crypto/bn/bn_conv.c

   1 /*
   2  * Copyright 1995-2017 The OpenSSL Project Authors. All Rights Reserved.
   3  *
   4  * Licensed under the Apache License 2.0 (the "License").  You may not use
   5  * this file except in compliance with the License.  You can obtain a copy
   6  * in the file LICENSE in the source distribution or at
   7  * https://www.openssl.org/source/license.html
   8  */
   9
  10 #include <openssl/err.h>
  11 #include "internal/ctype.h"
  12 #include "bn_lcl.h"
  13
  14 static const char Hex[] = "0123456789ABCDEF";
  15
  16 /* Must 'OPENSSL_free' the returned data */
  17 char *BN_bn2hex(const BIGNUM *a)
  18 {
  19     int i, j, v, z = 0;
  20     char *buf;
  21     char *p;
  22
  23     if (BN_is_zero(a))
  24         return OPENSSL_strdup("0");
  25     buf = OPENSSL_malloc(a->top * BN_BYTES * 2 + 2);
  26     if (buf == NULL) {
  27         BNerr(BN_F_BN_BN2HEX, ERR_R_MALLOC_FAILURE);
  28         goto err;
  29     }
  30     p = buf;
  31     if (a->neg)
  32         *p++ = '-';
  33     for (i = a->top - 1; i >= 0; i--) {
  34         for (j = BN_BITS2 - 8; j >= 0; j -= 8) {
  35             /* strip leading zeros */
  36             v = (int)((a->d[i] >> j) & 0xff);
  37             if (z || v != 0) {
  38                 *p++ = Hex[v >> 4];
  39                 *p++ = Hex[v & 0x0f];
  40                 z = 1;
  41             }
  42         }
  43     }
  44     *p = '\0';
  45  err:
  46     return buf;
  47 }
  48
  49 #ifndef FIPS_MODE
  50 /* No BIO_snprintf in FIPS_MODE */
  51 /* Must 'OPENSSL_free' the returned data */
  52 char *BN_bn2dec(const BIGNUM *a)
  53 {
  54     int i = 0, num, ok = 0, n, tbytes;
  55     char *buf = NULL;
  56     char *p;
  57     BIGNUM *t = NULL;
  58     BN_ULONG *bn_data = NULL, *lp;
  59     int bn_data_num;
  60
  61     /*-
  62      * get an upper bound for the length of the decimal integer
  63      * num <= (BN_num_bits(a) + 1) * log(2)
  64      *     <= 3 * BN_num_bits(a) * 0.101 + log(2) + 1     (rounding error)
  65      *     <= 3 * BN_num_bits(a) / 10 + 3 * BN_num_bits / 1000 + 1 + 1
  66      */
  67     i = BN_num_bits(a) * 3;
  68     num = (i / 10 + i / 1000 + 1) + 1;
  69     tbytes = num + 3;   /* negative and terminator and one spare? */
  70     bn_data_num = num / BN_DEC_NUM + 1;
  71     bn_data = OPENSSL_malloc(bn_data_num * sizeof(BN_ULONG));
  72     buf = OPENSSL_malloc(tbytes);
  73     if (buf == NULL || bn_data == NULL) {
  74         BNerr(BN_F_BN_BN2DEC, ERR_R_MALLOC_FAILURE);
  75         goto err;
  76     }
  77     if ((t = BN_dup(a)) == NULL)
  78         goto err;
  79
  80     p = buf;
  81     lp = bn_data;
  82     if (BN_is_zero(t)) {
  83         *p++ = '0';
  84         *p++ = '\0';
  85     } else {
  86         if (BN_is_negative(t))
  87             *p++ = '-';
  88
  89         while (!BN_is_zero(t)) {
  90             if (lp - bn_data >= bn_data_num)
  91                 goto err;
  92             *lp = BN_div_word(t, BN_DEC_CONV);
  93             if (*lp == (BN_ULONG)-1)
  94                 goto err;
  95             lp++;
  96         }
  97         lp--;
  98         /*
  99          * We now have a series of blocks, BN_DEC_NUM chars in length, where
 100          * the last one needs truncation. The blocks need to be reversed in
 101          * order.
