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authorJakob Unterwurzacher2018-09-08 17:41:17 +0200
committerJakob Unterwurzacher2018-09-08 17:41:17 +0200
commit9ec9d0c49cfbdc9ceba10d7534b77e527c0a3cdc (patch)
treea7beb635c6ac0d7580e95811d1803f9750c431aa /internal/syscallcompat
parentbc14f8dcb65740dac792b50f2582372762e782b8 (diff)
syscallcompat: untangle OpenNofollow and rename to OpenDirNofollow
The function used to do two things: 1) Walk the directory tree in a manner safe from symlink attacks 2) Open the final component in the mode requested by the caller This change drops (2), which was only used once, and lets the caller handle it. This simplifies the function and makes it fit for reuse in forward mode in openBackingPath(), and for using O_PATH on Linux.
Diffstat (limited to 'internal/syscallcompat')
-rw-r--r--internal/syscallcompat/open_nofollow.go23
-rw-r--r--internal/syscallcompat/open_nofollow_test.go10
2 files changed, 16 insertions, 17 deletions
diff --git a/internal/syscallcompat/open_nofollow.go b/internal/syscallcompat/open_nofollow.go
index 4f75bd6..d440fc3 100644
--- a/internal/syscallcompat/open_nofollow.go
+++ b/internal/syscallcompat/open_nofollow.go
@@ -8,18 +8,18 @@ import (
"github.com/rfjakob/gocryptfs/internal/tlog"
)
-// OpenNofollow opens the file/dir at "relPath" in a way that is secure against
+// OpenDirNofollow opens the dir at "relPath" in a way that is secure against
// symlink attacks. Symlinks that are part of "relPath" are never followed.
// This function is implemented by walking the directory tree, starting at
// "baseDir", using the Openat syscall with the O_NOFOLLOW flag.
// Symlinks that are part of the "baseDir" path are followed.
-func OpenNofollow(baseDir string, relPath string, flags int, mode uint32) (fd int, err error) {
+func OpenDirNofollow(baseDir string, relPath string) (fd int, err error) {
if !filepath.IsAbs(baseDir) {
- tlog.Warn.Printf("BUG: OpenNofollow called with relative baseDir=%q", baseDir)
+ tlog.Warn.Printf("BUG: OpenDirNofollow called with relative baseDir=%q", baseDir)
return -1, syscall.EINVAL
}
if filepath.IsAbs(relPath) {
- tlog.Warn.Printf("BUG: OpenNofollow called with absolute relPath=%q", relPath)
+ tlog.Warn.Printf("BUG: OpenDirNofollow called with absolute relPath=%q", relPath)
return -1, syscall.EINVAL
}
// Open the base dir (following symlinks)
@@ -31,14 +31,11 @@ func OpenNofollow(baseDir string, relPath string, flags int, mode uint32) (fd in
if relPath == "" {
return dirfd, nil
}
- // Split the path into components and separate intermediate directories
- // and the final basename
+ // Split the path into components
parts := strings.Split(relPath, "/")
- dirs := parts[:len(parts)-1]
- final := parts[len(parts)-1]
- // Walk intermediate directories
+ // Walk the directory tree
var dirfd2 int
- for _, name := range dirs {
+ for _, name := range parts {
dirfd2, err = Openat(dirfd, name, syscall.O_RDONLY|syscall.O_NOFOLLOW|syscall.O_DIRECTORY, 0)
syscall.Close(dirfd)
if err != nil {
@@ -46,8 +43,6 @@ func OpenNofollow(baseDir string, relPath string, flags int, mode uint32) (fd in
}
dirfd = dirfd2
}
- defer syscall.Close(dirfd)
- // Open the final component with the flags and permissions requested by
- // the user plus forced NOFOLLOW.
- return Openat(dirfd, final, flags|syscall.O_NOFOLLOW, mode)
+ // Return fd to final directory
+ return dirfd, nil
}
diff --git a/internal/syscallcompat/open_nofollow_test.go b/internal/syscallcompat/open_nofollow_test.go
index 1f21557..1eeac3a 100644
--- a/internal/syscallcompat/open_nofollow_test.go
+++ b/internal/syscallcompat/open_nofollow_test.go
@@ -12,7 +12,11 @@ func TestOpenNofollow(t *testing.T) {
t.Fatal(err)
}
// Create a file
- fd, err := OpenNofollow(tmpDir, "d1/d2/d3/f1", syscall.O_RDWR|syscall.O_CREAT|syscall.O_EXCL, 0600)
+ dirfd, err := OpenDirNofollow(tmpDir, "d1/d2/d3")
+ if err != nil {
+ t.Fatal(err)
+ }
+ fd, err := Openat(dirfd, "f1", syscall.O_RDWR|syscall.O_CREAT|syscall.O_EXCL, 0600)
if err != nil {
t.Fatal(err)
}
@@ -27,7 +31,7 @@ func TestOpenNofollow(t *testing.T) {
t.Fatal(err)
}
os.Symlink(tmpDir+"/d1.renamed", tmpDir+"/d1")
- fd, err = OpenNofollow(tmpDir, "d1/d2/d3/f1", syscall.O_RDWR|syscall.O_CREAT, 0600)
+ fd, err = OpenDirNofollow(tmpDir, "d1/d2/d3")
if err == nil {
t.Fatalf("should have failed")
}
@@ -35,7 +39,7 @@ func TestOpenNofollow(t *testing.T) {
t.Errorf("expected ELOOP or ENOTDIR, got %v", err)
}
// Check to see that the base dir can be opened as well
- fd, err = OpenNofollow(tmpDir, "", syscall.O_RDONLY, 0)
+ fd, err = OpenDirNofollow(tmpDir, "")
if err != nil {
t.Errorf("cannot open base dir: %v", err)
} else {