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-rw-r--r--src/transports/smtp_socks.c415
1 files changed, 415 insertions, 0 deletions
diff --git a/src/transports/smtp_socks.c b/src/transports/smtp_socks.c
new file mode 100644
index 0000000..0e58732
--- /dev/null
+++ b/src/transports/smtp_socks.c
@@ -0,0 +1,415 @@
+/*************************************************
+* Exim - an Internet mail transport agent *
+*************************************************/
+
+/* Copyright (c) The Exim Maintainers 2021 - 2022 */
+/* Copyright (c) Jeremy Harris 2015 - 2018 */
+/* See the file NOTICE for conditions of use and distribution. */
+
+/* SOCKS version 5 proxy, client-mode */
+
+#include "../exim.h"
+#include "smtp.h"
+
+#ifdef SUPPORT_SOCKS /* entire file */
+
+#ifndef nelem
+# define nelem(arr) (sizeof(arr)/sizeof(*arr))
+#endif
+
+
+/* Defaults */
+#define SOCKS_PORT 1080
+#define SOCKS_TIMEOUT 5
+#define SOCKS_WEIGHT 1
+#define SOCKS_PRIORITY 1
+
+#define AUTH_NONE 0
+#define AUTH_NAME 2 /* user/password per RFC 1929 */
+#define AUTH_NAME_VER 1
+
+struct socks_err
+ {
+ uschar * reason;
+ int errcode;
+ } socks_errs[] =
+ {
+ {NULL, 0},
+ {US"general SOCKS server failure", EIO},
+ {US"connection not allowed by ruleset", EACCES},
+ {US"Network unreachable", ENETUNREACH},
+ {US"Host unreachable", EHOSTUNREACH},
+ {US"Connection refused", ECONNREFUSED},
+ {US"TTL expired", ECANCELED},
+ {US"Command not supported", EOPNOTSUPP},
+ {US"Address type not supported", EAFNOSUPPORT}
+ };
+
+typedef struct
+ {
+ const uschar * proxy_host;
+ uschar auth_type; /* RFC 1928 encoding */
+ const uschar * auth_name;
+ const uschar * auth_pwd;
+ short port;
+ BOOL is_failed;
+ unsigned timeout;
+ unsigned weight;
+ unsigned priority;
+ } socks_opts;
+
+static void
+socks_option_defaults(socks_opts * sob)
+{
+sob->proxy_host = NULL;
+sob->auth_type = AUTH_NONE;
+sob->auth_name = US"";
+sob->auth_pwd = US"";
+sob->is_failed = FALSE;
+sob->port = SOCKS_PORT;
+sob->timeout = SOCKS_TIMEOUT;
+sob->weight = SOCKS_WEIGHT;
+sob->priority = SOCKS_PRIORITY;
+}
+
+static void
+socks_option(socks_opts * sob, const uschar * opt)
+{
+if (Ustrncmp(opt, "auth=", 5) == 0)
+ {
+ opt += 5;
+ if (Ustrcmp(opt, "none") == 0) sob->auth_type = AUTH_NONE;
+ else if (Ustrcmp(opt, "name") == 0) sob->auth_type = AUTH_NAME;
+ }
+else if (Ustrncmp(opt, "name=", 5) == 0)
+ sob->auth_name = opt + 5;
+else if (Ustrncmp(opt, "pass=", 5) == 0)
+ sob->auth_pwd = opt + 5;
+else if (Ustrncmp(opt, "port=", 5) == 0)
+ sob->port = atoi(CCS opt + 5);
+else if (Ustrncmp(opt, "tmo=", 4) == 0)
+ sob->timeout = atoi(CCS opt + 4);
+else if (Ustrncmp(opt, "pri=", 4) == 0)
+ sob->priority = atoi(CCS opt + 4);
+else if (Ustrncmp(opt, "weight=", 7) == 0)
