NeoMutt  2022-04-29-249-gaae397
Teaching an old dog new tricks
DOXYGEN
auth_cram.c
Go to the documentation of this file.
1
29#include "config.h"
30#include <stdio.h>
31#include <string.h>
32#include "private.h"
33#include "mutt/lib.h"
34#include "conn/lib.h"
35#include "adata.h"
36#include "auth.h"
37
38#define MD5_BLOCK_LEN 64
39#define MD5_DIGEST_LEN 16
40
47static void hmac_md5(const char *password, char *challenge, unsigned char *response)
48{
49 struct Md5Ctx md5ctx;
50 unsigned char ipad[MD5_BLOCK_LEN] = { 0 };
51 unsigned char opad[MD5_BLOCK_LEN] = { 0 };
52 unsigned char secret[MD5_BLOCK_LEN + 1];
53 size_t secret_len;
54
55 secret_len = strlen(password);
56
57 /* passwords longer than MD5_BLOCK_LEN bytes are substituted with their MD5
58 * digests */
59 if (secret_len > MD5_BLOCK_LEN)
60 {
61 unsigned char hash_passwd[MD5_DIGEST_LEN];
62 mutt_md5_bytes(password, secret_len, hash_passwd);
63 mutt_str_copy((char *) secret, (char *) hash_passwd, MD5_DIGEST_LEN);
64 secret_len = MD5_DIGEST_LEN;
65 }
66 else
67 mutt_str_copy((char *) secret, password, sizeof(secret));
68
69 memcpy(ipad, secret, secret_len);
70 memcpy(opad, secret, secret_len);
71
72 for (int i = 0; i < MD5_BLOCK_LEN; i++)
73 {
74 ipad[i] ^= 0x36;
75 opad[i] ^= 0x5c;
76 }
77
78 /* inner hash: challenge and ipadded secret */
79 mutt_md5_init_ctx(&md5ctx);
81 mutt_md5_process(challenge, &md5ctx);
82 mutt_md5_finish_ctx(&md5ctx, response);
83
84 /* outer hash: inner hash and opadded secret */
85 mutt_md5_init_ctx(&md5ctx);
87 mutt_md5_process_bytes(response, MD5_DIGEST_LEN, &md5ctx);
88 mutt_md5_finish_ctx(&md5ctx, response);
89}
90
94enum ImapAuthRes imap_auth_cram_md5(struct ImapAccountData *adata, const char *method)
95{
96 char ibuf[2048], obuf[1024];
97 unsigned char hmac_response[MD5_DIGEST_LEN];
98 int len;
99 int rc;
100
101 if (!(adata->capabilities & IMAP_CAP_AUTH_CRAM_MD5))
102 return IMAP_AUTH_UNAVAIL;
103
104 // L10N: (%s) is the method name, e.g. Anonymous, CRAM-MD5, GSSAPI, SASL
105 mutt_message(_("Authenticating (%s)..."), "CRAM-MD5");
106
107 /* get auth info */
108 if (mutt_account_getlogin(&adata->conn->account) < 0)
109 return IMAP_AUTH_FAILURE;
110 if (mutt_account_getpass(&adata->conn->account) < 0)
111 return IMAP_AUTH_FAILURE;
112
113 imap_cmd_start(adata, "AUTHENTICATE CRAM-MD5");
114
115 /* From RFC2195:
116 * The data encoded in the first ready response contains a presumptively
117 * arbitrary string of random digits, a timestamp, and the fully-qualified
118 * primary host name of the server. The syntax of the unencoded form must
119 * correspond to that of an RFC822 'msg-id' [RFC822] as described in [POP3]. */
120 do
121 {
122 rc = imap_cmd_step(adata);
123 } while (rc == IMAP_RES_CONTINUE);
124
125 if (rc != IMAP_RES_RESPOND)
126 {
127 mutt_debug(LL_DEBUG1, "Invalid response from server: %s\n", ibuf);
128 goto bail;
129 }
130
131 len = mutt_b64_decode(adata->buf + 2, obuf, sizeof(obuf));
132 if (len == -1)
133 {
134 mutt_debug(LL_DEBUG1, "Error decoding base64 response\n");
135 goto bail;
136 }
137
138 obuf[len] = '\0';
139 mutt_debug(LL_DEBUG2, "CRAM challenge: %s\n", obuf);
140
141 /* The client makes note of the data and then responds with a string
142 * consisting of the user name, a space, and a 'digest'. The latter is
143 * computed by applying the keyed MD5 algorithm from [KEYED-MD5] where the
144 * key is a shared secret and the digested text is the timestamp (including
145 * angle-brackets).
