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platform_system_core
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init: harden socket creation against symlinks 

Instead of using chown, use the symlink safe lchown.

Instead of using chmod, use the symlink safe fchmodat
with AT_SYMLINK_NOFOLLOW.

Fix a bug where the SELinux filesystem creation context may
not be restored, and some memory not freed, if bind() fails.

Check the return values from the chown/chmod calls and unlink
the files if it ever fails.

Bug: 27337831
Change-Id: I3343786f5a4eefda7bbb8317f2eca16bd21003c0
This commit is contained in:
Nick Kralevich 2016-02-24 15:50:52 -08:00
parent b236ff7156
commit ab5629c197
1 changed files with 17 additions and 7 deletions
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24
init/util.cpp
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@ -102,7 +102,7 @@ int create_socket(const char *name, int type, mode_t perm, uid_t uid,
gid_t gid, const char *socketcon)
{
struct sockaddr_un addr;
int fd, ret;
int fd, ret, savederrno;
char *filecon;
if (socketcon) {
@ -140,16 +140,26 @@ int create_socket(const char *name, int type, mode_t perm, uid_t uid,
}
ret = bind(fd, (struct sockaddr *) &addr, sizeof (addr));
if (ret) {
ERROR("Failed to bind socket '%s': %s\n", name, strerror(errno));
goto out_unlink;
}
savederrno = errno;
setfscreatecon(NULL);
freecon(filecon);
chown(addr.sun_path, uid, gid);
chmod(addr.sun_path, perm);
if (ret) {
ERROR("Failed to bind socket '%s': %s\n", name, strerror(savederrno));
goto out_unlink;
}
ret = lchown(addr.sun_path, uid, gid);
if (ret) {
ERROR("Failed to lchown socket '%s': %s\n", addr.sun_path, strerror(errno));
goto out_unlink;
}
ret = fchmodat(AT_FDCWD, addr.sun_path, perm, AT_SYMLINK_NOFOLLOW);
if (ret) {
ERROR("Failed to fchmodat socket '%s': %s\n", addr.sun_path, strerror(errno));
goto out_unlink;
}
INFO("Created socket '%s' with mode '%o', user '%d', group '%d'\n",
addr.sun_path, perm, uid, gid);