* Exim - an Internet mail transport agent *
*************************************************/
+/* Copyright (c) The Exim Maintainers 2020 - 2022 */
/* Copyright (c) University of Cambridge 1995 - 2018 */
/* See the file NOTICE for conditions of use and distribution. */
+/* SPDX-License-Identifier: GPL-2.0-only */
/* This module provides TLS (aka SSL) support for Exim. The code for OpenSSL is
based on a patch that was originally contributed by Steve Haslam. It was
#include "exim.h"
#include "transports/smtp.h"
-#if defined(MACRO_PREDEF) && defined(SUPPORT_TLS)
-# ifndef USE_GNUTLS
-# include "macro_predef.h"
+#if !defined(DISABLE_TLS) && !defined(USE_OPENSSL) && !defined(USE_GNUTLS)
+# error One of USE_OPENSSL or USE_GNUTLS must be defined for a TLS build
+#endif
+
+
+/* Forward decl. */
+static void tls_client_resmption_key(tls_support *, smtp_connect_args *,
+ smtp_transport_options_block *);
+
+
+#if defined(MACRO_PREDEF) && !defined(DISABLE_TLS)
+# include "macro_predef.h"
+# ifdef USE_GNUTLS
+# include "tls-gnu.c"
+# else
# include "tls-openssl.c"
# endif
#endif
#ifndef MACRO_PREDEF
+static void tls_per_lib_daemon_init(void);
+static void tls_per_lib_daemon_tick(void);
+static unsigned tls_server_creds_init(void);
+static void tls_server_creds_invalidate(void);
+static void tls_client_creds_init(transport_instance *, BOOL);
+static void tls_client_creds_invalidate(transport_instance *);
+static void tls_daemon_creds_reload(void);
+static BOOL opt_set_and_noexpand(const uschar *);
+static BOOL opt_unset_or_noexpand(const uschar *);
+
+
+
/* This module is compiled only when it is specifically requested in the
build-time configuration. However, some compilers don't like compiling empty
modules, so keep them happy with a dummy when skipping the rest. Make it
in a dummy argument to stop even pickier compilers complaining about infinite
loops. */
-#ifndef SUPPORT_TLS
+#ifdef DISABLE_TLS
static void dummy(int x) { dummy(x-1); }
-#else
+#else /* most of the rest of the file */
+
+const exim_tlslib_state null_tls_preload = {0};
/* Static variables that are used for buffering data by both sets of
functions and the common functions below.
can switch, so we can do TLS callouts during ACLs. */
static const int ssl_xfer_buffer_size = 4096;
-#ifndef USE_GNUTLS
+#ifdef USE_OPENSSL
static uschar *ssl_xfer_buffer = NULL;
static int ssl_xfer_buffer_lwm = 0;
static int ssl_xfer_buffer_hwm = 0;
static BOOL ssl_xfer_error = FALSE;
#endif
-uschar *tls_channelbinding_b64 = NULL;
+#ifdef EXIM_HAVE_KEVENT
+# define KEV_SIZE 16 /* Eight file,dir pairs */
+static struct kevent kev[KEV_SIZE];
+static int kev_used = 0;
+#endif
+static unsigned tls_creds_expire = 0;
/*************************************************
* Expand string; give error on failure *
}
+#if defined(EXIM_HAVE_INOTIFY) || defined(EXIM_HAVE_KEVENT)
+/* Add the directory for a filename to the inotify handle, creating that if
+needed. This is enough to see changes to files in that dir.
+Return boolean success.
+
+The word "system" fails, which is on the safe side as we don't know what
+directory it implies nor if the TLS library handles a watch for us.
+
+The string "system,cache" is recognised and explicitly accepted without
+setting a watch. This permits the system CA bundle to be cached even though
+we have no way to tell when it gets modified by an update.
+The call chain for OpenSSL uses a (undocumented) call into the library
+to discover the actual file. We don't know what GnuTLS uses.
+
+A full set of caching including the CAs takes 35ms output off of the
+server tls_init() (GnuTLS, Fedora 32, 2018-class x86_64 laptop hardware).
