diff options
Diffstat (limited to 'src/smtp_out.c')
| -rw-r--r-- | src/smtp_out.c | 768 |
1 files changed, 768 insertions, 0 deletions
diff --git a/src/smtp_out.c b/src/smtp_out.c new file mode 100644 index 0000000..9bd90c7 --- /dev/null +++ b/src/smtp_out.c @@ -0,0 +1,768 @@ +/************************************************* +* Exim - an Internet mail transport agent * +*************************************************/ + +/* Copyright (c) University of Cambridge 1995 - 2018 */ +/* See the file NOTICE for conditions of use and distribution. */ + +/* A number of functions for driving outgoing SMTP calls. */ + + +#include "exim.h" +#include "transports/smtp.h" + + + +/************************************************* +* Find an outgoing interface * +*************************************************/ + +/* This function is called from the smtp transport and also from the callout +code in verify.c. Its job is to expand a string to get a list of interfaces, +and choose a suitable one (IPv4 or IPv6) for the outgoing address. + +Arguments: + istring string interface setting, may be NULL, meaning "any", in + which case the function does nothing + host_af AF_INET or AF_INET6 for the outgoing IP address + addr the mail address being handled (for setting errors) + interface point this to the interface + msg to add to any error message + +Returns: TRUE on success, FALSE on failure, with error message + set in addr and transport_return set to PANIC +*/ + +BOOL +smtp_get_interface(uschar *istring, int host_af, address_item *addr, + uschar **interface, uschar *msg) +{ +const uschar * expint; +uschar *iface; +int sep = 0; + +if (!istring) return TRUE; + +if (!(expint = expand_string(istring))) + { + if (f.expand_string_forcedfail) return TRUE; + addr->transport_return = PANIC; + addr->message = string_sprintf("failed to expand \"interface\" " + "option for %s: %s", msg, expand_string_message); + return FALSE; + } + +while (isspace(*expint)) expint++; +if (*expint == 0) return TRUE; + +while ((iface = string_nextinlist(&expint, &sep, big_buffer, + big_buffer_size))) + { + if (string_is_ip_address(iface, NULL) == 0) + { + addr->transport_return = PANIC; + addr->message = string_sprintf("\"%s\" is not a valid IP " + "address for the \"interface\" option for %s", + iface, msg); + return FALSE; + } + + if (((Ustrchr(iface, ':') == NULL)? AF_INET:AF_INET6) == host_af) + break; + } + +if (iface) *interface = string_copy(iface); +return TRUE; +} + + + +/************************************************* +* Find an outgoing port * +*************************************************/ + +/* This function is called from the smtp transport and also from the callout +code in verify.c. Its job is to find a port number. Note that getservbyname() +produces the number in network byte order. + +Arguments: + rstring raw (unexpanded) string representation of the port + addr the mail address being handled (for setting errors) + port stick the port in here + msg for adding to error message + +Returns: TRUE on success, FALSE on failure, with error message set + in addr, and transport_return set to PANIC +*/ + +BOOL +smtp_get_port(uschar *rstring, address_item *addr, int *port, uschar *msg) +{ +uschar *pstring = expand_string(rstring); + +if (!pstring) + { + addr->transport_return = PANIC; + addr->message = string_sprintf("failed to expand \"%s\" (\"port\" option) " + "for %s: %s", rstring, msg, expand_string_message); + return FALSE; + } + +if (isdigit(*pstring)) + { + uschar *end; + *port = Ustrtol(pstring, &end, 0); + if (end != pstring + Ustrlen(pstring)) + { + addr->transport_return = PANIC; + addr->message = string_sprintf("invalid port number for %s: %s", msg, + pstring); + return FALSE; + } + } + +else + { + struct