+ sob->weight = atoi(CCS opt + 7);
+return;
+}
+
+static int
+socks_auth(int fd, int method, socks_opts * sob, time_t tmo)
+{
+uschar * s;
+int len, i, j;
+
+switch(method)
+ {
+ default:
+ log_write(0, LOG_MAIN|LOG_PANIC,
+ "Unrecognised socks auth method %d", method);
+ return FAIL;
+ case AUTH_NONE:
+ return OK;
+ case AUTH_NAME:
+ HDEBUG(D_transport|D_acl|D_v) debug_printf_indent(" socks auth NAME '%s' '%s'\n",
+ sob->auth_name, sob->auth_pwd);
+ i = Ustrlen(sob->auth_name);
+ j = Ustrlen(sob->auth_pwd);
+ s = string_sprintf("%c%c%.255s%c%.255s", AUTH_NAME_VER,
+ i, sob->auth_name, j, sob->auth_pwd);
+ len = i + j + 3;
+ HDEBUG(D_transport|D_acl|D_v)
+ {
+ debug_printf_indent(" SOCKS>>");
+ for (int i = 0; i<len; i++) debug_printf(" %02x", s[i]);
+ debug_printf("\n");
+ }
+ if (send(fd, s, len, 0) < 0)
+ return FAIL;
+#ifdef TCP_QUICKACK
+ (void) setsockopt(fd, IPPROTO_TCP, TCP_QUICKACK, US &off, sizeof(off));
+#endif
+ if (!fd_ready(fd, tmo) || read(fd, s, 2) != 2)
+ return FAIL;
+ HDEBUG(D_transport|D_acl|D_v)
+ debug_printf_indent(" SOCKS<< %02x %02x\n", s[0], s[1]);
+ if (s[0] == AUTH_NAME_VER && s[1] == 0)
+ {
+ HDEBUG(D_transport|D_acl|D_v) debug_printf_indent(" socks auth OK\n");
+ return OK;
+ }
+
+ log_write(0, LOG_MAIN|LOG_PANIC, "socks auth failed");
+ errno = EPROTO;
+ return FAIL;
+ }
+}
+
+
+
+/* Find a suitable proxy to use from the list.
+Possible common code with spamd_get_server() ?
+
+Return: index into proxy spec array, or -1
+*/
+
+static int
+socks_get_proxy(socks_opts * proxies, unsigned nproxies)
+{
+unsigned int i;
+socks_opts * sd;
+socks_opts * lim = &proxies[nproxies];
+long rnd, weights;
+unsigned pri;
+
+if (nproxies == 1) /* shortcut, if we have only 1 server */
+ return (proxies[0].is_failed ? -1 : 0);
+
+/* scan for highest pri */
+for (pri = 0, sd = proxies; sd < lim; sd++)
+ if (!sd->is_failed && sd->priority > pri)
+ pri = sd->priority;
+
+/* get sum of weights at this pri */
+for (weights = 0, sd = proxies; sd < lim; sd++)
+ if (!sd->is_failed && sd->priority == pri)
+ weights += sd->weight;
+if (weights == 0) /* all servers failed */
+ return -1;
+
+for (rnd = random_number(weights), i = 0; i < nproxies; i++)
+ {
+ sd = &proxies[i];
+ if (!sd->is_failed && sd->priority == pri)
+ if ((rnd -= sd->weight) < 0)
+ return i;
+ }
+
+log_write(0, LOG_MAIN|LOG_PANIC,
+ "%s unknown error (memory/cpu corruption?)", __FUNCTION__);
+return -1;
+}
+
+
+
+/* Make a connection via a socks proxy
+
+Arguments:
+ host smtp target host
+ host_af address family
+ port remote tcp port number
+ interface local interface
+ tb transport
+ timeout connection timeout (zero for indefinite)
+
+Return value:
+ 0 on success; -1 on failure, with errno set
+*/
+
+int