+*/
+static BOOL
+tls_set_one_watch(const uschar * filename)
+# ifdef EXIM_HAVE_INOTIFY
+{
+uschar buf[PATH_MAX];
+ssize_t len;
+uschar * s;
+
+if (Ustrcmp(filename, "system,cache") == 0) return TRUE;
+if (!(s = Ustrrchr(filename, '/'))) return FALSE;
+
+for (unsigned loop = 20;
+ (len = readlink(CCS filename, CS buf, sizeof(buf))) >= 0; )
+ { /* a symlink */
+ if (--loop == 0) { errno = ELOOP; return FALSE; }
+ filename = buf[0] == '/'
+ ? string_copyn(buf, (unsigned)len) /* mem released by tls_set_watch */
+ : string_sprintf("%.*s/%.*s", (int)(s - filename), filename, (int)len, buf);
+ s = Ustrrchr(filename, '/');
+ }
+if (errno != EINVAL)
+ return FALSE; /* other error */
+
+/* not a symlink */
+s = string_copyn(filename, s - filename); /* mem released by tls_set_watch */
+
+DEBUG(D_tls) debug_printf("watch dir '%s'\n", s);
+
+if (inotify_add_watch(tls_watch_fd, CCS s,
+ IN_ONESHOT | IN_CLOSE_WRITE | IN_DELETE | IN_DELETE_SELF
+ | IN_MOVED_FROM | IN_MOVED_TO | IN_MOVE_SELF) >= 0)
+ return TRUE;
+DEBUG(D_tls) debug_printf("notify_add_watch: %s\n", strerror(errno));
+return FALSE;
+}
+# endif
+# ifdef EXIM_HAVE_KEVENT
+{
+uschar * s, * t;
+int fd1, fd2, i, j, cnt = 0;
+struct stat sb;
+#ifdef OpenBSD
+struct kevent k_dummy;
+struct timespec ts = {0};
+#endif
+
+errno = 0;
+if (Ustrcmp(filename, "system,cache") == 0) return TRUE;
+
+for (;;)
+ {
+ if (kev_used > KEV_SIZE-2) { s = US"out of kev space"; goto bad; }
+ if (!(s = Ustrrchr(filename, '/'))) return FALSE;
+ s = string_copyn(filename, s - filename); /* mem released by tls_set_watch */
+
+ /* The dir open will fail if there is a symlink on the path. Fine; it's too
+ much effort to handle all possible cases; just refuse the preload. */
+
+ if ((fd2 = open(CCS s, O_RDONLY | O_NOFOLLOW)) < 0) { s = US"open dir"; goto bad; }
+
+ if ((lstat(CCS filename, &sb)) < 0) { s = US"lstat"; goto bad; }
+ if (!S_ISLNK(sb.st_mode))
+ {
+ if ((fd1 = open(CCS filename, O_RDONLY | O_NOFOLLOW)) < 0)
+ { s = US"open file"; goto bad; }
+ DEBUG(D_tls) debug_printf("watch file '%s':\t%d\n", filename, fd1);
+ EV_SET(&kev[kev_used++],
+ (uintptr_t)fd1,
+ EVFILT_VNODE,
+ EV_ADD | EV_ENABLE | EV_ONESHOT,
+ NOTE_DELETE | NOTE_WRITE | NOTE_EXTEND
+ | NOTE_ATTRIB | NOTE_RENAME | NOTE_REVOKE,
+ 0,
+ NULL);
+ cnt++;
+ }
+ DEBUG(D_tls) debug_printf("watch dir '%s':\t%d\n", s, fd2);
+ EV_SET(&kev[kev_used++],
+ (uintptr_t)fd2,
+ EVFILT_VNODE,
+ EV_ADD | EV_ENABLE | EV_ONESHOT,
+ NOTE_DELETE | NOTE_WRITE | NOTE_EXTEND
+ | NOTE_ATTRIB | NOTE_RENAME | NOTE_REVOKE,
+ 0,
+ NULL);
+ cnt++;
+
+ if (!(S_ISLNK(sb.st_mode))) break;
+
+ t = store_get(1024, GET_UNTAINTED);
+ Ustrncpy(t, s, 1022);
+ j = Ustrlen(s);
+ t[j++] = '/';
+ if ((i = readlink(CCS filename, (void *)(t+j), 1023-j)) < 0) { s = US"readlink"; goto bad; }
+ filename = t;
+ *(t += i+j) = '\0';
+ store_release_above(t+1);
+ }
+
+#ifdef OpenBSD
+if (kevent(tls_watch_fd, &kev[kev_used-cnt], cnt, &k_dummy, 1, &ts) >= 0)
+ return TRUE;
+#else
+if (kevent(tls_watch_fd, &kev[kev_used-cnt], cnt, NULL, 0, NULL) >= 0)
+ return TRUE;
+#endif
+s = US"kevent";
+
+bad:
+DEBUG(D_tls)
+ if (errno)
+ debug_printf("%s: %s: %s\n", __FUNCTION__, s, strerror(errno));
+ else
+ debug_printf("%s: %s\n", __FUNCTION__, s);
+return FALSE;
+}
+# endif /*EXIM_HAVE_KEVENT*/
+
+
+/* Create an inotify facility if needed.
