sudo_term_is_raw: only try to lock the fd if it is a tty

This moves sudo_isatty() to libsudo_util so sudo_term_is_raw() can
use it.  Fixes GitHub issue #335

include/sudo_util.h

@@ -325,6 +325,8 @@ extern int (*sudo_printf)(int msg_type, const char * restrict fmt, ...);
 /* term.c */
 #define SUDO_TERM_ISIG	0x01U
 #define SUDO_TERM_OFLAG	0x02U
+sudo_dso_public bool sudo_isatty_v1(int fd, struct stat *sbp);
+#define sudo_isatty(_a, _b) sudo_isatty_v1((_a), (_b))
 sudo_dso_public bool sudo_term_cbreak_v1(int fd);
 #define sudo_term_cbreak(_a) sudo_term_cbreak_v1((_a))
 sudo_dso_public bool sudo_term_copy_v1(int src, int dst);

lib/util/term.c

@@ -24,6 +24,7 @@
 #include <config.h>
 
 #include <sys/ioctl.h>
+#include <sys/stat.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -286,6 +287,9 @@ sudo_term_is_raw_v1(int fd)
     struct termios term = { 0 };
     debug_decl(sudo_term_is_raw, SUDO_DEBUG_UTIL);
 
+    if (!sudo_isatty(fd, NULL))
+	debug_return_bool(false);
+
     sudo_lock_file(fd, SUDO_LOCK);
     if (tcgetattr(fd, &term) == -1) {
 	sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_ERRNO,
@@ -457,3 +461,31 @@ unlock:
     sudo_lock_file(src, SUDO_UNLOCK);
     debug_return_bool(ret);
 }
+
+/*
+ * Like isatty(3) but stats the fd and stores the result in sb.
+ * Only calls isatty(3) if fd is a character special device.
+ * Returns true if a tty, else returns false and sets errno.
+ */
+bool
+sudo_isatty_v1(int fd, struct stat *sbp)
+{
+    bool ret = false;
+    struct stat sb;
+    debug_decl(sudo_isatty, SUDO_DEBUG_EXEC);
+
+    if (sbp == NULL)
+	sbp = &sb;
+
+    if (fstat(fd, sbp) == 0) {
+        if (!S_ISCHR(sbp->st_mode)) {
+            errno = ENOTTY;
+        } else {
+            ret = isatty(fd) == 1;
+        }
+    } else if (sbp != &sb) {
+        /* Always initialize sbp. */
+        memset(sbp, 0, sizeof(*sbp));
+    }
+    debug_return_bool(ret);
+}

lib/util/ttysize.c

@@ -39,13 +39,15 @@ get_ttysize_ioctl(int fd, int *rowp, int *colp)
     struct winsize wsize;
     debug_decl(get_ttysize_ioctl, SUDO_DEBUG_UTIL);
 
-    if (fd != -1 && isatty(fd) && ioctl(fd, TIOCGWINSZ, &wsize) == 0) {
+    if (fd != -1 && sudo_isatty(fd, NULL)) {
+	if (ioctl(fd, TIOCGWINSZ, &wsize) == 0) {
 	    if (wsize.ws_row != 0 && wsize.ws_col != 0) {
 		*rowp = wsize.ws_row;
 		*colp = wsize.ws_col;
 		debug_return_int(0);
 	    }
 	}
+    }
     debug_return_int(-1);
 }
 

lib/util/util.exp.in

@@ -96,6 +96,7 @@ sudo_gettime_awake_v1
 sudo_gettime_mono_v1
 sudo_gettime_real_v1
 sudo_hexchar_v1
+sudo_isatty_v1
 sudo_json_add_value_as_object_v1
 sudo_json_add_value_v1
 sudo_json_close_array_v1

src/sudo.h

@@ -318,7 +318,6 @@ int get_net_ifs(char **addrinfo);
 
 /* ttyname.c */
 dev_t get_process_ttyname(char *name, size_t namelen);
-bool sudo_isatty(int fd, struct stat *sb);
 
 /* signal.c */
 struct sigaction;

src/ttyname.c

@@ -405,27 +405,3 @@ get_process_ttyname(char *name, size_t namelen)
     debug_return_dev_t((dev_t)-1);
 }
 #endif
-
-/*
- * Like isatty(3) but stats the fd and stores the result in sb.
- * Only calls isatty(3) if fd is a character special device.
- * Returns true if a tty, else returns false and sets errno.
- */
-bool
-sudo_isatty(int fd, struct stat *sb)
-{
-    bool ret = false;
-    debug_decl(sudo_isatty, SUDO_DEBUG_EXEC);
-
-    if (fstat(fd, sb) == 0) {
-        if (!S_ISCHR(sb->st_mode)) {
-            errno = ENOTTY;
-        } else {
-            ret = isatty(fd) == 1;
-        }
-    } else {
-	/* Always initialize sb. */
-	memset(sb, 0, sizeof(*sb));
-    }
-    debug_return_bool(ret);
-}