+socks_sock_connect(host_item * host, int host_af, int port, uschar * interface,
+ transport_instance * tb, int timeout)
+{
+smtp_transport_options_block * ob =
+ (smtp_transport_options_block *)tb->options_block;
+const uschar * proxy_list;
+const uschar * proxy_spec;
+int sep = 0;
+int fd;
+time_t tmo;
+const uschar * state;
+uschar buf[24];
+socks_opts proxies[32]; /* max #proxies handled */
+unsigned nproxies;
+socks_opts * sob = NULL;
+unsigned size;
+blob early_data;
+
+if (!timeout) timeout = 24*60*60; /* use 1 day for "indefinite" */
+tmo = time(NULL) + timeout;
+
+if (!(proxy_list = expand_string(ob->socks_proxy)))
+ {
+ log_write(0, LOG_MAIN|LOG_PANIC, "Bad expansion for socks_proxy in %s",
+ tb->name);
+ return -1;
+ }
+
+/* Read proxy list */
+
+for (nproxies = 0;
+ nproxies < nelem(proxies)
+ && (proxy_spec = string_nextinlist(&proxy_list, &sep, NULL, 0));
+ nproxies++)
+ {
+ int subsep = -' ';
+ const uschar * option;
+
+ socks_option_defaults(sob = &proxies[nproxies]);
+
+ if (!(sob->proxy_host = string_nextinlist(&proxy_spec, &subsep, NULL, 0)))
+ {
+ /* paniclog config error */
+ return -1;
+ }
+
+ /*XXX consider global options eg. "hide socks_password = wibble" on the tpt */
+ /* extract any further per-proxy options */
+ while ((option = string_nextinlist(&proxy_spec, &subsep, NULL, 0)))
+ socks_option(sob, option);
+ }
+if (!sob) return -1;
+
+/* Set up the socks protocol method-selection message,
+for sending on connection */
+
+state = US"method select";
+buf[0] = 5; buf[1] = 1; buf[2] = sob->auth_type;
+early_data.data = buf;
+early_data.len = 3;
+
+/* Try proxies until a connection succeeds */
+
+for(;;)
+ {
+ int idx;
+ host_item proxy;
+ smtp_connect_args sc = {.sock = -1};
+
+ if ((idx = socks_get_proxy(proxies, nproxies)) < 0)
+ {
+ HDEBUG(D_transport|D_acl|D_v) debug_printf_indent(" no proxies left\n");
+ errno = EBUSY;
+ return -1;
+ }
+ sob = &proxies[idx];
+
+ /* bodge up a host struct for the proxy */
+ proxy.address = proxy.name = sob->proxy_host;
+ proxy.port = sob->port;
+
+ sc.tblock = tb;
+ sc.ob = ob;
+ sc.host = &proxy;
+ sc.host_af = Ustrchr(sob->proxy_host, ':') ? AF_INET6 : AF_INET;
+ sc.interface = interface;
+
+ /*XXX we trust that the method-select command is idempotent */
+ if ((fd = smtp_sock_connect(&sc, sob->timeout, &early_data)) >= 0)
+ {
+ proxy_local_address = string_copy(proxy.address);
+ proxy_local_port = sob->port;
+ break;
+ }
+
+ log_write(0, LOG_MAIN, "%s: %s", __FUNCTION__, strerror(errno));
+ sob->is_failed = TRUE;
+ }
+
+/* Do the socks protocol stuff */
+
+HDEBUG(D_transport|D_acl|D_v) debug_printf_indent(" SOCKS>> 05 01 %02x\n", sob->auth_type);
+
+/* expect method response */
+
+#ifdef TCP_QUICKACK
+(void) setsockopt(fd, IPPROTO_TCP, TCP_QUICKACK, US &off, sizeof(off));
