boringssl/crypto/asn1/a_int.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 <string.h>
#include <limits.h>

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

#include "../internal.h"


ASN1_INTEGER *ASN1_INTEGER_dup(const ASN1_INTEGER *x)
{
    return M_ASN1_INTEGER_dup(x);
}

int ASN1_INTEGER_cmp(const ASN1_INTEGER *x, const ASN1_INTEGER *y)
{
    int neg, ret;
    /* Compare signs */
    neg = x->type & V_ASN1_NEG;
    if (neg != (y->type & V_ASN1_NEG)) {
        if (neg)
            return -1;
        else
            return 1;
    }

    ret = ASN1_STRING_cmp(x, y);

    if (neg)
        return -ret;
    else
        return ret;
}

/*
 * This converts an ASN1 INTEGER into its content encoding.
 * The internal representation is an ASN1_STRING whose data is a big endian
 * representation of the value, ignoring the sign. The sign is determined by
 * the type: V_ASN1_INTEGER for positive and V_ASN1_NEG_INTEGER for negative.
 *
 * Positive integers are no problem: they are almost the same as the DER
 * encoding, except if the first byte is >= 0x80 we need to add a zero pad.
 *
 * Negative integers are a bit trickier...
 * The DER representation of negative integers is in 2s complement form.
 * The internal form is converted by complementing each octet and finally
 * adding one to the result. This can be done less messily with a little trick.
 * If the internal form has trailing zeroes then they will become FF by the
 * complement and 0 by the add one (due to carry) so just copy as many trailing
 * zeros to the destination as there are in the source. The carry will add one
 * to the last none zero octet: so complement this octet and add one and finally
 * complement any left over until you get to the start of the string.
 *
 * Padding is a little trickier too. If the first bytes is > 0x80 then we pad
 * with 0xff. However if the first byte is 0x80 and one of the following bytes
 * is non-zero we pad with 0xff. The reason for this distinction is that 0x80
 * followed by optional zeros isn't padded.
 */

int i2c_ASN1_INTEGER(const ASN1_INTEGER *a, unsigned char **pp)
{
    int pad = 0, ret, i, neg;
    unsigned char *p, *n, pb = 0;

    if (a == NULL)
        return (0);
    neg = a->type & V_ASN1_NEG;
    if (a->length == 0)
        ret = 1;
    else {
        ret = a->length;
        i = a->data[0];
        if (ret == 1 && i == 0)
            neg = 0;
        if (!neg && (i > 127)) {
            pad = 1;
            pb = 0;
        } else if (neg) {
            if (i > 128) {
                pad = 1;
                pb = 0xFF;
            } else if (i == 128) {
                /*
                 * Special case: if any other bytes non zero we pad:
                 * otherwise we don't.
                 */
                for (i = 1; i < a->length; i++)
                    if (a->data[i]) {
                        pad = 1;
                        pb = 0xFF;
                        break;
                    }
            }
        }
        ret += pad;
    }
    if (pp == NULL)
        return (ret);
    p = *pp;

    if (pad)
        *(p++) = pb;
    if (a->length == 0)
        *(p++) = 0;
    else if (!neg)
        OPENSSL_memcpy(p, a->data, (unsigned int)a->length);
    else {
        /* Begin at the end of the encoding */
        n = a->data + a->length - 1;
        p += a->length - 1;
        i = a->length;
        /* Copy zeros to destination as long as source is zero */
        while (!*n && i > 1) {
            *(p--) = 0;
            n--;
            i--;
        }
        /* Complement and increment next octet */
        *(p--) = ((*(n--)) ^ 0xff) + 1;
        i--;
        /* Complement any octets left */
        for (; i > 0; i--)
            *(p--) = *(n--) ^ 0xff;
    }

    *pp += ret;
    return (ret);
}

/* Convert just ASN1 INTEGER content octets to ASN1_INTEGER structure */

ASN1_INTEGER *c2i_ASN1_INTEGER(ASN1_INTEGER **a, const unsigned char **pp,
                               long len)
{
    ASN1_INTEGER *ret = NULL;
    const unsigned char *p, *pend;
    unsigned char *to, *s;
    int i;

    /*
     * This function can handle lengths up to INT_MAX - 1, but the rest of the
     * legacy ASN.1 code mixes integer types, so avoid exposing it to
     * ASN1_INTEGERS with larger lengths.
     */
    if (len < 0 || len > INT_MAX / 2) {
        OPENSSL_PUT_ERROR(ASN1, ASN1_R_TOO_LONG);
        return NULL;
    }

    if ((a == NULL) || ((*a) == NULL)) {
        if ((ret = M_ASN1_INTEGER_new()) == NULL)
            return (NULL);
        ret->type = V_ASN1_INTEGER;
    } else
        ret = (*a);

    p = *pp;
    pend = p + len;

