From 5906a5c26c392b9687d14951a6da3a5195b576be Mon Sep 17 00:00:00 2001
From: Ryan Mallon <rmallon@gmail.com>
Date: Tue, 8 Oct 2013 14:52:49 +0200
Subject: [PATCH] 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>
---
 include/libbb.h       |  9 ++++++---
 libbb/xfuncs_printf.c | 45 ++++++++++++++++++++++++++++++++++---------
 2 files changed, 42 insertions(+), 12 deletions(-)

diff --git a/include/libbb.h b/include/libbb.h
index 1315e5f8f..3ab1d6b46 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -461,6 +461,8 @@ void record_signo(int signo); /* not FAST_FUNC! */
 
 void xsetgid(gid_t gid) FAST_FUNC;
 void xsetuid(uid_t uid) FAST_FUNC;
+void xsetegid(gid_t egid) FAST_FUNC;
+void xseteuid(uid_t euid) FAST_FUNC;
 void xchdir(const char *path) FAST_FUNC;
 void xchroot(const char *path) FAST_FUNC;
 void xsetenv(const char *key, const char *value) FAST_FUNC;
@@ -469,11 +471,12 @@ void bb_unsetenv_and_free(char *key) FAST_FUNC;
 void xunlink(const char *pathname) FAST_FUNC;
 void xstat(const char *pathname, struct stat *buf) FAST_FUNC;
 void xfstat(int fd, struct stat *buf, const char *errmsg) FAST_FUNC;
+int open3_or_warn(const char *pathname, int flags, int mode) FAST_FUNC;
+int open_or_warn(const char *pathname, int flags) FAST_FUNC;
+int xopen3(const char *pathname, int flags, int mode) FAST_FUNC;
 int xopen(const char *pathname, int flags) FAST_FUNC;
 int xopen_nonblocking(const char *pathname) FAST_FUNC;
-int xopen3(const char *pathname, int flags, int mode) FAST_FUNC;
-int open_or_warn(const char *pathname, int flags) FAST_FUNC;
-int open3_or_warn(const char *pathname, int flags, int mode) FAST_FUNC;
+int xopen_as_uid_gid(const char *pathname, int flags, uid_t u, gid_t g) FAST_FUNC;
 int open_or_warn_stdin(const char *pathname) FAST_FUNC;
 int xopen_stdin(const char *pathname) FAST_FUNC;
 void xrename(const char *oldpath, const char *newpath) FAST_FUNC;
diff --git a/libbb/xfuncs_printf.c b/libbb/xfuncs_printf.c
index a70683241..e4ac6a002 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)
 {