+Then set watches on the dir containing the given file or (optionally)
+list of files. Return boolean success. */
+
+static BOOL
+tls_set_watch(const uschar * filename, BOOL list)
+{
+rmark r;
+BOOL rc = FALSE;
+
+if (!filename || !*filename) return TRUE;
+if (Ustrncmp(filename, "system", 6) == 0) return TRUE;
+
+DEBUG(D_tls) debug_printf("tls_set_watch: '%s'\n", filename);
+
+if ( tls_watch_fd < 0
+# ifdef EXIM_HAVE_INOTIFY
+ && (tls_watch_fd = inotify_init1(O_CLOEXEC)) < 0
+# endif
+# ifdef EXIM_HAVE_KEVENT
+ && (tls_watch_fd = kqueue()) < 0
+# endif
+ )
+ {
+ DEBUG(D_tls) debug_printf("inotify_init: %s\n", strerror(errno));
+ return FALSE;
+ }
+
+r = store_mark();
+
+if (list)
+ {
+ int sep = 0;
+ for (uschar * s; s = string_nextinlist(&filename, &sep, NULL, 0); )
+ if (!(rc = tls_set_one_watch(s))) break;
+ }
+else
+ rc = tls_set_one_watch(filename);
+
+store_reset(r);
+if (!rc) DEBUG(D_tls) debug_printf("tls_set_watch() fail on '%s': %s\n", filename, strerror(errno));
+return rc;
+}
+
+
+void
+tls_watch_discard_event(int fd)
+{
+#ifdef EXIM_HAVE_INOTIFY
+(void) read(fd, big_buffer, big_buffer_size);
+#endif
+#ifdef EXIM_HAVE_KEVENT
+struct kevent kev;
+struct timespec t = {0};
+(void) kevent(fd, NULL, 0, &kev, 1, &t);
+#endif
+}
+#endif /*EXIM_HAVE_INOTIFY*/
+
+
+void
+tls_client_creds_reload(BOOL watch)
+{
+for(transport_instance * t = transports; t; t = t->next)
+ if (Ustrcmp(t->driver_name, "smtp") == 0)
+ {
+ tls_client_creds_invalidate(t);
+ tls_client_creds_init(t, watch);
+ }
+}
+
+
+void
+tls_watch_invalidate(void)
+{
+if (tls_watch_fd < 0) return;
+
+#ifdef EXIM_HAVE_KEVENT
+/* Close the files we had open for kevent */
+for (int i = 0; i < kev_used; i++)
+ {
+ DEBUG(D_tls) debug_printf("closing watch fd: %d\n", (int) kev[i].ident);
+ (void) close((int) kev[i].ident);
+ kev[i].ident = (uintptr_t)-1;
+ }
+kev_used = 0;
+#endif
+
+close(tls_watch_fd);
+tls_watch_fd = -1;
+}
+
+
+static void
+tls_daemon_creds_reload(void)
+{
+unsigned lifetime;
+
+#ifdef EXIM_HAVE_KEVENT
+tls_watch_invalidate();
+#endif
+
+tls_server_creds_invalidate();
+
+/* _expire is for a time-limited selfsign server cert */
+tls_creds_expire = (lifetime = tls_server_creds_init())
+ ? time(NULL) + lifetime : 0;
+
+tls_client_creds_reload(TRUE);
+}
+
+
+/* Utility predicates for use by the per-library code */
+static BOOL
+opt_set_and_noexpand(const uschar * opt)
+{ return opt && *opt && Ustrchr(opt, '$') == NULL; }
+
+static BOOL
+opt_unset_or_noexpand(const uschar * opt)
+{ return !opt || Ustrchr(opt, '$') == NULL; }
+
+
+
+/* Called every time round the daemon loop.
+
+If we reloaded fd-watcher, return the old watch fd
+having modified the global for the new one. Otherwise
+return -1.
