/*

 * Copyright 2026 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

 */

#include <stdbool.h>

#include <openssl/evp.h>

#include <openssl/kdf.h>

#include <openssl/bn.h>

#include <openssl/core_names.h>

#include <openssl/proverr.h>

#include "internal/cryptlib.h"

#include "internal/fips.h"

#include "prov/provider_ctx.h"

#include "prov/providercommon.h"

#include "prov/implementations.h"

#include "prov/provider_util.h"

#include "providers/implementations/kdfs/srtpkdf.inc"

#define KDF_SRTP_AUTH_KEY_LEN 20

#define KDF_SRTP_SALT_KEY_LEN 14

#define KDF_SRTCP_AUTH_KEY_LEN KDF_SRTP_AUTH_KEY_LEN

#define KDF_SRTCP_SALT_KEY_LEN KDF_SRTP_SALT_KEY_LEN

#define KDF_SRTP_SALT_LEN 14

#define KDF_SRTP_KDR_LEN 6

#define KDF_SRTP_IDX_LEN 6

#define KDF_SRTCP_IDX_LEN 4

#define KDF_SRTP_IV_LEN 16

#define KDF_SRTP_MAX_KDR 24

#define KDF_SRTP_MAX_LABEL 7

#define KDF_SRTP_MAX_SALT_LEN (KDF_SRTP_SALT_LEN + 2)

/* See RFC 3711, Section 4.3.3 */

static OSSL_FUNC_kdf_newctx_fn kdf_srtpkdf_new;

static OSSL_FUNC_kdf_dupctx_fn kdf_srtpkdf_dup;

static OSSL_FUNC_kdf_freectx_fn kdf_srtpkdf_free;

static OSSL_FUNC_kdf_reset_fn kdf_srtpkdf_reset;

static OSSL_FUNC_kdf_derive_fn kdf_srtpkdf_derive;

static OSSL_FUNC_kdf_settable_ctx_params_fn kdf_srtpkdf_settable_ctx_params;

static OSSL_FUNC_kdf_set_ctx_params_fn kdf_srtpkdf_set_ctx_params;

static OSSL_FUNC_kdf_gettable_ctx_params_fn kdf_srtpkdf_gettable_ctx_params;

static OSSL_FUNC_kdf_get_ctx_params_fn kdf_srtpkdf_get_ctx_params;

static int SRTPKDF(OSSL_LIB_CTX *provctx, const EVP_CIPHER *cipher,

    const uint8_t *mkey, const uint8_t *msalt,

    const uint8_t *index, size_t index_len,

    const uint32_t kdr, const uint32_t kdr_n,

    const uint32_t label, uint8_t *obuffer, const size_t keylen);

typedef struct {

    /* Warning: Any changes to this structure may require you to update kdf_srtpkdf_dup */

    void *provctx;

    PROV_CIPHER cipher;

    unsigned char *key;

    size_t key_len;

    unsigned char *salt;

    size_t salt_len;

    unsigned char *index;

    size_t index_len;

    uint32_t kdr;

    uint32_t kdr_n; /* 2 ** kdr_n = kdr */

    uint32_t label;

} KDF_SRTPKDF;

static void *kdf_srtpkdf_new(void *provctx)

{

    KDF_SRTPKDF *ctx;

    if (!ossl_prov_is_running())

        return NULL;

#ifdef FIPS_MODULE

    if (!ossl_deferred_self_test(PROV_LIBCTX_OF(provctx),

            ST_ID_KDF_SRTPKDF))

        return NULL;

#endif

    if ((ctx = OPENSSL_zalloc(sizeof(*ctx))) != NULL)

        ctx->provctx = provctx;

    return ctx;

}

static void *kdf_srtpkdf_dup(void *vsrc)

{

    const KDF_SRTPKDF *src = (const KDF_SRTPKDF *)vsrc;

    KDF_SRTPKDF *dest;

    dest = kdf_srtpkdf_new(src->provctx);

    if (dest != NULL) {

        if (!ossl_prov_memdup(src->key, src->key_len,

                &dest->key, &dest->key_len)

            || !ossl_prov_memdup(src->salt, src->salt_len,

                &dest->salt, &dest->salt_len)

            || !ossl_prov_memdup(src->index, src->index_len,

                &dest->index, &dest->index_len)

            || !ossl_prov_cipher_copy(&dest->cipher, &src->cipher))

            goto err;

        dest->kdr = src->kdr;

        dest->kdr_n = src->kdr_n;

        dest->label = src->label;

    }

    return dest;

err:

    kdf_srtpkdf_free(dest);

    return NULL;

}

static void kdf_srtpkdf_free(void *vctx)

{

    KDF_SRTPKDF *ctx = (KDF_SRTPKDF *)vctx;

    if (ctx != NULL) {

        kdf_srtpkdf_reset(ctx);

