Refactoring: Split off the non-recursive canonicalisePathMetaData()

Also, change the file mode before changing the owner.  This prevents a
slight time window in which a setuid binary would be setuid root.
This commit is contained in:
Eelco Dolstra 2013-02-27 16:35:46 +01:00
parent 826dc0d07d
commit b008674e46
3 changed files with 52 additions and 37 deletions

View File

@ -465,39 +465,8 @@ void LocalStore::makeStoreWritable()
const time_t mtimeStore = 1; /* 1 second into the epoch */
void canonicalisePathMetaData(const Path & path, bool recurse, uid_t fromUid)
static void canonicaliseTimestampAndPermissions(const Path & path, const struct stat & st)
{
checkInterrupt();
struct stat st;
if (lstat(path.c_str(), &st))
throw SysError(format("getting attributes of path `%1%'") % path);
/* Really make sure that the path is of a supported type. This
has already been checked in dumpPath(). */
assert(S_ISREG(st.st_mode) || S_ISDIR(st.st_mode) || S_ISLNK(st.st_mode));
if (fromUid != (uid_t) -1 && st.st_uid != fromUid)
throw BuildError(format("invalid ownership on file `%1%'") % path);
/* Change ownership to the current uid. If it's a symlink, use
lchown if available, otherwise don't bother. Wrong ownership
of a symlink doesn't matter, since the owning user can't change
the symlink and can't delete it because the directory is not
writable. The only exception is top-level paths in the Nix
store (since that directory is group-writable for the Nix build
users group); we check for this case below. */
if (st.st_uid != geteuid()) {
#if HAVE_LCHOWN
if (lchown(path.c_str(), geteuid(), (gid_t) -1) == -1)
#else
if (!S_ISLNK(st.st_mode) &&
chown(path.c_str(), geteuid(), (gid_t) -1) == -1)
#endif
throw SysError(format("changing owner of `%1%' to %2%")
% path % geteuid());
}
if (!S_ISLNK(st.st_mode)) {
/* Mask out all type related bits. */
@ -528,18 +497,64 @@ void canonicalisePathMetaData(const Path & path, bool recurse, uid_t fromUid)
#endif
throw SysError(format("changing modification time of `%1%'") % path);
}
}
if (recurse && S_ISDIR(st.st_mode)) {
void canonicaliseTimestampAndPermissions(const Path & path)
{
struct stat st;
if (lstat(path.c_str(), &st))
throw SysError(format("getting attributes of path `%1%'") % path);
canonicaliseTimestampAndPermissions(path, st);
}
static void canonicalisePathMetaData_(const Path & path, uid_t fromUid)
{
checkInterrupt();
struct stat st;
if (lstat(path.c_str(), &st))
throw SysError(format("getting attributes of path `%1%'") % path);
/* Really make sure that the path is of a supported type. This
has already been checked in dumpPath(). */
assert(S_ISREG(st.st_mode) || S_ISDIR(st.st_mode) || S_ISLNK(st.st_mode));
canonicaliseTimestampAndPermissions(path, st);
if (fromUid != (uid_t) -1 && st.st_uid != fromUid)
throw BuildError(format("invalid ownership on file `%1%'") % path);
/* Change ownership to the current uid. If it's a symlink, use
lchown if available, otherwise don't bother. Wrong ownership
of a symlink doesn't matter, since the owning user can't change
the symlink and can't delete it because the directory is not
writable. The only exception is top-level paths in the Nix
store (since that directory is group-writable for the Nix build
users group); we check for this case below. */
if (st.st_uid != geteuid()) {
#if HAVE_LCHOWN
if (lchown(path.c_str(), geteuid(), (gid_t) -1) == -1)
#else
if (!S_ISLNK(st.st_mode) &&
chown(path.c_str(), geteuid(), (gid_t) -1) == -1)
#endif
throw SysError(format("changing owner of `%1%' to %2%")
% path % geteuid());
}
if (S_ISDIR(st.st_mode)) {
Strings names = readDirectory(path);
foreach (Strings::iterator, i, names)
canonicalisePathMetaData(path + "/" + *i, true, fromUid);
canonicalisePathMetaData_(path + "/" + *i, fromUid);
}
}
void canonicalisePathMetaData(const Path & path, uid_t fromUid)
{
canonicalisePathMetaData(path, true, fromUid);
canonicalisePathMetaData_(path, fromUid);
/* On platforms that don't have lchown(), the top-level path can't
be a symlink, since we can't change its ownership. */

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@ -309,7 +309,7 @@ private:
in a setuid Nix installation. */
void canonicalisePathMetaData(const Path & path, uid_t fromUid);
void canonicalisePathMetaData(const Path & path, bool recurse, uid_t fromUid);
void canonicaliseTimestampAndPermissions(const Path & path);
MakeError(PathInUse, Error);

View File

@ -32,7 +32,7 @@ struct MakeReadOnly
{
try {
/* This will make the path read-only. */
if (path != "") canonicalisePathMetaData(path, false, -1);
if (path != "") canonicaliseTimestampAndPermissions(path);
} catch (...) {
ignoreException();
}