diff -r 26d5351649ac configure.in
--- a/configure.in	Wed Mar 16 19:49:27 2011 +0200
+++ b/configure.in	Thu Mar 17 13:54:55 2011 +0100
@@ -379,7 +379,8 @@
 	       setrlimit setproctitle seteuid setreuid setegid setresgid \
 	       strtoull strtoll strtouq strtoq \
 	       setpriority quotactl getmntent kqueue kevent backtrace_symbols \
-	       walkcontext dirfd clearenv malloc_usable_size glob fallocate)
+	       walkcontext dirfd clearenv malloc_usable_size glob fallocate \
+	       getpwnam_r)
 
 AC_CHECK_LIB(rt, clock_gettime, [
   AC_DEFINE(HAVE_CLOCK_GETTIME,, Define if you have the clock_gettime function)
diff -r 26d5351649ac src/auth/userdb-passwd.c
--- a/src/auth/userdb-passwd.c	Wed Mar 16 19:49:27 2011 +0200
+++ b/src/auth/userdb-passwd.c	Thu Mar 17 13:54:55 2011 +0100
@@ -9,12 +9,18 @@
 #include "userdb-static.h"
 
 #include <pwd.h>
+#include <unistd.h>
 
 #define USER_CACHE_KEY "%u"
 
 struct passwd_userdb_module {
 	struct userdb_module module;
 	struct userdb_static_template *tmpl;
+
+#ifdef HAVE_GETPWNAM_R
+	char *buf;
+	size_t bufsize;
+#endif
 };
 
 struct passwd_userdb_iterate_context {
@@ -33,15 +39,35 @@
 	struct passwd_userdb_module *module =
 		(struct passwd_userdb_module *)_module;
 	struct passwd *pw;
+#ifdef HAVE_GETPWNAM_R
+	struct passwd pw_data;
+	int err;
+#endif
 
 	auth_request_log_debug(auth_request, "passwd", "lookup");
 
+#ifdef HAVE_GETPWNAM_R
+	err = getpwnam_r(auth_request->user, &pw_data,
+			 module->buf, module->bufsize, &pw);
+	if (pw == NULL) {
+		if (err) {
+		    auth_request_log_error(auth_request, "passwd", "%s",
+					   strerror(err));
+		    callback(USERDB_RESULT_INTERNAL_FAILURE, auth_request);
+		    return;
+		}
+		auth_request_log_info(auth_request, "passwd", "unknown user");
+		callback(USERDB_RESULT_USER_UNKNOWN, auth_request);
+		return;
+	}
+#else
 	pw = getpwnam(auth_request->user);
 	if (pw == NULL) {
 		auth_request_log_info(auth_request, "passwd", "unknown user");
 		callback(USERDB_RESULT_USER_UNKNOWN, auth_request);
 		return;
 	}
+#endif
 
 	auth_request_set_field(auth_request, "user", pw->pw_name, NULL);
 
@@ -151,6 +177,13 @@
 	module->module.cache_key = USER_CACHE_KEY;
 	module->tmpl = userdb_static_template_build(pool, "passwd", args);
 
+#ifdef HAVE_GETPWNAM_R
+	module->bufsize = sysconf(_SC_GETPW_R_SIZE_MAX);
+	if (module->bufsize == (size_t)-1)
+	    module->bufsize = 16384;
+	module->buf = p_malloc(pool, module->bufsize);
+#endif
+
 	if (userdb_static_template_remove(module->tmpl, "blocking",
 					  &value)) {
 		module->module.blocking = value == NULL ||