* Exim - an Internet mail transport agent *
*************************************************/
-/* Copyright (c) University of Cambridge 1995 - 2009 */
+/* Copyright (c) University of Cambridge 1995 - 2018 */
/* See the file NOTICE for conditions of use and distribution. */
/* 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
adapted from stunnel, a GPL program by Michal Trojnara. The code for GNU TLS is
-based on a patch contributed by Nikos Mavroyanopoulos. Because these packages
+based on a patch contributed by Nikos Mavrogiannopoulos. Because these packages
are so very different, the functions for each are kept in separate files. The
relevant file is #included as required, after any any common functions.
#include "exim.h"
+#include "transports/smtp.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
+
+
+#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
/* This module is compiled only when it is specifically requested in the
build-time configuration. However, some compilers don't like compiling empty
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
/* Static variables that are used for buffering data by both sets of
-functions and the common functions below. */
+functions and the common functions below.
+We're moving away from this; GnuTLS is already using a state, which
+can switch, so we can do TLS callouts during ACLs. */
-static uschar *ssl_xfer_buffer = NULL;
static const int ssl_xfer_buffer_size = 4096;
+#ifdef USE_OPENSSL
+static uschar *ssl_xfer_buffer = NULL;
static int ssl_xfer_buffer_lwm = 0;
static int ssl_xfer_buffer_hwm = 0;
-static int ssl_xfer_eof = 0;
-static int ssl_xfer_error = 0;
-
-uschar *tls_channelbinding_b64 = NULL;
+static int ssl_xfer_eof = FALSE;
+static BOOL ssl_xfer_error = FALSE;
+#endif
/*************************************************
*/
static BOOL
-expand_check(const uschar *s, const uschar *name, uschar **result)
+expand_check(const uschar *s, const uschar *name, uschar **result, uschar ** errstr)
{
-if (s == NULL) *result = NULL; else
+if (!s)
+ *result = NULL;
+else if ( !(*result = expand_string(US s)) /* need to clean up const more */
+ && !f.expand_string_forcedfail
+ )
{
- *result = expand_string(US s); /* need to clean up const some more */
- if (*result == NULL && !expand_string_forcedfail)
- {
- log_write(0, LOG_MAIN|LOG_PANIC, "expansion of %s failed: %s", name,
- expand_string_message);
- return FALSE;
- }
+ *errstr = US"Internal error";
+ log_write(0, LOG_MAIN|LOG_PANIC, "expansion of %s failed: %s", name,
+ expand_string_message);
+ return FALSE;
}
return TRUE;
}
+/*************************************************
+* Timezone environment flipping *
+*************************************************/
+
+static uschar *
+to_tz(uschar * tz)
+{
+uschar * old = US getenv("TZ");
+(void) setenv("TZ", CCS tz, 1);
+tzset();
+return old;
+}
+
+static void
+restore_tz(uschar * tz)
+{
+if (tz)
+ (void) setenv("TZ", CCS tz, 1);
+else
+ (void) os_unsetenv(US"TZ");
+tzset();
+}
+
/*************************************************
* Many functions are package-specific *
*************************************************/
#ifdef USE_GNUTLS
-#include "tls-gnu.c"
-#else
-#include "tls-openssl.c"
+# 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
+
+#ifdef USE_OPENSSL
+# include "tls-openssl.c"
+# include "tlscert-openssl.c"
#endif
/* Puts a character back in the input buffer. Only ever
called once.
+Only used by the server-side TLS.
Arguments:
ch the character
*************************************************/
/* Tests for a previous EOF
+Only used by the server-side TLS.
Arguments: none
Returns: non-zero if the eof flag is set
int
tls_feof(void)
{
-return ssl_xfer_eof;
+return (int)ssl_xfer_eof;
}
/* Tests for a previous read error, and returns with errno
restored to what it was when the error was detected.
+Only used by the server-side TLS.
>>>>> Hmm. Errno not handled yet. Where do we get it from? >>>>>
int
tls_ferror(void)
{
-return ssl_xfer_error;
+return (int)ssl_xfer_error;
}
*************************************************/
/* Tests for unused chars in the TLS input buffer.
+Only used by the server-side TLS.
Arguments: none
Returns: TRUE/FALSE
}
-#endif /* SUPPORT_TLS */
+#endif /*DISABLE_TLS*/
+void
+tls_modify_variables(tls_support * dest_tsp)
+{
+modify_variable(US"tls_bits", &dest_tsp->bits);
+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);
+#ifdef USE_OPENSSL
+modify_variable(US"tls_sni", &dest_tsp->sni);
+#endif
+}
+
+
+#ifndef DISABLE_TLS
+/************************************************
+* TLS certificate name operations *
+************************************************/
+
+/* Convert an rfc4514 DN to an exim comma-sep list.
