crypto/asn1/a_bitstr.c

/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
 * All rights reserved.
 *
 * This package is an SSL implementation written
 * by Eric Young (eay@cryptsoft.com).
 * The implementation was written so as to conform with Netscapes SSL.
 *
 * This library is free for commercial and non-commercial use as long as
 * the following conditions are aheared to.  The following conditions
 * apply to all code found in this distribution, be it the RC4, RSA,
 * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
 * included with this distribution is covered by the same copyright terms
 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
 *
 * Copyright remains Eric Young's, and as such any Copyright notices in
 * the code are not to be removed.
 * If this package is used in a product, Eric Young should be given attribution
 * as the author of the parts of the library used.
 * This can be in the form of a textual message at program startup or
 * in documentation (online or textual) provided with the package.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *    "This product includes cryptographic software written by
 *     Eric Young (eay@cryptsoft.com)"
 *    The word 'cryptographic' can be left out if the rouines from the library
 *    being used are not cryptographic related :-).
 * 4. If you include any Windows specific code (or a derivative thereof) from
 *    the apps directory (application code) you must include an acknowledgement:
 *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
 *
 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * The licence and distribution terms for any publically available version or
 * derivative of this code cannot be changed.  i.e. this code cannot simply be
 * copied and put under another distribution licence
 * [including the GNU Public Licence.] */

#include <openssl/asn1.h>

#include <limits.h>
#include <string.h>

#include <openssl/err.h>
#include <openssl/mem.h>

#include "../internal.h"


int ASN1_BIT_STRING_set(ASN1_BIT_STRING *x, const unsigned char *d, int len)
{
    return ASN1_STRING_set(x, d, len);
}

static int asn1_bit_string_length(const ASN1_BIT_STRING *str,
                                  uint8_t *out_padding_bits) {
    int len = str->length;
    if (str->flags & ASN1_STRING_FLAG_BITS_LEFT) {
        // If the string is already empty, it cannot have padding bits.
        *out_padding_bits = len == 0 ? 0 : str->flags & 0x07;
        return len;
    }

    // TODO(davidben): If we move this logic to |ASN1_BIT_STRING_set_bit|, can
    // we remove this representation?
    while (len > 0 && str->data[len - 1] == 0) {
        len--;
    }
    uint8_t padding_bits = 0;
    if (len > 0) {
        uint8_t last = str->data[len - 1];
        assert(last != 0);
        for (; padding_bits < 7; padding_bits++) {
            if (last & (1 << padding_bits)) {
                break;
            }
        }
    }
    *out_padding_bits = padding_bits;
    return len;
}

int ASN1_BIT_STRING_num_bytes(const ASN1_BIT_STRING *str, size_t *out) {
    uint8_t padding_bits;
    int len = asn1_bit_string_length(str, &padding_bits);
    if (padding_bits != 0) {
        return 0;
    }
    *out = len;
    return 1;
}

int i2c_ASN1_BIT_STRING(const ASN1_BIT_STRING *a, unsigned char **pp)
{
    if (a == NULL) {
        return 0;
    }

    uint8_t bits;
    int len = asn1_bit_string_length(a, &bits);
    int ret = 1 + len;
    if (pp == NULL) {
        return ret;
    }

    uint8_t *p = *pp;
    *(p++) = bits;
    OPENSSL_memcpy(p, a->data, len);
    if (len > 0) {
        p[len - 1] &= (0xff << bits);
    }
    p += len;
    *pp = p;
    return (ret);
}

ASN1_BIT_STRING *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 padding;

    if (len < 1) {
        OPENSSL_PUT_ERROR(ASN1, ASN1_R_STRING_TOO_SHORT);
        goto err;
    }

    if (len > INT_MAX) {
      OPENSSL_PUT_ERROR(ASN1, 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;
    padding = *(p++);
    if (padding > 7) {
        OPENSSL_PUT_ERROR(ASN1, 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
     */
    ret->flags &= ~(ASN1_STRING_FLAG_BITS_LEFT | 0x07); /* clear */
    ret->flags |= (ASN1_STRING_FLAG_BITS_LEFT | padding); /* set */

    if (len-- > 1) {            /* using one because of the bits left byte */
        s = (unsigned char *)OPENSSL_malloc((int)len);
        if (s == NULL) {
            OPENSSL_PUT_ERROR(ASN1, ERR_R_MALLOC_FAILURE);
            goto err;
        }
        OPENSSL_memcpy(s, p, (int)len);
        s[len - 1] &= (0xff << padding);
        p += len;
    } else
        s = NULL;

    ret->length = (int)len;
    if (ret->data != NULL)
        OPENSSL_free(ret->data);
    ret->data = s;
    ret->type = V_ASN1_BIT_STRING;
    if (a != NULL)
        (*a) = ret;
    *pp = p;
    return (ret);
 err:
    if ((ret != NULL) && ((a == NULL) || (*a != ret)))
        ASN1_BIT_STRING_free(ret);
    return (NULL);
}

/*
 * These next 2 functions from Goetz Babin-Ebell <babinebell@trustcenter.de>
 */
int ASN1_BIT_STRING_set_bit(ASN1_BIT_STRING *a, int n, int value)
{
    int w, v, iv;
    unsigned char *c;

    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 */
        if (a->data == NULL)
            c = (unsigned char *)OPENSSL_malloc(w + 1);
        else
            c = (unsigned char *)OPENSSL_realloc(a->data, w + 1);
        if (c == NULL) {
            OPENSSL_PUT_ERROR(ASN1, ERR_R_MALLOC_FAILURE);
            return 0;
        }
        if (w + 1 - a->length > 0)
            OPENSSL_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--;
    return (1);
}

int ASN1_BIT_STRING_get_bit(const ASN1_BIT_STRING *a, int n)
{
    int w, v;

    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;
}