epan/tvbuff_base64.c

   1 /* tvbuff_base64.c
   2  * Base-64 tvbuff implementation (based on real tvb)
   3  *
   4  * Wireshark - Network traffic analyzer
   5  * By Gerald Combs <gerald@wireshark.org>
   6  * Copyright 1998 Gerald Combs
   7  *
   8  * SPDX-License-Identifier: GPL-2.0-or-later
   9  */
  10
  11 #include "config.h"
  12
  13 #include <glib.h>
  14
  15 #include <epan/tvbuff.h>
  16 #include "proto.h"
  17
  18 /* Copy of glib function modified for base64uri */
  19
  20 static const unsigned char mime_base64uri_rank[256] = {
  21   255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
  22   255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
  23   255,255,255,255,255,255,255,255,255,255,255, 255,255,63,255,255,
  24    52, 53, 54, 55, 56, 57, 58, 59, 60, 61,255,255,255,  0,255,255,
  25   255,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,
  26    15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,255,255,255,255, 63,
  27   255, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
  28    41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51,255,255,255,255,255,
  29   255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
  30   255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
  31   255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
  32   255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
  33   255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
  34   255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
  35   255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
  36   255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
  37 };
  38  /**
  39   * Copy of glib function modified for base64uri
  40   * g_base64uri_decode_step: (skip)
  41   * @in: (array length=len) (element-type uint8_t): binary input data
  42   * @len: max length of @in data to decode
  43   * @out: (out caller-allocates) (array) (element-type uint8_t): output buffer
  44   * @state: (inout): Saved state between steps, initialize to 0
  45   * @save: (inout): Saved state between steps, initialize to 0
  46   *
  47   * Incrementally decode a sequence of binary data from its Base-64 stringified
  48   * representation. By calling this function multiple times you can convert
  49   * data in chunks to avoid having to have the full encoded data in memory.
  50   *
  51   * The output buffer must be large enough to fit all the data that will
  52   * be written to it. Since base64 encodes 3 bytes in 4 chars you need
  53   * at least: (@len / 4) * 3 + 3 bytes (+ 3 may be needed in case of non-zero
  54   * state).
  55   *
  56   * Returns: The number of bytes of output that was written
  57   *
  58   * Since: 2.12
  59   **/
  60 static size_t
  61 g_base64uri_decode_step(const char* in,
  62     size_t        len,
  63     unsigned char* out,
  64     int* state,
  65     unsigned* save)
  66 {
  67     const unsigned char* inptr;
  68     unsigned char* outptr;
  69     const unsigned char* inend;
  70     unsigned char c, rank;
  71     unsigned char last[2];
  72     unsigned int v;
  73     int i;
  74
  75     g_return_val_if_fail(in != NULL || len == 0, 0);
  76     g_return_val_if_fail(out != NULL, 0);
  77     g_return_val_if_fail(state != NULL, 0);
  78     g_return_val_if_fail(save != NULL, 0);
  79
  80     if (len == 0)
  81         return 0;
  82
  83     inend = (const unsigned char*)in + len;
  84     outptr = out;
  85
  86     /* convert 4 base64 bytes to 3 normal bytes */
  87     v = *save;
  88     i = *state;
  89
  90     last[0] = last[1] = 0;
  91
  92     /* we use the sign in the state to determine if we got a padding character
  93        in the previous sequence */
  94     if (i < 0)
  95     {
  96         i = -i;
  97         last[0] = '=';
  98     }
  99
 100     inptr = (const unsigned char*)in;
 101     while (inptr < inend)
 102     {
 103         c = *inptr++;
 104         rank = mime_base64uri_rank[c];
 105         if (rank != 0xff)
 106         {
 107             last[1] = last[0];
 108             last[0] = c;
 109             v = (v << 6) | rank;
 110             i++;
 111             if (i == 4)
 112             {
 113                 *outptr++ = v >> 16;
 114                 if (last[1] != '=')
 115                     *outptr++ = v >> 8;
 116                 if (last[0] != '=')
 117                     *outptr++ = v;
 118                 i = 0;
 119             }
 120         }
 121     }
 122
 123     *save = v;
 124     *state = last[0] == '=' ? -i : i;
 125
 126     return outptr - out;
 127 }
 128  /**
 129   * Copy of glib function modified for base64uri
 130   * g_base64uri_decode:
 131   * @text: (not nullable): zero-terminated string with base64 text to decode
 132   * @out_len: (out): The length of the decoded data is written here
 133   *
 134   * Decode a sequence of Base-64 encoded text into binary data.  Note
 135   * that the returned binary data is not necessarily zero-terminated,
 136   * so it should not be used as a character string.
