/*

 * Copyright 2014-2025 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

 */

#include <string.h>

#include <openssl/crypto.h>

#include <openssl/err.h>

#include "crypto/modes.h"

#ifndef OPENSSL_NO_OCB

/*

 * Calculate the number of binary trailing zero's in any given number

 */

static u32 ocb_ntz(u64 n)

{

    u32 cnt = 0;

    /*

     * We do a right-to-left simple sequential search. This is surprisingly

     * efficient as the distribution of trailing zeros is not uniform,

     * e.g. the number of possible inputs with no trailing zeros is equal to

     * the number with 1 or more; the number with exactly 1 is equal to the

     * number with 2 or more, etc. Checking the last two bits covers 75% of

     * all numbers. Checking the last three covers 87.5%

     */

    while (!(n & 1)) {

        n >>= 1;

        cnt++;

    }

    return cnt;

}

/*

 * Shift a block of 16 bytes left by shift bits

 */

static void ocb_block_lshift(const unsigned char *in, size_t shift,

    unsigned char *out)

{

    int i;

    unsigned char carry = 0, carry_next;

    for (i = 15; i >= 0; i--) {

        carry_next = in[i] >> (8 - shift);

        out[i] = (in[i] << shift) | carry;

        carry = carry_next;

    }

}

/*

 * Perform a "double" operation as per OCB spec

 */

static void ocb_double(OCB_BLOCK *in, OCB_BLOCK *out)

{

    unsigned char mask;

    /*

     * Calculate the mask based on the most significant bit. There are more

     * efficient ways to do this - but this way is constant time

     */

    mask = in->c[0] & 0x80;

    mask >>= 7;

    mask = (0 - mask) & 0x87;

    ocb_block_lshift(in->c, 1, out->c);

    out->c[15] ^= mask;

}

/*

 * Perform an xor on in1 and in2 - each of len bytes. Store result in out

 */

static void ocb_block_xor(const unsigned char *in1,

    const unsigned char *in2, size_t len,

    unsigned char *out)

{

    size_t i;

    for (i = 0; i < len; i++) {

        out[i] = in1[i] ^ in2[i];

    }

}

/*

 * Lookup L_index in our lookup table. If we haven't already got it we need to

 * calculate it

 */

static OCB_BLOCK *ocb_lookup_l(OCB128_CONTEXT *ctx, size_t idx)

{

    size_t l_index = ctx->l_index;

    if (idx <= l_index) {

        return ctx->l + idx;

    }

    /* We don't have it - so calculate it */

    if (idx >= ctx->max_l_index) {

        void *tmp_ptr;

        /*

         * Each additional entry allows to process almost double as

         * much data, so that in linear world the table will need to

         * be expanded with smaller and smaller increments. Originally

         * it was doubling in size, which was a waste. Growing it

         * linearly is not formally optimal, but is simpler to implement.

         * We grow table by minimally required 4*n that would accommodate

         * the index.

         */

        ctx->max_l_index += (idx - ctx->max_l_index + 4) & ~3;

        tmp_ptr = OPENSSL_realloc_array(ctx->l, ctx->max_l_index, sizeof(OCB_BLOCK));

        if (tmp_ptr == NULL) /* prevent ctx->l from being clobbered */

            return NULL;

        ctx->l = tmp_ptr;

    }

    while (l_index < idx) {

        ocb_double(ctx->l + l_index, ctx->l + l_index + 1);

        l_index++;

    }

    ctx->l_index = l_index;

    return ctx->l + idx;

}

/*

 * Create a new OCB128_CONTEXT

 */

OCB128_CONTEXT *CRYPTO_ocb128_new(void *keyenc, void *keydec,

    block128_f encrypt, block128_f decrypt,

    ocb128_f stream)

{

    OCB128_CONTEXT *octx;

    int ret;

    if ((octx = OPENSSL_malloc(sizeof(*octx))) != NULL) {

        ret = CRYPTO_ocb128_init(octx, keyenc, keydec, encrypt, decrypt,

            stream);

        if (ret)

            return octx;

