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-rw-r--r--pkg/sentry/fsimpl/verity/filesystem.go256
-rw-r--r--pkg/sentry/fsimpl/verity/verity.go224
-rw-r--r--pkg/sentry/fsimpl/verity/verity_test.go290
3 files changed, 534 insertions, 236 deletions
diff --git a/pkg/sentry/fsimpl/verity/filesystem.go b/pkg/sentry/fsimpl/verity/filesystem.go
index 4e8d63d51..59fcff498 100644
--- a/pkg/sentry/fsimpl/verity/filesystem.go
+++ b/pkg/sentry/fsimpl/verity/filesystem.go
@@ -16,6 +16,7 @@ package verity
import (
"bytes"
+ "encoding/json"
"fmt"
"io"
"strconv"
@@ -31,6 +32,7 @@ import (
"gvisor.dev/gvisor/pkg/sentry/vfs"
"gvisor.dev/gvisor/pkg/sync"
"gvisor.dev/gvisor/pkg/syserror"
+ "gvisor.dev/gvisor/pkg/usermem"
)
// Sync implements vfs.FilesystemImpl.Sync.
@@ -105,8 +107,10 @@ func (fs *filesystem) renameMuUnlockAndCheckDrop(ctx context.Context, ds **[]*de
// Dentries which may have a reference count of zero, and which therefore
// should be dropped once traversal is complete, are appended to ds.
//
-// Preconditions: fs.renameMu must be locked. d.dirMu must be locked.
-// !rp.Done().
+// Preconditions:
+// * fs.renameMu must be locked.
+// * d.dirMu must be locked.
+// * !rp.Done().
func (fs *filesystem) stepLocked(ctx context.Context, rp *vfs.ResolvingPath, d *dentry, mayFollowSymlinks bool, ds **[]*dentry) (*dentry, error) {
if !d.isDir() {
return nil, syserror.ENOTDIR
@@ -156,15 +160,19 @@ afterSymlink:
return child, nil
}
-// verifyChild verifies the hash of child against the already verified hash of
-// the parent to ensure the child is expected. verifyChild triggers a sentry
-// panic if unexpected modifications to the file system are detected. In
+// verifyChildLocked verifies the hash of child against the already verified
+// hash of the parent to ensure the child is expected. verifyChild triggers a
+// sentry panic if unexpected modifications to the file system are detected. In
// noCrashOnVerificationFailure mode it returns a syserror instead.
-// Preconditions: fs.renameMu must be locked. d.dirMu must be locked.
+//
+// Preconditions:
+// * fs.renameMu must be locked.
+// * d.dirMu must be locked.
+//
// TODO(b/166474175): Investigate all possible errors returned in this
// function, and make sure we differentiate all errors that indicate unexpected
// modifications to the file system from the ones that are not harmful.
-func (fs *filesystem) verifyChild(ctx context.Context, parent *dentry, child *dentry) (*dentry, error) {
+func (fs *filesystem) verifyChildLocked(ctx context.Context, parent *dentry, child *dentry) (*dentry, error) {
vfsObj := fs.vfsfs.VirtualFilesystem()
// Get the path to the child dentry. This is only used to provide path
@@ -266,35 +274,44 @@ func (fs *filesystem) verifyChild(ctx context.Context, parent *dentry, child *de
// contain the hash of the children in the parent Merkle tree when
// Verify returns with success.
var buf bytes.Buffer
- if _, err := merkletree.Verify(&merkletree.VerifyParams{
- Out: &buf,
- File: &fdReader,
- Tree: &fdReader,
- Size: int64(parentSize),
- Name: parent.name,
- Mode: uint32(parentStat.Mode),
- UID: parentStat.UID,
- GID: parentStat.GID,
+ parent.hashMu.RLock()
+ _, err = merkletree.Verify(&merkletree.VerifyParams{
+ Out: &buf,
+ File: &fdReader,
+ Tree: &fdReader,
+ Size: int64(parentSize),
+ Name: parent.name,
+ Mode: uint32(parentStat.Mode),
+ UID: parentStat.UID,
+ GID: parentStat.GID,
+ Children: parent.childrenNames,
//TODO(b/156980949): Support passing other hash algorithms.
