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+/*++
+/* NAME
+/* maillog_client 3
+/* SUMMARY
+/* choose between syslog client and postlog client
+/* SYNOPSIS
+/* #include <maillog_client.h>
+/*
+/* int maillog_client_init(
+/* const char *progname,
+/* int flags)
+/* DESCRIPTION
+/* maillog_client_init() chooses between logging to the syslog
+/* service or to the internal postlog service.
+/*
+/* maillog_client_init() may be called before configuration
+/* parameters are initialized. During this time, logging is
+/* controlled by the presence or absence of POSTLOG_SERVICE
+/* in the process environment (this is ignored if a program
+/* runs with set-uid or set-gid permissions).
+/*
+/* maillog_client_init() may also be called after configuration
+/* parameters are initialized. During this time, logging is
+/* controlled by the "maillog_file" parameter value.
+/*
+/* Arguments:
+/* .IP progname
+/* The program name that will be prepended to logfile records.
+/* .IP flags
+/* Specify one of the following:
+/* .RS
+/* .IP MAILLOG_CLIENT_FLAG_NONE
+/* No special processing.
+/* .IP MAILLOG_CLIENT_FLAG_LOGWRITER_FALLBACK
+/* Try to fall back to writing the "maillog_file" directly,
+/* if logging to the internal postlog service is enabled, but
+/* the postlog service is unavailable. If the fallback fails,
+/* die with a fatal error.
+/* .RE
+/* ENVIRONMENT
+/* .ad
+/* .fi
+/* When logging to the internal postlog service is enabled,
+/* each process exports the following information, to help
+/* initialize the logging in a child process, before the child
+/* has initialized its configuration parameters.
+/* .IP POSTLOG_SERVICE
+/* The pathname of the public postlog service endpoint, usually
+/* "$queue_directory/public/$postlog_service_name".
+/* .IP POSTLOG_HOSTNAME
+/* The hostname to prepend to information that is sent to the
+/* internal postlog logging service, usually "$myhostname".
+/* CONFIGURATION PARAMETERS
+/* .ad
+/* .fi
+/* .IP "maillog_file (empty)"
+/* The name of an optional logfile. If the value is empty, or
+/* unitialized and the process environment does not specify
+/* POSTLOG_SERVICE, the program will log to the syslog service
+/* instead.
+/* .IP "myhostname (default: see postconf -d output)"
+/* The internet hostname of this mail system.
+/* .IP "postlog_service_name (postlog)"
+/* The name of the internal postlog logging service.
+/* SEE ALSO
+/* msg_syslog(3) syslog client
+/* msg_logger(3) internal logger
+/* LICENSE
+/* .ad
+/* .fi
+/* The Secure Mailer license must be distributed with this
+/* software.
+/* AUTHOR(S)
+/* Wietse Venema
+/* Google, Inc.
+/* 111 8th Avenue
+/* New York, NY 10011, USA
+/*--*/
+
+ /*
+ * System library.
+ */
+#include <sys_defs.h>
+#include <string.h>
+
+ /*
+ * Utility library.
+ */
+#include <argv.h>
+#include <logwriter.h>
+#include <msg_logger.h>
+#include <msg_syslog.h>
+#include <safe.h>
+#include <stringops.h>
+
+ /*
+ * Global library.
+ */
+#include <mail_params.h>
+#include <mail_proto.h>
+#include <maillog_client.h>
+#include <msg.h>
+
+ /*
+ * Using logging to debug logging is painful.
+ */
+#define MAILLOG_CLIENT_DEBUG 0
+
+ /*
+ * Application-specific.
+ */
+static int maillog_client_flags;
+
+#define POSTLOG_SERVICE_ENV "POSTLOG_SERVICE"
+#define POSTLOG_HOSTNAME_ENV "POSTLOG_HOSTNAME"
+
+/* maillog_client_logwriter_fallback - fall back to logfile writer or bust */
+
+static void maillog_client_logwriter_fallback(const char *text)
+{
+ static int fallback_guard = 0;
+
+ /*
+ * Guard against recursive calls.
+ *
+ * If an error happened before the maillog_file parameter was initialized,
+ * or if maillog_file logging is disabled, then we cannot fall back to a
+ * logfile. All we can do is to hope that stderr logging will bring out
+ * the bad news.
+ */
+ if (fallback_guard == 0 && var_maillog_file && *var_maillog_file
+ && logwriter_one_shot(var_maillog_file, text, strlen(text)) < 0) {
+ fallback_guard = 1;
+ msg_fatal("logfile '%s' write error: %m", var_maillog_file);
+ }
+}
+
+/* maillog_client_init - set up syslog or internal log client */
+
+void maillog_client_init(const char *progname, int flags)
+{
+ char *import_service_path;
+ char *import_hostname;
+
+ /*
+ * Crucially, only one logger mode can be in effect at any time,
+ * otherwise postlogd(8) may go into a loop.
+ */
+ enum {
+ MAILLOG_CLIENT_MODE_SYSLOG, MAILLOG_CLIENT_MODE_POSTLOG,
+ } logger_mode;
+
+ /*
+ * Security: this code may run before the import_environment setting has
+ * taken effect. It has to guard against privilege escalation attacks on
+ * setgid programs, using malicious environment settings.
+ *
+ * Import the postlog service name and hostname from the environment.
+ *
+ * - These will be used and kept if the process has not yet initialized its
+ * configuration parameters.
+ *
+ * - These will be set or updated if the configuration enables postlog
+ * logging.
+ *
+ * - These will be removed if the configuration does not enable postlog
+ * logging.