 102          */
 103         n = BIO_snprintf(p, tbytes - (size_t)(p - buf), BN_DEC_FMT1, *lp);
 104         if (n < 0)
 105             goto err;
 106         p += n;
 107         while (lp != bn_data) {
 108             lp--;
 109             n = BIO_snprintf(p, tbytes - (size_t)(p - buf), BN_DEC_FMT2, *lp);
 110             if (n < 0)
 111                 goto err;
 112             p += n;
 113         }
 114     }
 115     ok = 1;
 116  err:
 117     OPENSSL_free(bn_data);
 118     BN_free(t);
 119     if (ok)
 120         return buf;
 121     OPENSSL_free(buf);
 122     return NULL;
 123 }
 124 #endif
 125
 126 int BN_hex2bn(BIGNUM **bn, const char *a)
 127 {
 128     BIGNUM *ret = NULL;
 129     BN_ULONG l = 0;
 130     int neg = 0, h, m, i, j, k, c;
 131     int num;
 132
 133     if (a == NULL || *a == '\0')
 134         return 0;
 135
 136     if (*a == '-') {
 137         neg = 1;
 138         a++;
 139     }
 140
 141     for (i = 0; i <= INT_MAX / 4 && ossl_isxdigit(a[i]); i++)
 142         continue;
 143
 144     if (i == 0 || i > INT_MAX / 4)
 145         goto err;
 146
 147     num = i + neg;
 148     if (bn == NULL)
 149         return num;
 150
 151     /* a is the start of the hex digits, and it is 'i' long */
 152     if (*bn == NULL) {
 153         if ((ret = BN_new()) == NULL)
 154             return 0;
 155     } else {
 156         ret = *bn;
 157         BN_zero(ret);
 158     }
 159
 160     /* i is the number of hex digits */
 161     if (bn_expand(ret, i * 4) == NULL)
 162         goto err;
 163
 164     j = i;                      /* least significant 'hex' */
 165     m = 0;
 166     h = 0;
 167     while (j > 0) {
 168         m = (BN_BYTES * 2 <= j) ? BN_BYTES * 2 : j;
 169         l = 0;
 170         for (;;) {
 171             c = a[j - m];
 172             k = OPENSSL_hexchar2int(c);
 173             if (k < 0)
 174                 k = 0;          /* paranoia */
 175             l = (l << 4) | k;
 176
 177             if (--m <= 0) {
 178                 ret->d[h++] = l;
 179                 break;
 180             }
 181         }
 182         j -= BN_BYTES * 2;
 183     }
 184     ret->top = h;
 185     bn_correct_top(ret);
 186
 187     *bn = ret;
 188     bn_check_top(ret);
 189     /* Don't set the negative flag if it's zero. */
 190     if (ret->top != 0)
 191         ret->neg = neg;
 192     return num;
 193  err:
 194     if (*bn == NULL)
 195         BN_free(ret);
 196     return 0;
 197 }
 198
 199 int BN_dec2bn(BIGNUM **bn, const char *a)
 200 {
 201     BIGNUM *ret = NULL;
 202     BN_ULONG l = 0;
 203     int neg = 0, i, j;
 204     int num;
 205
 206     if (a == NULL || *a == '\0')
 207         return 0;
 208     if (*a == '-') {
 209         neg = 1;
 210         a++;
 211     }
 212
 213     for (i = 0; i <= INT_MAX / 4 && ossl_isdigit(a[i]); i++)
 214         continue;
 215
 216     if (i == 0 || i > INT_MAX / 4)
 217         goto err;
 218
 219     num = i + neg;
 220     if (bn == NULL)
 221         return num;
 222
 223     /*
 224      * a is the start of the digits, and it is 'i' long. We chop it into
 225      * BN_DEC_NUM digits at a time
 226      */
 227     if (*bn == NULL) {
 228         if ((ret = BN_new()) == NULL)
 229             return 0;
 230     } else {
 231         ret = *bn;
 232         BN_zero(ret);
 233     }
 234
 235     /* i is the number of digits, a bit of an over expand */
 236     if (bn_expand(ret, i * 4) == NULL)
 237         goto err;
 238
 239     j = BN_DEC_NUM - i % BN_DEC_NUM;
 240     if (j == BN_DEC_NUM)
 241         j = 0;
 242     l = 0;
 243     while (--i >= 0) {
 244         l *= 10;
 245         l += *a - '0';
 246         a++;
 247         if (++j == BN_DEC_NUM) {
 248             if (!BN_mul_word(ret, BN_DEC_CONV)
 249                 || !BN_add_word(ret, l))
 250                 goto err;
 251             l = 0;
 252             j = 0;
 253         }
 254     }
 255
 256     bn_correct_top(ret);
 257     *bn = ret;
 258     bn_check_top(ret);
 259     /* Don't set the negative flag if it's zero. */
 260     if (ret->top != 0)
 261         ret->neg = neg;
 262     return num;
 263  err:
 264     if (*bn == NULL)
 265         BN_free(ret);
 266     return 0;
 267 }
 268
 269 int BN_asc2bn(BIGNUM **bn, const char *a)
 270 {
 271     const char *p = a;
 272
 273     if (*p == '-')
 274         p++;
 275
 276     if (p[0] == '0' && (p[1] == 'X' || p[1] == 'x')) {
 277         if (!BN_hex2bn(bn, p + 2))
 278             return 0;
 279     } else {
 280         if (!BN_dec2bn(bn, p))
 281             return 0;
 282     }
 283     /* Don't set the negative flag if it's zero. */
 284     if (*a == '-' && (*bn)->top != 0)
 285         (*bn)->neg = 1;
 286     return 1;
 287 }