summaryrefslogtreecommitdiffstats
path: root/src/smtpd/smtpd_proxy.c
diff options
context:
space:
mode:
authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-10 19:59:03 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-10 19:59:03 +0000
commita848231ae0f346dc7cc000973fbeb65b0894ee92 (patch)
tree44b60b367c86723cc78383ef247885d72b388afe /src/smtpd/smtpd_proxy.c
parentInitial commit. (diff)
downloadpostfix-a848231ae0f346dc7cc000973fbeb65b0894ee92.tar.xz
postfix-a848231ae0f346dc7cc000973fbeb65b0894ee92.zip
Adding upstream version 3.8.5.upstream/3.8.5
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'src/smtpd/smtpd_proxy.c')
-rw-r--r--src/smtpd/smtpd_proxy.c1171
1 files changed, 1171 insertions, 0 deletions
diff --git a/src/smtpd/smtpd_proxy.c b/src/smtpd/smtpd_proxy.c
new file mode 100644
index 0000000..1c1f9fc
--- /dev/null
+++ b/src/smtpd/smtpd_proxy.c
@@ -0,0 +1,1171 @@
+/*++
+/* NAME
+/* smtpd_proxy 3
+/* SUMMARY
+/* SMTP server pass-through proxy client
+/* SYNOPSIS
+/* #include <smtpd.h>
+/* #include <smtpd_proxy.h>
+/*
+/* typedef struct {
+/* .in +4
+/* VSTREAM *stream; /* SMTP proxy or replay log */
+/* VSTRING *buffer; /* last SMTP proxy response */
+/* /* other fields... */
+/* .in -4
+/* } SMTPD_PROXY;
+/*
+/* int smtpd_proxy_create(state, flags, service, timeout,
+/* ehlo_name, mail_from)
+/* SMTPD_STATE *state;
+/* int flags;
+/* const char *service;
+/* int timeout;
+/* const char *ehlo_name;
+/* const char *mail_from;
+/*
+/* int proxy->cmd(state, expect, format, ...)
+/* SMTPD_PROXY *proxy;
+/* SMTPD_STATE *state;
+/* int expect;
+/* const char *format;
+/*
+/* void smtpd_proxy_free(state)
+/* SMTPD_STATE *state;
+/*
+/* int smtpd_proxy_parse_opts(param_name, param_val)
+/* const char *param_name;
+/* const char *param_val;
+/* RECORD-LEVEL ROUTINES
+/* int proxy->rec_put(proxy->stream, rec_type, data, len)
+/* SMTPD_PROXY *proxy;
+/* int rec_type;
+/* const char *data;
+/* ssize_t len;
+/*
+/* int proxy->rec_fprintf(proxy->stream, rec_type, format, ...)
+/* SMTPD_PROXY *proxy;
+/* int rec_type;
+/* cont char *format;
+/* DESCRIPTION
+/* The functions in this module implement a pass-through proxy
+/* client.
+/*
+/* In order to minimize the intrusiveness of pass-through
+/* proxying, 1) the proxy server must support the same MAIL
+/* FROM/RCPT syntax that Postfix supports, 2) the record-level
+/* routines for message content proxying have the same interface
+/* as the routines that are used for non-proxied mail.
+/*
+/* smtpd_proxy_create() takes a description of a before-queue
+/* filter. Depending on flags, it either arranges to buffer
+/* up commands and message content until the entire message
+/* is received, or it immediately connects to the proxy service,
+/* sends EHLO, sends client information with the XFORWARD
+/* command if possible, sends the MAIL FROM command, and
+/* receives the reply.
+/* A non-zero result value means trouble: either the proxy is
+/* unavailable, or it did not send the expected reply.
+/* All results are reported via the proxy->buffer field in a
+/* form that can be sent to the SMTP client. An unexpected
+/* 2xx or 3xx proxy server response is replaced by a generic
+/* error response to avoid support problems.
+/* In case of error, smtpd_proxy_create() updates the
+/* state->error_mask and state->err fields, and leaves the
+/* SMTPD_PROXY handle in an unconnected state. Destroy the
+/* handle after reporting the error reply in the proxy->buffer
+/* field.
+/*
+/* proxy->cmd() formats and either buffers up the command and
+/* expected response until the entire message is received, or
+/* it immediately sends the specified command to the proxy
+/* server, and receives the proxy server reply.
+/* A non-zero result value means trouble: either the proxy is
+/* unavailable, or it did not send the expected reply.
+/* All results are reported via the proxy->buffer field in a
+/* form that can be sent to the SMTP client. An unexpected
+/* 2xx or 3xx proxy server response is replaced by a generic
+/* error response to avoid support problems.
+/* In case of error, proxy->cmd() updates the state->error_mask
+/* and state->err fields.
+/*
+/* smtpd_proxy_free() destroys a proxy server handle and resets
+/* the state->proxy field.
+/*
+/* smtpd_proxy_parse_opts() parses main.cf processing options.
+/*
+/* proxy->rec_put() is a rec_put() clone that either buffers
+/* up arbitrary message content records until the entire message
+/* is received, or that immediately sends it to the proxy
+/* server.
+/* All data is expected to be in SMTP dot-escaped form.
+/* All errors are reported as a REC_TYPE_ERROR result value,
+/* with the state->error_mask, state->err and proxy-buffer
+/* fields given appropriate values.
+/*
+/* proxy->rec_fprintf() is a rec_fprintf() clone that formats
+/* message content and either buffers up the record until the
+/* entire message is received, or that immediately sends it
+/* to the proxy server.
+/* All data is expected to be in SMTP dot-escaped form.
+/* All errors are reported as a REC_TYPE_ERROR result value,
+/* with the state->error_mask, state->err and proxy-buffer
+/* fields given appropriate values.
+/*
+/* Arguments:
+/* .IP flags
+/* Zero, or SMTPD_PROXY_FLAG_SPEED_ADJUST to buffer up the entire
+/* message before contacting a before-queue content filter.