        OPENSSL_free(octx);

    }

    return NULL;

}

/*

 * Initialise an existing OCB128_CONTEXT

 */

int CRYPTO_ocb128_init(OCB128_CONTEXT *ctx, void *keyenc, void *keydec,

    block128_f encrypt, block128_f decrypt,

    ocb128_f stream)

{

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

    ctx->l_index = 0;

    ctx->max_l_index = 5;

    if ((ctx->l = OPENSSL_malloc_array(ctx->max_l_index, 16)) == NULL)

        return 0;

    /*

     * We set both the encryption and decryption key schedules - decryption

     * needs both. Don't really need decryption schedule if only doing

     * encryption - but it simplifies things to take it anyway

     */

    ctx->encrypt = encrypt;

    ctx->decrypt = decrypt;

    ctx->stream = stream;

    ctx->keyenc = keyenc;

    ctx->keydec = keydec;

    /* L_* = ENCIPHER(K, zeros(128)) */

    ctx->encrypt(ctx->l_star.c, ctx->l_star.c, ctx->keyenc);

    /* L_$ = double(L_*) */

    ocb_double(&ctx->l_star, &ctx->l_dollar);

    /* L_0 = double(L_$) */

    ocb_double(&ctx->l_dollar, ctx->l);

    /* L_{i} = double(L_{i-1}) */

    ocb_double(ctx->l, ctx->l + 1);

    ocb_double(ctx->l + 1, ctx->l + 2);

    ocb_double(ctx->l + 2, ctx->l + 3);

    ocb_double(ctx->l + 3, ctx->l + 4);

    ctx->l_index = 4; /* enough to process up to 496 bytes */

    return 1;

}

/*

 * Copy an OCB128_CONTEXT object

 */

int CRYPTO_ocb128_copy_ctx(OCB128_CONTEXT *dest, OCB128_CONTEXT *src,

    void *keyenc, void *keydec)

{

    memcpy(dest, src, sizeof(OCB128_CONTEXT));

    if (keyenc)

        dest->keyenc = keyenc;

    if (keydec)

        dest->keydec = keydec;

    if (src->l) {

        if ((dest->l = OPENSSL_malloc_array(src->max_l_index, 16)) == NULL)

            return 0;

        memcpy(dest->l, src->l, (src->l_index + 1) * 16);

    }

    return 1;

}

/*

 * Set the IV to be used for this operation. Must be 1 - 15 bytes.

 */

int CRYPTO_ocb128_setiv(OCB128_CONTEXT *ctx, const unsigned char *iv,

    size_t len, size_t taglen)

{

    unsigned char ktop[16], tmp[16], mask;

    unsigned char stretch[24], nonce[16];

    size_t bottom, shift;

    /*

     * Spec says IV is 120 bits or fewer - it allows non byte aligned lengths.

     * We don't support this at this stage

     */

    if ((len > 15) || (len < 1) || (taglen > 16) || (taglen < 1)) {

        return -1;

    }

    /* Reset nonce-dependent variables */

    memset(&ctx->sess, 0, sizeof(ctx->sess));

    /* Nonce = num2str(TAGLEN mod 128,7) || zeros(120-bitlen(N)) || 1 || N */

    nonce[0] = ((taglen * 8) % 128) << 1;

    memset(nonce + 1, 0, 15);

    memcpy(nonce + 16 - len, iv, len);

    nonce[15 - len] |= 1;

    /* Ktop = ENCIPHER(K, Nonce[1..122] || zeros(6)) */

    memcpy(tmp, nonce, 16);

    tmp[15] &= 0xc0;

    ctx->encrypt(tmp, ktop, ctx->keyenc);

    /* Stretch = Ktop || (Ktop[1..64] xor Ktop[9..72]) */

    memcpy(stretch, ktop, 16);

    ocb_block_xor(ktop, ktop + 1, 8, stretch + 16);

