libbb: Add xsetegid(), xseteuid(), xopen_as_uid_gid() functions

Signed-off-by: Ryan Mallon <rmallon@gmail.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 36 insertions, 9 deletions

diff --git a/libbb/xfuncs_printf.c b/libbb/xfuncs_printf.c
index a706832..e4ac6a0 100644
--- a/libbb/xfuncs_printf.c
+++ b/libbb/xfuncs_printf.c
@@ -140,15 +140,6 @@ int FAST_FUNC xopen(const char *pathname, int flags)
 	return xopen3(pathname, flags, 0666);
 }
 
-/* Die if we can't open an existing file readonly with O_NONBLOCK
- * and return the fd.
- * Note that for ioctl O_RDONLY is sufficient.
- */
-int FAST_FUNC xopen_nonblocking(const char *pathname)
-{
-	return xopen(pathname, O_RDONLY | O_NONBLOCK);
-}
-
 // Warn if we can't open a file and return a fd.
 int FAST_FUNC open3_or_warn(const char *pathname, int flags, int mode)
 {
@@ -167,6 +158,32 @@ int FAST_FUNC open_or_warn(const char *pathname, int flags)
 	return open3_or_warn(pathname, flags, 0666);
 }
 
+/* Die if we can't open an existing file readonly with O_NONBLOCK
+ * and return the fd.
+ * Note that for ioctl O_RDONLY is sufficient.
+ */
+int FAST_FUNC xopen_nonblocking(const char *pathname)
+{
+	return xopen(pathname, O_RDONLY | O_NONBLOCK);
+}
+
+int FAST_FUNC xopen_as_uid_gid(const char *pathname, int flags, uid_t u, gid_t g)
+{
+	int fd;
+	uid_t old_euid = geteuid();
+	gid_t old_egid = getegid();
+
+	xsetegid(g);
+	xseteuid(u);
+
+	fd = xopen(pathname, flags);
+
+	xseteuid(old_euid);
+	xsetegid(old_egid);
+
+	return fd;
+}
+
 void FAST_FUNC xunlink(const char *pathname)
 {
 	if (unlink(pathname))
@@ -351,6 +368,16 @@ void FAST_FUNC xsetuid(uid_t uid)
 	if (setuid(uid)) bb_perror_msg_and_die("setuid");
 }
 
+void FAST_FUNC xsetegid(gid_t egid)
+{
+	if (setegid(egid)) bb_perror_msg_and_die("setegid");
+}
+
+void FAST_FUNC xseteuid(uid_t euid)
+{
+	if (seteuid(euid)) bb_perror_msg_and_die("seteuid");
+}
+
 // Die if we can't chdir to a new path.
 void FAST_FUNC xchdir(const char *path)
 {