+/* Note: when this feature is requested, the before-queue
+/* filter MUST use the same 2xx, 4xx or 5xx reply code for all
+/* recipients of a multi-recipient message.
+/* .IP server
+/* The SMTP proxy server host:port. The host or host: part is optional.
+/* This argument is not duplicated.
+/* .IP timeout
+/* Time limit for connecting to the proxy server and for
+/* sending and receiving proxy server commands and replies.
+/* .IP ehlo_name
+/* The EHLO Hostname that will be sent to the proxy server.
+/* This argument is not duplicated.
+/* .IP mail_from
+/* The MAIL FROM command. This argument is not duplicated.
+/* .IP state
+/* SMTP server state.
+/* .IP expect
+/* Expected proxy server reply status code range. A warning is logged
+/* when an unexpected reply is received. Specify one of the following:
+/* .RS
+/* .IP SMTPD_PROX_WANT_OK
+/* The caller expects a reply in the 200 range.
+/* .IP SMTPD_PROX_WANT_MORE
+/* The caller expects a reply in the 300 range.
+/* .IP SMTPD_PROX_WANT_ANY
+/* The caller has no expectation. Do not warn for unexpected replies.
+/* .IP SMTPD_PROX_WANT_NONE
+/* Do not bother waiting for a reply.
+/* .RE
+/* .IP format
+/* A format string.
+/* .IP stream
+/* Connection to proxy server.
+/* .IP data
+/* Pointer to the content of one message content record.
+/* .IP len
+/* The length of a message content record.
+/* SEE ALSO
+/* smtpd(8) Postfix smtp server
+/* DIAGNOSTICS
+/* Panic: internal API violations.
+/*
+/* Fatal errors: memory allocation problem.
+/*
+/* Warnings: unexpected response from proxy server, unable
+/* to connect to proxy server, proxy server read/write error,
+/* proxy speed-adjust buffer read/write error.
+/* 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
+/*--*/
+
+/* System library. */
+
+#include <sys_defs.h>
+#include <ctype.h>
+#include <unistd.h>
+
+#ifdef STRCASECMP_IN_STRINGS_H
+#include <strings.h>
+#endif
+
+/* Utility library. */
+
+#include <msg.h>
+#include <vstream.h>
+#include <vstring.h>
+#include <stringops.h>
+#include <connect.h>
+#include <name_code.h>
+#include <mymalloc.h>
+
+/* Global library. */
+
+#include <mail_error.h>
+#include <smtp_stream.h>
+#include <cleanup_user.h>
+#include <mail_params.h>
+#include <rec_type.h>
+#include <mail_proto.h>
+#include <xtext.h>
+#include <record.h>
+#include <mail_queue.h>
+
+/* Application-specific. */
+
+#include <smtpd.h>
+#include <smtpd_proxy.h>
+
+ /*
+ * XFORWARD server features, recognized by the pass-through proxy client.
+ */
+#define SMTPD_PROXY_XFORWARD_NAME (1<<0) /* client name */
+#define SMTPD_PROXY_XFORWARD_ADDR (1<<1) /* client address */
+#define SMTPD_PROXY_XFORWARD_PROTO (1<<2) /* protocol */
+#define SMTPD_PROXY_XFORWARD_HELO (1<<3) /* client helo */
+#define SMTPD_PROXY_XFORWARD_IDENT (1<<4) /* message identifier */
+#define SMTPD_PROXY_XFORWARD_DOMAIN (1<<5) /* origin type */
+#define SMTPD_PROXY_XFORWARD_PORT (1<<6) /* client port */
+
+ /*
+ * Spead-matching: we use an unlinked file for transient storage.
+ */
+static VSTREAM *smtpd_proxy_replay_stream;
+
+ /*
+ * Forward declarations.
+ */
+static void smtpd_proxy_fake_server_reply(SMTPD_STATE *, int);
+static int smtpd_proxy_rdwr_error(SMTPD_STATE *, int);
+static int PRINTFLIKE(3, 4) smtpd_proxy_cmd(SMTPD_STATE *, int, const char *,...);
+static int smtpd_proxy_rec_put(VSTREAM *, int, const char *, ssize_t);
+
+ /*
+ * SLMs.
+ */
+#define STR(x) vstring_str(x)
+#define LEN(x) VSTRING_LEN(x)
+#define STREQ(x, y) (strcmp((x), (y)) == 0)
+
+/* smtpd_proxy_xforward_flush - flush forwarding information */
+
+static int smtpd_proxy_xforward_flush(SMTPD_STATE *state, VSTRING *buf)
+{
+ int ret;
+
+ if (VSTRING_LEN(buf) > 0) {
+ ret = smtpd_proxy_cmd(state, SMTPD_PROX_WANT_OK,
+ XFORWARD_CMD "%s", STR(buf));
+ VSTRING_RESET(buf);
+ return (ret);
+ }
+ return (0);
+}
+
+/* smtpd_proxy_xforward_send - send forwarding information */
+
+static int smtpd_proxy_xforward_send(SMTPD_STATE *state, VSTRING *buf,
+ const char *name,
+ int value_available,
+ const char *value)
+{
+ size_t new_len;
+ int ret;
+
+#define CONSTR_LEN(s) (sizeof(s) - 1)
+#define PAYLOAD_LIMIT (512 - CONSTR_LEN("250 " XFORWARD_CMD "\r\n"))
+
+ if (!value_available)
+ value = XFORWARD_UNAVAILABLE;
+
+ /*
+ * Encode the attribute value.
+ */
+ if (state->expand_buf == 0)
+ state->expand_buf = vstring_alloc(100);
+ xtext_quote(state->expand_buf, value, "");
+
+ /*
+ * How much space does this attribute need? SPACE name = value.
