/*

 * Copyright 1995-2026 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 <limits.h>

#include <stdio.h>

#include "internal/cryptlib.h"

#include <openssl/asn1.h>

#include "asn1_local.h"

#include <crypto/asn1.h>

static void

asn1_bit_string_clear_unused_bits(ASN1_BIT_STRING *abs)

{

    abs->flags &= ~(ASN1_STRING_FLAG_BITS_LEFT | 0x07);

}

static int asn1_bit_string_set_unused_bits(ASN1_BIT_STRING *abs,

    uint8_t unused_bits)

{

    if (unused_bits > 7)

        return 0;

    asn1_bit_string_clear_unused_bits(abs);

    abs->flags |= ASN1_STRING_FLAG_BITS_LEFT | unused_bits;

    return 1;

}

int ASN1_BIT_STRING_set(ASN1_BIT_STRING *x, unsigned char *d, int len)

{

    return ASN1_STRING_set(x, d, len);

}

int ossl_i2c_ASN1_BIT_STRING(const ASN1_BIT_STRING *a, unsigned char **pp)

{

    int ret = 0, bits = 0, len;

    unsigned char *p, *d;

    if (a == NULL)

        goto err;

    len = a->length;

    if (len > INT_MAX - 1)

        goto err;

    if ((len > 0) && (a->flags & ASN1_STRING_FLAG_BITS_LEFT))

        bits = (int)a->flags & 0x07;

    if (pp == NULL)

        goto done;

    p = *pp;

    *(p++) = (unsigned char)bits;

    d = a->data;

    if (len > 0) {

        memcpy(p, d, len);

        p += len;

        p[-1] &= (0xff << bits);

    }

    *pp = p;

done:

    ret = len + 1;

err:

    return ret;

}

ASN1_BIT_STRING *ossl_c2i_ASN1_BIT_STRING(ASN1_BIT_STRING **a,

    const unsigned char **pp, long len)

{

    ASN1_BIT_STRING *ret = NULL;

    const unsigned char *p;

    unsigned char *s;

    int i = 0;

    if (len < 1) {

        i = ASN1_R_STRING_TOO_SHORT;

        goto err;

    }

    if (len > INT_MAX) {

        i = ASN1_R_STRING_TOO_LONG;

        goto err;

    }

    if ((a == NULL) || ((*a) == NULL)) {

        if ((ret = ASN1_BIT_STRING_new()) == NULL)

            return NULL;

    } else

        ret = (*a);

    p = *pp;

    i = *(p++);

    if (i > 7) {

        i = ASN1_R_INVALID_BIT_STRING_BITS_LEFT;

        goto err;

    }

    /*

     * We do this to preserve the settings.  If we modify the settings, via

     * the _set_bit function, we will recalculate on output

     */

    ossl_asn1_string_set_bits_left(ret, i);

    if (len-- > 1) { /* using one because of the bits left byte */

        s = OPENSSL_malloc((int)len);

        if (s == NULL) {

            goto err;

        }

        memcpy(s, p, (int)len);

        s[len - 1] &= (0xff << i);

        p += len;

    } else

        s = NULL;

    ASN1_STRING_set0(ret, s, (int)len);

    ret->type = V_ASN1_BIT_STRING;

    if (a != NULL)

        (*a) = ret;

    *pp = p;

    return ret;

err:

    if (i != 0)

        ERR_raise(ERR_LIB_ASN1, i);

    if ((a == NULL) || (*a != ret))

        ASN1_BIT_STRING_free(ret);

    return NULL;

}

/*

 * These next 2 functions from Goetz Babin-Ebell.