        OPENSSL_free(ctx);

    }

}

static void kdf_srtpkdf_reset(void *vctx)

{

    KDF_SRTPKDF *ctx = (KDF_SRTPKDF *)vctx;

    void *provctx = ctx->provctx;

    ossl_prov_cipher_reset(&ctx->cipher);

    OPENSSL_clear_free(ctx->key, ctx->key_len);

    OPENSSL_clear_free(ctx->index, ctx->index_len);

    OPENSSL_clear_free(ctx->salt, ctx->salt_len);

    memset(ctx, 0, sizeof(*ctx));

    ctx->provctx = provctx;

}

static int srtpkdf_set_membuf(unsigned char **dst, size_t *dst_len,

    const OSSL_PARAM *p)

{

    OPENSSL_clear_free(*dst, *dst_len);

    *dst = NULL;

    *dst_len = 0;

    return OSSL_PARAM_get_octet_string(p, (void **)dst, 0, dst_len);

}

static int is_power_of_two(uint32_t x, uint32_t *n)

{

    /* Check if we've been given an exact power of two */

    if (x == 0 || (x & (x - 1)) != 0) {

        *n = 0;

        return 0;

    }

    /* Count the number of trailing bits in the passed value */

#ifdef __GNUC__

    *n = __builtin_ctz(x);

#else

    {

        uint32_t count = 0;

        while ((x & 1) == 0) {

            count++;

            x >>= 1;

        }

        *n = count;

    }

#endif

    return 1;

}

static int kdf_srtpkdf_check_key(KDF_SRTPKDF *ctx)

{

    const EVP_CIPHER *cipher = ossl_prov_cipher_cipher(&ctx->cipher);

    if (cipher != NULL) {

        if (ctx->key == NULL) {

            ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_KEY);

            return 0;

        }

        if (ctx->key_len != (size_t)EVP_CIPHER_get_key_length(cipher)) {

            ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_KEY_LENGTH);

            return 0;

        }

    }

    return 1;

}

static int kdf_srtpkdf_derive(void *vctx, unsigned char *key, size_t keylen,

    const OSSL_PARAM params[])

{

    KDF_SRTPKDF *ctx = (KDF_SRTPKDF *)vctx;

    const EVP_CIPHER *cipher;

    OSSL_LIB_CTX *libctx;

    if (!ossl_prov_is_running() || !kdf_srtpkdf_set_ctx_params(ctx, params))

        return 0;

    libctx = PROV_LIBCTX_OF(ctx->provctx);

    cipher = ossl_prov_cipher_cipher(&ctx->cipher);

    if (cipher == NULL) {

        ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_CIPHER);

        return 0;

    }

    if (!kdf_srtpkdf_check_key(ctx))

        return 0;

    if (ctx->salt == NULL) {

        ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_SALT);

        return 0;

    }

    return SRTPKDF(libctx, cipher, ctx->key, ctx->salt,

        ctx->index, ctx->index_len, ctx->kdr, ctx->kdr_n, ctx->label,

        key, keylen);

}

static int kdf_srtpkdf_set_ctx_params(void *vctx, const OSSL_PARAM params[])

{

    struct srtp_set_ctx_params_st p;

    KDF_SRTPKDF *ctx = vctx;

    OSSL_LIB_CTX *libctx;

    if (params == NULL)

        return 1;

    if (ctx == NULL || !srtp_set_ctx_params_decoder(params, &p))

        return 0;

    libctx = PROV_LIBCTX_OF(ctx->provctx);

    if (p.cipher != NULL) {

        const EVP_CIPHER *cipher = NULL;

        if (!ossl_prov_cipher_load(&ctx->cipher, p.cipher, p.propq, libctx))

            return 0;

        cipher = ossl_prov_cipher_cipher(&ctx->cipher);

        if (cipher == NULL)

            return 0;

        if (!EVP_CIPHER_is_a(cipher, "AES-128-CTR")

            && !EVP_CIPHER_is_a(cipher, "AES-192-CTR")

            && !EVP_CIPHER_is_a(cipher, "AES-256-CTR")) {

            ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_CIPHER);

            return 0;

        }

    }

    if (p.key != NULL) {

        if (!srtpkdf_set_membuf(&ctx->key, &ctx->key_len, p.key))

            return 0;

        if (!kdf_srtpkdf_check_key(ctx))

            return 0;

    }

    if (p.salt != NULL) {

        if (!srtpkdf_set_membuf(&ctx->salt, &ctx->salt_len, p.salt))

            return 0;

        if (ctx->salt_len < KDF_SRTP_SALT_LEN) {

            ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_SALT_LENGTH);

            return 0;