HashAlgorithms: fs.alg.toLinuxHashAlg(),
ReadOffset: int64(offset),
ReadSize: int64(merkletree.DigestSize(fs.alg.toLinuxHashAlg())),
Expected: parent.hash,
DataAndTreeInSameFile: true,
- }); err != nil && err != io.EOF {
+ })
+ parent.hashMu.RUnlock()
+ if err != nil && err != io.EOF {
return nil, alertIntegrityViolation(fmt.Sprintf("Verification for %s failed: %v", childPath, err))
}
// Cache child hash when it's verified the first time.
+ child.hashMu.Lock()
if len(child.hash) == 0 {
child.hash = buf.Bytes()
}
+ child.hashMu.Unlock()
return child, nil
}
-// verifyStat verifies the stat against the verified hash. The mode/uid/gid of
-// the file is cached after verified.
-func (fs *filesystem) verifyStat(ctx context.Context, d *dentry, stat linux.Statx) error {
+// verifyStatAndChildrenLocked verifies the stat and children names against the
+// verified hash. The mode/uid/gid and childrenNames of the file is cached
+// after verified.
+//
+// Preconditions: d.dirMu must be locked.
+func (fs *filesystem) verifyStatAndChildrenLocked(ctx context.Context, d *dentry, stat linux.Statx) error {
vfsObj := fs.vfsfs.VirtualFilesystem()
// Get the path to the child dentry. This is only used to provide path
@@ -337,20 +354,65 @@ func (fs *filesystem) verifyStat(ctx context.Context, d *dentry, stat linux.Stat
return alertIntegrityViolation(fmt.Sprintf("Failed to convert xattr %s for %s to int: %v", merkleSizeXattr, childPath, err))
}
+ if d.isDir() && len(d.childrenNames) == 0 {
+ childrenOffString, err := fd.GetXattr(ctx, &vfs.GetXattrOptions{
+ Name: childrenOffsetXattr,
+ Size: sizeOfStringInt32,
+ })
+
+ if err == syserror.ENODATA {
+ return alertIntegrityViolation(fmt.Sprintf("Failed to get xattr %s for merkle file of %s: %v", childrenOffsetXattr, childPath, err))
+ }
+ if err != nil {
+ return err
+ }
+ childrenOffset, err := strconv.Atoi(childrenOffString)
+ if err != nil {
+ return alertIntegrityViolation(fmt.Sprintf("Failed to convert xattr %s to int: %v", childrenOffsetXattr, err))
+ }
+
+ childrenSizeString, err := fd.GetXattr(ctx, &vfs.GetXattrOptions{
+ Name: childrenSizeXattr,
+ Size: sizeOfStringInt32,
+ })
+
+ if err == syserror.ENODATA {
+ return alertIntegrityViolation(fmt.Sprintf("Failed to get xattr %s for merkle file of %s: %v", childrenSizeXattr, childPath, err))
+ }
+ if err != nil {
+ return err
+ }
+ childrenSize, err := strconv.Atoi(childrenSizeString)
+ if err != nil {
+ return alertIntegrityViolation(fmt.Sprintf("Failed to convert xattr %s to int: %v", childrenSizeXattr, err))
+ }
+
+ childrenNames := make([]byte, childrenSize)
+ if _, err := fd.PRead(ctx, usermem.BytesIOSequence(childrenNames), int64(childrenOffset), vfs.ReadOptions{}); err != nil {
+ return alertIntegrityViolation(fmt.Sprintf("Failed to read children map for %s: %v", childPath, err))
+ }
+
+ if err := json.Unmarshal(childrenNames, &d.childrenNames); err != nil {
+ return alertIntegrityViolation(fmt.Sprintf("Failed to deserialize childrenNames of %s: %v", childPath, err))
+ }
+ }
+
fdReader := vfs.FileReadWriteSeeker{
FD: fd,
Ctx: ctx,
}
var buf bytes.Buffer
+ d.hashMu.RLock()
params := &merkletree.VerifyParams{
- Out: &buf,
- Tree: &fdReader,
- Size: int64(size),
- Name: d.name,
- Mode: uint32(stat.Mode),
- UID: stat.UID,
- GID: stat.GID,
+ Out: &buf,
+ Tree: &fdReader,
+ Size: int64(size),
+ Name: d.name,
+ Mode: uint32(stat.Mode),
+ UID: stat.UID,
+ GID: stat.GID,
+ Children: d.childrenNames,
//TODO(b/156980949): Support passing other hash algorithms.
