add vsyslog() for systems without it.

MANIFEST

@@ -111,6 +111,7 @@ lib/util/parseln.c
 lib/util/progname.c
 lib/util/pw_dup.c
 lib/util/reallocarray.c
+lib/util/vsyslog.c
 lib/util/regress/atofoo/atofoo_test.c
 lib/util/regress/fnmatch/fnm_test.c
 lib/util/regress/fnmatch/fnm_test.in

configure

@@ -2663,7 +2663,6 @@ as_fn_append ac_func_list " pwrite"
 as_fn_append ac_func_list " openat"
 as_fn_append ac_func_list " faccessat"
 as_fn_append ac_func_list " wordexp"
-as_fn_append ac_func_list " vsyslog"
 as_fn_append ac_func_list " seteuid"
 # Check that the precious variables saved in the cache have kept the same
 # value.
@@ -18096,8 +18095,6 @@ done
 
 
 
-
-
 
 
 case "$host_os" in
@@ -19894,6 +19891,32 @@ esac
     done
 
 fi
+for ac_func in vsyslog
+do :
+  ac_fn_c_check_func "$LINENO" "vsyslog" "ac_cv_func_vsyslog"
+if test "x$ac_cv_func_vsyslog" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_VSYSLOG 1
+_ACEOF
+
+else
+
+    case " $LIBOBJS " in
+  *" vsyslog.$ac_objext "* ) ;;
+  *) LIBOBJS="$LIBOBJS vsyslog.$ac_objext"
+ ;;
+esac
+
+
+    for _sym in sudo_vsyslog; do
+	COMPAT_EXP="${COMPAT_EXP}${_sym}
+"
+    done
+
+
+fi
+done
+
 if test X"$with_noexec" != X"no"; then
     # Check for non-standard exec functions
     for ac_func in exect execvP execvpe

configure.ac

@@ -2408,7 +2408,7 @@ dnl
 dnl Function checks
 dnl
 AC_FUNC_GETGROUPS
-AC_CHECK_FUNCS_ONCE([fexecve killpg nl_langinfo strftime pread pwrite openat faccessat wordexp vsyslog])
+AC_CHECK_FUNCS_ONCE([fexecve killpg nl_langinfo strftime pread pwrite openat faccessat wordexp])
 case "$host_os" in
     hpux*)
 	if test X"$ac_cv_func_pread" = X"yes"; then
@@ -2692,6 +2692,10 @@ if test X"$FOUND_SHA2" = X"no"; then
     AC_LIBOBJ(sha2)
     SUDO_APPEND_COMPAT_EXP(sudo_SHA224Final sudo_SHA224Init sudo_SHA224Pad sudo_SHA224Transform sudo_SHA224Update sudo_SHA256Final sudo_SHA256Init sudo_SHA256Pad sudo_SHA256Transform sudo_SHA256Update sudo_SHA384Final sudo_SHA384Init sudo_SHA384Pad sudo_SHA384Transform sudo_SHA384Update sudo_SHA512Final sudo_SHA512Init sudo_SHA512Pad sudo_SHA512Transform sudo_SHA512Update)
 fi
+AC_CHECK_FUNCS([vsyslog], [], [
+    AC_LIBOBJ(vsyslog)
+    SUDO_APPEND_COMPAT_EXP(sudo_vsyslog)
+])
 dnl
 dnl Function checks for sudo_noexec
 dnl

include/sudo_compat.h

@@ -487,5 +487,10 @@ __dso_public void *sudo_reallocarray(void *ptr, size_t nmemb, size_t size);
 # undef reallocarray
 # define reallocarray(_a, _b, _c) sudo_reallocarray((_a), (_b), (_c))
 #endif /* HAVE_REALLOCARRAY */
+#ifndef HAVE_VSYSLOG
+__dso_public void sudo_vsyslog(int pri, const char *fmt, va_list ap);
+# undef vsyslog
+# define vsyslog(_a, _b, _c) sudo_vsyslog((_a), (_b), (_c))
+#endif /* HAVE_VSYSLOG */
 
 #endif /* SUDO_COMPAT_H */

lib/util/vsyslog.c

@@ -0,0 +1,68 @@
+/*
+ * Copyright (c) 2016 Todd C. Miller <Todd.Miller@courtesan.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <config.h>
+
+#include <errno.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#ifdef HAVE_STRING_H
+# include <string.h>
+#endif /* HAVE_STRING_H */
+#ifdef HAVE_STRINGS_H
+# include <strings.h>
+#endif /* HAVE_STRINGS_H */
+#include <syslog.h>
+
+#include "sudo_compat.h"
+
+#ifndef HAVE_VSYSLOG
+void
+sudo_vsyslog(int pri, const char *fmt, va_list ap)
+{
+    int saved_errno = errno;
+    char *buf, *cp, *ep, new_fmt[1024];
+    size_t len;
+
+    /* Rewrite fmt, replacing %m with an errno string. */
+    for (cp = new_fmt, ep = new_fmt + sizeof(new_fmt); *fmt != '\0'; fmt++) {
+	if (fmt[0] == '%' && fmt[1] == 'm') {
+	    fmt++;
+	    len = strlcpy(cp, strerror(saved_errno), (ep - cp));
+	    if (len >= (size_t)(ep - cp))
+		len = (size_t)(ep - cp) - 1;
+	    cp += len;
+	    break;
+	} else {
+	    if (fmt[0] == '%' && fmt[1] == '%') {
+		    fmt++;
+		    if (cp < ep - 1)
+			*cp++ = '%';
+	    }
+	    if (cp < ep - 1)
+		*cp++ = *fmt;
+	}
+    }
+    *cp = '\0';
+
+    /* Format message and log it. */
+    if (vasprintf(&buf, new_fmt, ap) != -1) {
+	syslog(pri, "%s", buf);
+	free(buf);
+    }
+}
+#endif /* HAVE_VSYSLOG */

plugins/sudoers/logging.c

@@ -66,8 +66,6 @@ static char *new_logline(const char *, int);
  * We do an openlog(3)/closelog(3) for each message because some
  * authentication methods (notably PAM) use syslog(3) for their
  * own nefarious purposes and may call openlog(3) and closelog(3).
- * Note that because we don't want to assume that all systems have
- * vsyslog(3) (HP-UX doesn't) "%m" will not be expanded.
  */
 static void
 mysyslog(int pri, const char *fmt, ...)
@@ -77,19 +75,7 @@ mysyslog(int pri, const char *fmt, ...)
 
     va_start(ap, fmt);
     openlog("sudo", 0, def_syslog);
-#ifdef HAVE_VSYSLOG
     vsyslog(pri, fmt, ap);
-#else
-    do {
-	char *buf;
-	if (vasprintf(&buf, fmt, ap) == -1) {
-	    sudo_warnx(U_("%s: %s"), __func__, U_("unable to allocate memory"));
-	} else {
-	    syslog(pri, "%s", buf);
-	    free(buf);
-	}
-    } while (0);
-#endif
     va_end(ap);
     closelog();
     debug_return;