146 *
147 * Note: The user name shouldn't be quoted. Since the digest can't contain
148 * spaces, there is no ambiguity. Some servers get this wrong, we'll work
149 * around them when the bug report comes in. Until then, we'll remain
150 * blissfully RFC-compliant. */
151 hmac_md5(adata->conn->account.pass, obuf, hmac_response);
152 /* dubious optimisation I saw elsewhere: make the whole string in one call */
153 int off = snprintf(obuf, sizeof(obuf), "%s ", adata->conn->account.user);
154 mutt_md5_toascii(hmac_response, obuf + off);
155 mutt_debug(LL_DEBUG2, "CRAM response: %s\n", obuf);
156
157 /* ibuf must be long enough to store the base64 encoding of obuf,
158 * plus the additional debris */
159 mutt_b64_encode(obuf, strlen(obuf), ibuf, sizeof(ibuf) - 2);
160 mutt_str_cat(ibuf, sizeof(ibuf), "\r\n");
161 mutt_socket_send(adata->conn, ibuf);
162
163 do
164 {
165 rc = imap_cmd_step(adata);
166 } while (rc == IMAP_RES_CONTINUE);
167
168 if (rc != IMAP_RES_OK)
169 {
170 mutt_debug(LL_DEBUG1, "Error receiving server response\n");
171 goto bail;
172 }
173
174 if (imap_code(adata->buf))
175 return IMAP_AUTH_SUCCESS;
176
177bail:
178 // L10N: %s is the method name, e.g. Anonymous, CRAM-MD5, GSSAPI, SASL
179 mutt_error(_("%s authentication failed"), "CRAM-MD5");
180 return IMAP_AUTH_FAILURE;
181}
IMAP authenticator multiplexor.
ImapAuthRes
Results of IMAP Authentication.
Definition: auth.h:38
@ IMAP_AUTH_FAILURE
Authentication failed.
Definition: auth.h:40
@ IMAP_AUTH_SUCCESS
Authentication successful.
Definition: auth.h:39
@ IMAP_AUTH_UNAVAIL
Authentication method not permitted.
Definition: auth.h:41
enum ImapAuthRes imap_auth_cram_md5(struct ImapAccountData *adata, const char *method)
Authenticate using CRAM-MD5 - Implements ImapAuth::authenticate()
Definition: auth_cram.c:94
#define MD5_BLOCK_LEN
Definition: auth_cram.c:38
static void hmac_md5(const char *password, char *challenge, unsigned char *response)
Produce CRAM-MD5 challenge response.
Definition: auth_cram.c:47
#define MD5_DIGEST_LEN
Definition: auth_cram.c:39
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
int mutt_b64_decode(const char *in, char *out, size_t olen)
Convert null-terminated base64 string to raw bytes.
Definition: base64.c:136
Connection Library.
int mutt_account_getpass(struct ConnAccount *cac)
Fetch password into ConnAccount, if necessary.
Definition: connaccount.c:130
int mutt_account_getlogin(struct ConnAccount *cac)
Retrieve login info into ConnAccount, if necessary.
Definition: connaccount.c:100
#define mutt_error(...)
Definition: logging.h:87
#define mutt_message(...)
Definition: logging.h:86
#define mutt_debug(LEVEL,...)
Definition: logging.h:84
int imap_cmd_start(struct ImapAccountData *adata, const char *cmdstr)
Given an IMAP command, send it to the server.
Definition: command.c:1062
int imap_cmd_step(struct ImapAccountData *adata)
Reads server responses from an IMAP command.
Definition: command.c:1076
bool imap_code(const char *s)
Was the command successful.
Definition: command.c:1199
#define IMAP_CAP_AUTH_CRAM_MD5
RFC2195: CRAM-MD5 authentication.
Definition: private.h:128
#define IMAP_RES_RESPOND
+
Definition: private.h:58
#define IMAP_RES_OK
<tag> OK ...
Definition: private.h:56
#define IMAP_RES_CONTINUE
* ...
Definition: private.h:57
@ LL_DEBUG2
Log at debug level 2.
Definition: logging.h:41
@ LL_DEBUG1
Log at debug level 1.
Definition: logging.h:40
void mutt_md5_process_bytes(const void *buf, size_t buflen, struct Md5Ctx *md5ctx)
Process a block of data.
Definition: md5.c:374
void * mutt_md5_bytes(const void *buffer, size_t len, void *resbuf)
Calculate the MD5 hash of a buffer.
Definition: md5.c:337
void mutt_md5_process(const char *str, struct Md5Ctx *md5ctx)
Process a NULL-terminated string.
Definition: md5.c:356
void mutt_md5_init_ctx(struct Md5Ctx *md5ctx)
Initialise the MD5 computation.
Definition: md5.c:262
void * mutt_md5_finish_ctx(struct Md5Ctx *md5ctx, void *resbuf)
Process the remaining bytes in the buffer.
Definition: md5.c:286
void mutt_md5_toascii(const void *digest, char *resbuf)
Convert a binary MD5 digest into ASCII Hexadecimal.
Definition: md5.c:457
Convenience wrapper for the library headers.
#define _(a)
Definition: message.h:28
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:652
char * mutt_str_cat(char *buf, size_t buflen, const char *s)
Concatenate two strings.
Definition: string.c:265
Pop-specific Account data.
GUI display the mailboxes in a side panel.
#define mutt_socket_send(conn, buf)
Definition: socket.h:59
char user[128]
Username.
Definition: connaccount.h:56
char pass[256]
Password.
Definition: connaccount.h:57
struct ConnAccount account
Account details: username, password, etc.
Definition: connection.h:50
IMAP-specific Account data -.
Definition: adata.h:40
ImapCapFlags capabilities
Capability flags.
Definition: adata.h:55
char * buf
Definition: adata.h:59
struct Connection * conn
Connection to IMAP server.
Definition: adata.h:41
Cursor for the MD5 hashing.
Definition: md5.h:37