1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
|
/*++
/* NAME
/* postscreen_starttls 3
/* SUMMARY
/* postscreen TLS proxy support
/* SYNOPSIS
/* #include <postscreen.h>
/*
/* int psc_starttls_open(state, resume_event)
/* PSC_STATE *state;
/* void (*resume_event)(int unused_event, char *context);
/* DESCRIPTION
/* This module inserts the tlsproxy(8) proxy between the
/* postscreen(8) server and the remote SMTP client. The entire
/* process happens in the background, including notification
/* of completion to the remote SMTP client and to the calling
/* application.
/*
/* Before calling psc_starttls_open() the caller must turn off
/* all pending timer and I/O event requests on the SMTP client
/* stream.
/*
/* psc_starttls_open() starts the first transaction in the
/* tlsproxy(8) hand-off protocol, and sets up event handlers
/* for the successive protocol stages.
/*
/* Upon completion, the event handlers call resume_event()
/* which must reset the SMTP helo/sender/etc. state when the
/* PSC_STATE_FLAG_USING_TLS is set, and set up timer and read
/* event requests to receive the next SMTP command.
/* LICENSE
/* .ad
/* .fi
/* The Secure Mailer license must be distributed with this software.
/* AUTHOR(S)
/* Wietse Venema
/* IBM T.J. Watson Research
/* P.O. Box 704
/* Yorktown Heights, NY 10598, USA
/*
/* Wietse Venema
/* Google, Inc.
/* 111 8th Avenue
/* New York, NY 10011, USA
/*--*/
/* System library. */
#include <sys_defs.h>
/* Utility library. */
#include <msg.h>
#include <mymalloc.h>
#include <connect.h>
#include <stringops.h> /* concatenate() */
#include <vstring.h>
/* Global library. */
#include <mail_params.h>
#include <mail_proto.h>
/* TLS library. */
#include <tls_proxy.h>
/* Application-specific. */
#include <postscreen.h>
/*
* For now, this code is built into the postscreen(8) daemon. In the future
* it may be abstracted into a reusable library module for use by other
* event-driven programs (perhaps smtp-source and smtp-sink).
*/
/*
* Transient state for the portscreen(8)-to-tlsproxy(8) hand-off protocol.
*/
typedef struct {
VSTREAM *tlsproxy_stream; /* hand-off negotiation */
EVENT_NOTIFY_FN resume_event; /* call-back handler */
PSC_STATE *smtp_state; /* SMTP session state */
} PSC_STARTTLS;
#define TLSPROXY_INIT_TIMEOUT 10
static char *psc_tlsp_service = 0;
/* psc_starttls_finish - complete negotiation with TLS proxy */
static void psc_starttls_finish(int event, void *context)
{
const char *myname = "psc_starttls_finish";
PSC_STARTTLS *starttls_state = (PSC_STARTTLS *) context;
PSC_STATE *smtp_state = starttls_state->smtp_state;
VSTREAM *tlsproxy_stream = starttls_state->tlsproxy_stream;
int status;
if (msg_verbose)
msg_info("%s: send client handle on proxy socket %d"
" for smtp socket %d from [%s]:%s flags=%s",
myname, vstream_fileno(tlsproxy_stream),
vstream_fileno(smtp_state->smtp_client_stream),
smtp_state->smtp_client_addr, smtp_state->smtp_client_port,
psc_print_state_flags(smtp_state->flags, myname));
/*
* We leave read-event notification enabled on the postscreen to TLS
* proxy stream, to avoid two kqueue/epoll/etc. system calls: one here,
* and one when resuming the dummy SMTP engine.
*/
if (event != EVENT_TIME)
event_cancel_timer(psc_starttls_finish, (void *) starttls_state);
/*
* Receive the "TLS is available" indication.
*
* This may seem out of order, but we must have a read transaction between
* sending the request attributes and sending the SMTP client file
* descriptor. We can't assume UNIX-domain socket semantics here.
*/
if (event != EVENT_READ
|| attr_scan(tlsproxy_stream, ATTR_FLAG_STRICT,
RECV_ATTR_INT(MAIL_ATTR_STATUS, &status),
ATTR_TYPE_END) != 1 || status == 0) {
/*
* The TLS proxy reports that the TLS engine is not available (due to
* configuration error, or other causes).
*/
event_disable_readwrite(vstream_fileno(tlsproxy_stream));
vstream_fclose(tlsproxy_stream);
PSC_SEND_REPLY(smtp_state,
"454 4.7.0 TLS not available due to local problem\r\n");
}
/*
* Send the remote SMTP client file descriptor.
*/
else if (LOCAL_SEND_FD(vstream_fileno(tlsproxy_stream),
vstream_fileno(smtp_state->smtp_client_stream)) < 0) {
/*
* Some error: drop the TLS proxy stream.