        }

    }

    if (p.kdr != NULL) {

        if (!OSSL_PARAM_get_uint32(p.kdr, &ctx->kdr))

            return 0;

        if (ctx->kdr > 0) {

            uint32_t n = 0;

            if (!is_power_of_two(ctx->kdr, &n)

                || n > KDF_SRTP_MAX_KDR) {

                ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_KDR);

                return 0;

            }

            ctx->kdr_n = n;

        }

    }

    if (p.label != NULL) {

        if (!OSSL_PARAM_get_uint32(p.label, &ctx->label))

            return 0;

        if (ctx->label > KDF_SRTP_MAX_LABEL) {

            ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_LABEL);

            return 0;

        }

    }

    if (p.index != NULL) {

        if (!srtpkdf_set_membuf(&ctx->index, &ctx->index_len, p.index))

            return 0;

        /*

         * Defer checking the index until the derive() since it is dependant

         * on values of kdr and label.

         */

    }

    return 1;

}

static const OSSL_PARAM *kdf_srtpkdf_settable_ctx_params(ossl_unused void *ctx,

    ossl_unused void *p_ctx)

{

    return srtp_set_ctx_params_list;

}

static int kdf_srtpkdf_get_ctx_params(void *vctx, OSSL_PARAM params[])

{

    struct srtp_get_ctx_params_st p;

    KDF_SRTPKDF *ctx = vctx;

    if (ctx == NULL || !srtp_get_ctx_params_decoder(params, &p))

        return 0;

    if (p.size != NULL) {

        size_t sz = EVP_CIPHER_key_length(ossl_prov_cipher_cipher(&ctx->cipher));

        if (!OSSL_PARAM_set_size_t(p.size, sz))

            return 0;

    }

    return 1;

}

static const OSSL_PARAM *kdf_srtpkdf_gettable_ctx_params(ossl_unused void *ctx,

    ossl_unused void *p_ctx)

{

    return srtp_get_ctx_params_list;

}

const OSSL_DISPATCH ossl_kdf_srtpkdf_functions[] = {

    { OSSL_FUNC_KDF_NEWCTX, (void (*)(void))kdf_srtpkdf_new },

    { OSSL_FUNC_KDF_DUPCTX, (void (*)(void))kdf_srtpkdf_dup },

    { OSSL_FUNC_KDF_FREECTX, (void (*)(void))kdf_srtpkdf_free },

    { OSSL_FUNC_KDF_RESET, (void (*)(void))kdf_srtpkdf_reset },

    { OSSL_FUNC_KDF_DERIVE, (void (*)(void))kdf_srtpkdf_derive },

    { OSSL_FUNC_KDF_SETTABLE_CTX_PARAMS,

        (void (*)(void))kdf_srtpkdf_settable_ctx_params },

    { OSSL_FUNC_KDF_SET_CTX_PARAMS,

        (void (*)(void))kdf_srtpkdf_set_ctx_params },

    { OSSL_FUNC_KDF_GETTABLE_CTX_PARAMS,

        (void (*)(void))kdf_srtpkdf_gettable_ctx_params },

    { OSSL_FUNC_KDF_GET_CTX_PARAMS,

        (void (*)(void))kdf_srtpkdf_get_ctx_params },

    { 0, NULL }

};

static bool is_srtp(uint32_t label)

{

    static const bool strp_table[] = {

        true, /* 0 */

        true, /* 1 */

        true, /* 2 */

        false, /* 3 */

        false, /* 4 */

        false, /* 5 */

        true, /* 6 */

        true, /* 7 */

    };

    return strp_table[label];

}

/*

 * SRTPKDF - In compliance with SP800-135 and RFC3711, calculate

 *           various keys defined by label using a master key,

 *           master salt, kdr(if non-zero) and index.

 *

 * Denote the cryptographic key (encryption key, cipher salt or

 * authentication key(HMAC key), etc) to be derived as K. The

 * length of K is denoted by L. Below is a description of the KDF.

 *

 * master_salt: a random non-salt value.

 * kdr: the key derivation rate. kdr is a number from the set

 *   factor of 2.

 * index: a 48-bit value in RTP or a 32-bit value in RTCP.

 *   See Sections 3.2.1 and 4.3.2 of RFC 3711 for details.

 * A function, DIV, is defined as followed:

 *   a and x are non-negative integers.

 *   a DIV x =  a | x (a DIV x) is represented as a bit string whose

 *   length (in bits) is the same as a.

 * label: an 8-bit value represented by two hexadecimal numbers from

 *   the set of {0x00,0x01, 0x02, 0x03, 0x04, 0x05}.

 *   https://www.ietf.org/archive/id/draft-ietf-avtcore-srtp-encrypted-header-ext-01.html

 *   The values 06 and 07 are used.