+ */
+ new_len = strlen(name) + strlen(STR(state->expand_buf)) + 2;
+ if (new_len > PAYLOAD_LIMIT)
+ msg_warn("%s command payload %s=%.10s... exceeds SMTP protocol limit",
+ XFORWARD_CMD, name, value);
+
+ /*
+ * Flush the buffer if we need to, and store the attribute.
+ */
+ if (VSTRING_LEN(buf) > 0 && VSTRING_LEN(buf) + new_len > PAYLOAD_LIMIT)
+ if ((ret = smtpd_proxy_xforward_flush(state, buf)) < 0)
+ return (ret);
+ vstring_sprintf_append(buf, " %s=%s", name, STR(state->expand_buf));
+
+ return (0);
+}
+
+/* smtpd_proxy_connect - open proxy connection */
+
+static int smtpd_proxy_connect(SMTPD_STATE *state)
+{
+ SMTPD_PROXY *proxy = state->proxy;
+ int fd;
+ char *lines;
+ char *words;
+ VSTRING *buf;
+ int bad;
+ char *word;
+ static const NAME_CODE known_xforward_features[] = {
+ XFORWARD_NAME, SMTPD_PROXY_XFORWARD_NAME,
+ XFORWARD_ADDR, SMTPD_PROXY_XFORWARD_ADDR,
+ XFORWARD_PORT, SMTPD_PROXY_XFORWARD_PORT,
+ XFORWARD_PROTO, SMTPD_PROXY_XFORWARD_PROTO,
+ XFORWARD_HELO, SMTPD_PROXY_XFORWARD_HELO,
+ XFORWARD_IDENT, SMTPD_PROXY_XFORWARD_IDENT,
+ XFORWARD_DOMAIN, SMTPD_PROXY_XFORWARD_DOMAIN,
+ 0, 0,
+ };
+ int server_xforward_features;
+ int (*connect_fn) (const char *, int, int);
+ const char *endpoint;
+
+ /*
+ * Find connection method (default inet)
+ */
+ if (strncasecmp("unix:", proxy->service_name, 5) == 0) {
+ endpoint = proxy->service_name + 5;
+ connect_fn = unix_connect;
+ } else {
+ if (strncasecmp("inet:", proxy->service_name, 5) == 0)
+ endpoint = proxy->service_name + 5;
+ else
+ endpoint = proxy->service_name;
+ connect_fn = inet_connect;
+ }
+
+ /*
+ * Connect to proxy.
+ */
+ if ((fd = connect_fn(endpoint, BLOCKING, proxy->timeout)) < 0) {
+ msg_warn("connect to proxy filter %s: %m", proxy->service_name);
+ return (smtpd_proxy_rdwr_error(state, 0));
+ }
+ proxy->service_stream = vstream_fdopen(fd, O_RDWR);
+ /* Needed by our DATA-phase record emulation routines. */
+ vstream_control(proxy->service_stream,
+ CA_VSTREAM_CTL_CONTEXT((void *) state),
+ CA_VSTREAM_CTL_END);
+ /* Avoid poor performance when TCP MSS > VSTREAM_BUFSIZE. */
+ if (connect_fn == inet_connect)
+ vstream_tweak_tcp(proxy->service_stream);
+ smtp_timeout_setup(proxy->service_stream, proxy->timeout);
+
+ /*
+ * Get server greeting banner.
+ *
+ * If this fails then we have a problem because the proxy should always
+ * accept our connection. Make up our own response instead of passing
+ * back a negative greeting banner: the proxy open is delayed to the
+ * point that the client expects a MAIL FROM or RCPT TO reply.
+ */
+ if (smtpd_proxy_cmd(state, SMTPD_PROX_WANT_OK, "%s", "")) {
+ smtpd_proxy_fake_server_reply(state, CLEANUP_STAT_PROXY);
+ smtpd_proxy_close(state);
+ return (-1);
+ }
+
+ /*
+ * Send our own EHLO command. If this fails then we have a problem
+ * because the proxy should always accept our EHLO command. Make up our
+ * own response instead of passing back a negative EHLO reply: the proxy
+ * open is delayed to the point that the remote SMTP client expects a
+ * MAIL FROM or RCPT TO reply.
+ */
+ if (smtpd_proxy_cmd(state, SMTPD_PROX_WANT_OK, "EHLO %s",
+ proxy->ehlo_name)) {
+ smtpd_proxy_fake_server_reply(state, CLEANUP_STAT_PROXY);
+ smtpd_proxy_close(state);
+ return (-1);
+ }
+
+ /*
+ * Parse the EHLO reply and see if we can forward logging information.
+ */
+ server_xforward_features = 0;
+ lines = STR(proxy->reply);
+ while ((words = mystrtok(&lines, "\r\n")) != 0) {
+ if (mystrtok(&words, "- ") && (word = mystrtok(&words, " \t")) != 0) {
+ if (strcasecmp(word, XFORWARD_CMD) == 0)
+ while ((word = mystrtok(&words, " \t")) != 0)
+ server_xforward_features |=
+ name_code(known_xforward_features,
+ NAME_CODE_FLAG_NONE, word);
+ }
+ }
+
+ /*
+ * Send XFORWARD attributes. For robustness, explicitly specify what SMTP
+ * session attributes are known and unknown. Make up our own response
+ * instead of passing back a negative XFORWARD reply: the proxy open is
+ * delayed to the point that the remote SMTP client expects a MAIL FROM
+ * or RCPT TO reply.