HashAlgorithms: fs.alg.toLinuxHashAlg(),
ReadOffset: 0,
@@ -359,6 +421,7 @@ func (fs *filesystem) verifyStat(ctx context.Context, d *dentry, stat linux.Stat
Expected: d.hash,
DataAndTreeInSameFile: false,
}
+ d.hashMu.RUnlock()
if atomic.LoadUint32(&d.mode)&linux.S_IFMT == linux.S_IFDIR {
params.DataAndTreeInSameFile = true
}
@@ -373,7 +436,9 @@ func (fs *filesystem) verifyStat(ctx context.Context, d *dentry, stat linux.Stat
return nil
}
-// Preconditions: fs.renameMu must be locked. d.dirMu must be locked.
+// Preconditions:
+// * fs.renameMu must be locked.
+// * parent.dirMu must be locked.
func (fs *filesystem) getChildLocked(ctx context.Context, parent *dentry, name string, ds **[]*dentry) (*dentry, error) {
if child, ok := parent.children[name]; ok {
// If verity is enabled on child, we should check again whether
@@ -422,7 +487,7 @@ func (fs *filesystem) getChildLocked(ctx context.Context, parent *dentry, name s
// be cached before enabled.
if fs.allowRuntimeEnable {
if parent.verityEnabled() {
- if _, err := fs.verifyChild(ctx, parent, child); err != nil {
+ if _, err := fs.verifyChildLocked(ctx, parent, child); err != nil {
return nil, err
}
}
@@ -438,7 +503,7 @@ func (fs *filesystem) getChildLocked(ctx context.Context, parent *dentry, name s
if err != nil {
return nil, err
}
- if err := fs.verifyStat(ctx, child, stat); err != nil {
+ if err := fs.verifyStatAndChildrenLocked(ctx, child, stat); err != nil {
return nil, err
}
}
@@ -458,96 +523,64 @@ func (fs *filesystem) getChildLocked(ctx context.Context, parent *dentry, name s
return child, nil
}
-// Preconditions: fs.renameMu must be locked. parent.dirMu must be locked.
+// Preconditions:
+// * fs.renameMu must be locked.
+// * parent.dirMu must be locked.
func (fs *filesystem) lookupAndVerifyLocked(ctx context.Context, parent *dentry, name string) (*dentry, error) {
vfsObj := fs.vfsfs.VirtualFilesystem()
- childVD, childErr := parent.getLowerAt(ctx, vfsObj, name)
- // We will handle ENOENT separately, as it may indicate unexpected
- // modifications to the file system, and may cause a sentry panic.
- if childErr != nil && childErr != syserror.ENOENT {
- return nil, childErr
+ if parent.verityEnabled() {
+ if _, ok := parent.childrenNames[name]; !ok {
+ return nil, syserror.ENOENT
+ }
}
- // The dentry needs to be cleaned up if any error occurs. IncRef will be
- // called if a verity child dentry is successfully created.
- if childErr == nil {
- defer childVD.DecRef(ctx)
+ parentPath, err := vfsObj.PathnameWithDeleted(ctx, parent.fs.rootDentry.lowerVD, parent.lowerVD)
+ if err != nil {
+ return nil, err
}
- childMerkleVD, childMerkleErr := parent.getLowerAt(ctx, vfsObj, merklePrefix+name)
- // We will handle ENOENT separately, as it may indicate unexpected
- // modifications to the file system, and may cause a sentry panic.
- if childMerkleErr != nil && childMerkleErr != syserror.ENOENT {
- return nil, childMerkleErr
+ childVD, err := parent.getLowerAt(ctx, vfsObj, name)
+ if err == syserror.ENOENT {
+ return nil, alertIntegrityViolation(fmt.Sprintf("file %s expected but not found", parentPath+"/"+name))
+ }
+ if err != nil {
+ return nil, err
}
// The dentry needs to be cleaned up if any error occurs. IncRef will be
// called if a verity child dentry is successfully created.
- if childMerkleErr == nil {
- defer childMerkleVD.DecRef(ctx)
- }
+ defer childVD.DecRef(ctx)
- // Get the path to the parent dentry. This is only used to provide path
- // information in failure case.
