providers/implementations/ciphers/ciphercommon_block.c

   1 /*
   2  * Copyright 2019 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 <assert.h>
  11 #include "ciphercommon_local.h"
  12 #include "prov/providercommonerr.h"
  13
  14 /*
  15  * Fills a single block of buffered data from the input, and returns the amount
  16  * of data remaining in the input that is a multiple of the blocksize. The buffer
  17  * is only filled if it already has some data in it, isn't full already or we
  18  * don't have at least one block in the input.
  19  *
  20  * buf: a buffer of blocksize bytes
  21  * buflen: contains the amount of data already in buf on entry. Updated with the
  22  *         amount of data in buf at the end. On entry *buflen must always be
  23  *         less than the blocksize
  24  * blocksize: size of a block. Must be greater than 0 and a power of 2
  25  * in: pointer to a pointer containing the input data
  26  * inlen: amount of input data available
  27  *
  28  * On return buf is filled with as much data as possible up to a full block,
  29  * *buflen is updated containing the amount of data in buf. *in is updated to
  30  * the new location where input data should be read from, *inlen is updated with
  31  * the remaining amount of data in *in. Returns the largest value <= *inlen
  32  * which is a multiple of the blocksize.
  33  */
  34 size_t fillblock(unsigned char *buf, size_t *buflen, size_t blocksize,
  35                  const unsigned char **in, size_t *inlen)
  36 {
  37     size_t blockmask = ~(blocksize - 1);
  38     size_t bufremain = blocksize - *buflen;
  39
  40     assert(*buflen <= blocksize);
  41     assert(blocksize > 0 && (blocksize & (blocksize - 1)) == 0);
  42
  43     if (*inlen < bufremain)
  44         bufremain = *inlen;
  45     memcpy(buf + *buflen, *in, bufremain);
  46     *in += bufremain;
  47     *inlen -= bufremain;
  48     *buflen += bufremain;
  49
  50     return *inlen & blockmask;
  51 }
  52
  53 /*
  54  * Fills the buffer with trailing data from an encryption/decryption that didn't
  55  * fit into a full block.
  56  */
  57 int trailingdata(unsigned char *buf, size_t *buflen, size_t blocksize,
  58                  const unsigned char **in, size_t *inlen)
  59 {
  60     if (*inlen == 0)
  61         return 1;
  62
  63     if (*buflen + *inlen > blocksize) {
  64         ERR_raise(ERR_LIB_PROV, ERR_R_INTERNAL_ERROR);
  65         return 0;
  66     }
  67
  68     memcpy(buf + *buflen, *in, *inlen);
  69     *buflen += *inlen;
  70     *inlen = 0;
  71
  72     return 1;
  73 }
  74
  75 /* Pad the final block for encryption */
  76 void padblock(unsigned char *buf, size_t *buflen, size_t blocksize)
  77 {
  78     size_t i;
  79     unsigned char pad = (unsigned char)(blocksize - *buflen);
  80
  81     for (i = *buflen; i < blocksize; i++)
  82         buf[i] = pad;
  83 }
  84
  85 int unpadblock(unsigned char *buf, size_t *buflen, size_t blocksize)
  86 {
  87     size_t pad, i;
  88     size_t len = *buflen;
  89
  90     if(len != blocksize) {
  91         ERR_raise(ERR_LIB_PROV, ERR_R_INTERNAL_ERROR);
  92         return 0;
  93     }
  94
  95     /*
  96      * The following assumes that the ciphertext has been authenticated.
  97      * Otherwise it provides a padding oracle.
  98      */
  99     pad = buf[blocksize - 1];
 100     if (pad == 0 || pad > blocksize) {
 101         ERR_raise(ERR_LIB_PROV, PROV_R_BAD_DECRYPT);
 102         return 0;
 103     }
 104     for (i = 0; i < pad; i++) {
 105         if (buf[--len] != pad) {
 106             ERR_raise(ERR_LIB_PROV, PROV_R_BAD_DECRYPT);
 107             return 0;
 108         }
 109     }
 110     *buflen = len;
 111     return 1;
 112 }