 */

int ASN1_BIT_STRING_set_bit(ASN1_BIT_STRING *a, int n, int value)

{

    int w, v, iv;

    unsigned char *c;

    if (n < 0)

        return 0;

    w = n / 8;

    v = 1 << (7 - (n & 0x07));

    iv = ~v;

    if (!value)

        v = 0;

    if (a == NULL)

        return 0;

    a->flags &= ~(ASN1_STRING_FLAG_BITS_LEFT | 0x07); /* clear, set on write */

    if ((a->length < (w + 1)) || (a->data == NULL)) {

        if (!value)

            return 1; /* Don't need to set */

        c = OPENSSL_clear_realloc(a->data, a->length, w + 1);

        if (c == NULL)

            return 0;

        if (w + 1 - a->length > 0)

            memset(c + a->length, 0, w + 1 - a->length);

        a->data = c;

        a->length = w + 1;

    }

    a->data[w] = ((a->data[w]) & iv) | v;

    while ((a->length > 0) && (a->data[a->length - 1] == 0))

        a->length--;

    if (a->length > 0) {

        uint8_t u8 = a->data[a->length - 1];

        uint8_t unused_bits = 7;

        /* Only keep least significant bit; count trailing zeroes. */

        u8 &= 0x100 - u8;

        if ((u8 & 0x0f) != 0)

            unused_bits -= 4;

        if ((u8 & 0x33) != 0)

            unused_bits -= 2;

        if ((u8 & 0x55) != 0)

            unused_bits -= 1;

        if (!asn1_bit_string_set_unused_bits(a, unused_bits))

            return 0;

    }

    return 1;

}

int ASN1_BIT_STRING_get_bit(const ASN1_BIT_STRING *a, int n)

{

    int w, v;

    if (n < 0)

        return 0;

    w = n / 8;

    v = 1 << (7 - (n & 0x07));

    if ((a == NULL) || (a->length < (w + 1)) || (a->data == NULL))

        return 0;

    return ((a->data[w] & v) != 0);

}

/*

 * Checks if the given bit string contains only bits specified by

 * the flags vector. Returns 0 if there is at least one bit set in 'a'

 * which is not specified in 'flags', 1 otherwise.

 * 'len' is the length of 'flags'.

 */

int ASN1_BIT_STRING_check(const ASN1_BIT_STRING *a,

    const unsigned char *flags, int flags_len)

{

    int i, ok;

    /* Check if there is one bit set at all. */

    if (!a || !a->data)

        return 1;

    /*

     * Check each byte of the internal representation of the bit string.

     */

    ok = 1;

    for (i = 0; i < a->length && ok; ++i) {

        unsigned char mask = i < flags_len ? ~flags[i] : 0xff;

        /* We are done if there is an unneeded bit set. */

        ok = (a->data[i] & mask) == 0;

    }

    return ok;

}

int ASN1_BIT_STRING_get_length(const ASN1_BIT_STRING *abs, size_t *out_length,

    int *out_unused_bits)

{

    size_t length;

    int unused_bits;

    if (abs == NULL || abs->type != V_ASN1_BIT_STRING)

        return 0;

    if (out_length == NULL || out_unused_bits == NULL)

        return 0;

    length = abs->length;

    unused_bits = 0;

    if ((abs->flags & ASN1_STRING_FLAG_BITS_LEFT) != 0)

        unused_bits = abs->flags & 0x07;

    if (length == 0 && unused_bits != 0)

        return 0;

    if (unused_bits != 0) {

        unsigned char mask = (1 << unused_bits) - 1;

        if ((abs->data[length - 1] & mask) != 0)

            return 0;

    }

    *out_length = length;

    *out_unused_bits = unused_bits;

    return 1;

}

int ASN1_BIT_STRING_set1(ASN1_BIT_STRING *abs, const uint8_t *data, size_t length,

    int unused_bits)

{

    if (abs == NULL)

        return 0;

    if (length > INT_MAX || unused_bits < 0 || unused_bits > 7)

        return 0;

    if (length == 0 && unused_bits != 0)

        return 0;

    if (length > 0 && (data[length - 1] & ((1 << unused_bits) - 1)) != 0)

        return 0;

    /*

     * XXX - ASN1_STRING_set() and asn1_bit_string_set_unused_bits() preserve the

     * state of flags irrelevant to ASN1_BIT_STRING. Should we explicitly

     * clear them?

     */

    if (!ASN1_STRING_set(abs, data, (int)length))

        return 0;

    abs->type = V_ASN1_BIT_STRING;

    return asn1_bit_string_set_unused_bits(abs, unused_bits);

}