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auth_cram.c File Reference

IMAP CRAM-MD5 authentication method. More...

#include "config.h"
#include <stdio.h>
#include <string.h>
#include "private.h"
#include "mutt/lib.h"
#include "conn/lib.h"
#include "adata.h"
#include "auth.h"
+ Include dependency graph for auth_cram.c:

Go to the source code of this file.

Macros

#define MD5_BLOCK_LEN   64
 
#define MD5_DIGEST_LEN   16
 

Functions

static void hmac_md5 (const char *password, char *challenge, unsigned char *response)
 Produce CRAM-MD5 challenge response.
 
enum ImapAuthRes imap_auth_cram_md5 (struct ImapAccountData *adata, const char *method)
 Authenticate using CRAM-MD5 - Implements ImapAuth::authenticate()
 

Detailed Description

IMAP CRAM-MD5 authentication method.

Authors
  • Brendan Cully
Copyright
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, see http://www.gnu.org/licenses/.

Definition in file auth_cram.c.

Macro Definition Documentation

◆ MD5_BLOCK_LEN

#define MD5_BLOCK_LEN   64

Definition at line 38 of file auth_cram.c.

◆ MD5_DIGEST_LEN

#define MD5_DIGEST_LEN   16

Definition at line 39 of file auth_cram.c.

Function Documentation

◆ hmac_md5()

static void hmac_md5 ( const char *  password,
char *  challenge,
unsigned char *  response 
)
static

Produce CRAM-MD5 challenge response.

Parameters
[in]passwordPassword to encrypt
[in]challengeChallenge from server
[out]responseBuffer for the response

Definition at line 47 of file auth_cram.c.

48{
49 struct Md5Ctx md5ctx = { 0 };
50 unsigned char ipad[MD5_BLOCK_LEN] = { 0 };
51 unsigned char opad[MD5_BLOCK_LEN] = { 0 };
52 unsigned char secret[MD5_BLOCK_LEN + 1] = { 0 };
53
54 size_t secret_len = strlen(password);
55
56 /* passwords longer than MD5_BLOCK_LEN bytes are substituted with their MD5
57 * digests */
58 if (secret_len > MD5_BLOCK_LEN)
59 {
60 unsigned char hash_passwd[MD5_DIGEST_LEN];
61 mutt_md5_bytes(password, secret_len, hash_passwd);
62 mutt_str_copy((char *) secret, (char *) hash_passwd, MD5_DIGEST_LEN);
63 secret_len = MD5_DIGEST_LEN;
64 }
65 else
66 {
67 mutt_str_copy((char *) secret, password, sizeof(secret));
68 }
69
70 memcpy(ipad, secret, secret_len);
71 memcpy(opad, secret, secret_len);
72
73 for (int i = 0; i < MD5_BLOCK_LEN; i++)
74 {
75 ipad[i] ^= 0x36;
76 opad[i] ^= 0x5c;
77 }
78
79 /* inner hash: challenge and ipadded secret */
80 mutt_md5_init_ctx(&md5ctx);
81 mutt_md5_process_bytes(ipad, MD5_BLOCK_LEN, &md5ctx);
82 mutt_md5_process(challenge, &md5ctx);
83 mutt_md5_finish_ctx(&md5ctx, response);
84
85 /* outer hash: inner hash and opadded secret */
86 mutt_md5_init_ctx(&md5ctx);
87 mutt_md5_process_bytes(opad, MD5_BLOCK_LEN, &md5ctx);
88 mutt_md5_process_bytes(response, MD5_DIGEST_LEN, &md5ctx);
89 mutt_md5_finish_ctx(&md5ctx, response);
90}
MD5_BLOCK_LEN
#define MD5_BLOCK_LEN
Definition: auth_cram.c:38
MD5_DIGEST_LEN
#define MD5_DIGEST_LEN
Definition: auth_cram.c:39
mutt_md5_process_bytes
void mutt_md5_process_bytes(const void *buf, size_t buflen, struct Md5Ctx *md5ctx)
Process a block of data.
Definition: md5.c:373
mutt_md5_bytes
void * mutt_md5_bytes(const void *buffer, size_t len, void *resbuf)
Calculate the MD5 hash of a buffer.
Definition: md5.c:336
mutt_md5_process
void mutt_md5_process(const char *str, struct Md5Ctx *md5ctx)
Process a NULL-terminated string.
Definition: md5.c:355
mutt_md5_init_ctx
void mutt_md5_init_ctx(struct Md5Ctx *md5ctx)
Initialise the MD5 computation.
Definition: md5.c:261
mutt_md5_finish_ctx
void * mutt_md5_finish_ctx(struct Md5Ctx *md5ctx, void *resbuf)
Process the remaining bytes in the buffer.
Definition: md5.c:285
mutt_str_copy
size_t mutt_str_copy(char *dest, const char *src, size_t dsize)
Copy a string into a buffer (guaranteeing NUL-termination)
Definition: string.c:653
Md5Ctx
Cursor for the MD5 hashing.
Definition: md5.h:37
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◆ imap_auth_cram_md5()

