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/* -*-mode:c; c-style:k&r; c-basic-offset:4; -*- */
/* Balsa E-Mail Client
* Copyright (C) 1997-2003 Stuart Parmenter and others,
* See the file AUTHORS for a list
*
* Copyright (C) 1999-2000 Brendan Cully <brendan@kublai.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111, USA.
*/
/* IMAP login/authentication code */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <glib.h>
#include "imap-auth.h"
#include "md5-utils.h"
#include "util.h"
#include "imap_private.h"
#define LONG_STRING 1024
#define MD5_DIGEST_LEN 16
/* forward declarations */
static void hmac_md5(const char* password, char* challenge,
unsigned char* response);
/* imap_auth_cram_md5: AUTH=CRAM-MD5 support. */
ImapResult
imap_auth_cram(ImapMboxHandle* handle)
{
char ibuf[LONG_STRING*2], obuf[LONG_STRING];
unsigned char hmac_response[MD5_DIGEST_LEN];
unsigned cmdno;
int len, rc, ok;
char *user = NULL, *pass = NULL;
if (!imap_mbox_handle_can_do(handle, IMCAP_ACRAM_MD5))
return IMAP_AUTH_UNAVAIL;
ok = 0;
if(!ok && handle->user_cb)
handle->user_cb(IME_GET_USER_PASS, handle->user_arg,
"CRAM-MD5", &user, &pass, &ok);
if(!ok || user == NULL || pass == NULL) {
imap_mbox_handle_set_msg(handle, "Authentication cancelled");
return IMAP_AUTH_CANCELLED;
}
/* start the interaction */
if(imap_cmd_start(handle, "AUTHENTICATE CRAM-MD5", &cmdno) <0)
return IMAP_AUTH_FAILURE;
/* From RFC 2195:
* The data encoded in the first ready response contains a presumptively
* arbitrary string of random digits, a timestamp, and the fully-qualified
* primary host name of the server. The syntax of the unencoded form must
* correspond to that of an RFC 822 'msg-id' [RFC822] as described in [POP3].
*/
imap_handle_flush(handle);
do
rc = imap_cmd_step(handle, cmdno);
while(rc == IMR_UNTAGGED);
if (rc != IMR_RESPOND) {
g_warning("cram-md5: unexpected response:\n");
return IMAP_AUTH_FAILURE;
}
imap_mbox_gets(handle, ibuf, sizeof(ibuf)); /* check error */
if ((len = lit_conv_from_base64(obuf, ibuf)) <0) {
g_warning("Error decoding base64 response(%s), digit=%d:%d[%c]).\n",
ibuf, len, ibuf[-len-1],ibuf[-len-1]);
return IMAP_AUTH_FAILURE;
}
obuf[len] = '\0';
/* The client makes note of the data and then responds with a string
* consisting of the user name, a space, and a 'digest'. The latter is
* computed by applying the keyed MD5 algorithm from [KEYED-MD5] where the
* key is a shared secret and the digested text is the timestamp (including
* angle-brackets).
*
* Note: The user name shouldn't be quoted. Since the digest can't contain
* spaces, there is no ambiguity. Some servers get this wrong, we'll work
* around them when the bug report comes in. Until then, we'll remain
* blissfully RFC-compliant.
*/
hmac_md5 (pass, obuf, hmac_response);
g_snprintf (obuf, sizeof (obuf),
"%s %02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x",
user,
hmac_response[0], hmac_response[1], hmac_response[2], hmac_response[3],
hmac_response[4], hmac_response[5], hmac_response[6], hmac_response[7],
hmac_response[8], hmac_response[9], hmac_response[10], hmac_response[11],
hmac_response[12], hmac_response[13], hmac_response[14], hmac_response[15]);
/* XXX - ibuf must be long enough to store the base64 encoding of obuf,
* plus the additional debris
*/
lit_conv_to_base64(ibuf, obuf, strlen (obuf), sizeof(ibuf)-2);
strncat (ibuf, "\r\n", sizeof (ibuf));
imap_handle_write(handle, ibuf, strlen(ibuf));
imap_handle_flush(handle);
g_free(user); g_free(pass); /* FIXME: clean passwd first */
do
rc = imap_cmd_step (handle, cmdno);
while (rc == IMR_UNTAGGED);
return rc == IMR_OK ? IMAP_SUCCESS : IMAP_AUTH_FAILURE;
}
/* hmac_md5: produce CRAM-MD5 challenge response. */
#define MD5_BLOCK_LEN 64
static void
hmac_md5 (const char* password, char* challenge,
unsigned char* response)
{
MD5Context ctx;
unsigned char ipad[MD5_BLOCK_LEN], opad[MD5_BLOCK_LEN];
unsigned char secret[MD5_BLOCK_LEN+1];
unsigned char hash_passwd[MD5_DIGEST_LEN];
unsigned int secret_len, chal_len;
int i;
secret_len = strlen(password);
chal_len = strlen(challenge);
/* passwords longer than MD5_BLOCK_LEN bytes are substituted with their MD5
* digests */
if (secret_len > MD5_BLOCK_LEN) {
md5_init (&ctx);
md5_update (&ctx, (unsigned char*) password, secret_len);
md5_final (&ctx, hash_passwd);
strncpy ((char*) secret, (char*) hash_passwd, MD5_DIGEST_LEN);
secret_len = MD5_DIGEST_LEN;
}
else
strncpy ((char *) secret, password, sizeof (secret));
memset (ipad, 0, sizeof(ipad));
memset (opad, 0, sizeof(opad));
memcpy (ipad, secret, secret_len);
memcpy (opad, secret, secret_len);
for (i=0; i<MD5_BLOCK_LEN; i++) {
ipad[i] ^= 0x36;
opad[i] ^= 0x5c;
}
/* inner hash: challenge and ipadded secret */
md5_init (&ctx);
md5_update (&ctx, ipad, MD5_BLOCK_LEN);
md5_update (&ctx, (unsigned char*) challenge, chal_len);
md5_final (&ctx, response);
/* outer hash: inner hash and opadded secret */
md5_init (&ctx);
md5_update (&ctx, opad, MD5_BLOCK_LEN);
md5_update (&ctx, response, MD5_DIGEST_LEN);
md5_final (&ctx, response);
}
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