    /*
     * We must OPENSSL_malloc stuff, even for 0 bytes otherwise it signifies
     * a missing NULL parameter.
     */
    s = (unsigned char *)OPENSSL_malloc((int)len + 1);
    if (s == NULL) {
        i = ERR_R_MALLOC_FAILURE;
        goto err;
    }
    to = s;
    if (!len) {
        /*
         * Strictly speaking this is an illegal INTEGER but we tolerate it.
         */
        ret->type = V_ASN1_INTEGER;
    } else if (*p & 0x80) {     /* a negative number */
        ret->type = V_ASN1_NEG_INTEGER;
        if ((*p == 0xff) && (len != 1)) {
            p++;
            len--;
        }
        i = len;
        p += i - 1;
        to += i - 1;
        while ((!*p) && i) {
            *(to--) = 0;
            i--;
            p--;
        }
        /*
         * Special case: if all zeros then the number will be of the form FF
         * followed by n zero bytes: this corresponds to 1 followed by n zero
         * bytes. We've already written n zeros so we just append an extra
         * one and set the first byte to a 1. This is treated separately
         * because it is the only case where the number of bytes is larger
         * than len.
         */
        if (!i) {
            *s = 1;
            s[len] = 0;
            len++;
        } else {
            *(to--) = (*(p--) ^ 0xff) + 1;
            i--;
            for (; i > 0; i--)
                *(to--) = *(p--) ^ 0xff;
        }
    } else {
        ret->type = V_ASN1_INTEGER;
        if ((*p == 0) && (len != 1)) {
            p++;
            len--;
        }
        OPENSSL_memcpy(s, p, (int)len);
    }

    if (ret->data != NULL)
        OPENSSL_free(ret->data);
    ret->data = s;
    ret->length = (int)len;
    if (a != NULL)
        (*a) = ret;
    *pp = pend;
    return (ret);
 err:
    OPENSSL_PUT_ERROR(ASN1, i);
    if ((ret != NULL) && ((a == NULL) || (*a != ret)))
        M_ASN1_INTEGER_free(ret);
    return (NULL);
}

int ASN1_INTEGER_set(ASN1_INTEGER *a, long v)
{
    if (v >= 0) {
        return ASN1_INTEGER_set_uint64(a, (uint64_t) v);
    }

    if (!ASN1_INTEGER_set_uint64(a, 0 - (uint64_t) v)) {
        return 0;
    }

    a->type = V_ASN1_NEG_INTEGER;
    return 1;
}

int ASN1_INTEGER_set_uint64(ASN1_INTEGER *out, uint64_t v)
{
    uint8_t *const newdata = OPENSSL_malloc(sizeof(uint64_t));
    if (newdata == NULL) {
        OPENSSL_PUT_ERROR(ASN1, ERR_R_MALLOC_FAILURE);
        return 0;
    }

    OPENSSL_free(out->data);
    out->data = newdata;
    v = CRYPTO_bswap8(v);
    memcpy(out->data, &v, sizeof(v));

    out->type = V_ASN1_INTEGER;

    size_t leading_zeros;
    for (leading_zeros = 0; leading_zeros < sizeof(uint64_t) - 1;
         leading_zeros++) {
        if (out->data[leading_zeros] != 0) {
            break;
        }
    }

    out->length = sizeof(uint64_t) - leading_zeros;
    OPENSSL_memmove(out->data, out->data + leading_zeros, out->length);

    return 1;
}

long ASN1_INTEGER_get(const ASN1_INTEGER *a)
{
    int neg = 0, i;

    if (a == NULL)
        return (0L);
    i = a->type;
    if (i == V_ASN1_NEG_INTEGER)
        neg = 1;
    else if (i != V_ASN1_INTEGER)
        return -1;

    OPENSSL_STATIC_ASSERT(sizeof(uint64_t) >= sizeof(long),
                          "long larger than uint64_t");

    if (a->length > (int)sizeof(uint64_t)) {
        /* hmm... a bit ugly, return all ones */
        return -1;
    }

    uint64_t r64 = 0;
    if (a->data != NULL) {
      for (i = 0; i < a->length; i++) {
          r64 <<= 8;
          r64 |= (unsigned char)a->data[i];
      }

      if (r64 > LONG_MAX) {
          return -1;
      }
    }

    long r = (long) r64;
    if (neg)
        r = -r;

    return r;
}

ASN1_INTEGER *BN_to_ASN1_INTEGER(const BIGNUM *bn, ASN1_INTEGER *ai)
{
    ASN1_INTEGER *ret;
    int len, j;

    if (ai == NULL)
        ret = M_ASN1_INTEGER_new();
    else
        ret = ai;
    if (ret == NULL) {
        OPENSSL_PUT_ERROR(ASN1, ASN1_R_NESTED_ASN1_ERROR);
        goto err;
    }
    if (BN_is_negative(bn) && !BN_is_zero(bn))
        ret->type = V_ASN1_NEG_INTEGER;
    else
        ret->type = V_ASN1_INTEGER;
    j = BN_num_bits(bn);
    len = ((j == 0) ? 0 : ((j / 8) + 1));
    if (ret->length < len + 4) {
        unsigned char *new_data = OPENSSL_realloc(ret->data, len + 4);
        if (!new_data) {
            OPENSSL_PUT_ERROR(ASN1, ERR_R_MALLOC_FAILURE);
            goto err;
        }
        ret->data = new_data;
    }
    ret->length = BN_bn2bin(bn, ret->data);
    /* Correct zero case */
    if (!ret->length) {
        ret->data[0] = 0;
        ret->length = 1;
    }
    return (ret);
 err:
    if (ret != ai)
        M_ASN1_INTEGER_free(ret);
    return (NULL);
}

BIGNUM *ASN1_INTEGER_to_BN(const ASN1_INTEGER *ai, BIGNUM *bn)
{
    BIGNUM *ret;

    if ((ret = BN_bin2bn(ai->data, ai->length, bn)) == NULL)
        OPENSSL_PUT_ERROR(ASN1, ASN1_R_BN_LIB);
    else if (ai->type == V_ASN1_NEG_INTEGER)
        BN_set_negative(ret, 1);
    return (ret);
}