsigned char *pass;
    size_t pass_len;
    unsigned char *salt;
    size_t salt_len;
    uint64_t iter;
    PROV_DIGEST digest;
    int lower_bound_checks;
    OSSL_FIPS_IND_DECLARE
} KDF_PBKDF2;

static int pbkdf2_derive(KDF_PBKDF2 *ctx, const char *pass, size_t passlen,
    const unsigned char *salt, int saltlen, uint64_t iter,
    const EVP_MD *digest, unsigned char *key,
    size_t keylen, int lower_bound_checks);

static void kdf_pbkdf2_init(KDF_PBKDF2 *ctx);

static void *kdf_pbkdf2_new_no_init(void *provctx)
{
    KDF_PBKDF2 *ctx;

    if (!ossl_prov_is_running())
        return NULL;

#ifdef FIPS_MODULE
    if (!ossl_deferred_self_test(PROV_LIBCTX_OF(provctx),
            ST_ID_KDF_PBKDF2))
        return NULL;
#endif

    ctx = OPENSSL_zalloc(sizeof(*ctx));
    if (ctx == NULL)
        return NULL;
    ctx->provctx = provctx;
    OSSL_FIPS_IND_INIT(ctx);
    return ctx;
}

static void *kdf_pbkdf2_new(void *provctx)
{
    KDF_PBKDF2 *ctx = kdf_pbkdf2_new_no_init(provctx);

    if (ctx != NULL)
        kdf_pbkdf2_init(ctx);
    return ctx;
}

static void kdf_pbkdf2_cleanup(KDF_PBKDF2 *ctx)
{
    ossl_prov_digest_reset(&ctx->digest);
#ifdef OPENSSL_PEDANTIC_ZEROIZATION
    OPENSSL_clear_free(ctx->salt, ctx->salt_len);
#else
    OPENSSL_free(ctx->salt);
#endif
    OPENSSL_clear_free(ctx->pass, ctx->pass_len);
    memset(ctx, 0, sizeof(*ctx));
}

static void kdf_pbkdf2_free(void *vctx)
{
    KDF_PBKDF2 *ctx = (KDF_PBKDF2 *)vctx;

    if (ctx != NULL) {
        kdf_pbkdf2_cleanup(ctx);
        OPENSSL_free(ctx);
    }
}

static void kdf_pbkdf2_reset(void *vctx)
{
    KDF_PBKDF2 *ctx = (KDF_PBKDF2 *)vctx;
    void *provctx = ctx->provctx;

    kdf_pbkdf2_cleanup(ctx);
    ctx->provctx = provctx;
    kdf_pbkdf2_init(ctx);
}

static void *kdf_pbkdf2_dup(void *vctx)
{
    const KDF_PBKDF2 *src = (const KDF_PBKDF2 *)vctx;
    KDF_PBKDF2 *dest;

    /* We need a new PBKDF2 object but uninitialised since we're filling it */
    dest = kdf_pbkdf2_new_no_init(src->provctx);
    if (dest != NULL) {
        if (!ossl_prov_memdup(src->salt, src->salt_len,
                &dest->salt, &dest->salt_len)
            || !ossl_prov_memdup(src->pass, src->pass_len,
                &dest->pass, &dest->pass_len)
            || !ossl_prov_digest_copy(&dest->digest, &src->digest))
            goto err;
        dest->iter = src->iter;
        dest->lower_bound_checks = src->lower_bound_checks;
        OSSL_FIPS_IND_COPY(dest, src)
    }
    return dest;

err:
    kdf_pbkdf2_free(dest);
    return NULL;
}

static void kdf_pbkdf2_init(KDF_PBKDF2 *ctx)
{
    OSSL_PARAM param;
    OSSL_LIB_CTX *provctx = PROV_LIBCTX_OF(ctx->provctx);

    param = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_DIGEST,
        SN_sha1, 0);
    if (!ossl_prov_digest_load(&ctx->digest, &param, NULL, provctx))
        /* This is an error, but there is no way to indicate such directly */
        ossl_prov_digest_reset(&ctx->digest);
    ctx->iter = PKCS5_DEFAULT_ITER;
#ifdef FIPS_MODULE
    ctx->lower_bound_checks = 1;
#else
    ctx->lower_bound_checks = 0;
#endif
}