- parentPath, err := vfsObj.PathnameWithDeleted(ctx, parent.fs.rootDentry.lowerVD, parent.lowerVD)
- if err != nil {
+ childMerkleVD, err := parent.getLowerAt(ctx, vfsObj, merklePrefix+name)
+ if err == syserror.ENOENT {
+ if !fs.allowRuntimeEnable {
+ return nil, alertIntegrityViolation(fmt.Sprintf("Merkle file for %s expected but not found", parentPath+"/"+name))
+ }
+ childMerkleFD, err := vfsObj.OpenAt(ctx, fs.creds, &vfs.PathOperation{
+ Root: parent.lowerVD,
+ Start: parent.lowerVD,
+ Path: fspath.Parse(merklePrefix + name),
+ }, &vfs.OpenOptions{
+ Flags: linux.O_RDWR | linux.O_CREAT,
+ Mode: 0644,
+ })
+ if err != nil {
+ return nil, err
+ }
+ childMerkleFD.DecRef(ctx)
+ childMerkleVD, err = parent.getLowerAt(ctx, vfsObj, merklePrefix+name)
+ if err != nil {
+ return nil, err
+ }
+ }
+ if err != nil && err != syserror.ENOENT {
return nil, err
}
- // TODO(b/166474175): Investigate all possible errors of childErr and
- // childMerkleErr, and make sure we differentiate all errors that
- // indicate unexpected modifications to the file system from the ones
- // that are not harmful.
- if childErr == syserror.ENOENT && childMerkleErr == nil {
- // Failed to get child file/directory dentry. However the
- // corresponding Merkle tree is found. This indicates an
- // unexpected modification to the file system that
- // removed/renamed the child.
- return nil, alertIntegrityViolation(fmt.Sprintf("Target file %s is expected but missing", parentPath+"/"+name))
- } else if childErr == nil && childMerkleErr == syserror.ENOENT {
- // If in allowRuntimeEnable mode, and the Merkle tree file is
- // not created yet, we create an empty Merkle tree file, so that
- // if the file is enabled through ioctl, we have the Merkle tree
- // file open and ready to use.
- // This may cause empty and unused Merkle tree files in
- // allowRuntimeEnable mode, if they are never enabled. This
- // does not affect verification, as we rely on cached hash to
- // decide whether to perform verification, not the existence of
- // the Merkle tree file. Also, those Merkle tree files are
- // always hidden and cannot be accessed by verity fs users.
- if fs.allowRuntimeEnable {
- childMerkleFD, err := vfsObj.OpenAt(ctx, fs.creds, &vfs.PathOperation{
- Root: parent.lowerVD,
- Start: parent.lowerVD,
- Path: fspath.Parse(merklePrefix + name),
- }, &vfs.OpenOptions{
- Flags: linux.O_RDWR | linux.O_CREAT,
- Mode: 0644,
- })
- if err != nil {
- return nil, err
- }
- childMerkleFD.DecRef(ctx)
- childMerkleVD, err = parent.getLowerAt(ctx, vfsObj, merklePrefix+name)
- if err != nil {
- return nil, err
- }
- } else {
- // If runtime enable is not allowed. This indicates an
- // unexpected modification to the file system that
- // removed/renamed the Merkle tree file.
- return nil, alertIntegrityViolation(fmt.Sprintf("Expected Merkle file for target %s but none found", parentPath+"/"+name))
- }
- } else if childErr == syserror.ENOENT && childMerkleErr == syserror.ENOENT {
- // Both the child and the corresponding Merkle tree are missing.
- // This could be an unexpected modification or due to incorrect
- // parameter.
- // TODO(b/167752508): Investigate possible ways to differentiate
- // cases that both files are deleted from cases that they never
- // exist in the file system.
- return nil, alertIntegrityViolation(fmt.Sprintf("Failed to find file %s", parentPath+"/"+name))
- }
+ // The dentry needs to be cleaned up if any error occurs. IncRef will be
+ // called if a verity child dentry is successfully created.