+#endif
+
+if ( !fd_ready(fd, tmo)
+ || read(fd, buf, 2) != 2
+ )
+ goto rcv_err;
+HDEBUG(D_transport|D_acl|D_v)
+ debug_printf_indent(" SOCKS<< %02x %02x\n", buf[0], buf[1]);
+if ( buf[0] != 5
+ || socks_auth(fd, buf[1], sob, tmo) != OK
+ )
+ goto proxy_err;
+
+ {
+ union sockaddr_46 sin;
+ (void) ip_addr(&sin, host_af, host->address, port);
+
+ /* send connect (ipver, ipaddr, port) */
+
+ buf[0] = 5; buf[1] = 1; buf[2] = 0; buf[3] = host_af == AF_INET6 ? 4 : 1;
+ #if HAVE_IPV6
+ if (host_af == AF_INET6)
+ {
+ memcpy(buf+4, &sin.v6.sin6_addr, sizeof(sin.v6.sin6_addr));
+ memcpy(buf+4+sizeof(sin.v6.sin6_addr),
+ &sin.v6.sin6_port, sizeof(sin.v6.sin6_port));
+ size = 4+sizeof(sin.v6.sin6_addr)+sizeof(sin.v6.sin6_port);
+ }
+ else
+ #endif
+ {
+ memcpy(buf+4, &sin.v4.sin_addr.s_addr, sizeof(sin.v4.sin_addr.s_addr));
+ memcpy(buf+4+sizeof(sin.v4.sin_addr.s_addr),
+ &sin.v4.sin_port, sizeof(sin.v4.sin_port));
+ size = 4+sizeof(sin.v4.sin_addr.s_addr)+sizeof(sin.v4.sin_port);
+ }
+ }
+
+state = US"connect";
+HDEBUG(D_transport|D_acl|D_v)
+ {
+ debug_printf_indent(" SOCKS>>");
+ for (int i = 0; i<size; i++) debug_printf(" %02x", buf[i]);
+ debug_printf("\n");
+ }
+if (send(fd, buf, size, 0) < 0)
+ goto snd_err;
+
+/* expect conn-reply (success, local(ipver, addr, port))
+of same length as conn-request, or non-success fail code */
+
+if ( !fd_ready(fd, tmo)
+ || (size = read(fd, buf, size)) < 2
+ )
+ goto rcv_err;
+HDEBUG(D_transport|D_acl|D_v)
+ {
+ debug_printf_indent(" SOCKS>>");
+ for (int i = 0; i<size; i++) debug_printf(" %02x", buf[i]);
+ debug_printf("\n");
+ }
+if ( buf[0] != 5
+ || buf[1] != 0
+ )
+ goto proxy_err;
+
+proxy_external_address = string_copy(
+ host_ntoa(buf[3] == 4 ? AF_INET6 : AF_INET, buf+4, NULL, NULL));
+proxy_external_port = ntohs(*((uint16_t *)(buf + (buf[3] == 4 ? 20 : 8))));
+proxy_session = TRUE;
+
+HDEBUG(D_transport|D_acl|D_v)
+ debug_printf_indent(" proxy farside: [%s]:%d\n", proxy_external_address, proxy_external_port);
+
+return fd;
+
+snd_err:
+ HDEBUG(D_transport|D_acl|D_v) debug_printf_indent(" proxy snd_err %s: %s\n", state, strerror(errno));
+ return -1;
+
+proxy_err:
+ {
+ struct socks_err * se =
+ buf[1] > nelem(socks_errs) ? NULL : socks_errs + buf[1];
+ HDEBUG(D_transport|D_acl|D_v)
+ debug_printf_indent(" proxy %s: %s\n", state, se ? se->reason : US"unknown error code received");
+ errno = se ? se->errcode : EPROTO;
+ }
+
+rcv_err:
+ HDEBUG(D_transport|D_acl|D_v) debug_printf_indent(" proxy rcv_err %s: %s\n", state, strerror(errno));
+ if (!errno) errno = EPROTO;
+ else if (errno == ENOENT) errno = ECONNABORTED;
+ return -1;
+}
+
+#endif /* entire file */
+/* vi: aw ai sw=2
+*/
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