servent *smtp_service = getservbyname(CS pstring, "tcp"); + if (!smtp_service) + { + addr->transport_return = PANIC; + addr->message = string_sprintf("TCP port \"%s\" is not defined for %s", + pstring, msg); + return FALSE; + } + *port = ntohs(smtp_service->s_port); + } + +return TRUE; +} + + + + +#ifdef TCP_FASTOPEN +static void +tfo_out_check(int sock) +{ +# if defined(TCP_INFO) && defined(EXIM_HAVE_TCPI_UNACKED) +struct tcp_info tinfo; +socklen_t len = sizeof(tinfo); + +switch (tcp_out_fastopen) + { + /* This is a somewhat dubious detection method; totally undocumented so likely + to fail in future kernels. There seems to be no documented way. What we really + want to know is if the server sent smtp-banner data before our ACK of his SYN,ACK + hit him. What this (possibly?) detects is whether we sent a TFO cookie with our + SYN, as distinct from a TFO request. This gets a false-positive when the server + key is rotated; we send the old one (which this test sees) but the server returns + the new one and does not send its SMTP banner before we ACK his SYN,ACK. + To force that rotation case: + '# echo -n "00000000-00000000-00000000-0000000" >/proc/sys/net/ipv4/tcp_fastopen_key' + The kernel seems to be counting unack'd packets. */ + + case TFO_ATTEMPTED_NODATA: + if ( getsockopt(sock, IPPROTO_TCP, TCP_INFO, &tinfo, &len) == 0 + && tinfo.tcpi_state == TCP_SYN_SENT + && tinfo.tcpi_unacked > 1 + ) + { + DEBUG(D_transport|D_v) + debug_printf("TCP_FASTOPEN tcpi_unacked %d\n", tinfo.tcpi_unacked); + tcp_out_fastopen = TFO_USED_NODATA; + } + break; + + /* When called after waiting for received data we should be able + to tell if data we sent was accepted. */ + + case TFO_ATTEMPTED_DATA: + if ( getsockopt(sock, IPPROTO_TCP, TCP_INFO, &tinfo, &len) == 0 + && tinfo.tcpi_state == TCP_ESTABLISHED + ) + if (tinfo.tcpi_options & TCPI_OPT_SYN_DATA) + { + DEBUG(D_transport|D_v) debug_printf("TFO: data was acked\n"); + tcp_out_fastopen = TFO_USED_DATA; + } + else + { + DEBUG(D_transport|D_v) debug_printf("TFO: had to retransmit\n"); + tcp_out_fastopen = TFO_NOT_USED; + } + break; + } +# endif +} +#endif + + +/* Arguments as for smtp_connect(), plus + early_data if non-NULL, idenmpotent data to be sent - + preferably in the TCP SYN segment + +Returns: connected socket number, or -1 with errno set +*/ + +int +smtp_sock_connect(host_item * host, int host_af, int port, uschar * interface, + transport_instance * tb, int timeout, const blob * early_data) +{ +smtp_transport_options_block * ob = + (smtp_transport_options_block *)tb->options_block; +const uschar * dscp = ob->dscp; +int dscp_value; +int dscp_level; +int dscp_option; +int sock; +int save_errno = 0; +const blob * fastopen_blob = NULL; + + +#ifndef DISABLE_EVENT +deliver_host_address = host->address; +deliver_host_port = port; +if (event_raise(tb->event_action, US"tcp:connect", NULL)) return -1; +#endif + +if ((sock = ip_socket(SOCK_STREAM, host_af)) < 0) return -1; + +/* Set TCP_NODELAY; Exim does its own buffering. */ + +if (setsockopt(sock, IPPROTO_TCP, TCP_NODELAY, US &on, sizeof(on))) + HDEBUG(D_transport|D_acl|D_v) + debug_printf_indent("failed to set NODELAY: %s ", strerror(errno)); + +/* Set DSCP value, if we can. For now, if we fail to set the value, we don't +bomb out, just log it and continue in default traffic class. */ + +if (dscp && dscp_lookup(dscp, host_af, &dscp_level, &dscp_option, &dscp_value)) + { + HDEBUG(D_transport|D_acl|D_v) + debug_printf_indent("DSCP \"%s\"=%x ", dscp, dscp_value); + if (setsockopt(sock, dscp_level, dscp_option, &dscp_value, sizeof(dscp_value)) < 0) + HDEBUG(D_transport|D_acl|D_v) + debug_printf_indent("failed to set DSCP: %s ", strerror(errno)); + /* If the kernel supports IPv4 and IPv6 on an