*/
msg_warn("%s sending file handle to %s service",
event == EVENT_TIME ? "timeout" : "problem",
psc_tlsp_service);
event_disable_readwrite(vstream_fileno(tlsproxy_stream));
vstream_fclose(tlsproxy_stream);
PSC_SEND_REPLY(smtp_state,
"454 4.7.0 TLS not available due to local problem\r\n");
}
/*
* After we send the plaintext 220 greeting, the client-side TLS engine
* is supposed to talk first, then the server-side TLS engine. However,
* postscreen(8) will not participate in that conversation.
*/
else {
PSC_SEND_REPLY(smtp_state, "220 2.0.0 Ready to start TLS\r\n");
/*
* Replace our SMTP client stream by the TLS proxy stream. Once the
* TLS handshake is done, the TLS proxy will deliver plaintext SMTP
* commands to postscreen(8).
*
* Swap the file descriptors from under the VSTREAM so that we don't
* have to worry about loss of user-configurable VSTREAM attributes.
*/
vstream_fpurge(smtp_state->smtp_client_stream, VSTREAM_PURGE_BOTH);
vstream_control(smtp_state->smtp_client_stream,
CA_VSTREAM_CTL_SWAP_FD(tlsproxy_stream),
CA_VSTREAM_CTL_END);
vstream_fclose(tlsproxy_stream); /* direct-to-client stream! */
smtp_state->flags |= PSC_STATE_FLAG_USING_TLS;
}
/*
* Resume the postscreen(8) dummy SMTP engine and clean up.
*/
starttls_state->resume_event(event, (void *) smtp_state);
myfree((void *) starttls_state);
}
/* psc_starttls_open - open negotiations with TLS proxy */
void psc_starttls_open(PSC_STATE *smtp_state, EVENT_NOTIFY_FN resume_event)
{
const char *myname = "psc_starttls_open";
PSC_STARTTLS *starttls_state;
VSTREAM *tlsproxy_stream;
int fd;
static VSTRING *remote_endpt = 0;
if (psc_tlsp_service == 0) {
psc_tlsp_service = concatenate(MAIL_CLASS_PRIVATE "/",
var_tlsproxy_service, (char *) 0);
remote_endpt = vstring_alloc(20);
}
/*
* Connect to the tlsproxy(8) daemon. We report all errors
* asynchronously, to avoid having to maintain multiple delivery paths.
*/
if ((fd = LOCAL_CONNECT(psc_tlsp_service, NON_BLOCKING, 1)) < 0) {
msg_warn("connect to %s service: %m", psc_tlsp_service);
PSC_SEND_REPLY(smtp_state,
"454 4.7.0 TLS not available due to local problem\r\n");
event_request_timer(resume_event, (void *) smtp_state, 0);
return;
}
if (msg_verbose)
msg_info("%s: send client name/address on proxy socket %d"
" for smtp socket %d from [%s]:%s flags=%s",
myname, fd, vstream_fileno(smtp_state->smtp_client_stream),
smtp_state->smtp_client_addr, smtp_state->smtp_client_port,
psc_print_state_flags(smtp_state->flags, myname));
/*
* Initial handshake. Send the data attributes now, and send the client
* file descriptor in a later transaction. We report all errors
* asynchronously, to avoid having to maintain multiple delivery paths.
*
* XXX The formatted endpoint should be a state member. Then, we can
* simplify all the format strings throughout the program.
*/
tlsproxy_stream = vstream_fdopen(fd, O_RDWR);
vstring_sprintf(remote_endpt, "[%s]:%s", smtp_state->smtp_client_addr,
smtp_state->smtp_client_port);
attr_print(tlsproxy_stream, ATTR_FLAG_NONE,
SEND_ATTR_STR(TLS_ATTR_REMOTE_ENDPT, STR(remote_endpt)),
SEND_ATTR_INT(TLS_ATTR_FLAGS, TLS_PROXY_FLAG_ROLE_SERVER),
SEND_ATTR_INT(TLS_ATTR_TIMEOUT, psc_normal_cmd_time_limit),
SEND_ATTR_INT(TLS_ATTR_TIMEOUT, psc_normal_cmd_time_limit),
SEND_ATTR_STR(TLS_ATTR_SERVERID, MAIL_SERVICE_SMTPD), /* XXX */
ATTR_TYPE_END);
if (vstream_fflush(tlsproxy_stream) != 0) {
msg_warn("error sending request to %s service: %m", psc_tlsp_service);
vstream_fclose(tlsproxy_stream);
PSC_SEND_REPLY(smtp_state,
"454 4.7.0 TLS not available due to local problem\r\n");
event_request_timer(resume_event, (void *) smtp_state, 0);
return;
}
/*
* Set up a read event for the next phase of the TLS proxy handshake.
*/
starttls_state = (PSC_STARTTLS *) mymalloc(sizeof(*starttls_state));
starttls_state->tlsproxy_stream = tlsproxy_stream;
starttls_state->resume_event = resume_event;
starttls_state->smtp_state = smtp_state;
PSC_READ_EVENT_REQUEST(vstream_fileno(tlsproxy_stream), psc_starttls_finish,
(void *) starttls_state, TLSPROXY_INIT_TIMEOUT);
}
|