+*/
+
+int
+tls_daemon_tick(void)
+{
+int old_watch_fd = tls_watch_fd;
+
+tls_per_lib_daemon_tick();
+#if defined(EXIM_HAVE_INOTIFY) || defined(EXIM_HAVE_KEVENT)
+if (tls_creds_expire && time(NULL) >= tls_creds_expire)
+ {
+ /* The server cert is a selfsign, with limited lifetime. Dump it and
+ generate a new one. Reload the rest of the creds also as the machinery
+ is all there. */
+
+ DEBUG(D_tls) debug_printf("selfsign cert rotate\n");
+ tls_creds_expire = 0;
+ tls_daemon_creds_reload();
+ return old_watch_fd;
+ }
+else if (tls_watch_trigger_time && time(NULL) >= tls_watch_trigger_time + 5)
+ {
+ /* Called, after a delay for multiple file ops to get done, from
+ the daemon when any of the watches added (above) fire.
+ Dump the set of watches and arrange to reload cached creds (which
+ will set up new watches). */
+
+ DEBUG(D_tls) debug_printf("watch triggered\n");
+ tls_watch_trigger_time = tls_creds_expire = 0;
+ tls_daemon_creds_reload();
+ return old_watch_fd;
+ }
+#endif
+return -1;
+}
+
+/* Called once at daemon startup */
+
+void
+tls_daemon_init(void)
+{
+tls_per_lib_daemon_init();
+}
+
+
/*************************************************
* Timezone environment flipping *
*************************************************/
#ifdef USE_GNUTLS
# include "tls-gnu.c"
# include "tlscert-gnu.c"
-
# define ssl_xfer_buffer (state_server.xfer_buffer)
# define ssl_xfer_buffer_lwm (state_server.xfer_buffer_lwm)
# define ssl_xfer_buffer_hwm (state_server.xfer_buffer_hwm)
# define ssl_xfer_eof (state_server.xfer_eof)
# define ssl_xfer_error (state_server.xfer_error)
+#endif
-#else
+#ifdef USE_OPENSSL
# include "tls-openssl.c"
# include "tlscert-openssl.c"
#endif
int
tls_ungetc(int ch)
{
+if (ssl_xfer_buffer_lwm <= 0)
+ log_write(0, LOG_MAIN|LOG_PANIC_DIE, "buffer underflow in tls_ungetc");
+
ssl_xfer_buffer[--ssl_xfer_buffer_lwm] = ch;
return ch;
}
}
-#endif /* SUPPORT_TLS */
+#endif /*DISABLE_TLS*/
void
tls_modify_variables(tls_support * dest_tsp)
modify_variable(US"tls_certificate_verified", &dest_tsp->certificate_verified);
modify_variable(US"tls_cipher", &dest_tsp->cipher);
modify_variable(US"tls_peerdn", &dest_tsp->peerdn);
-#if defined(SUPPORT_TLS) && !defined(USE_GNUTLS)
+#ifdef USE_OPENSSL
modify_variable(US"tls_sni", &dest_tsp->sni);
#endif
}
-#ifdef SUPPORT_TLS
+#ifndef DISABLE_TLS
/************************************************
* TLS certificate name operations *
************************************************/
static void
dn_to_list(uschar * dn)
{
-uschar * cp;
-for (cp = dn; *cp; cp++)
+for (uschar * cp = dn; *cp; cp++)
if (cp[0] == '\\' && cp[1] == ',')
*cp++ = ',';
}
}
return FALSE;
}
-#endif /*SUPPORT_TLS*/
+
+/* Environment cleanup: The GnuTLS library uses SSLKEYLOGFILE in the environment
+and writes a file by that name. Our OpenSSL code does the same, using keying
+info from the library API.
+The GnuTLS support only works if exim is run by root, not taking advantage of
+the setuid bit.
+You can use either the external environment (modulo the keep_environment config)
+or the add_environment config option for SSLKEYLOGFILE; the latter takes
+precedence.
+
+If the path is absolute, require it starts with the spooldir; otherwise delete
+the env variable. If relative, prefix the spooldir.
+*/
+void
+tls_clean_env(void)
+{
+uschar * path = US getenv("SSLKEYLOGFILE");
+if (path)
+ if (!*path)
+ unsetenv("SSLKEYLOGFILE");
+ else if (*path != '/')
+ {
+ DEBUG(D_tls)
+ debug_printf("prepending spooldir to env SSLKEYLOGFILE\n");
+ setenv("SSLKEYLOGFILE", CCS string_sprintf("%s/%s", spool_directory, path), 1);
+ }
+ else if (Ustrncmp(path, spool_directory, Ustrlen(spool_directory)) != 0)
+ {
+ DEBUG(D_tls)
+ debug_printf("removing env SSLKEYLOGFILE=%s: not under spooldir\n", path);
+ unsetenv("SSLKEYLOGFILE");
+ }
+}
+
+/*************************************************
+* Drop privs for checking TLS config *
+*************************************************/
+
+/* We want to validate TLS options during readconf, but do not want to be
+root when we call into the TLS library, in case of library linkage errors
+which cause segfaults; before this check, those were always done as the Exim
+runtime user and it makes sense to continue with that.