 * key_id = label || (index DIV kdr)

 *

 * Input:

 *   cipher - AES cipher

 *   mkey - pointer to master key

 *   msalt - pointer to master salt

 *   index - pointer to index

 *   idxlen - size of the index buffer

 *   kdr - key derivation rate

 *   kdr_n - power of kdr (2**kdr_n = kdr)

 *   label - 8-bit label

 *   keylen - size of obuffer

 * Output:

 *   obuffer - filled with derived key

 *   return - 1 on pass, 0 fail

 */

int SRTPKDF(OSSL_LIB_CTX *provctx, const EVP_CIPHER *cipher,

    const uint8_t *mkey, const uint8_t *msalt,

    const uint8_t *index, size_t idxlen,

    const uint32_t kdr, const uint32_t kdr_n,

    const uint32_t label, uint8_t *obuffer, const size_t keylen)

{

    EVP_CIPHER_CTX *ctx = NULL;

    int outl, i, index_len = 0, o_len = 0, salt_len = 0;

    uint8_t buf[EVP_MAX_KEY_LENGTH];

    uint8_t iv[KDF_SRTP_IV_LEN];

    uint8_t local_salt[KDF_SRTP_MAX_SALT_LEN];

    uint8_t master_salt[KDF_SRTP_MAX_SALT_LEN];

    BIGNUM *bn_index = NULL, *bn_salt = NULL;

    int ret, iv_len = KDF_SRTP_IV_LEN, rv = 0;

    if (obuffer == NULL || keylen > INT_MAX)

        return rv;

    /* get label-specific lengths */

    switch (label) {

    case 0:

    case 3:

    case 6:

        o_len = EVP_CIPHER_key_length(cipher);

        break;

    case 1:

        o_len = KDF_SRTP_AUTH_KEY_LEN;

        break;

    case 4:

        o_len = KDF_SRTCP_AUTH_KEY_LEN;

        break;

    case 2:

    case 7:

        o_len = KDF_SRTP_SALT_KEY_LEN;

        break;

    case 5:

        o_len = KDF_SRTCP_SALT_KEY_LEN;

        break;

    default:

        return rv;

    }

    if (o_len > (int)keylen)

        return rv;

    /* set up a couple of work areas for the final logic on the salt */

    salt_len = KDF_SRTP_SALT_LEN;

    memset(iv, 0, KDF_SRTP_IV_LEN);

    memset(master_salt, 0, sizeof(master_salt));

    memcpy(master_salt, msalt, salt_len);

    /* gather some bignums for some math */

    bn_index = BN_new();

    bn_salt = BN_new();

    if ((bn_index == NULL) || (bn_salt == NULL)) {

        BN_free(bn_index);

        BN_free(bn_salt);

        return rv;

    }

    index_len = is_srtp(label) ? KDF_SRTP_IDX_LEN : KDF_SRTCP_IDX_LEN;

    /* if index is NULL or kdr=0, then index and kdr are not in play */

    if (index != NULL && idxlen > 0 && kdr > 0) {

        if ((int)idxlen < index_len) {

            ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_INDEX_LENGTH);

            goto err;

        }

        if (!BN_bin2bn(index, index_len, bn_index))

            goto err;

        ret = BN_rshift(bn_salt, bn_index, kdr_n);

        if (!ret)

            goto err;

        iv_len = BN_bn2bin(bn_salt, iv);

        for (i = 1; i <= iv_len; i++)

            master_salt[salt_len - i] ^= iv[iv_len - i];

    }

    /* take the munged up salt from above and add the label */

    memset(local_salt, 0, KDF_SRTP_MAX_SALT_LEN);

    memcpy(local_salt, master_salt, salt_len);

    local_salt[((KDF_SRTP_SALT_LEN - 1) - index_len)] ^= label;

    /* perform the AES encryption on the master key and derived salt */

    memset(buf, 0, o_len);

    if (!(ctx = EVP_CIPHER_CTX_new())

        || (EVP_EncryptInit_ex(ctx, cipher, NULL, mkey, local_salt) <= 0)

        || (EVP_CIPHER_CTX_set_padding(ctx, 0) <= 0)

        || (EVP_EncryptUpdate(ctx, (unsigned char *)obuffer, &outl, buf, o_len) <= 0)

        || (EVP_EncryptFinal_ex(ctx, (unsigned char *)obuffer, &outl) <= 0))

        goto err;

    rv = 1;

err:

    EVP_CIPHER_CTX_free(ctx);

    OPENSSL_cleanse(iv, KDF_SRTP_IV_LEN);

    OPENSSL_cleanse(local_salt, KDF_SRTP_MAX_SALT_LEN);

    OPENSSL_cleanse(master_salt, KDF_SRTP_IV_LEN);

    BN_clear_free(bn_index);

    BN_clear_free(bn_salt);

    return rv;

}