    /* bottom = str2num(Nonce[123..128]) */

    bottom = nonce[15] & 0x3f;

    /* Offset_0 = Stretch[1+bottom..128+bottom] */

    shift = bottom % 8;

    ocb_block_lshift(stretch + (bottom / 8), shift, ctx->sess.offset.c);

    mask = 0xff;

    mask <<= 8 - shift;

    ctx->sess.offset.c[15] |= (*(stretch + (bottom / 8) + 16) & mask) >> (8 - shift);

    return 1;

}

/*

 * Provide any AAD. This can be called multiple times. Only the final time can

 * have a partial block

 */

int CRYPTO_ocb128_aad(OCB128_CONTEXT *ctx, const unsigned char *aad,

    size_t len)

{

    u64 i, all_num_blocks;

    size_t num_blocks, last_len;

    OCB_BLOCK tmp;

    /* Calculate the number of blocks of AAD provided now, and so far */

    num_blocks = len / 16;

    all_num_blocks = num_blocks + ctx->sess.blocks_hashed;

    /* Loop through all full blocks of AAD */

    for (i = ctx->sess.blocks_hashed + 1; i <= all_num_blocks; i++) {

        OCB_BLOCK *lookup;

        /* Offset_i = Offset_{i-1} xor L_{ntz(i)} */

        lookup = ocb_lookup_l(ctx, ocb_ntz(i));

        if (lookup == NULL)

            return 0;

        ocb_block16_xor(&ctx->sess.offset_aad, lookup, &ctx->sess.offset_aad);

        memcpy(tmp.c, aad, 16);

        aad += 16;

        /* Sum_i = Sum_{i-1} xor ENCIPHER(K, A_i xor Offset_i) */

        ocb_block16_xor(&ctx->sess.offset_aad, &tmp, &tmp);

        ctx->encrypt(tmp.c, tmp.c, ctx->keyenc);

        ocb_block16_xor(&tmp, &ctx->sess.sum, &ctx->sess.sum);

    }

    /*

     * Check if we have any partial blocks left over. This is only valid in the

     * last call to this function

     */

    last_len = len % 16;

    if (last_len > 0) {

        /* Offset_* = Offset_m xor L_* */

        ocb_block16_xor(&ctx->sess.offset_aad, &ctx->l_star,

            &ctx->sess.offset_aad);

        /* CipherInput = (A_* || 1 || zeros(127-bitlen(A_*))) xor Offset_* */

        memset(tmp.c, 0, 16);

        memcpy(tmp.c, aad, last_len);

        tmp.c[last_len] = 0x80;

        ocb_block16_xor(&ctx->sess.offset_aad, &tmp, &tmp);

        /* Sum = Sum_m xor ENCIPHER(K, CipherInput) */

        ctx->encrypt(tmp.c, tmp.c, ctx->keyenc);

        ocb_block16_xor(&tmp, &ctx->sess.sum, &ctx->sess.sum);

    }

    ctx->sess.blocks_hashed = all_num_blocks;

    return 1;

}

/*

 * Provide any data to be encrypted. This can be called multiple times. Only

 * the final time can have a partial block

 */

int CRYPTO_ocb128_encrypt(OCB128_CONTEXT *ctx,

    const unsigned char *in, unsigned char *out,

    size_t len)

{

    u64 i, all_num_blocks;

    size_t num_blocks, last_len;

    /*

     * Calculate the number of blocks of data to be encrypted provided now, and

     * so far

     */

    num_blocks = len / 16;

    all_num_blocks = num_blocks + ctx->sess.blocks_processed;

    if (num_blocks && all_num_blocks == (size_t)all_num_blocks

        && ctx->stream != NULL) {

        size_t max_idx = 0, top = (size_t)all_num_blocks;

        /*

         * See how many L_{i} entries we need to process data at hand

         * and pre-compute missing entries in the table [if any]...