 137   *
 138   * Returns: (transfer full) (array length=out_len) (element-type uint8_t):
 139   *               newly allocated buffer containing the binary data
 140   *               that @text represents. The returned buffer must
 141   *               be freed with g_free().
 142   *
 143   * Since: 2.12
 144   */
 145 static unsigned char*
 146 g_base64uri_decode(const char* text,
 147     size_t* out_len)
 148 {
 149     unsigned char* ret;
 150     size_t input_length;
 151     int state = 0;
 152     unsigned save = 0;
 153
 154     g_return_val_if_fail(text != NULL, NULL);
 155     g_return_val_if_fail(out_len != NULL, NULL);
 156
 157     input_length = strlen(text);
 158
 159     /* We can use a smaller limit here, since we know the saved state is 0,
 160        +1 used to avoid calling g_malloc0(0), and hence returning NULL */
 161     ret = (unsigned char * )g_malloc0((input_length / 4) * 3 + 1);
 162
 163     *out_len = g_base64uri_decode_step(text, input_length, ret, &state, &save);
 164
 165     return ret;
 166 }
 167
 168 tvbuff_t *
 169 base64_to_tvb(tvbuff_t *parent, const char *base64)
 170 {
 171   tvbuff_t *tvb;
 172   char *data;
 173   size_t len;
 174
 175   data = g_base64_decode(base64, &len);
 176   tvb = tvb_new_child_real_data(parent, (const uint8_t *)data, (int)len, (int)len);
 177
 178   tvb_set_free_cb(tvb, g_free);
 179
 180   return tvb;
 181 }
 182
 183 tvbuff_t*
 184 base64_tvb_to_new_tvb(tvbuff_t* parent, int offset, int length)
 185 {
 186     tvbuff_t* tvb;
 187     char* data, *tmp;
 188     size_t len;
 189
 190     tmp = tvb_get_string_enc(NULL, parent, offset, length, ENC_ASCII);
 191     data = g_base64_decode(tmp, &len);
 192     wmem_free(NULL, tmp);
 193
 194     tvb = tvb_new_child_real_data(parent, (const uint8_t*)data, (int)len, (int)len);
 195
 196     tvb_set_free_cb(tvb, g_free);
 197
 198     return tvb;
 199 }
 200
 201 tvbuff_t*
 202 base64uri_tvb_to_new_tvb(tvbuff_t* parent, int offset, int length)
 203 {
 204     tvbuff_t* tvb;
 205     char* data, *tmp;
 206     size_t len = 0;
 207
 208     tmp = tvb_get_string_enc(NULL, parent, offset, length, ENC_ASCII);
 209     data = g_base64uri_decode(tmp, &len);
 210     wmem_free(NULL, tmp);
 211
 212     tvb = tvb_new_child_real_data(parent, (const uint8_t*)data, (int)len, (int)len);
 213
 214     tvb_set_free_cb(tvb, g_free);
 215
 216     return tvb;
 217 }
 218 /*
 219  * Editor modelines  -  https://www.wireshark.org/tools/modelines.html
 220  *
 221  * Local Variables:
 222  * c-basic-offset: 2
 223  * tab-width: 8
 224  * indent-tabs-mode: nil
 225  * End:
 226  *
 227  * ex: set shiftwidth=2 tabstop=8 expandtab:
 228  * :indentSize=2:tabSize=8:noTabs=true:
 229  */