+ */
+ if (server_xforward_features) {
+ buf = vstring_alloc(100);
+ bad =
+ (((server_xforward_features & SMTPD_PROXY_XFORWARD_NAME)
+ && smtpd_proxy_xforward_send(state, buf, XFORWARD_NAME,
+ IS_AVAIL_CLIENT_NAME(FORWARD_NAME(state)),
+ FORWARD_NAME(state)))
+ || ((server_xforward_features & SMTPD_PROXY_XFORWARD_ADDR)
+ && smtpd_proxy_xforward_send(state, buf, XFORWARD_ADDR,
+ IS_AVAIL_CLIENT_ADDR(FORWARD_ADDR(state)),
+ FORWARD_ADDR(state)))
+ || ((server_xforward_features & SMTPD_PROXY_XFORWARD_PORT)
+ && smtpd_proxy_xforward_send(state, buf, XFORWARD_PORT,
+ IS_AVAIL_CLIENT_PORT(FORWARD_PORT(state)),
+ FORWARD_PORT(state)))
+ || ((server_xforward_features & SMTPD_PROXY_XFORWARD_HELO)
+ && smtpd_proxy_xforward_send(state, buf, XFORWARD_HELO,
+ IS_AVAIL_CLIENT_HELO(FORWARD_HELO(state)),
+ FORWARD_HELO(state)))
+ || ((server_xforward_features & SMTPD_PROXY_XFORWARD_IDENT)
+ && smtpd_proxy_xforward_send(state, buf, XFORWARD_IDENT,
+ IS_AVAIL_CLIENT_IDENT(FORWARD_IDENT(state)),
+ FORWARD_IDENT(state)))
+ || ((server_xforward_features & SMTPD_PROXY_XFORWARD_PROTO)
+ && smtpd_proxy_xforward_send(state, buf, XFORWARD_PROTO,
+ IS_AVAIL_CLIENT_PROTO(FORWARD_PROTO(state)),
+ FORWARD_PROTO(state)))
+ || ((server_xforward_features & SMTPD_PROXY_XFORWARD_DOMAIN)
+ && smtpd_proxy_xforward_send(state, buf, XFORWARD_DOMAIN, 1,
+ STREQ(FORWARD_DOMAIN(state), MAIL_ATTR_RWR_LOCAL) ?
+ XFORWARD_DOM_LOCAL : XFORWARD_DOM_REMOTE))
+ || smtpd_proxy_xforward_flush(state, buf));
+ vstring_free(buf);
+ if (bad) {
+ smtpd_proxy_fake_server_reply(state, CLEANUP_STAT_PROXY);
+ smtpd_proxy_close(state);
+ return (-1);
+ }
+ }
+
+ /*
+ * Pass-through the remote SMTP client's MAIL FROM command. If this
+ * fails, then we have a problem because the proxy should always accept
+ * any MAIL FROM command that was accepted by us.
+ */
+ if (smtpd_proxy_cmd(state, SMTPD_PROX_WANT_OK, "%s",
+ proxy->mail_from) != 0) {
+ /* NOT: smtpd_proxy_fake_server_reply(state, CLEANUP_STAT_PROXY); */
+ smtpd_proxy_close(state);
+ return (-1);
+ }
+ return (0);
+}
+
+/* smtpd_proxy_fake_server_reply - produce generic error response */
+
+static void smtpd_proxy_fake_server_reply(SMTPD_STATE *state, int status)
+{
+ const CLEANUP_STAT_DETAIL *detail;
+
+ /*
+ * Either we have no server reply (connection refused), or we have an
+ * out-of-protocol server reply, so we make up a generic server error
+ * response instead.
+ */
+ detail = cleanup_stat_detail(status);
+ vstring_sprintf(state->proxy->reply,
+ "%d %s Error: %s",
+ detail->smtp, detail->dsn, detail->text);
+}
+
+/* smtpd_proxy_replay_rdwr_error - report replay log I/O error */
+
+static int smtpd_proxy_replay_rdwr_error(SMTPD_STATE *state)
+{
+
+ /*
+ * Log an appropriate warning message.
+ */
+ msg_warn("proxy speed-adjust log I/O error: %m");
+
+ /*
+ * Set the appropriate flags and server reply.
+ */
+ state->error_mask |= MAIL_ERROR_RESOURCE;
+ /* Update state->err in case we are past the client's DATA command. */
+ state->err |= CLEANUP_STAT_PROXY;
+ smtpd_proxy_fake_server_reply(state, CLEANUP_STAT_PROXY);
+ return (-1);
+}
+
+/* smtpd_proxy_rdwr_error - report proxy communication error */
+
+static int smtpd_proxy_rdwr_error(SMTPD_STATE *state, int err)
+{
+ const char *myname = "smtpd_proxy_rdwr_error";
+ SMTPD_PROXY *proxy = state->proxy;
+
+ /*
+ * Sanity check.
+ */
+ if (err != 0 && err != SMTP_ERR_NONE && proxy == 0)
+ msg_panic("%s: proxy error %d without proxy handle", myname, err);
+
+ /*
+ * Log an appropriate warning message.
+ */
+ switch (err) {
+ case 0:
+ case SMTP_ERR_NONE:
+ break;
+ case SMTP_ERR_EOF:
+ msg_warn("lost connection with proxy %s", proxy->service_name);
+ break;
+ case SMTP_ERR_TIME:
+ msg_warn("timeout talking to proxy %s", proxy->service_name);
+ break;
+ default:
+ msg_panic("%s: unknown proxy %s error %d",
+ myname, proxy->service_name, err);
+ }
+
+ /*
+ * Set the appropriate flags and server reply.
+ */
+ state->error_mask |= MAIL_ERROR_SOFTWARE;
+ /* Update state->err in case we are past the client's DATA command. */
+ state->err |= CLEANUP_STAT_PROXY;
+ smtpd_proxy_fake_server_reply(state, CLEANUP_STAT_PROXY);
+ return (-1);
+}
+
+/* smtpd_proxy_replay_send - replay saved SMTP session from speed-match log */
+
+static int smtpd_proxy_replay_send(SMTPD_STATE *state)
+{
+ const char *myname = "smtpd_proxy_replay_send";
+ static VSTRING *replay_buf = 0;
+ SMTPD_PROXY *proxy = state->proxy;
+ int rec_type;
+ int expect = SMTPD_PROX_WANT_BAD;
+
+ /*
+ * Sanity check.