+ defer childMerkleVD.DecRef(ctx)
mask := uint32(linux.STATX_TYPE | linux.STATX_MODE | linux.STATX_UID | linux.STATX_GID)
stat, err := vfsObj.StatAt(ctx, fs.creds, &vfs.PathOperation{
@@ -577,18 +610,19 @@ func (fs *filesystem) lookupAndVerifyLocked(ctx context.Context, parent *dentry,
child.mode = uint32(stat.Mode)
child.uid = stat.UID
child.gid = stat.GID
+ child.childrenNames = make(map[string]struct{})
// Verify child hash. This should always be performed unless in
// allowRuntimeEnable mode and the parent directory hasn't been enabled
// yet.
if parent.verityEnabled() {
- if _, err := fs.verifyChild(ctx, parent, child); err != nil {
+ if _, err := fs.verifyChildLocked(ctx, parent, child); err != nil {
child.destroyLocked(ctx)
return nil, err
}
}
if child.verityEnabled() {
- if err := fs.verifyStat(ctx, child, stat); err != nil {
+ if err := fs.verifyStatAndChildrenLocked(ctx, child, stat); err != nil {
child.destroyLocked(ctx)
return nil, err
}
@@ -602,7 +636,9 @@ func (fs *filesystem) lookupAndVerifyLocked(ctx context.Context, parent *dentry,
// rp.Start().Impl().(*dentry)). It does not check that the returned directory
// is searchable by the provider of rp.
//
-// Preconditions: fs.renameMu must be locked. !rp.Done().
+// Preconditions:
+// * fs.renameMu must be locked.
+// * !rp.Done().
func (fs *filesystem) walkParentDirLocked(ctx context.Context, rp *vfs.ResolvingPath, d *dentry, ds **[]*dentry) (*dentry, error) {
for !rp.Final() {
d.dirMu.Lock()
@@ -943,11 +979,13 @@ func (fs *filesystem) StatAt(ctx context.Context, rp *vfs.ResolvingPath, opts vf
if err != nil {
return linux.Statx{}, err
}
+ d.dirMu.Lock()
if d.verityEnabled() {
- if err := fs.verifyStat(ctx, d, stat); err != nil {
+ if err := fs.verifyStatAndChildrenLocked(ctx, d, stat); err != nil {
return linux.Statx{}, err
}
}
+ d.dirMu.Unlock()
return stat, nil
}
diff --git a/pkg/sentry/fsimpl/verity/verity.go b/pkg/sentry/fsimpl/verity/verity.go
index faa862c55..46346e54d 100644
--- a/pkg/sentry/fsimpl/verity/verity.go
+++ b/pkg/sentry/fsimpl/verity/verity.go
@@ -19,9 +19,22 @@
// The verity file system is read-only, except for one case: when
// allowRuntimeEnable is true, additional Merkle files can be generated using
// the FS_IOC_ENABLE_VERITY ioctl.
+//
+// Lock order:
+//
+// filesystem.renameMu
+// dentry.dirMu
+// fileDescription.mu
+// filesystem.verityMu
+// dentry.hashMu
+//
+// Locking dentry.dirMu in multiple dentries requires that parent dentries are
+// locked before child dentries, and that filesystem.renameMu is locked to
+// stabilize this relationship.
package verity
import (
+ "encoding/json"
"fmt"
"math"
"strconv"
@@ -60,6 +73,15 @@ const (
// file size. For a directory, this is the size of all its children's hashes.
merkleSizeXattr = "user.merkle.size"
+ // childrenOffsetXattr is the extended attribute name specifying the
+ // names of the offset of the serialized children names in the Merkle
+ // tree file.
+ childrenOffsetXattr = "user.merkle.childrenOffset"
+
+ // childrenSizeXattr is the extended attribute name specifying the size
+ // of the serialized children names.
+ childrenSizeXattr = "user.merkle.childrenSize"
+
// sizeOfStringInt32 is the size for a 32 bit integer stored as string in
// extended attributes. The maximum value of a 32 bit integer has 10 digits.
sizeOfStringInt32 = 10
@@ -299,14 +321,77 @@ func (fstype FilesystemType) GetFilesystem(ctx context.Context, vfsObj *vfs.Virt
d.uid = stat.UID
d.gid = stat.GID
d.hash = make([]byte, len(iopts.RootHash))
+ d.childrenNames = make(map[string]struct{})
if !fs.allowRuntimeEnable {
- if err := fs.verifyStat(ctx, d, stat); err != nil {
+ // Get children names from the underlying file system.