static int pbkdf2_set_membuf(unsigned char **buffer, size_t *buflen,
    const OSSL_PARAM *p)
{
    OPENSSL_clear_free(*buffer, *buflen);
    *buffer = NULL;
    *buflen = 0;

    if (p->data_size == 0) {
        if ((*buffer = OPENSSL_malloc(1)) == NULL)
            return 0;
    } else if (p->data != NULL) {
        if (!OSSL_PARAM_get_octet_string(p, (void **)buffer, 0, buflen))
            return 0;
    }
    return 1;
}

static int pbkdf2_lower_bound_check_passed(int saltlen, uint64_t iter,
    size_t keylen, size_t passlen,
    int *error, const char **desc)
{
    uint64_t min_iter = KDF_PBKDF2_MIN_ITERATIONS;

    if (passlen < KDF_PBKDF2_MIN_PASSWORD_LEN) {
        *error = PROV_R_PASSWORD_STRENGTH_TOO_WEAK;
        if (desc != NULL)
            *desc = "Weak password";
        return 0;
    }
    if ((keylen * 8) < KDF_PBKDF2_MIN_KEY_LEN_BITS) {
        *error = PROV_R_KEY_SIZE_TOO_SMALL;
        if (desc != NULL)
            *desc = "Key size";
        return 0;
    }
    if (saltlen < KDF_PBKDF2_MIN_SALT_LEN) {
        *error = PROV_R_INVALID_SALT_LENGTH;
        if (desc != NULL)
            *desc = "Salt size";
        return 0;
    }
#ifdef FIPS_MODULE
    /* Modify this check during self-test. See FIPS 140-3 IG 10.3.A.8 */
    if (ossl_self_test_in_progress(ST_ID_KDF_PBKDF2)) {
        min_iter = KDF_PBKDF2_FIPS_SELF_TEST_ITERATIONS;
    }
#endif
    if (iter < min_iter) {
        *error = PROV_R_INVALID_ITERATION_COUNT;
        if (desc != NULL)
            *desc = "Iteration count";
        return 0;
    }

    return 1;
}

#ifdef FIPS_MODULE
static int fips_lower_bound_check_passed(KDF_PBKDF2 *ctx, int saltlen,
    uint64_t iter, size_t keylen,
    size_t passlen)
{
    OSSL_LIB_CTX *libctx = PROV_LIBCTX_OF(ctx->provctx);
    int error = 0;
    const char *desc = NULL;
    int approved = pbkdf2_lower_bound_check_passed(saltlen, iter, keylen,
        passlen, &error, &desc);

    if (!approved) {
        if (!OSSL_FIPS_IND_ON_UNAPPROVED(ctx, OSSL_FIPS_IND_SETTABLE0, libctx,
                "PBKDF2", desc,
                ossl_fips_config_pbkdf2_lower_bound_check)) {
            ERR_raise(ERR_LIB_PROV, error);
            return 0;
        }
    }
    return 1;
}
#endif

static int lower_bound_check_passed(KDF_PBKDF2 *ctx, int saltlen, uint64_t iter,
    size_t keylen, size_t passlen,
    int lower_bound_checks)
{
#ifdef FIPS_MODULE
    if (!fips_lower_bound_check_passed(ctx, saltlen, iter, keylen, passlen))
        return 0;
#else
    if (lower_bound_checks) {
        int error = 0;
        int passed = pbkdf2_lower_bound_check_passed(saltlen, iter, keylen,
            passlen, &error, NULL);

        if (!passed) {
            ERR_raise(ERR_LIB_PROV, error);
            return 0;
        }
    } else if (iter < 1) {
        ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_ITERATION_COUNT);
        return 0;
    }
#endif

    return 1;
}

static int kdf_pbkdf2_derive(void *vctx, unsigned char *key, size_t keylen,
    const OSSL_PARAM params[])
{
    KDF_PBKDF2 *ctx = (KDF_PBKDF2 *)vctx;
    const EVP_MD *md;

    if (!ossl_prov_is_running() || !kdf_pbkdf2_set_ctx_params(ctx, params))
        return 0;

    if (ctx->pass == NULL) {
        ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_PASS);
        return 0;
    }

    if (ctx->salt == NULL) {
        ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_SALT);
        return 0;
    }