+ */
+ if (smtpd_proxy_replay_stream == 0)
+ msg_panic("%s: no before-queue filter speed-adjust log", myname);
+
+ /*
+ * Errors first.
+ */
+ if (vstream_ferror(smtpd_proxy_replay_stream)
+ || vstream_feof(smtpd_proxy_replay_stream)
+ || rec_put(smtpd_proxy_replay_stream, REC_TYPE_END, "", 0) != REC_TYPE_END
+ || vstream_fflush(smtpd_proxy_replay_stream))
+ /* NOT: fsync(vstream_fileno(smtpd_proxy_replay_stream)) */
+ return (smtpd_proxy_replay_rdwr_error(state));
+
+ /*
+ * Delayed connection to the before-queue filter.
+ */
+ if (smtpd_proxy_connect(state) < 0)
+ return (-1);
+
+ /*
+ * Replay the speed-match log. We do sanity check record content, but we
+ * don't implement a protocol state engine here, since we are reading
+ * from a file that we just wrote ourselves.
+ *
+ * This is different than the MailChannels patented solution that
+ * multiplexes a large number of slowed-down inbound connections over a
+ * small number of fast connections to a local MTA.
+ *
+ * - MailChannels receives mail directly from the Internet. It uses one
+ * connection to the local MTA to reject invalid recipients before
+ * receiving the entire email message at reduced bit rates, and then uses
+ * a different connection to quickly deliver the message to the local
+ * MTA.
+ *
+ * - Postfix receives mail directly from the Internet. The Postfix SMTP
+ * server rejects invalid recipients before receiving the entire message
+ * over the Internet, and then delivers the message quickly to a local
+ * SMTP-based content filter.
+ */
+ if (replay_buf == 0)
+ replay_buf = vstring_alloc(100);
+ if (vstream_fseek(smtpd_proxy_replay_stream, (off_t) 0, SEEK_SET) < 0)
+ return (smtpd_proxy_replay_rdwr_error(state));
+
+ for (;;) {
+ switch (rec_type = rec_get(smtpd_proxy_replay_stream, replay_buf,
+ REC_FLAG_NONE)) {
+
+ /*
+ * Message content.
+ */
+ case REC_TYPE_NORM:
+ case REC_TYPE_CONT:
+ if (smtpd_proxy_rec_put(proxy->service_stream, rec_type,
+ STR(replay_buf), LEN(replay_buf)) < 0)
+ return (-1);
+ break;
+
+ /*
+ * Expected server reply type.
+ */
+ case REC_TYPE_RCPT:
+ if (!alldig(STR(replay_buf))
+ || (expect = atoi(STR(replay_buf))) == SMTPD_PROX_WANT_BAD)
+ msg_panic("%s: malformed server reply type: %s",
+ myname, STR(replay_buf));
+ break;
+
+ /*
+ * Client command, or void. Bail out on the first negative proxy
+ * response. This is OK, because the filter must use the same
+ * reply code for all recipients of a multi-recipient message.
+ */
+ case REC_TYPE_FROM:
+ if (expect == SMTPD_PROX_WANT_BAD)
+ msg_panic("%s: missing server reply type", myname);
+ if (smtpd_proxy_cmd(state, expect, "%s", STR(replay_buf)) < 0)
+ return (-1);
+ expect = SMTPD_PROX_WANT_BAD;
+ break;
+
+ /*
+ * Explicit end marker, instead of implicit EOF.
+ */
+ case REC_TYPE_END:
+ return (0);
+
+ /*
+ * Errors.
+ */
+ case REC_TYPE_ERROR:
+ return (smtpd_proxy_replay_rdwr_error(state));
+ default:
+ msg_panic("%s: unexpected record type; %d", myname, rec_type);
+ }
+ }
+}
+
+/* smtpd_proxy_save_cmd - save SMTP command + expected response to replay log */
+
+static int PRINTFLIKE(3, 4) smtpd_proxy_save_cmd(SMTPD_STATE *state, int expect, const char *fmt,...)
+{
+ va_list ap;
+
+ /*
+ * Errors first.
+ */
+ if (vstream_ferror(smtpd_proxy_replay_stream)
+ || vstream_feof(smtpd_proxy_replay_stream))
+ return (smtpd_proxy_replay_rdwr_error(state));
+
+ /*
+ * Save the expected reply first, so that the replayer can safely
+ * overwrite the input buffer with the command.
+ */
+ rec_fprintf(smtpd_proxy_replay_stream, REC_TYPE_RCPT, "%d", expect);
+
+ /*
+ * The command can be omitted at the start of an SMTP session. This is
+ * not documented as part of the official interface because it is used
+ * only internally to this module.
+ */
+
+ /*
+ * Save the command to the replay log, and send it to the before-queue
+ * filter after we have received the entire message.
+ */
+ va_start(ap, fmt);
+ rec_vfprintf(smtpd_proxy_replay_stream, REC_TYPE_FROM, fmt, ap);
+ va_end(ap);
+
+ /*
+ * If we just saved the "." command, replay the log.
+ */
+ return (strcmp(fmt, ".") ? 0 : smtpd_proxy_replay_send(state));
+}
+
+/* smtpd_proxy_cmd - send command to proxy, receive reply */
+
+static int smtpd_proxy_cmd(SMTPD_STATE *state, int expect, const char *fmt,...)
+{
+ SMTPD_PROXY *proxy = state->proxy;
+ va_list ap;
+ char *cp;
+ int last_char;
+ int err = 0;
+ static VSTRING *buffer = 0;
+
+ /*
+ * Errors first. Be prepared for delayed errors from the DATA phase.
+ */
+ if (vstream_ferror(proxy->service_stream)
+ || vstream_feof(proxy->service_stream)
+ || (err = vstream_setjmp(proxy->service_stream)) != 0) {
+ return (smtpd_proxy_rdwr_error(state, err));
+ }
+
+ /*
+ * Format the command.