+ offString, err := vfsObj.GetXattrAt(ctx, creds, &vfs.PathOperation{
+ Root: lowerMerkleVD,
+ Start: lowerMerkleVD,
+ }, &vfs.GetXattrOptions{
+ Name: childrenOffsetXattr,
+ Size: sizeOfStringInt32,
+ })
+ if err == syserror.ENOENT || err == syserror.ENODATA {
+ return nil, nil, alertIntegrityViolation(fmt.Sprintf("Failed to get xattr %s: %v", childrenOffsetXattr, err))
+ }
+ if err != nil {
+ return nil, nil, err
+ }
+
+ off, err := strconv.Atoi(offString)
+ if err != nil {
+ return nil, nil, alertIntegrityViolation(fmt.Sprintf("Failed to convert xattr %s to int: %v", childrenOffsetXattr, err))
+ }
+
+ sizeString, err := vfsObj.GetXattrAt(ctx, creds, &vfs.PathOperation{
+ Root: lowerMerkleVD,
+ Start: lowerMerkleVD,
+ }, &vfs.GetXattrOptions{
+ Name: childrenSizeXattr,
+ Size: sizeOfStringInt32,
+ })
+ if err == syserror.ENOENT || err == syserror.ENODATA {
+ return nil, nil, alertIntegrityViolation(fmt.Sprintf("Failed to get xattr %s: %v", childrenSizeXattr, err))
+ }
+ if err != nil {
+ return nil, nil, err
+ }
+ size, err := strconv.Atoi(sizeString)
+ if err != nil {
+ return nil, nil, alertIntegrityViolation(fmt.Sprintf("Failed to convert xattr %s to int: %v", childrenSizeXattr, err))
+ }
+
+ lowerMerkleFD, err := vfsObj.OpenAt(ctx, fs.creds, &vfs.PathOperation{
+ Root: lowerMerkleVD,
+ Start: lowerMerkleVD,
+ }, &vfs.OpenOptions{
+ Flags: linux.O_RDONLY,
+ })
+ if err == syserror.ENOENT {
+ return nil, nil, alertIntegrityViolation(fmt.Sprintf("Failed to open root Merkle file: %v", err))
+ }
+ if err != nil {
+ return nil, nil, err
+ }
+
+ childrenNames := make([]byte, size)
+ if _, err := lowerMerkleFD.PRead(ctx, usermem.BytesIOSequence(childrenNames), int64(off), vfs.ReadOptions{}); err != nil {
+ return nil, nil, alertIntegrityViolation(fmt.Sprintf("Failed to read root children map: %v", err))
+ }
+
+ if err := json.Unmarshal(childrenNames, &d.childrenNames); err != nil {
+ return nil, nil, alertIntegrityViolation(fmt.Sprintf("Failed to deserialize childrenNames: %v", err))
+ }
+
+ if err := fs.verifyStatAndChildrenLocked(ctx, d, stat); err != nil {
return nil, nil, err
}
}
+ d.hashMu.Lock()
copy(d.hash, iopts.RootHash)
+ d.hashMu.Unlock()
d.vfsd.Init(d)
fs.rootDentry = d
@@ -331,7 +416,8 @@ type dentry struct {
fs *filesystem
// mode, uid, gid and size are the file mode, owner, group, and size of
- // the file in the underlying file system.
+ // the file in the underlying file system. They are set when a dentry
+ // is initialized, and never modified.
mode uint32
uid uint32
gid uint32
@@ -352,15 +438,24 @@ type dentry struct {
dirMu sync.Mutex `state:"nosave"`
children map[string]*dentry
- // lowerVD is the VirtualDentry in the underlying file system.
+ // childrenNames stores the name of all children of the dentry. This is
+ // used by verity to check whether a child is expected. This is only
+ // populated by enableVerity. childrenNames is also protected by dirMu.
+ childrenNames map[string]struct{}
+
+ // lowerVD is the VirtualDentry in the underlying file system. It is
+ // never modified after initialized.
lowerVD vfs.VirtualDentry
// lowerMerkleVD is the VirtualDentry of the corresponding Merkle tree
- // in the underlying file system.
+ // in the underlying file system. It is never modified after
+ // initialized.
lowerMerkleVD vfs.VirtualDentry
- // hash is the calculated hash for the current file or directory.
- hash []byte
+ // hash is the calculated hash for the current file or directory. hash
+ // is protected by hashMu.
+ hashMu sync.RWMutex `state:"nosave"`
+ hash []byte
}
// newDentry creates a new dentry representing the given verity file. The
@@ -443,7 +538,9 @@ func (d *dentry) checkDropLocked(ctx context.Context) {
// destroyLocked destroys the dentry.