    md = ossl_prov_digest_md(&ctx->digest);
    return pbkdf2_derive(ctx, (char *)ctx->pass, ctx->pass_len,
        ctx->salt, (int)ctx->salt_len, ctx->iter,
        md, key, keylen, ctx->lower_bound_checks);
}

static int kdf_pbkdf2_set_ctx_params(void *vctx, const OSSL_PARAM params[])
{
    struct pbkdf2_set_ctx_params_st p;
    KDF_PBKDF2 *ctx = vctx;
    OSSL_LIB_CTX *provctx;
    int pkcs5;
    uint64_t iter;
    const EVP_MD *md;

    if (ctx == NULL || !pbkdf2_set_ctx_params_decoder(params, &p))
        return 0;

    provctx = PROV_LIBCTX_OF(ctx->provctx);

    if (p.digest != NULL) {
        if (!ossl_prov_digest_load(&ctx->digest, p.digest, p.propq, provctx))
            return 0;
        md = ossl_prov_digest_md(&ctx->digest);
        if (EVP_MD_xof(md)) {
            ERR_raise(ERR_LIB_PROV, PROV_R_XOF_DIGESTS_NOT_ALLOWED);
            return 0;
        }
    }

    if (p.pkcs5 != NULL) {
        if (!OSSL_PARAM_get_int(p.pkcs5, &pkcs5))
            return 0;
        ctx->lower_bound_checks = pkcs5 == 0;
#ifdef FIPS_MODULE
        ossl_FIPS_IND_set_settable(OSSL_FIPS_IND_GET(ctx),
            OSSL_FIPS_IND_SETTABLE0,
            ctx->lower_bound_checks);
#endif
    }

    if (p.pw != NULL) {
        if (ctx->lower_bound_checks != 0
            && p.pw->data_size < KDF_PBKDF2_MIN_PASSWORD_LEN) {
            ERR_raise(ERR_LIB_PROV, PROV_R_PASSWORD_STRENGTH_TOO_WEAK);
            return 0;
        }
        if (!pbkdf2_set_membuf(&ctx->pass, &ctx->pass_len, p.pw))
            return 0;
    }

    if (p.salt != NULL) {
        if (!lower_bound_check_passed(ctx, (int)p.salt->data_size, UINT64_MAX, SIZE_MAX,
                SIZE_MAX, ctx->lower_bound_checks))
            return 0;
        if (!pbkdf2_set_membuf(&ctx->salt, &ctx->salt_len, p.salt))
            return 0;
    }

    if (p.iter != NULL) {
        if (!OSSL_PARAM_get_uint64(p.iter, &iter))
            return 0;
        if (!lower_bound_check_passed(ctx, INT_MAX, iter, SIZE_MAX,
                SIZE_MAX, ctx->lower_bound_checks))
            return 0;
        ctx->iter = iter;
    }
    return 1;
}

static const OSSL_PARAM *kdf_pbkdf2_settable_ctx_params(ossl_unused void *ctx,
    ossl_unused void *p_ctx)
{
    return pbkdf2_set_ctx_params_list;
}

static int kdf_pbkdf2_get_ctx_params(void *vctx, OSSL_PARAM params[])
{
    KDF_PBKDF2 *ctx = vctx;
    struct pbkdf2_get_ctx_params_st p;

    if (ctx == NULL || !pbkdf2_get_ctx_params_decoder(params, &p))
        return 0;

    if (p.size != NULL && !OSSL_PARAM_set_size_t(p.size, SIZE_MAX))
        return 0;

    if (!OSSL_FIPS_IND_GET_CTX_FROM_PARAM(ctx, p.ind))
        return 0;
    return 1;
}

static const OSSL_PARAM *kdf_pbkdf2_gettable_ctx_params(ossl_unused void *ctx,
    ossl_unused void *p_ctx)
{
    return pbkdf2_get_ctx_params_list;
}