enum ImapAuthRes imap_auth_cram_md5 ( struct ImapAccountData *  adata,
const char *  method 
)

Authenticate using CRAM-MD5 - Implements ImapAuth::authenticate()

Definition at line 95 of file auth_cram.c.

96{
97 char ibuf[2048], obuf[1024];
98 unsigned char hmac_response[MD5_DIGEST_LEN];
99 int len;
100 int rc;
101
102 if (!(adata->capabilities & IMAP_CAP_AUTH_CRAM_MD5))
103 return IMAP_AUTH_UNAVAIL;
104
105 // L10N: (%s) is the method name, e.g. Anonymous, CRAM-MD5, GSSAPI, SASL
106 mutt_message(_("Authenticating (%s)..."), "CRAM-MD5");
107
108 /* get auth info */
109 if (mutt_account_getlogin(&adata->conn->account) < 0)
110 return IMAP_AUTH_FAILURE;
111 if (mutt_account_getpass(&adata->conn->account) < 0)
112 return IMAP_AUTH_FAILURE;
113
114 imap_cmd_start(adata, "AUTHENTICATE CRAM-MD5");
115
116 /* From RFC2195:
117 * The data encoded in the first ready response contains a presumptively
118 * arbitrary string of random digits, a timestamp, and the fully-qualified
119 * primary host name of the server. The syntax of the unencoded form must
120 * correspond to that of an RFC822 'msg-id' [RFC822] as described in [POP3]. */
121 do
122 {
123 rc = imap_cmd_step(adata);
124 } while (rc == IMAP_RES_CONTINUE);
125
126 if (rc != IMAP_RES_RESPOND)
127 {
128 mutt_debug(LL_DEBUG1, "Invalid response from server: %s\n", ibuf);
129 goto bail;
130 }
131
132 len = mutt_b64_decode(adata->buf + 2, obuf, sizeof(obuf));
133 if (len == -1)
134 {
135 mutt_debug(LL_DEBUG1, "Error decoding base64 response\n");
136 goto bail;
137 }
138
139 obuf[len] = '\0';
140 mutt_debug(LL_DEBUG2, "CRAM challenge: %s\n", obuf);
141
142 /* The client makes note of the data and then responds with a string
143 * consisting of the user name, a space, and a 'digest'. The latter is
144 * computed by applying the keyed MD5 algorithm from [KEYED-MD5] where the
145 * key is a shared secret and the digested text is the timestamp (including
146 * angle-brackets).
147 *
148 * Note: The user name shouldn't be quoted. Since the digest can't contain
149 * spaces, there is no ambiguity. Some servers get this wrong, we'll work
150 * around them when the bug report comes in. Until then, we'll remain
151 * blissfully RFC-compliant. */
152 hmac_md5(adata->conn->account.pass, obuf, hmac_response);
153 /* dubious optimisation I saw elsewhere: make the whole string in one call */
154 int off = snprintf(obuf, sizeof(obuf), "%s ", adata->conn->account.user);
155 mutt_md5_toascii(hmac_response, obuf + off);
156 mutt_debug(LL_DEBUG2, "CRAM response: %s\n", obuf);
157
158 /* ibuf must be long enough to store the base64 encoding of obuf,
159 * plus the additional debris */
160 mutt_b64_encode(obuf, strlen(obuf), ibuf, sizeof(ibuf) - 2);
161 mutt_str_cat(ibuf, sizeof(ibuf), "\r\n");
162 mutt_socket_send(adata->conn, ibuf);
163
164 do
165 {
166 rc = imap_cmd_step(adata);
167 } while (rc == IMAP_RES_CONTINUE);
168
169 if (rc != IMAP_RES_OK)
170 {
171 mutt_debug(LL_DEBUG1, "Error receiving server response\n");
172 goto bail;
173 }
174
175 if (imap_code(adata->buf))
176 return IMAP_AUTH_SUCCESS;
177
178bail:
179 // L10N: %s is the method name, e.g. Anonymous, CRAM-MD5, GSSAPI, SASL