//
-// Preconditions: d.fs.renameMu must be locked for writing. d.refs == 0.
+// Preconditions:
+// * d.fs.renameMu must be locked for writing.
+// * d.refs == 0.
func (d *dentry) destroyLocked(ctx context.Context) {
switch atomic.LoadInt64(&d.refs) {
case 0:
@@ -523,6 +620,8 @@ func (d *dentry) checkPermissions(creds *auth.Credentials, ats vfs.AccessTypes)
// mode, it returns true if the target has been enabled with
// ioctl(FS_IOC_ENABLE_VERITY).
func (d *dentry) verityEnabled() bool {
+ d.hashMu.RLock()
+ defer d.hashMu.RUnlock()
return !d.fs.allowRuntimeEnable || len(d.hash) != 0
}
@@ -602,11 +701,13 @@ func (fd *fileDescription) Stat(ctx context.Context, opts vfs.StatOptions) (linu
if err != nil {
return linux.Statx{}, err
}
+ fd.d.dirMu.Lock()
if fd.d.verityEnabled() {
- if err := fd.d.fs.verifyStat(ctx, fd.d, stat); err != nil {
+ if err := fd.d.fs.verifyStatAndChildrenLocked(ctx, fd.d, stat); err != nil {
return linux.Statx{}, err
}
}
+ fd.d.dirMu.Unlock()
return stat, nil
}
@@ -642,13 +743,15 @@ func (fd *fileDescription) Seek(ctx context.Context, offset int64, whence int32)
return offset, nil
}
-// generateMerkle generates a Merkle tree file for fd. If fd points to a file
-// /foo/bar, a Merkle tree file /foo/.merkle.verity.bar is generated. The hash
-// of the generated Merkle tree and the data size is returned. If fd points to
-// a regular file, the data is the content of the file. If fd points to a
-// directory, the data is all hahes of its children, written to the Merkle tree
-// file.
-func (fd *fileDescription) generateMerkle(ctx context.Context) ([]byte, uint64, error) {
+// generateMerkleLocked generates a Merkle tree file for fd. If fd points to a
+// file /foo/bar, a Merkle tree file /foo/.merkle.verity.bar is generated. The
+// hash of the generated Merkle tree and the data size is returned. If fd
+// points to a regular file, the data is the content of the file. If fd points
+// to a directory, the data is all hahes of its children, written to the Merkle
+// tree file.
+//
+// Preconditions: fd.d.fs.verityMu must be locked.
+func (fd *fileDescription) generateMerkleLocked(ctx context.Context) ([]byte, uint64, error) {
fdReader := vfs.FileReadWriteSeeker{
FD: fd.lowerFD,
Ctx: ctx,
@@ -664,6 +767,7 @@ func (fd *fileDescription) generateMerkle(ctx context.Context) ([]byte, uint64,
params := &merkletree.GenerateParams{
TreeReader: &merkleReader,
TreeWriter: &merkleWriter,
+ Children: fd.d.childrenNames,
//TODO(b/156980949): Support passing other hash algorithms.
HashAlgorithms: fd.d.fs.alg.toLinuxHashAlg(),
}
@@ -716,9 +820,48 @@ func (fd *fileDescription) generateMerkle(ctx context.Context) ([]byte, uint64,
return hash, uint64(params.Size), err
}
+// recordChildrenLocked writes the names of fd's children into the
+// corresponding Merkle tree file, and saves the offset/size of the map into
+// xattrs.
+//
+// Preconditions:
+// * fd.d.fs.verityMu must be locked.
+// * fd.d.isDir() == true.
+func (fd *fileDescription) recordChildrenLocked(ctx context.Context) error {
+ // Record the children names in the Merkle tree file.
+ childrenNames, err := json.Marshal(fd.d.childrenNames)
+ if err != nil {
+ return err
+ }
+
+ stat, err := fd.merkleWriter.Stat(ctx, vfs.StatOptions{})
+ if err != nil {
+ return err
+ }
+
+ if err := fd.merkleWriter.SetXattr(ctx, &vfs.SetXattrOptions{
+ Name: childrenOffsetXattr,
+ Value: strconv.Itoa(int(stat.Size)),
+ }); err != nil {
+ return err
+ }
+ if err := fd.merkleWriter.SetXattr(ctx, &vfs.SetXattrOptions{
+ Name: childrenSizeXattr,
+ Value: strconv.Itoa(len(childrenNames)),
+ }); err != nil {
+ return err
+ }
+
+ if _, err = fd.merkleWriter.Write(ctx, usermem.BytesIOSequence(childrenNames), vfs.WriteOptions{}); err != nil {
+ return err
+ }
+
+ return nil
+}
+
// enableVerity enables verity features on fd by generating a Merkle tree file
// and stores its hash in its parent directory's Merkle tree.
