jcs.org
mutt stable branch with some hacks
1/*
2 * Copyright (C) 1999-2001,2005 Brendan Cully <brendan@kublai.com>
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 2 of the License, or
7 * (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
17 */
18
19/* IMAP login/authentication code */
20
21#if HAVE_CONFIG_H
22# include "config.h"
23#endif
24
25#include "mutt.h"
26#include "imap_private.h"
27#include "auth.h"
28#include "md5.h"
29
30#define MD5_BLOCK_LEN 64
31#define MD5_DIGEST_LEN 16
32
33/* forward declarations */
34static void hmac_md5 (const char* password, char* challenge,
35 unsigned char* response);
36
37/* imap_auth_cram_md5: AUTH=CRAM-MD5 support. */
38imap_auth_res_t imap_auth_cram_md5 (IMAP_DATA* idata, const char* method)
39{
40 char ibuf[LONG_STRING*2], obuf[LONG_STRING];
41 unsigned char hmac_response[MD5_DIGEST_LEN];
42 int len;
43 int rc;
44
45 if (!mutt_bit_isset (idata->capabilities, ACRAM_MD5))
46 return IMAP_AUTH_UNAVAIL;
47
48 mutt_message _("Authenticating (CRAM-MD5)...");
49
50 /* get auth info */
51 if (mutt_account_getlogin (&idata->conn->account))
52 return IMAP_AUTH_FAILURE;
53 if (mutt_account_getpass (&idata->conn->account))
54 return IMAP_AUTH_FAILURE;
55
56 imap_cmd_start (idata, "AUTHENTICATE CRAM-MD5");
57
58 /* From RFC 2195:
59 * The data encoded in the first ready response contains a presumptively
60 * arbitrary string of random digits, a timestamp, and the fully-qualified
61 * primary host name of the server. The syntax of the unencoded form must
62 * correspond to that of an RFC 822 'msg-id' [RFC822] as described in [POP3].
63 */
64 do
65 rc = imap_cmd_step (idata);
66 while (rc == IMAP_CMD_CONTINUE);
67
68 if (rc != IMAP_CMD_RESPOND)
69 {
70 dprint (1, (debugfile, "Invalid response from server: %s\n", ibuf));
71 goto bail;
72 }
73
74 if ((len = mutt_from_base64 (obuf, idata->buf + 2)) == -1)
75 {
76 dprint (1, (debugfile, "Error decoding base64 response.\n"));
77 goto bail;
78 }
79
80 obuf[len] = '\0';
81 dprint (2, (debugfile, "CRAM challenge: %s\n", obuf));
82
83 /* The client makes note of the data and then responds with a string
84 * consisting of the user name, a space, and a 'digest'. The latter is
85 * computed by applying the keyed MD5 algorithm from [KEYED-MD5] where the
86 * key is a shared secret and the digested text is the timestamp (including
87 * angle-brackets).
88 *
89 * Note: The user name shouldn't be quoted. Since the digest can't contain
90 * spaces, there is no ambiguity. Some servers get this wrong, we'll work
91 * around them when the bug report comes in. Until then, we'll remain
92 * blissfully RFC-compliant.
93 */
94 hmac_md5 (idata->conn->account.pass, obuf, hmac_response);
95 /* dubious optimisation I saw elsewhere: make the whole string in one call */
96 snprintf (obuf, sizeof (obuf),
97 "%s %02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x",
98 idata->conn->account.user,
99 hmac_response[0], hmac_response[1], hmac_response[2], hmac_response[3],
100 hmac_response[4], hmac_response[5], hmac_response[6], hmac_response[7],
101 hmac_response[8], hmac_response[9], hmac_response[10], hmac_response[11],
102 hmac_response[12], hmac_response[13], hmac_response[14], hmac_response[15]);
103 dprint(2, (debugfile, "CRAM response: %s\n", obuf));
104
105 /* XXX - ibuf must be long enough to store the base64 encoding of obuf,
106 * plus the additional debris
107 */
108
109 mutt_to_base64 ((unsigned char*) ibuf, (unsigned char*) obuf, strlen (obuf),
110 sizeof (ibuf) - 2);
111 safe_strcat (ibuf, sizeof (ibuf), "\r\n");
112 mutt_socket_write (idata->conn, ibuf);
113
114 do
115 rc = imap_cmd_step (idata);
116 while (rc == IMAP_CMD_CONTINUE);
117
118 if (rc != IMAP_CMD_OK)
119 {
120 dprint (1, (debugfile, "Error receiving server response.\n"));
121 goto bail;
122 }
123
124 if (imap_code (idata->buf))
125 return IMAP_AUTH_SUCCESS;
126
127 bail:
128 mutt_error _("CRAM-MD5 authentication failed.");
129 mutt_sleep (2);
130 return IMAP_AUTH_FAILURE;
131}
132
133/* hmac_md5: produce CRAM-MD5 challenge response. */
134static void hmac_md5 (const char* password, char* challenge,
135 unsigned char* response)
136{
137 struct md5_ctx ctx;
138 unsigned char ipad[MD5_BLOCK_LEN], opad[MD5_BLOCK_LEN];
139 unsigned char secret[MD5_BLOCK_LEN+1];
140 unsigned char hash_passwd[MD5_DIGEST_LEN];
141 unsigned int secret_len, chal_len;
142 int i;
143
144 secret_len = strlen (password);
145 chal_len = strlen (challenge);
146
147 /* passwords longer than MD5_BLOCK_LEN bytes are substituted with their MD5
148 * digests */
149 if (secret_len > MD5_BLOCK_LEN)
150 {
151 md5_buffer (password, secret_len, hash_passwd);
152 strfcpy ((char*) secret, (char*) hash_passwd, MD5_DIGEST_LEN);
153 secret_len = MD5_DIGEST_LEN;
154 }
155 else
156 strfcpy ((char *) secret, password, sizeof (secret));
157
158 memset (ipad, 0, sizeof (ipad));
159 memset (opad, 0, sizeof (opad));
160 memcpy (ipad, secret, secret_len);
161 memcpy (opad, secret, secret_len);
162
163 for (i = 0; i < MD5_BLOCK_LEN; i++)
164 {
165 ipad[i] ^= 0x36;
166 opad[i] ^= 0x5c;
167 }
168
169 /* inner hash: challenge and ipadded secret */
170 md5_init_ctx (&ctx);
171 md5_process_bytes (ipad, MD5_BLOCK_LEN, &ctx);
172 md5_process_bytes (challenge, chal_len, &ctx);
173 md5_finish_ctx (&ctx, response);
174
175 /* outer hash: inner hash and opadded secret */
176 md5_init_ctx (&ctx);
177 md5_process_bytes (opad, MD5_BLOCK_LEN, &ctx);
178 md5_process_bytes (response, MD5_DIGEST_LEN, &ctx);
179 md5_finish_ctx (&ctx, response);
180}