const OSSL_DISPATCH ossl_kdf_pbkdf2_functions[] = {
    { OSSL_FUNC_KDF_NEWCTX, (void (*)(void))kdf_pbkdf2_new },
    { OSSL_FUNC_KDF_DUPCTX, (void (*)(void))kdf_pbkdf2_dup },
    { OSSL_FUNC_KDF_FREECTX, (void (*)(void))kdf_pbkdf2_free },
    { OSSL_FUNC_KDF_RESET, (void (*)(void))kdf_pbkdf2_reset },
    { OSSL_FUNC_KDF_DERIVE, (void (*)(void))kdf_pbkdf2_derive },
    { OSSL_FUNC_KDF_SETTABLE_CTX_PARAMS,
        (void (*)(void))kdf_pbkdf2_settable_ctx_params },
    { OSSL_FUNC_KDF_SET_CTX_PARAMS, (void (*)(void))kdf_pbkdf2_set_ctx_params },
    { OSSL_FUNC_KDF_GETTABLE_CTX_PARAMS,
        (void (*)(void))kdf_pbkdf2_gettable_ctx_params },
    { OSSL_FUNC_KDF_GET_CTX_PARAMS, (void (*)(void))kdf_pbkdf2_get_ctx_params },
    OSSL_DISPATCH_END
};

/*
 * This is an implementation of PKCS#5 v2.0 password based encryption key
 * derivation function PBKDF2. SHA1 version verified against test vectors
 * posted by Peter Gutmann to the PKCS-TNG mailing list.
 *
 * The constraints specified by SP800-132 have been added i.e.
 *  - Check the range of the key length.
 *  - Minimum iteration count of 1000.
 *  - Randomly-generated portion of the salt shall be at least 128 bits.
 */
static int pbkdf2_derive(KDF_PBKDF2 *ctx, const char *pass, size_t passlen,
    const unsigned char *salt, int saltlen, uint64_t iter,
    const EVP_MD *digest, unsigned char *key,
    size_t keylen, int lower_bound_checks)
{
    int ret = 0;
    unsigned char digtmp[EVP_MAX_MD_SIZE], *p, itmp[4];
    int cplen, k, tkeylen, mdlen;
    uint64_t j;
    unsigned long i = 1;
    HMAC_CTX *hctx_tpl = NULL, *hctx = NULL;

    mdlen = EVP_MD_get_size(digest);
    if (mdlen <= 0)
        return 0;

    /*
     * This check should always be done because keylen / mdlen >= (2^32 - 1)
     * results in an overflow of the loop counter 'i'.
     */
    if ((keylen / mdlen) >= KDF_PBKDF2_MAX_KEY_LEN_DIGEST_RATIO) {
        ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_KEY_LENGTH);
        return 0;
    }

    if (!lower_bound_check_passed(ctx, saltlen, iter, keylen, passlen, lower_bound_checks))
        return 0;

    hctx_tpl = HMAC_CTX_new();
    if (hctx_tpl == NULL)
        return 0;
    p = key;
    tkeylen = (int)keylen;
    if (!HMAC_Init_ex(hctx_tpl, pass, (int)passlen, digest, NULL))
        goto err;
    hctx = HMAC_CTX_new();
    if (hctx == NULL)
        goto err;
    while (tkeylen) {
        if (tkeylen > mdlen)
            cplen = mdlen;
        else
            cplen = tkeylen;
        /*
         * We are unlikely to ever use more than 256 blocks (5120 bits!) but
         * just in case...
         */
        itmp[0] = (unsigned char)((i >> 24) & 0xff);
        itmp[1] = (unsigned char)((i >> 16) & 0xff);
        itmp[2] = (unsigned char)((i >> 8) & 0xff);
        itmp[3] = (unsigned char)(i & 0xff);
        if (!HMAC_CTX_copy(hctx, hctx_tpl))
            goto err;
        if (!HMAC_Update(hctx, salt, saltlen)
            || !HMAC_Update(hctx, itmp, 4)
            || !HMAC_Final(hctx, digtmp, NULL))
            goto err;
        memcpy(p, digtmp, cplen);
        for (j = 1; j < iter; j++) {
            if (!HMAC_CTX_copy(hctx, hctx_tpl))
                goto err;
            if (!HMAC_Update(hctx, digtmp, mdlen)
                || !HMAC_Final(hctx, digtmp, NULL))
                goto err;
            for (k = 0; k < cplen; k++)
                p[k] ^= digtmp[k];
        }
        tkeylen -= cplen;
        i++;
        p += cplen;
    }
    ret = 1;

err:
    HMAC_CTX_free(hctx);
    HMAC_CTX_free(hctx_tpl);
    return ret;
}