+ */
+ va_start(ap, fmt);
+ vstring_vsprintf(proxy->request, fmt, ap);
+ va_end(ap);
+
+ /*
+ * The command can be omitted at the start of an SMTP session. This is
+ * not documented as part of the official interface because it is used
+ * only internally to this module.
+ */
+ if (LEN(proxy->request) > 0) {
+
+ /*
+ * Optionally log the command first, so that we can see in the log
+ * what the program is trying to do.
+ */
+ if (msg_verbose)
+ msg_info("> %s: %s", proxy->service_name, STR(proxy->request));
+
+ /*
+ * Send the command to the proxy server. Since we're going to read a
+ * reply immediately, there is no need to flush buffers.
+ */
+ smtp_fputs(STR(proxy->request), LEN(proxy->request),
+ proxy->service_stream);
+ }
+
+ /*
+ * Early return if we don't want to wait for a server reply (such as
+ * after sending QUIT).
+ */
+ if (expect == SMTPD_PROX_WANT_NONE)
+ return (0);
+
+ /*
+ * Censor out non-printable characters in server responses and save
+ * complete multi-line responses if possible.
+ *
+ * We can't parse or store input that exceeds var_line_limit, so we just
+ * skip over it to simplify the remainder of the code below.
+ */
+ VSTRING_RESET(proxy->reply);
+ if (buffer == 0)
+ buffer = vstring_alloc(10);
+ for (;;) {
+ last_char = smtp_get(buffer, proxy->service_stream, var_line_limit,
+ SMTP_GET_FLAG_SKIP);
+ printable(STR(buffer), '?');
+ if (last_char != '\n')
+ msg_warn("%s: response longer than %d: %.30s...",
+ proxy->service_name, var_line_limit,
+ STR(buffer));
+ if (msg_verbose)
+ msg_info("< %s: %.100s", proxy->service_name, STR(buffer));
+
+ /*
+ * Defend against a denial of service attack by limiting the amount
+ * of multi-line text that we are willing to store.
+ */
+ if (LEN(proxy->reply) < var_line_limit) {
+ if (VSTRING_LEN(proxy->reply))
+ vstring_strcat(proxy->reply, "\r\n");
+ vstring_strcat(proxy->reply, STR(buffer));
+ }
+
+ /*
+ * Parse the response into code and text. Ignore unrecognized
+ * garbage. This means that any character except space (or end of
+ * line) will have the same effect as the '-' line continuation
+ * character.
+ */
+ for (cp = STR(buffer); *cp && ISDIGIT(*cp); cp++)
+ /* void */ ;
+ if (cp - STR(buffer) == 3) {
+ if (*cp == '-')
+ continue;
+ if (*cp == ' ' || *cp == 0)
+ break;
+ }
+ msg_warn("received garbage from proxy %s: %.100s",
+ proxy->service_name, STR(buffer));
+ }
+
+ /*
+ * Log a warning in case the proxy does not send the expected response.
+ * Silently accept any response when the client expressed no expectation.
+ *
+ * Starting with Postfix 2.6 we don't pass through unexpected 2xx or 3xx
+ * proxy replies. They are a source of support problems, so we replace
+ * them by generic server error replies.
+ */
+ if (expect != SMTPD_PROX_WANT_ANY && expect != *STR(proxy->reply)) {
+ msg_warn("proxy %s rejected \"%s\": \"%s\"",
+ proxy->service_name, LEN(proxy->request) == 0 ?
+ "connection request" : STR(proxy->request),
+ STR(proxy->reply));
+ if (*STR(proxy->reply) == SMTPD_PROX_WANT_OK
+ || *STR(proxy->reply) == SMTPD_PROX_WANT_MORE) {
+ smtpd_proxy_rdwr_error(state, 0);
+ }
+ return (-1);
+ } else {
+ return (0);
+ }
+}
+
+/* smtpd_proxy_save_rec_put - save message content to replay log */
+
+static int smtpd_proxy_save_rec_put(VSTREAM *stream, int rec_type,
+ const char *data, ssize_t len)
+{
+ const char *myname = "smtpd_proxy_save_rec_put";
+ int ret;
+
+#define VSTREAM_TO_SMTPD_STATE(s) ((SMTPD_STATE *) vstream_context(s))
+
+ /*
+ * Sanity check.
+ */
+ if (stream == 0)
+ msg_panic("%s: attempt to use closed stream", myname);
+
+ /*
+ * Send one content record. Errors and results must be as with rec_put().
+ */
+ if (rec_type == REC_TYPE_NORM || rec_type == REC_TYPE_CONT)
+ ret = rec_put(stream, rec_type, data, len);
+ else
+ msg_panic("%s: need REC_TYPE_NORM or REC_TYPE_CONT", myname);
+
+ /*
+ * Errors last.
+ */
+ if (ret != rec_type) {
+ (void) smtpd_proxy_replay_rdwr_error(VSTREAM_TO_SMTPD_STATE(stream));
+ return (REC_TYPE_ERROR);
+ }
+ return (rec_type);
+}
+
+/* smtpd_proxy_rec_put - send message content, rec_put() clone */
+
+static int smtpd_proxy_rec_put(VSTREAM *stream, int rec_type,
+ const char *data, ssize_t len)
+{
+ const char *myname = "smtpd_proxy_rec_put";
+ int err = 0;
+
+ /*
+ * Errors first.
+ */
+ if (vstream_ferror(stream) || vstream_feof(stream)
+ || (err = vstream_setjmp(stream)) != 0) {
+ (void) smtpd_proxy_rdwr_error(VSTREAM_TO_SMTPD_STATE(stream), err);
+ return (REC_TYPE_ERROR);
+ }
+
+ /*
+ * Send one content record. Errors and results must be as with rec_put().