+ */
+ if ((import_service_path = safe_getenv(POSTLOG_SERVICE_ENV)) != 0
+ && *import_service_path == 0)
+ import_service_path = 0;
+ if ((import_hostname = safe_getenv(POSTLOG_HOSTNAME_ENV)) != 0
+ && *import_hostname == 0)
+ import_hostname = 0;
+
+#if MAILLOG_CLIENT_DEBUG
+#define STRING_OR_NULL(s) ((s) ? (s) : "(null)")
+ msg_syslog_init(progname, LOG_PID, LOG_FACILITY);
+ msg_info("import_service_path=%s", STRING_OR_NULL(import_service_path));
+ msg_info("import_hostname=%s", STRING_OR_NULL(import_hostname));
+#endif
+
+ /*
+ * Before configuration parameters are initialized, the logging mode is
+ * controlled by the presence or absence of POSTLOG_SERVICE in the
+ * process environment. After configuration parameters are initialized,
+ * the logging mode is controlled by the "maillog_file" parameter value.
+ *
+ * The configured mode may change after a process is started. The
+ * postlogd(8) server will proxy logging to syslogd where needed.
+ */
+ if (var_maillog_file ? *var_maillog_file == 0 : import_service_path == 0) {
+ logger_mode = MAILLOG_CLIENT_MODE_SYSLOG;
+ } else {
+ /* var_maillog_file ? *var_maillog_file : import_service_path != 0 */
+ logger_mode = MAILLOG_CLIENT_MODE_POSTLOG;
+ }
+
+ /*
+ * Postlog logging is enabled. Update the 'progname' as that may have
+ * changed since an earlier call, and update the environment settings if
+ * they differ from configuration settings. This blends two code paths,
+ * one code path where configuration parameters are initialized (the
+ * preferred path), and one code path that uses imports from environment.
+ */
+ if (logger_mode == MAILLOG_CLIENT_MODE_POSTLOG) {
+ char *myhostname;
+ char *service_path;
+
+ if (var_maillog_file && *var_maillog_file) {
+ ARGV *good_prefixes = argv_split(var_maillog_file_pfxs,
+ CHARS_COMMA_SP);
+ char **cpp;
+
+ for (cpp = good_prefixes->argv; /* see below */ ; cpp++) {
+ if (*cpp == 0)
+ msg_fatal("%s value '%s' does not match any prefix in %s",
+ VAR_MAILLOG_FILE, var_maillog_file,
+ VAR_MAILLOG_FILE_PFXS);
+ if (strncmp(var_maillog_file, *cpp, strlen(*cpp)) == 0)
+ break;
+ }
+ argv_free(good_prefixes);
+ }
+ if (var_myhostname && *var_myhostname) {
+ myhostname = var_myhostname;
+ } else if ((myhostname = import_hostname) == 0) {
+ myhostname = "amnesiac";
+ }
+#if MAILLOG_CLIENT_DEBUG
+ msg_info("myhostname=%s", STRING_OR_NULL(myhostname));
+#endif
+ if (var_postlog_service) {
+ service_path = concatenate(var_queue_dir, "/", MAIL_CLASS_PUBLIC,
+ "/", var_postlog_service, (char *) 0);
+ } else {
+ service_path = import_service_path;
+ }
+ maillog_client_flags = flags;
+ msg_logger_init(progname, myhostname, service_path,
+ (flags & MAILLOG_CLIENT_FLAG_LOGWRITER_FALLBACK) ?
+ maillog_client_logwriter_fallback :
+ (MSG_LOGGER_FALLBACK_FN) 0);
+
+ /*
+ * Export or update the exported postlog service pathname and the
+ * hostname, so that a child process can bootstrap postlog logging
+ * before it has processed main.cf and command-line options.
+ */
+ if (import_service_path == 0
+ || strcmp(service_path, import_service_path) != 0) {
+#if MAILLOG_CLIENT_DEBUG
+ msg_info("export %s=%s", POSTLOG_SERVICE_ENV, service_path);
+#endif
+ if (setenv(POSTLOG_SERVICE_ENV, service_path, 1) < 0)
+ msg_fatal("setenv: %m");
+ }
+ if (import_hostname == 0 || strcmp(myhostname, import_hostname) != 0) {
+#if MAILLOG_CLIENT_DEBUG
+ msg_info("export %s=%s", POSTLOG_HOSTNAME_ENV, myhostname);
+#endif
+ if (setenv(POSTLOG_HOSTNAME_ENV, myhostname, 1) < 0)
+ msg_fatal("setenv: %m");
+ }
+ if (service_path != import_service_path)
+ myfree(service_path);
+ }
+
+ /*
+ * Postlog logging is disabled. Silence the msg_logger client, and remove
+ * the environment settings that bootstrap postlog logging in a child
+ * process.
+ */
+ else {
+ msg_logger_control(CA_MSG_LOGGER_CTL_DISABLE, CA_MSG_LOGGER_CTL_END);
+ if ((import_service_path && unsetenv(POSTLOG_SERVICE_ENV))
+ || (import_hostname && unsetenv(POSTLOG_HOSTNAME_ENV)))
+ msg_fatal("unsetenv: %m");
+ }
+
+ /*
+ * Syslog logging is enabled. Update the 'progname' as that may have
+ * changed since an earlier call.
+ */
+ if (logger_mode == MAILLOG_CLIENT_MODE_SYSLOG) {
+ msg_syslog_init(progname, LOG_PID, LOG_FACILITY);
+ }
+
+ /*
+ * Syslog logging is disabled, silence the syslog client.
+ */
+ else {
+ msg_syslog_disable();
+ }
+}