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Revert "Remove open_readonly_workaround"

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Caused a regression: https://github.com/vgough/encfs/issues/181

Without this, "umask 0777 ; echo foo > bar" fails.

This reverts commit c2e046b694a42a6e17ec4a47a517638a098f928a.
This commit is contained in:
Jakob Unterwurzacher 2016-06-25 14:48:45 +02:00
parent 2b3e6031eb
commit 4a691dc0bb
1 changed files with 31 additions and 0 deletions
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31
encfs/RawFileIO.cpp
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@ -75,6 +75,32 @@ RawFileIO::~RawFileIO() {
Interface RawFileIO::interface() const { return RawFileIO_iface; } Interface RawFileIO::interface() const { return RawFileIO_iface; }
/*
Workaround for opening a file for write when permissions don't allow.
Since the kernel has already checked permissions, we can assume it is ok to
provide access. So force it by changing permissions temporarily. Should
be called with a lock around it so that there won't be a race condition
with calls to lstat picking up the wrong permissions.
This works around the problem described in https://github.com/vgough/encfs/issues/181
Without this, "umask 0777 ; echo foo > bar" fails.
*/
static int open_readonly_workaround(const char *path, int flags) {
int fd = -1;
struct stat stbuf;
memset(&stbuf, 0, sizeof(struct stat));
if (lstat(path, &stbuf) != -1) {
// make sure user has read/write permission..
chmod(path, stbuf.st_mode | 0600);
fd = ::open(path, flags);
chmod(path, stbuf.st_mode);
} else {
RLOG(INFO) << "can't stat file " << path;
}
return fd;
}
/* /*
We shouldn't have to support all possible open flags, so untaint the flags We shouldn't have to support all possible open flags, so untaint the flags
argument by only taking ones we understand and accept. argument by only taking ones we understand and accept.
@ -107,6 +133,11 @@ int RawFileIO::open(int flags) {
VLOG(1) << "open file with flags " << finalFlags << ", result = " << newFd; VLOG(1) << "open file with flags " << finalFlags << ", result = " << newFd;
if ((newFd == -1) && (errno == EACCES)) {
VLOG(1) << "using readonly workaround for open";
newFd = open_readonly_workaround(name.c_str(), finalFlags);
}
if (newFd >= 0) { if (newFd >= 0) {
if (oldfd >= 0) { if (oldfd >= 0) {
RLOG(ERROR) << "leaking FD?: oldfd = " << oldfd << ", fd = " << fd RLOG(ERROR) << "leaking FD?: oldfd = " << oldfd << ", fd = " << fd