180 mutt_error(_("%s authentication failed"), "CRAM-MD5");
181 return IMAP_AUTH_FAILURE;
182}
IMAP_AUTH_FAILURE
@ IMAP_AUTH_FAILURE
Authentication failed.
Definition: auth.h:40
IMAP_AUTH_SUCCESS
@ IMAP_AUTH_SUCCESS
Authentication successful.
Definition: auth.h:39
IMAP_AUTH_UNAVAIL
@ IMAP_AUTH_UNAVAIL
Authentication method not permitted.
Definition: auth.h:41
hmac_md5
static void hmac_md5(const char *password, char *challenge, unsigned char *response)
Produce CRAM-MD5 challenge response.
Definition: auth_cram.c:47
mutt_b64_encode
size_t mutt_b64_encode(const char *in, size_t inlen, char *out, size_t outlen)
Convert raw bytes to null-terminated base64 string.
Definition: base64.c:88
mutt_b64_decode
int mutt_b64_decode(const char *in, char *out, size_t olen)
Convert null-terminated base64 string to raw bytes.
Definition: base64.c:136
mutt_account_getpass
int mutt_account_getpass(struct ConnAccount *cac)
Fetch password into ConnAccount, if necessary.
Definition: connaccount.c:129
mutt_account_getlogin
int mutt_account_getlogin(struct ConnAccount *cac)
Retrieve login info into ConnAccount, if necessary.
Definition: connaccount.c:99
mutt_error
#define mutt_error(...)
Definition: logging2.h:92
mutt_message
#define mutt_message(...)
Definition: logging2.h:91
mutt_debug
#define mutt_debug(LEVEL,...)
Definition: logging2.h:89
imap_cmd_start
int imap_cmd_start(struct ImapAccountData *adata, const char *cmdstr)
Given an IMAP command, send it to the server.
Definition: command.c:1115
imap_cmd_step
int imap_cmd_step(struct ImapAccountData *adata)
Reads server responses from an IMAP command.
Definition: command.c:1129
imap_code
bool imap_code(const char *s)
Was the command successful.
Definition: command.c:1256
IMAP_CAP_AUTH_CRAM_MD5
#define IMAP_CAP_AUTH_CRAM_MD5
RFC2195: CRAM-MD5 authentication.
Definition: private.h:126
IMAP_RES_RESPOND
#define IMAP_RES_RESPOND
+
Definition: private.h:57
IMAP_RES_OK
#define IMAP_RES_OK
<tag> OK ...
Definition: private.h:55
IMAP_RES_CONTINUE
#define IMAP_RES_CONTINUE
* ...
Definition: private.h:56
LL_DEBUG2
@ LL_DEBUG2
Log at debug level 2.
Definition: logging2.h:44
LL_DEBUG1
@ LL_DEBUG1
Log at debug level 1.
Definition: logging2.h:43
mutt_md5_toascii
void mutt_md5_toascii(const void *digest, char *resbuf)
Convert a binary MD5 digest into ASCII Hexadecimal.
Definition: md5.c:456
_
#define _(a)
Definition: message.h:28
mutt_str_cat
char * mutt_str_cat(char *buf, size_t buflen, const char *s)
Concatenate two strings.
Definition: string.c:266
mutt_socket_send
#define mutt_socket_send(conn, buf)
Definition: socket.h:59
ConnAccount::user
char user[128]
Username.
Definition: connaccount.h:56
ConnAccount::pass
char pass[256]
Password.
Definition: connaccount.h:57
Connection::account
struct ConnAccount account
Account details: username, password, etc.
Definition: connection.h:50
ImapAccountData::capabilities
ImapCapFlags capabilities
Capability flags.
Definition: adata.h:55
ImapAccountData::buf
char * buf
Definition: adata.h:59
ImapAccountData::conn
struct Connection * conn
Connection to IMAP server.
Definition: adata.h:41
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