+ */
+ if (rec_type == REC_TYPE_NORM)
+ smtp_fputs(data, len, stream);
+ else if (rec_type == REC_TYPE_CONT)
+ smtp_fwrite(data, len, stream);
+ else
+ msg_panic("%s: need REC_TYPE_NORM or REC_TYPE_CONT", myname);
+ return (rec_type);
+}
+
+/* smtpd_proxy_save_rec_fprintf - save message content to replay log */
+
+static int smtpd_proxy_save_rec_fprintf(VSTREAM *stream, int rec_type,
+ const char *fmt,...)
+{
+ const char *myname = "smtpd_proxy_save_rec_fprintf";
+ va_list ap;
+ int ret;
+
+ /*
+ * Sanity check.
+ */
+ if (stream == 0)
+ msg_panic("%s: attempt to use closed stream", myname);
+
+ /*
+ * Save one content record. Errors and results must be as with
+ * rec_fprintf().
+ */
+ va_start(ap, fmt);
+ if (rec_type == REC_TYPE_NORM)
+ ret = rec_vfprintf(stream, rec_type, fmt, ap);
+ else
+ msg_panic("%s: need REC_TYPE_NORM", myname);
+ va_end(ap);
+
+ /*
+ * Errors last.
+ */
+ if (ret != rec_type) {
+ (void) smtpd_proxy_replay_rdwr_error(VSTREAM_TO_SMTPD_STATE(stream));
+ return (REC_TYPE_ERROR);
+ }
+ return (rec_type);
+}
+
+/* smtpd_proxy_rec_fprintf - send message content, rec_fprintf() clone */
+
+static int smtpd_proxy_rec_fprintf(VSTREAM *stream, int rec_type,
+ const char *fmt,...)
+{
+ const char *myname = "smtpd_proxy_rec_fprintf";
+ va_list ap;
+ int err = 0;
+
+ /*
+ * Errors first.
+ */
+ if (vstream_ferror(stream) || vstream_feof(stream)
+ || (err = vstream_setjmp(stream)) != 0) {
+ (void) smtpd_proxy_rdwr_error(VSTREAM_TO_SMTPD_STATE(stream), err);
+ return (REC_TYPE_ERROR);
+ }
+
+ /*
+ * Send one content record. Errors and results must be as with
+ * rec_fprintf().
+ */
+ va_start(ap, fmt);
+ if (rec_type == REC_TYPE_NORM)
+ smtp_vprintf(stream, fmt, ap);
+ else
+ msg_panic("%s: need REC_TYPE_NORM", myname);
+ va_end(ap);
+ return (rec_type);
+}
+
+#ifndef NO_TRUNCATE
+
+/* smtpd_proxy_replay_setup - prepare the replay logfile */
+
+static int smtpd_proxy_replay_setup(SMTPD_STATE *state)
+{
+ const char *myname = "smtpd_proxy_replay_setup";
+ off_t file_offs;
+
+ /*
+ * Where possible reuse an existing replay logfile, because creating a
+ * file is expensive compared to reading or writing. For security reasons
+ * we must truncate the file before reuse. For performance reasons we
+ * should truncate the file immediately after the end of a mail
+ * transaction. We enforce the security guarantee upon reuse, by
+ * requiring that no I/O happened since the file was truncated. This is
+ * less expensive than truncating the file redundantly.
+ */
+ if (smtpd_proxy_replay_stream != 0) {
+ /* vstream_ftell() won't invoke the kernel, so all errors are mine. */
+ if ((file_offs = vstream_ftell(smtpd_proxy_replay_stream)) != 0)
+ msg_panic("%s: bad before-queue filter speed-adjust log offset %lu",
+ myname, (unsigned long) file_offs);
+ vstream_clearerr(smtpd_proxy_replay_stream);
+ if (msg_verbose)
+ msg_info("%s: reuse speed-adjust stream fd=%d", myname,
+ vstream_fileno(smtpd_proxy_replay_stream));
+ /* Here, smtpd_proxy_replay_stream != 0 */
+ }
+
+ /*
+ * Create a new replay logfile.
+ */
+ if (smtpd_proxy_replay_stream == 0) {
+ smtpd_proxy_replay_stream = mail_queue_enter(MAIL_QUEUE_INCOMING, 0,
+ (struct timeval *) 0);
+ if (smtpd_proxy_replay_stream == 0)
+ return (smtpd_proxy_replay_rdwr_error(state));
+ if (unlink(VSTREAM_PATH(smtpd_proxy_replay_stream)) < 0)
+ msg_warn("remove before-queue filter speed-adjust log %s: %m",
+ VSTREAM_PATH(smtpd_proxy_replay_stream));
+ if (msg_verbose)
+ msg_info("%s: new speed-adjust stream fd=%d", myname,
+ vstream_fileno(smtpd_proxy_replay_stream));
+ }
+
+ /*
+ * Needed by our DATA-phase record emulation routines.
+ */
+ vstream_control(smtpd_proxy_replay_stream,
+ CA_VSTREAM_CTL_CONTEXT((void *) state),
+ CA_VSTREAM_CTL_END);
+ return (0);
+}
+
+#endif
+
+/* smtpd_proxy_create - set up smtpd proxy handle */
+
+int smtpd_proxy_create(SMTPD_STATE *state, int flags, const char *service,
+ int timeout, const char *ehlo_name,
+ const char *mail_from)
+{
+ SMTPD_PROXY *proxy;
+
+ /*
+ * When an operation has many arguments it is safer to use named
+ * parameters, and have the compiler enforce the argument count.
+ */
+#define SMTPD_PROXY_ALLOC(p, a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12) \
+ ((p) = (SMTPD_PROXY *) mymalloc(sizeof(*(p))), (p)->a1, (p)->a2, \
+ (p)->a3, (p)->a4, (p)->a5, (p)->a6, (p)->a7, (p)->a8, (p)->a9, \
+ (p)->a10, (p)->a11, (p)->a12, (p))
+
+ /*
+ * Sanity check.
+ */
+ if (state->proxy != 0)
+ msg_panic("smtpd_proxy_create: handle still exists");
+
+ /*
+ * Connect to the before-queue filter immediately.