         */

        while (top >>= 1)

            max_idx++;

        if (ocb_lookup_l(ctx, max_idx) == NULL)

            return 0;

        ctx->stream(in, out, num_blocks, ctx->keyenc,

            (size_t)ctx->sess.blocks_processed + 1, ctx->sess.offset.c,

            (const unsigned char (*)[16])ctx->l, ctx->sess.checksum.c);

    } else {

        /* Loop through all full blocks to be encrypted */

        for (i = ctx->sess.blocks_processed + 1; i <= all_num_blocks; i++) {

            OCB_BLOCK *lookup;

            OCB_BLOCK tmp;

            /* Offset_i = Offset_{i-1} xor L_{ntz(i)} */

            lookup = ocb_lookup_l(ctx, ocb_ntz(i));

            if (lookup == NULL)

                return 0;

            ocb_block16_xor(&ctx->sess.offset, lookup, &ctx->sess.offset);

            memcpy(tmp.c, in, 16);

            in += 16;

            /* Checksum_i = Checksum_{i-1} xor P_i */

            ocb_block16_xor(&tmp, &ctx->sess.checksum, &ctx->sess.checksum);

            /* C_i = Offset_i xor ENCIPHER(K, P_i xor Offset_i) */

            ocb_block16_xor(&ctx->sess.offset, &tmp, &tmp);

            ctx->encrypt(tmp.c, tmp.c, ctx->keyenc);

            ocb_block16_xor(&ctx->sess.offset, &tmp, &tmp);

            memcpy(out, tmp.c, 16);

            out += 16;

        }

    }

    /*

     * Check if we have any partial blocks left over. This is only valid in the

     * last call to this function

     */

    last_len = len % 16;

    if (last_len > 0) {

        OCB_BLOCK pad;

        /* Offset_* = Offset_m xor L_* */

        ocb_block16_xor(&ctx->sess.offset, &ctx->l_star, &ctx->sess.offset);

        /* Pad = ENCIPHER(K, Offset_*) */

        ctx->encrypt(ctx->sess.offset.c, pad.c, ctx->keyenc);

        /* C_* = P_* xor Pad[1..bitlen(P_*)] */

        ocb_block_xor(in, pad.c, last_len, out);

        /* Checksum_* = Checksum_m xor (P_* || 1 || zeros(127-bitlen(P_*))) */

        memset(pad.c, 0, 16); /* borrow pad */

        memcpy(pad.c, in, last_len);

        pad.c[last_len] = 0x80;

        ocb_block16_xor(&pad, &ctx->sess.checksum, &ctx->sess.checksum);

    }

    ctx->sess.blocks_processed = all_num_blocks;

    return 1;

}

/*

 * Provide any data to be decrypted. This can be called multiple times. Only

 * the final time can have a partial block

 */

int CRYPTO_ocb128_decrypt(OCB128_CONTEXT *ctx,

    const unsigned char *in, unsigned char *out,

    size_t len)

{

    u64 i, all_num_blocks;

    size_t num_blocks, last_len;

    /*

     * Calculate the number of blocks of data to be decrypted provided now, and

     * so far

     */

    num_blocks = len / 16;

    all_num_blocks = num_blocks + ctx->sess.blocks_processed;

    if (num_blocks && all_num_blocks == (size_t)all_num_blocks

        && ctx->stream != NULL) {

        size_t max_idx = 0, top = (size_t)all_num_blocks;

        /*

         * See how many L_{i} entries we need to process data at hand

         * and pre-compute missing entries in the table [if any]...

