epan/tvbuff_hpackhuff.c

   1 /* @file
   2  * Decompression of the Huffman encoding used for HTTP fields in HPACK (HTTP/2)
   3  * and QPACK (HTTP/3)
   4  *
   5  * Wireshark - Network traffic analyzer
   6  * By Gerald Combs <gerald@wireshark.org>
   7  * Copyright 1998 Gerald Combs
   8  *
   9  * SPDX-License-Identifier: GPL-2.0-or-later
  10  */
  11
  12 #include "config.h"
  13
  14 #include <epan/tvbuff.h>
  15 #include <epan/nghttp2_hd_huffman.h>
  16
  17 static wmem_strbuf_t *
  18 get_hpack_huffman_strbuf(wmem_allocator_t *scope, const uint8_t *ptr, size_t len)
  19 {
  20     wmem_strbuf_t *strbuf;
  21     strbuf = wmem_strbuf_new_sized(scope, len + 1);
  22
  23     nghttp2_huff_decode node = {0, 0};
  24     const nghttp2_huff_decode *nodep = &node;
  25
  26     while (len > 0) {
  27         uint8_t ch = *ptr++;
  28
  29         nodep = &huff_decode_table[nodep->fstate & 0x1ff][ch >> 4];
  30         if (nodep->fstate & NGHTTP2_HUFF_SYM) {
  31             wmem_strbuf_append_c(strbuf, nodep->sym);
  32         }
  33
  34         nodep = &huff_decode_table[nodep->fstate & 0x1ff][ch & 0xf];
  35         if (nodep->fstate & NGHTTP2_HUFF_SYM) {
  36             wmem_strbuf_append_c(strbuf, nodep->sym);
  37         }
  38
  39         len--;
  40     }
  41
  42     if (!(nodep->fstate & NGHTTP2_HUFF_ACCEPTED)) {
  43         wmem_strbuf_destroy(strbuf);
  44         return NULL;
  45     }
  46
  47     return strbuf;
  48 }
  49
  50 wmem_strbuf_t *
  51 tvb_get_hpack_huffman_strbuf(wmem_allocator_t *scope, tvbuff_t *tvb, const int offset, const int len)
  52 {
  53     return get_hpack_huffman_strbuf(scope, tvb_get_ptr(tvb, offset, len), len);
  54 }
  55
  56 tvbuff_t*
  57 tvb_child_uncompress_hpack_huff(tvbuff_t* parent, int offset, int length)
  58 {
  59     tvbuff_t* tvb = NULL;
  60     wmem_strbuf_t *strbuf;
  61     char* data;
  62     size_t len;
  63
  64     strbuf = tvb_get_hpack_huffman_strbuf(NULL, parent, offset, length);
  65
  66     if (strbuf) {
  67         len = wmem_strbuf_get_len(strbuf);
  68         data = wmem_strbuf_finalize(strbuf);
  69
  70         tvb = tvb_new_child_real_data(parent, (const uint8_t*)data, (unsigned)len, (int)len);
  71
  72         tvb_set_free_cb(tvb, g_free);
  73     }
  74
  75     return tvb;
  76 }