IPv6 socket, we need to set the + option for both; ignore failures here */ + if (host_af == AF_INET6 && + dscp_lookup(dscp, AF_INET, &dscp_level, &dscp_option, &dscp_value)) + (void) setsockopt(sock, dscp_level, dscp_option, &dscp_value, sizeof(dscp_value)); + } + +/* Bind to a specific interface if requested. Caller must ensure the interface +is the same type (IPv4 or IPv6) as the outgoing address. */ + +if (interface && ip_bind(sock, host_af, interface, 0) < 0) + { + save_errno = errno; + HDEBUG(D_transport|D_acl|D_v) + debug_printf_indent("unable to bind outgoing SMTP call to %s: %s", interface, + strerror(errno)); + } + +/* Connect to the remote host, and add keepalive to the socket before returning +it, if requested. If the build supports TFO, request it - and if the caller +requested some early-data then include that in the TFO request. If there is +early-data but no TFO support, send it after connecting. */ + +else + { +#ifdef TCP_FASTOPEN + if (verify_check_given_host(CUSS &ob->hosts_try_fastopen, host) == OK) + fastopen_blob = early_data ? early_data : &tcp_fastopen_nodata; +#endif + + if (ip_connect(sock, host_af, host->address, port, timeout, fastopen_blob) < 0) + save_errno = errno; + else if (early_data && !fastopen_blob && early_data->data && early_data->len) + { + HDEBUG(D_transport|D_acl|D_v) + debug_printf("sending %ld nonTFO early-data\n", (long)early_data->len); + +#ifdef TCP_QUICKACK + (void) setsockopt(sock, IPPROTO_TCP, TCP_QUICKACK, US &off, sizeof(off)); +#endif + if (send(sock, early_data->data, early_data->len, 0) < 0) + save_errno = errno; + } + } + +/* Either bind() or connect() failed */ + +if (save_errno != 0) + { + HDEBUG(D_transport|D_acl|D_v) + { + debug_printf_indent("failed: %s", CUstrerror(save_errno)); + if (save_errno == ETIMEDOUT) + debug_printf(" (timeout=%s)", readconf_printtime(timeout)); + debug_printf("\n"); + } + (void)close(sock); + errno = save_errno; + return -1; + } + +/* Both bind() and connect() succeeded, and any early-data */ + +else + { + union sockaddr_46 interface_sock; + EXIM_SOCKLEN_T size = sizeof(interface_sock); + + HDEBUG(D_transport|D_acl|D_v) debug_printf_indent("connected\n"); + if (getsockname(sock, (struct sockaddr *)(&interface_sock), &size) == 0) + sending_ip_address = host_ntoa(-1, &interface_sock, NULL, &sending_port); + else + { + log_write(0, LOG_MAIN | ((errno == ECONNRESET)? 0 : LOG_PANIC), + "getsockname() failed: %s", strerror(errno)); + close(sock); + return -1; + } + + if (ob->keepalive) ip_keepalive(sock, host->address, TRUE); +#ifdef TCP_FASTOPEN + tfo_out_check(sock); +#endif + return sock; + } +} + + + + + +void +smtp_port_for_connect(host_item * host, int port) +{ +if (host->port != PORT_NONE) + { + HDEBUG(D_transport|D_acl|D_v) + debug_printf_indent("Transport port=%d replaced by host-specific port=%d\n", port, + host->port); + port = host->port; + } +else host->port = port; /* Set the port actually used */ +} + + +/************************************************* +* Connect to remote host * +*************************************************/ + +/* Create a socket, and connect it to a remote host. IPv6 addresses are +detected by checking for a colon in the address. AF_INET6 is defined even on +non-IPv6 systems, to enable the code to be less messy. However, on such systems +host->address will always be an IPv4 address. + +Arguments: + sc details for making connection: host, af, interface, transport + early_data if non-NULL, data to be sent - preferably in the TCP SYN segment + +Returns: connected socket number, or -1 with errno set +*/ + +int +smtp_connect(smtp_connect_args * sc, const blob * early_data) +{ +int port = sc->host->port; +smtp_transport_options_block * ob = sc->ob; + +callout_address = string_sprintf("[%s]:%d", sc->host->address, port); + +HDEBUG(D_transport|D_acl|D_v) + { + uschar * s = US" "; + if (sc->interface) s = string_sprintf(" from %s ", sc->interface); +#ifdef SUPPORT_SOCKS + if (ob->socks_proxy) s = string_sprintf("%svia proxy ", s); +#endif + debug_printf_indent("Connecting to %s %s%s... ", sc->host->name, callout_address, s); + } + +/* Create and connect the socket */ + +#ifdef SUPPORT_SOCKS +if (ob->socks_proxy) + { + int sock = socks_sock_connect(sc->host, sc->host_af, port, sc->interface, + sc->tblock, ob->connect_timeout); + + if (sock >= 0) + { + if (early_data && early_data->data && early_data->len) + if (send(sock, early_data->data, early_data->len, 0) < 0) + { + int save_errno = errno; + HDEBUG(D_transport|D_acl|D_v) + { + debug_printf_indent("failed: %s", CUstrerror(save_errno)); + if (save_errno == ETIMEDOUT) + debug_printf(" (timeout=%s)", readconf_printtime(ob->connect_timeout)); + debug_printf("\n"); + } + (void)close(sock); + sock = -1; + errno = save_errno; + } + } + return sock; + } +#endif + +return smtp_sock_connect(sc->host, sc->host_af, port, sc->interface, + sc->tblock, ob->connect_timeout, early_data); +} + + +/************************************************* +* Flush outgoing command buffer * +*************************************************/ + +/* This function is called only from smtp_write_command() below. It flushes +the buffer of outgoing commands. There is more than one in the buffer only when +pipelining. + +Argument: + outblock the SMTP output block + mode further data expected, or plain + +Returns: TRUE if OK, FALSE on error, with errno set +*/ + +static BOOL +flush_buffer(smtp_outblock * outblock, int mode) +{ +int rc; +int n = outblock->ptr - outblock->buffer; +BOOL more = mode == SCMD_MORE; + +HDEBUG(D_transport|D_acl) debug_printf_indent("cmd buf flush %d bytes%s\n", n, + more ? " (more expected)" : ""); + +#ifdef SUPPORT_TLS +if (outblock->cctx->tls_ctx) + rc = tls_write(outblock->cctx->tls_ctx, outblock->buffer, n, more); +else +#endif + + { + if (outblock->conn_args) + { + blob early_data = { .data = outblock->buffer, .len = n }; + + /* We ignore the more-flag if we're doing a connect with early-data, which + means we won't get BDAT+data. A pity, but wise due to the idempotency + requirement: TFO with data can, in rare cases, replay the data to the + receiver. */ + + if ( (outblock->cctx->sock = smtp_connect(outblock->conn_args, &early_data)) + < 0) + return FALSE; + outblock->conn_args = NULL; + rc = n; + } + else + + rc = send(outblock->cctx->sock, outblock->buffer, n, +#ifdef MSG_MORE + more ? MSG_MORE : 0 +#else + 0 +#endif + ); + } + +if (rc <= 0) + { + HDEBUG(D_transport|D_acl) debug_printf_indent("send failed: %s\n", strerror(errno)); + return FALSE; + } + +outblock->ptr = outblock->buffer; +outblock->cmd_count = 0; +return TRUE; +} + + + +/************************************************* +* Write SMTP command * +*************************************************/ + +/* The formatted command is left in big_buffer so that it can be reflected in +any error message. + +Arguments: + sx SMTP connection, contains buffer for pipelining, and socket + mode buffer, write-with-more-likely, write + format a format, starting with one of + of HELO, MAIL FROM, RCPT TO, DATA, ".", or QUIT. + If NULL, flush pipeline buffer only. + ... data for the format + +Returns: 0 if command added to pipelining buffer, with nothing transmitted + +n if n commands transmitted (may still have buffered the new one) + -1 on error, with errno set +*/ + +int +smtp_write_command(void * sx, int mode, const char *format, ...) +{ +smtp_outblock * outblock = &((smtp_context *)sx)->outblock; +int rc = 0; + +if (format) + { + gstring gs = { .size = big_buffer_size, .ptr = 0, .s = big_buffer }; + va_list ap; + + va_start(ap, format); + if (!string_vformat(&gs, FALSE, CS format, ap)) + log_write(0, LOG_MAIN|LOG_PANIC_DIE, "overlong write_command in outgoing " + "SMTP"); + va_end(ap); + string_from_gstring(&gs); + + if (gs.ptr > outblock->buffersize) + log_write(0, LOG_MAIN|LOG_PANIC_DIE, "overlong write_command in outgoing " + "SMTP"); + + if (gs.ptr > outblock->buffersize - (outblock->ptr - outblock->buffer)) + { + rc = outblock->cmd_count; /* flush resets */ + if (!flush_buffer(outblock, SCMD_FLUSH)) return -1; + } + + Ustrncpy(CS outblock->ptr, gs.s, gs.ptr); + outblock->ptr += gs.ptr; + outblock->cmd_count++; + gs.ptr -= 2; string_from_gstring(&gs); /* remove \r\n for error message */ + + /* We want to hide the actual data sent in AUTH transactions from reflections + and logs. While authenticating, a flag is set in the outblock to enable this. + The AUTH command itself gets any data flattened. Other lines are flattened + completely. */ + + if (outblock->authenticating) + { + uschar *p = big_buffer; + if (Ustrncmp(big_buffer, "AUTH ", 5) == 0) + { + p += 5; + while (isspace(*p)) p++; + while (!isspace(*p)) p++; + while (isspace(*p)) p++; + } + while (*p != 0) *p++ = '*'; + } + + HDEBUG(D_transport|D_acl|D_v) debug_printf_indent(" SMTP>> %s\n", big_buffer); + } + +if (mode != SCMD_BUFFER) + { + rc += outblock->cmd_count; /* flush resets */ + if (!flush_buffer(outblock, mode)) return -1; + } + +return rc; +} + + + +/************************************************* +* Read one line of SMTP response * +*************************************************/ + +/* This function reads one line of SMTP response from the server host. This may +not be a complete response - it could be just part of a multiline response. We +have to use a buffer for incoming packets, because when pipelining or using +LMTP, there may well be more than one response in a single packet. This +function is called only from the one that follows. + +Arguments: + inblock the SMTP input block (contains holding buffer, socket, etc.) + buffer where to put the line + size space available for the line + timeout the timeout to use when reading a packet + +Returns: length of a line that has been put in the buffer + -1 otherwise, with errno set +*/ + +static int +read_response_line(smtp_inblock *inblock, uschar *buffer, int size, int timeout) +{ +uschar *p = buffer; +uschar *ptr = inblock->ptr; +uschar *ptrend = inblock->ptrend; +client_conn_ctx * cctx = inblock->cctx; + +/* Loop for reading multiple packets or reading another packet after emptying +a previously-read one. */ + +for (;;) + { + int rc; + + /* If there is data in the input buffer left over from last time, copy + characters from it until the end of a line, at which point we can return, + having removed any whitespace (which will include CR) at the end of the line. + The rules for SMTP say that lines end in CRLF, but there are have been cases + of hosts using just LF, and other MTAs are reported to handle this, so we + just look for LF. If we run out of characters before the end of a line, + carry on to read the next incoming packet. */ + + while (ptr < ptrend) + { + int c = *ptr++; + if (c == '\n') + { + while (p > buffer && isspace(p[-1])) p--; + *p = 0; + inblock->ptr = ptr; + return p - buffer; + } + *p++ = c; + if (--size < 4) + { + *p = 0; /* Leave malformed line for error message */ + errno = ERRNO_SMTPFORMAT; + return -1; + } + } + + /* Need to read a new input packet. */ + + if((rc = ip_recv(cctx, inblock->buffer, inblock->buffersize, timeout)) <= 0) + { + DEBUG(D_deliver|D_transport|D_acl) + debug_printf_indent(errno ? " SMTP(%s)<<\n" : " SMTP(closed)<<\n", + strerror(errno)); + break; + } + + /* Another