         */

        while (top >>= 1)

            max_idx++;

        if (ocb_lookup_l(ctx, max_idx) == NULL)

            return 0;

        ctx->stream(in, out, num_blocks, ctx->keydec,

            (size_t)ctx->sess.blocks_processed + 1, ctx->sess.offset.c,

            (const unsigned char (*)[16])ctx->l, ctx->sess.checksum.c);

    } else {

        OCB_BLOCK tmp;

        /* Loop through all full blocks to be decrypted */

        for (i = ctx->sess.blocks_processed + 1; i <= all_num_blocks; i++) {

            /* Offset_i = Offset_{i-1} xor L_{ntz(i)} */

            OCB_BLOCK *lookup = ocb_lookup_l(ctx, ocb_ntz(i));

            if (lookup == NULL)

                return 0;

            ocb_block16_xor(&ctx->sess.offset, lookup, &ctx->sess.offset);

            memcpy(tmp.c, in, 16);

            in += 16;

            /* P_i = Offset_i xor DECIPHER(K, C_i xor Offset_i) */

            ocb_block16_xor(&ctx->sess.offset, &tmp, &tmp);

            ctx->decrypt(tmp.c, tmp.c, ctx->keydec);

            ocb_block16_xor(&ctx->sess.offset, &tmp, &tmp);

            /* Checksum_i = Checksum_{i-1} xor P_i */

            ocb_block16_xor(&tmp, &ctx->sess.checksum, &ctx->sess.checksum);

            memcpy(out, tmp.c, 16);

            out += 16;

        }

    }

    /*

     * Check if we have any partial blocks left over. This is only valid in the

     * last call to this function

     */

    last_len = len % 16;

    if (last_len > 0) {

        OCB_BLOCK pad;

        /* Offset_* = Offset_m xor L_* */

        ocb_block16_xor(&ctx->sess.offset, &ctx->l_star, &ctx->sess.offset);

        /* Pad = ENCIPHER(K, Offset_*) */

        ctx->encrypt(ctx->sess.offset.c, pad.c, ctx->keyenc);

        /* P_* = C_* xor Pad[1..bitlen(C_*)] */

        ocb_block_xor(in, pad.c, last_len, out);

        /* Checksum_* = Checksum_m xor (P_* || 1 || zeros(127-bitlen(P_*))) */

        memset(pad.c, 0, 16); /* borrow pad */

        memcpy(pad.c, out, last_len);

        pad.c[last_len] = 0x80;

        ocb_block16_xor(&pad, &ctx->sess.checksum, &ctx->sess.checksum);

    }

    ctx->sess.blocks_processed = all_num_blocks;

    return 1;

}

static int ocb_finish(OCB128_CONTEXT *ctx, unsigned char *tag, size_t len,

    int write)

{

    OCB_BLOCK tmp;

    if (len > 16 || len < 1) {

        return -1;

    }

    /*

     * Tag = ENCIPHER(K, Checksum_* xor Offset_* xor L_$) xor HASH(K,A)

     */

    ocb_block16_xor(&ctx->sess.checksum, &ctx->sess.offset, &tmp);

    ocb_block16_xor(&ctx->l_dollar, &tmp, &tmp);

    ctx->encrypt(tmp.c, tmp.c, ctx->keyenc);

    ocb_block16_xor(&tmp, &ctx->sess.sum, &tmp);

    if (write) {

        memcpy(tag, &tmp, len);

        return 1;

    } else {

        return CRYPTO_memcmp(&tmp, tag, len);

    }

}

/*

 * Calculate the tag and verify it against the supplied tag

 */

int CRYPTO_ocb128_finish(OCB128_CONTEXT *ctx, const unsigned char *tag,

    size_t len)

{

    return ocb_finish(ctx, (unsigned char *)tag, len, 0);

}

/*

 * Retrieve the calculated tag

 */

int CRYPTO_ocb128_tag(OCB128_CONTEXT *ctx, unsigned char *tag, size_t len)

{

    return ocb_finish(ctx, tag, len, 1);

}

/*

 * Release all resources

 */

void CRYPTO_ocb128_cleanup(OCB128_CONTEXT *ctx)

{

    if (ctx) {

        OPENSSL_clear_free(ctx->l, ctx->max_l_index * 16);

        OPENSSL_cleanse(ctx, sizeof(*ctx));

    }

}

#endif /* OPENSSL_NO_OCB */