crypto/asn1/x_long.c

   1 /*
   2  * Copyright 2000-2017 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 <stdio.h>
  11 #include "internal/cryptlib.h"
  12 #include <openssl/asn1t.h>
  13
  14 #ifdef OPENSSL_NO_DEPRECATED_3_0
  15 NON_EMPTY_TRANSLATION_UNIT
  16 #else
  17
  18 #define COPY_SIZE(a, b) (sizeof(a) < sizeof(b) ? sizeof(a) : sizeof(b))
  19
  20 /*
  21  * Custom primitive type for long handling. This converts between an
  22  * ASN1_INTEGER and a long directly.
  23  */
  24
  25 static int long_new(ASN1_VALUE **pval, const ASN1_ITEM *it);
  26 static void long_free(ASN1_VALUE **pval, const ASN1_ITEM *it);
  27
  28 static int long_i2c(const ASN1_VALUE **pval, unsigned char *cont, int *putype,
  29                     const ASN1_ITEM *it);
  30 static int long_c2i(ASN1_VALUE **pval, const unsigned char *cont, int len,
  31                     int utype, char *free_cont, const ASN1_ITEM *it);
  32 static int long_print(BIO *out, const ASN1_VALUE **pval, const ASN1_ITEM *it,
  33                       int indent, const ASN1_PCTX *pctx);
  34
  35 static ASN1_PRIMITIVE_FUNCS long_pf = {
  36     NULL, 0,
  37     long_new,
  38     long_free,
  39     long_free,                  /* Clear should set to initial value */
  40     long_c2i,
  41     long_i2c,
  42     long_print
  43 };
  44
  45 ASN1_ITEM_start(LONG)
  46         ASN1_ITYPE_PRIMITIVE, V_ASN1_INTEGER, NULL, 0, &long_pf, ASN1_LONG_UNDEF, "LONG"
  47 ASN1_ITEM_end(LONG)
  48
  49 ASN1_ITEM_start(ZLONG)
  50         ASN1_ITYPE_PRIMITIVE, V_ASN1_INTEGER, NULL, 0, &long_pf, 0, "ZLONG"
  51 ASN1_ITEM_end(ZLONG)
  52
  53 static int long_new(ASN1_VALUE **pval, const ASN1_ITEM *it)
  54 {
  55     memcpy(pval, &it->size, COPY_SIZE(*pval, it->size));
  56     return 1;
  57 }
  58
  59 static void long_free(ASN1_VALUE **pval, const ASN1_ITEM *it)
  60 {
  61     memcpy(pval, &it->size, COPY_SIZE(*pval, it->size));
  62 }
  63
  64 /*
  65  * Originally BN_num_bits_word was called to perform this operation, but
  66  * trouble is that there is no guarantee that sizeof(long) equals to
  67  * sizeof(BN_ULONG). BN_ULONG is a configurable type that can be as wide
  68  * as long, but also double or half...
  69  */
  70 static int num_bits_ulong(unsigned long value)
  71 {
  72     size_t i;
  73     unsigned long ret = 0;
  74
  75     /*
  76      * It is argued that *on average* constant counter loop performs
  77      * not worse [if not better] than one with conditional break or
  78      * mask-n-table-lookup-style, because of branch misprediction
  79      * penalties.
  80      */
  81     for (i = 0; i < sizeof(value) * 8; i++) {
  82         ret += (value != 0);
  83         value >>= 1;
  84     }
  85
  86     return (int)ret;
  87 }
  88
  89 static int long_i2c(const ASN1_VALUE **pval, unsigned char *cont, int *putype,
  90                     const ASN1_ITEM *it)
  91 {
  92     long ltmp;
  93     unsigned long utmp, sign;
  94     int clen, pad, i;
  95
  96     memcpy(&ltmp, pval, COPY_SIZE(*pval, ltmp));
  97     if (ltmp == it->size)
  98         return -1;
  99     /*
 100      * Convert the long to positive: we subtract one if negative so we can
 101      * cleanly handle the padding if only the MSB of the leading octet is
 102      * set.
 103      */
 104     if (ltmp < 0) {
 105         sign = 0xff;
 106         utmp = 0 - (unsigned long)ltmp - 1;
 107     } else {
 108         sign = 0;
 109         utmp = ltmp;
 110     }
 111     clen = num_bits_ulong(utmp);
 112     /* If MSB of leading octet set we need to pad */
 113     if (!(clen & 0x7))
 114         pad = 1;
 115     else
 116         pad = 0;
 117
 118     /* Convert number of bits to number of octets */
 119     clen = (clen + 7) >> 3;
 120
 121     if (cont != NULL) {
 122         if (pad)
 123             *cont++ = (unsigned char)sign;
 124         for (i = clen - 1; i >= 0; i--) {
 125             cont[i] = (unsigned char)(utmp ^ sign);
 126             utmp >>= 8;
 127         }
 128     }
 129     return clen + pad;
 130 }
 131
 132 static int long_c2i(ASN1_VALUE **pval, const unsigned char *cont, int len,
 133                     int utype, char *free_cont, const ASN1_ITEM *it)
 134 {
 135     int i;
 136     long ltmp;
 137     unsigned long utmp = 0, sign = 0x100;
 138
 139     if (len > 1) {
 140         /*
 141          * Check possible pad byte.  Worst case, we're skipping past actual
 142          * content, but since that's only with 0x00 and 0xff and we set neg
 143          * accordingly, the result will be correct in the end anyway.
 144          */
 145         switch (cont[0]) {
 146         case 0xff:
 147             cont++;
 148             len--;
 149             sign = 0xff;
 150             break;
 151         case 0:
 152             cont++;
 153             len--;
 154             sign = 0;
 155             break;
 156         }
 157     }
 158     if (len > (int)sizeof(long)) {
 159         ASN1err(ASN1_F_LONG_C2I, ASN1_R_INTEGER_TOO_LARGE_FOR_LONG);
 160         return 0;
 161     }
 162
 163     if (sign == 0x100) {
 164         /* Is it negative? */
 165         if (len && (cont[0] & 0x80))
 166             sign = 0xff;
 167         else
 168             sign = 0;
 169     } else if (((sign ^ cont[0]) & 0x80) == 0) { /* same sign bit? */
 170         ASN1err(ASN1_F_LONG_C2I, ASN1_R_ILLEGAL_PADDING);
 171         return 0;
 172     }
 173     utmp = 0;
 174     for (i = 0; i < len; i++) {
 175         utmp <<= 8;
 176         utmp |= cont[i] ^ sign;
 177     }
 178     ltmp = (long)utmp;
 179     if (ltmp < 0) {
 180         ASN1err(ASN1_F_LONG_C2I, ASN1_R_INTEGER_TOO_LARGE_FOR_LONG);
 181         return 0;
 182     }
 183     if (sign)
 184         ltmp = -ltmp - 1;
 185     if (ltmp == it->size) {
 186         ASN1err(ASN1_F_LONG_C2I, ASN1_R_INTEGER_TOO_LARGE_FOR_LONG);
 187         return 0;
 188     }
 189     memcpy(pval, &ltmp, COPY_SIZE(*pval, ltmp));
 190     return 1;
 191 }
 192
 193 static int long_print(BIO *out, const ASN1_VALUE **pval, const ASN1_ITEM *it,
 194                       int indent, const ASN1_PCTX *pctx)
 195 {
 196     long l;
 197
 198     memcpy(&l, pval, COPY_SIZE(*pval, l));
 199     return BIO_printf(out, "%ld\n", l);
 200 }
 201 #endif