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#include "config.h"
#include "immutable.hh"
#include "util.hh"
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#if HAVE_LINUX_FS_H
#include <linux/fs.h>
#include <sys/ioctl.h>
#include <errno.h>
#endif
namespace nix {
void makeMutable(const Path & path)
{
#if defined(FS_IOC_SETFLAGS) && defined(FS_IOC_GETFLAGS) && defined(FS_IMMUTABLE_FL)
/* Don't even try if we're not root. One day we should support
the CAP_LINUX_IMMUTABLE capability. */
if (getuid() != 0) return;
/* The O_NOFOLLOW is important to prevent us from changing the
mutable bit on the target of a symlink (which would be a
security hole). */
AutoCloseFD fd = open(path.c_str(), O_RDONLY | O_NOFOLLOW);
if (fd == -1) {
if (errno == ELOOP) return; // it's a symlink
throw SysError(format("opening file `%1%'") % path);
}
unsigned int flags = 0, old;
/* Silently ignore errors getting/setting the immutable flag so
that we work correctly on filesystems that don't support it. */
if (ioctl(fd, FS_IOC_GETFLAGS, &flags)) return;
old = flags;
flags &= ~FS_IMMUTABLE_FL;
if (old == flags) return;
if (ioctl(fd, FS_IOC_SETFLAGS, &flags)) return;
#endif
}
}
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