X-Git-Url: https://git.exim.org/exim.git/blobdiff_plain/2e5d9e711eef27badbff206e17238661d14cc7c2..a85c067ba6c6940512cf57ec213277a370d87e70:/src/src/tls.c diff --git a/src/src/tls.c b/src/src/tls.c index 9c587e55d..9e20b5bca 100644 --- a/src/src/tls.c +++ b/src/src/tls.c @@ -2,8 +2,10 @@ * 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 @@ -24,6 +26,11 @@ functions from the OpenSSL or GNU TLS libraries. */ #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 @@ -35,6 +42,18 @@ functions from the OpenSSL or GNU TLS libraries. */ #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 @@ -44,7 +63,9 @@ loops. */ #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. @@ -61,8 +82,13 @@ static int ssl_xfer_eof = FALSE; 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 * @@ -97,6 +123,315 @@ return TRUE; } +#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 * *************************************************/ @@ -158,6 +493,9 @@ Returns: the character 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; } @@ -370,7 +708,6 @@ else if ((subjdn = tls_cert_subject(cert, NULL))) return FALSE; } - /* 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. @@ -399,10 +736,122 @@ if (path) else if (Ustrncmp(path, spool_directory, Ustrlen(spool_directory)) != 0) { DEBUG(D_tls) - debug_printf("removing env SSLKEYLOGFILE: not under spooldir\n"); + 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*/