+Backslashed commas need to be replaced by doublecomma
+for Exim's list quoting. We modify the given string
+inplace.
+*/
+
+static void
+dn_to_list(uschar * dn)
+{
+for (uschar * cp = dn; *cp; cp++)
+ if (cp[0] == '\\' && cp[1] == ',')
+ *cp++ = ',';
+}
+
+
+/* Extract fields of a given type from an RFC4514-
+format Distinguished Name. Return an Exim list.
+NOTE: We modify the supplied dn string during operation.
+
+Arguments:
+ dn Distinguished Name string
+ mod list containing optional output list-sep and
+ field selector match, comma-separated
+Return:
+ allocated string with list of matching fields,
+ field type stripped
+*/
+
+uschar *
+tls_field_from_dn(uschar * dn, const uschar * mod)
+{
+int insep = ',';
+uschar outsep = '\n';
+uschar * ele;
+uschar * match = NULL;
+int len;
+gstring * list = NULL;
+
+while ((ele = string_nextinlist(&mod, &insep, NULL, 0)))
+ if (ele[0] != '>')
+ match = ele; /* field tag to match */
+ else if (ele[1])
+ outsep = ele[1]; /* nondefault output separator */
+
+dn_to_list(dn);
+insep = ',';
+len = match ? Ustrlen(match) : -1;
+while ((ele = string_nextinlist(CUSS &dn, &insep, NULL, 0)))
+ if ( !match
+ || Ustrncmp(ele, match, len) == 0 && ele[len] == '='
+ )
+ list = string_append_listele(list, outsep, ele+len+1);
+return string_from_gstring(list);
+}
+
+
+/* Compare a domain name with a possibly-wildcarded name. Wildcards
+are restricted to a single one, as the first element of patterns
+having at least three dot-separated elements. Case-independent.
+Return TRUE for a match
+*/
+static BOOL
+is_name_match(const uschar * name, const uschar * pat)
+{
+uschar * cp;
+return *pat == '*' /* possible wildcard match */
+ ? *++pat == '.' /* starts star, dot */
+ && !Ustrchr(++pat, '*') /* has no more stars */
+ && Ustrchr(pat, '.') /* and has another dot. */
+ && (cp = Ustrchr(name, '.'))/* The name has at least one dot */
+ && strcmpic(++cp, pat) == 0 /* and we only compare after it. */
+ : !Ustrchr(pat+1, '*')
+ && strcmpic(name, pat) == 0;
+}
+
+/* Compare a list of names with the dnsname elements
+of the Subject Alternate Name, if any, and the
+Subject otherwise.
+
+Arguments:
+ namelist names to compare
+ cert certificate
+
+Returns:
+ TRUE/FALSE
+*/
+
+BOOL
+tls_is_name_for_cert(const uschar * namelist, void * cert)
+{
+uschar * altnames = tls_cert_subject_altname(cert, US"dns");
+uschar * subjdn;
+uschar * certname;
+int cmp_sep = 0;
+uschar * cmpname;
+
+if ((altnames = tls_cert_subject_altname(cert, US"dns")))
+ {
+ int alt_sep = '\n';
+ while ((cmpname = string_nextinlist(&namelist, &cmp_sep, NULL, 0)))
+ {
+ const uschar * an = altnames;
+ while ((certname = string_nextinlist(&an, &alt_sep, NULL, 0)))
+ if (is_name_match(cmpname, certname))
+ return TRUE;
+ }
+ }
+
+else if ((subjdn = tls_cert_subject(cert, NULL)))
+ {
+ int sn_sep = ',';
+
+ dn_to_list(subjdn);
+ while ((cmpname = string_nextinlist(&namelist, &cmp_sep, NULL, 0)))
+ {
+ const uschar * sn = subjdn;
+ while ((certname = string_nextinlist(&sn, &sn_sep, NULL, 0)))
+ if ( *certname++ == 'C'
+ && *certname++ == 'N'
+ && *certname++ == '='
+ && is_name_match(cmpname, certname)
+ )
+ return TRUE;
+ }
+ }
+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.
+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 = fork()) < 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(0);
+ }
+
+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;
+}
+
+
+
+
+#endif /*!DISABLE_TLS*/
+#endif /*!MACRO_PREDEF*/
+
+/* vi: aw ai sw=2
+*/
/* End of tls.c */
git://git.exim.org / exim.git / blobdiff