+
+Assumes: tls_require_ciphers has been set, if it will be
+ exim_user has been set, if it will be
+ exim_group has been set, if it will be
+
+Returns: bool for "okay"; false will cause caller to immediately exit.
+*/
+
+BOOL
+tls_dropprivs_validate_require_cipher(BOOL nowarn)
+{
+const uschar *errmsg;
+pid_t pid;
+int rc, status;
+void (*oldsignal)(int);
+
+/* If TLS will never be used, no point checking ciphers */
+
+if ( !tls_advertise_hosts
+ || !*tls_advertise_hosts
+ || Ustrcmp(tls_advertise_hosts, ":") == 0
+ )
+ return TRUE;
+else if (!nowarn && !tls_certificate)
+ log_write(0, LOG_MAIN,
+ "Warning: No server certificate defined; will use a selfsigned one.\n"
+ " Suggested action: either install a certificate or change tls_advertise_hosts option");
+
+oldsignal = signal(SIGCHLD, SIG_DFL);
+
+fflush(NULL);
+if ((pid = exim_fork(US"cipher-validate")) < 0)
+ log_write(0, LOG_MAIN|LOG_PANIC_DIE, "fork failed for TLS check");
+
+if (pid == 0)
+ {
+ /* in some modes, will have dropped privilege already */
+ if (!geteuid())
+ exim_setugid(exim_uid, exim_gid, FALSE,
+ US"calling tls_validate_require_cipher");
+
+ if ((errmsg = tls_validate_require_cipher()))
+ log_write(0, LOG_PANIC_DIE|LOG_CONFIG,
+ "tls_require_ciphers invalid: %s", errmsg);
+ fflush(NULL);
+ exim_underbar_exit(EXIT_SUCCESS);
+ }
+
+do {
+ rc = waitpid(pid, &status, 0);
+} while (rc < 0 && errno == EINTR);
+
+DEBUG(D_tls)
+ debug_printf("tls_validate_require_cipher child %d ended: status=0x%x\n",
+ (int)pid, status);
+
+signal(SIGCHLD, oldsignal);
+
+return status == 0;
+}
+
+
+
+
+static void
+tls_client_resmption_key(tls_support * tlsp, smtp_connect_args * conn_args,
+ smtp_transport_options_block * ob)
+{
+#ifndef DISABLE_TLS_RESUME
+hctx * h = &tlsp->resume_hctx;
+blob b;
+gstring * g;
+
+DEBUG(D_tls) if (conn_args->host_lbserver)
+ debug_printf("TLS: lbserver '%s'\n", conn_args->host_lbserver);
+
+# ifdef EXIM_HAVE_SHA2
+exim_sha_init(h, HASH_SHA2_256);
+# else
+exim_sha_init(h, HASH_SHA1);
+# endif
+exim_sha_update_string(h, conn_args->host_lbserver);
+# ifdef SUPPORT_DANE
+if (conn_args->dane)
+ exim_sha_update(h, CUS &conn_args->tlsa_dnsa, sizeof(dns_answer));
+# endif
+exim_sha_update_string(h, conn_args->host->address);
+exim_sha_update(h, CUS &conn_args->host->port, sizeof(conn_args->host->port));
+exim_sha_update_string(h, conn_args->sending_ip_address);
+exim_sha_update_string(h, openssl_options);
+exim_sha_update_string(h, ob->tls_require_ciphers);
+exim_sha_update_string(h, tlsp->sni);
+# ifdef EXIM_HAVE_ALPN
+exim_sha_update_string(h, ob->tls_alpn);
+# endif
+exim_sha_finish(h, &b);
+for (g = string_get(b.len*2+1); b.len-- > 0; )
+ g = string_fmt_append(g, "%02x", *b.data++);
+tlsp->resume_index = string_from_gstring(g);
+DEBUG(D_tls) debug_printf("TLS: resume session index %s\n", tlsp->resume_index);
+#endif
+}
+
+#endif /*!DISABLE_TLS*/
#endif /*!MACRO_PREDEF*/
/* vi: aw ai sw=2
git://git.exim.org / exim.git / blobdiff