block of data has been successfully read. Set up the pointers + and let the loop continue. */ + + ptrend = inblock->ptrend = inblock->buffer + rc; + ptr = inblock->buffer; + DEBUG(D_transport|D_acl) debug_printf_indent("read response data: size=%d\n", rc); + } + +/* Get here if there has been some kind of recv() error; errno is set, but we +ensure that the result buffer is empty before returning. */ + +*buffer = 0; +return -1; +} + + + + + +/************************************************* +* Read SMTP response * +*************************************************/ + +/* This function reads an SMTP response with a timeout, and returns the +response in the given buffer, as a string. A multiline response will contain +newline characters between the lines. The function also analyzes the first +digit of the reply code and returns FALSE if it is not acceptable. FALSE is +also returned after a reading error. In this case buffer[0] will be zero, and +the error code will be in errno. + +Arguments: + sx the SMTP connection (contains input block with holding buffer, + socket, etc.) + buffer where to put the response + size the size of the buffer + okdigit the expected first digit of the response + timeout the timeout to use, in seconds + +Returns: TRUE if a valid, non-error response was received; else FALSE +*/ +/*XXX could move to smtp transport; no other users */ + +BOOL +smtp_read_response(void * sx0, uschar *buffer, int size, int okdigit, + int timeout) +{ +smtp_context * sx = sx0; +uschar *ptr = buffer; +int count = 0; + +errno = 0; /* Ensure errno starts out zero */ + +#ifdef EXPERIMENTAL_PIPE_CONNECT +if (sx->pending_BANNER || sx->pending_EHLO) + if (smtp_reap_early_pipe(sx, &count) != OK) + { + DEBUG(D_transport) debug_printf("failed reaping pipelined cmd responsess\n"); + return FALSE; + } +#endif + +/* This is a loop to read and concatenate the lines that make up a multi-line +response. */ + +for (;;) + { + if ((count = read_response_line(&sx->inblock, ptr, size, timeout)) < 0) + return FALSE; + + HDEBUG(D_transport|D_acl|D_v) + debug_printf_indent(" %s %s\n", ptr == buffer ? "SMTP<<" : " ", ptr); + + /* Check the format of the response: it must start with three digits; if + these are followed by a space or end of line, the response is complete. If + they are followed by '-' this is a multi-line response and we must look for + another line until the final line is reached. The only use made of multi-line + responses is to pass them back as error messages. We therefore just + concatenate them all within the buffer, which should be large enough to + accept any reasonable number of lines. */ + + if (count < 3 || + !isdigit(ptr[0]) || + !isdigit(ptr[1]) || + !isdigit(ptr[2]) || + (ptr[3] != '-' && ptr[3] != ' ' && ptr[3] != 0)) + { + errno = ERRNO_SMTPFORMAT; /* format error */ + return FALSE; + } + + /* If the line we have just read is a terminal line, line, we are done. + Otherwise more data has to be read. */ + + if (ptr[3] != '-') break; + + /* Move the reading pointer upwards in the buffer and insert \n between the + components of a multiline response. Space is left for this by read_response_ + line(). */ + + ptr += count; + *ptr++ = '\n'; + size -= count + 1; + } + +#ifdef TCP_FASTOPEN + tfo_out_check(sx->cctx.sock); +#endif + +/* Return a value that depends on the SMTP return code. On some systems a +non-zero value of errno has been seen at this point, so ensure it is zero, +because the caller of this function looks at errno when FALSE is returned, to +distinguish between an unexpected return code and other errors such as +timeouts, lost connections, etc. */ + +errno = 0; +return buffer[0] == okdigit; +} + +/* End of smtp_out.c */ +/* vi: aw ai sw=2 +*/ |