xref: /third_party/curl/lib/vtls/keylog.c (revision 13498266) 
1/***************************************************************************
2 *                                  _   _ ____  _
3 *  Project                     ___| | | |  _ \| |
4 *                             / __| | | | |_) | |
5 *                            | (__| |_| |  _ <| |___
6 *                             \___|\___/|_| \_\_____|
7 *
8 * Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
9 *
10 * This software is licensed as described in the file COPYING, which
11 * you should have received as part of this distribution. The terms
12 * are also available at https://curl.se/docs/copyright.html.
13 *
14 * You may opt to use, copy, modify, merge, publish, distribute and/or sell
15 * copies of the Software, and permit persons to whom the Software is
16 * furnished to do so, under the terms of the COPYING file.
17 *
18 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
19 * KIND, either express or implied.
20 *
21 * SPDX-License-Identifier: curl
22 *
23 ***************************************************************************/
24#include "curl_setup.h"
25
26#if defined(USE_OPENSSL) || \
27  defined(USE_WOLFSSL) || \
28  (defined(USE_NGTCP2) && defined(USE_NGHTTP3)) || \
29  defined(USE_QUICHE)
30
31#include "keylog.h"
32#include <curl/curl.h>
33
34/* The last #include files should be: */
35#include "curl_memory.h"
36#include "memdebug.h"
37
38#define KEYLOG_LABEL_MAXLEN (sizeof("CLIENT_HANDSHAKE_TRAFFIC_SECRET") - 1)
39
40#define CLIENT_RANDOM_SIZE  32
41
42/*
43 * The master secret in TLS 1.2 and before is always 48 bytes. In TLS 1.3, the
44 * secret size depends on the cipher suite's hash function which is 32 bytes
45 * for SHA-256 and 48 bytes for SHA-384.
46 */
47#define SECRET_MAXLEN       48
48
49
50/* The fp for the open SSLKEYLOGFILE, or NULL if not open */
51static FILE *keylog_file_fp;
52
53void
54Curl_tls_keylog_open(void)
55{
56  char *keylog_file_name;
57
58  if(!keylog_file_fp) {
59    keylog_file_name = curl_getenv("SSLKEYLOGFILE");
60    if(keylog_file_name) {
61      keylog_file_fp = fopen(keylog_file_name, FOPEN_APPENDTEXT);
62      if(keylog_file_fp) {
63#ifdef _WIN32
64        if(setvbuf(keylog_file_fp, NULL, _IONBF, 0))
65#else
66        if(setvbuf(keylog_file_fp, NULL, _IOLBF, 4096))
67#endif
68        {
69          fclose(keylog_file_fp);
70          keylog_file_fp = NULL;
71        }
72      }
73      Curl_safefree(keylog_file_name);
74    }
75  }
76}
77
78void
79Curl_tls_keylog_close(void)
80{
81  if(keylog_file_fp) {
82    fclose(keylog_file_fp);
83    keylog_file_fp = NULL;
84  }
85}
86
87bool
88Curl_tls_keylog_enabled(void)
89{
90  return keylog_file_fp != NULL;
91}
92
93bool
94Curl_tls_keylog_write_line(const char *line)
95{
96  /* The current maximum valid keylog line length LF and NUL is 195. */
97  size_t linelen;
98  char buf[256];
99
100  if(!keylog_file_fp || !line) {
101    return false;
102  }
103
104  linelen = strlen(line);
105  if(linelen == 0 || linelen > sizeof(buf) - 2) {
106    /* Empty line or too big to fit in a LF and NUL. */
107    return false;
108  }
109
110  memcpy(buf, line, linelen);
111  if(line[linelen - 1] != '\n') {
112    buf[linelen++] = '\n';
113  }
114  buf[linelen] = '\0';
115
116  /* Using fputs here instead of fprintf since libcurl's fprintf replacement
117     may not be thread-safe. */
118  fputs(buf, keylog_file_fp);
119  return true;
120}
121
122bool
123Curl_tls_keylog_write(const char *label,
124                      const unsigned char client_random[CLIENT_RANDOM_SIZE],
125                      const unsigned char *secret, size_t secretlen)
126{
127  const char *hex = "0123456789ABCDEF";
128  size_t pos, i;
129  char line[KEYLOG_LABEL_MAXLEN + 1 + 2 * CLIENT_RANDOM_SIZE + 1 +
130            2 * SECRET_MAXLEN + 1 + 1];
131
132  if(!keylog_file_fp) {
133    return false;
134  }
135
136  pos = strlen(label);
137  if(pos > KEYLOG_LABEL_MAXLEN || !secretlen || secretlen > SECRET_MAXLEN) {
138    /* Should never happen - sanity check anyway. */
139    return false;
140  }
141
142  memcpy(line, label, pos);
143  line[pos++] = ' ';
144
145  /* Client Random */
146  for(i = 0; i < CLIENT_RANDOM_SIZE; i++) {
147    line[pos++] = hex[client_random[i] >> 4];
148    line[pos++] = hex[client_random[i] & 0xF];
149  }
150  line[pos++] = ' ';
151
152  /* Secret */
153  for(i = 0; i < secretlen; i++) {
154    line[pos++] = hex[secret[i] >> 4];
155    line[pos++] = hex[secret[i] & 0xF];
156  }
157  line[pos++] = '\n';
158  line[pos] = '\0';
159
160  /* Using fputs here instead of fprintf since libcurl's fprintf replacement
161     may not be thread-safe. */
162  fputs(line, keylog_file_fp);
163  return true;
164}
165
166#endif  /* TLS or QUIC backend */
167