+ */
+ if ((flags & SMTPD_PROXY_FLAG_SPEED_ADJUST) == 0) {
+ state->proxy =
+ SMTPD_PROXY_ALLOC(proxy, stream = 0, request = vstring_alloc(10),
+ reply = vstring_alloc(10),
+ cmd = smtpd_proxy_cmd,
+ rec_fprintf = smtpd_proxy_rec_fprintf,
+ rec_put = smtpd_proxy_rec_put,
+ flags = flags, service_stream = 0,
+ service_name = service, timeout = timeout,
+ ehlo_name = ehlo_name, mail_from = mail_from);
+ if (smtpd_proxy_connect(state) < 0) {
+ /* NOT: smtpd_proxy_free(state); we still need proxy->reply. */
+ return (-1);
+ }
+ proxy->stream = proxy->service_stream;
+ return (0);
+ }
+
+ /*
+ * Connect to the before-queue filter after we receive the entire
+ * message. Open the replay logfile early to simplify code. The file is
+ * reused for multiple mail transactions, so there is no need to minimize
+ * its life time.
+ */
+ else {
+#ifdef NO_TRUNCATE
+ msg_panic("smtpd_proxy_create: speed-adjust support is not available");
+#else
+ if (smtpd_proxy_replay_setup(state) < 0)
+ return (-1);
+ state->proxy =
+ SMTPD_PROXY_ALLOC(proxy, stream = smtpd_proxy_replay_stream,
+ request = vstring_alloc(10),
+ reply = vstring_alloc(10),
+ cmd = smtpd_proxy_save_cmd,
+ rec_fprintf = smtpd_proxy_save_rec_fprintf,
+ rec_put = smtpd_proxy_save_rec_put,
+ flags = flags, service_stream = 0,
+ service_name = service, timeout = timeout,
+ ehlo_name = ehlo_name, mail_from = mail_from);
+ return (0);
+#endif
+ }
+}
+
+/* smtpd_proxy_close - close proxy connection without destroying handle */
+
+void smtpd_proxy_close(SMTPD_STATE *state)
+{
+ SMTPD_PROXY *proxy = state->proxy;
+
+ /*
+ * Specify SMTPD_PROX_WANT_NONE so that the server reply will not clobber
+ * the END-OF-DATA reply.
+ */
+ if (proxy->service_stream != 0) {
+ if (vstream_feof(proxy->service_stream) == 0
+ && vstream_ferror(proxy->service_stream) == 0)
+ (void) smtpd_proxy_cmd(state, SMTPD_PROX_WANT_NONE,
+ SMTPD_CMD_QUIT);
+ (void) vstream_fclose(proxy->service_stream);
+ if (proxy->stream == proxy->service_stream)
+ proxy->stream = 0;
+ proxy->service_stream = 0;
+ }
+}
+
+/* smtpd_proxy_free - destroy smtpd proxy handle */
+
+void smtpd_proxy_free(SMTPD_STATE *state)
+{
+ SMTPD_PROXY *proxy = state->proxy;
+
+ /*
+ * Clean up.
+ */
+ if (proxy->service_stream != 0)
+ (void) smtpd_proxy_close(state);
+ if (proxy->request != 0)
+ vstring_free(proxy->request);
+ if (proxy->reply != 0)
+ vstring_free(proxy->reply);
+ myfree((void *) proxy);
+ state->proxy = 0;
+
+ /*
+ * Reuse the replay logfile if possible. For security reasons we must
+ * truncate the replay logfile before reuse. For performance reasons we
+ * should truncate the replay logfile immediately after the end of a mail
+ * transaction. We truncate the file here, and enforce the security
+ * guarantee by requiring that no I/O happens before the file is reused.
+ */
+ if (smtpd_proxy_replay_stream == 0)
+ return;
+ if (vstream_ferror(smtpd_proxy_replay_stream)) {
+ /* Errors are already reported. */
+ (void) vstream_fclose(smtpd_proxy_replay_stream);
+ smtpd_proxy_replay_stream = 0;
+ return;
+ }
+ /* Flush output from aborted transaction before truncating the file!! */
+ if (vstream_fseek(smtpd_proxy_replay_stream, (off_t) 0, SEEK_SET) < 0) {
+ msg_warn("seek before-queue filter speed-adjust log: %m");
+ (void) vstream_fclose(smtpd_proxy_replay_stream);
+ smtpd_proxy_replay_stream = 0;
+ return;
+ }
+ if (ftruncate(vstream_fileno(smtpd_proxy_replay_stream), (off_t) 0) < 0) {
+ msg_warn("truncate before-queue filter speed-adjust log: %m");
+ (void) vstream_fclose(smtpd_proxy_replay_stream);
+ smtpd_proxy_replay_stream = 0;
+ return;
+ }
+}
+
+/* smtpd_proxy_parse_opts - parse main.cf options */
+
+int smtpd_proxy_parse_opts(const char *param_name, const char *param_val)
+{
+ static const NAME_MASK proxy_opts_table[] = {
+ SMTPD_PROXY_NAME_SPEED_ADJUST, SMTPD_PROXY_FLAG_SPEED_ADJUST,
+ 0, 0,
+ };
+ int flags;
+
+ /*
+ * The optional before-filter speed-adjust buffers use disk space.
+ * However, we don't know if they compete for storage space with the
+ * after-filter queue, so we can't simply bump up the free space
+ * requirement to 2.5 * message_size_limit.
+ */
+ flags = name_mask(param_name, proxy_opts_table, param_val);
+ if (flags & SMTPD_PROXY_FLAG_SPEED_ADJUST) {
+#ifdef NO_TRUNCATE
+ msg_warn("smtpd_proxy %s support is not available",
+ SMTPD_PROXY_NAME_SPEED_ADJUST);
+ flags &= ~SMTPD_PROXY_FLAG_SPEED_ADJUST;
+#endif
+ }
+ return (flags);
+}