-func (fd *fileDescription) enableVerity(ctx context.Context, uio usermem.IO) (uintptr, error) {
+func (fd *fileDescription) enableVerity(ctx context.Context) (uintptr, error) {
if !fd.d.fs.allowRuntimeEnable {
return 0, syserror.EPERM
}
@@ -734,7 +877,7 @@ func (fd *fileDescription) enableVerity(ctx context.Context, uio usermem.IO) (ui
return 0, alertIntegrityViolation("Unexpected verity fd: missing expected underlying fds")
}
- hash, dataSize, err := fd.generateMerkle(ctx)
+ hash, dataSize, err := fd.generateMerkleLocked(ctx)
if err != nil {
return 0, err
}
@@ -761,6 +904,9 @@ func (fd *fileDescription) enableVerity(ctx context.Context, uio usermem.IO) (ui
}); err != nil {
return 0, err
}
+
+ // Add the current child's name to parent's childrenNames.
+ fd.d.parent.childrenNames[fd.d.name] = struct{}{}
}
// Record the size of the data being hashed for fd.
@@ -770,18 +916,29 @@ func (fd *fileDescription) enableVerity(ctx context.Context, uio usermem.IO) (ui
}); err != nil {
return 0, err
}
- fd.d.hash = append(fd.d.hash, hash...)
+
+ if fd.d.isDir() {
+ if err := fd.recordChildrenLocked(ctx); err != nil {
+ return 0, err
+ }
+ }
+ fd.d.hashMu.Lock()
+ fd.d.hash = hash
+ fd.d.hashMu.Unlock()
return 0, nil
}
// measureVerity returns the hash of fd, saved in verityDigest.
-func (fd *fileDescription) measureVerity(ctx context.Context, uio usermem.IO, verityDigest usermem.Addr) (uintptr, error) {
+func (fd *fileDescription) measureVerity(ctx context.Context, verityDigest usermem.Addr) (uintptr, error) {
t := kernel.TaskFromContext(ctx)
if t == nil {
return 0, syserror.EINVAL
}
var metadata linux.DigestMetadata
+ fd.d.hashMu.RLock()
+ defer fd.d.hashMu.RUnlock()
+
// If allowRuntimeEnable is true, an empty fd.d.hash indicates that
// verity is not enabled for the file. If allowRuntimeEnable is false,
// this is an integrity violation because all files should have verity
@@ -815,14 +972,16 @@ func (fd *fileDescription) measureVerity(ctx context.Context, uio usermem.IO, ve
return 0, err
}
-func (fd *fileDescription) verityFlags(ctx context.Context, uio usermem.IO, flags usermem.Addr) (uintptr, error) {
+func (fd *fileDescription) verityFlags(ctx context.Context, flags usermem.Addr) (uintptr, error) {
f := int32(0)
+ fd.d.hashMu.RLock()
// All enabled files should store a hash. This flag is not settable via
// FS_IOC_SETFLAGS.
if len(fd.d.hash) != 0 {
f |= linux.FS_VERITY_FL
}
+ fd.d.hashMu.RUnlock()
t := kernel.TaskFromContext(ctx)
if t == nil {
@@ -836,11 +995,11 @@ func (fd *fileDescription) verityFlags(ctx context.Context, uio usermem.IO, flag
func (fd *fileDescription) Ioctl(ctx context.Context, uio usermem.IO, args arch.SyscallArguments) (uintptr, error) {
switch cmd := args[1].Uint(); cmd {
case linux.FS_IOC_ENABLE_VERITY:
- return fd.enableVerity(ctx, uio)
+ return fd.enableVerity(ctx)
case linux.FS_IOC_MEASURE_VERITY:
- return fd.measureVerity(ctx, uio, args[2].Pointer())
+ return fd.measureVerity(ctx, args[2].Pointer())
case linux.FS_IOC_GETFLAGS:
- return fd.verityFlags(ctx, uio, args[2].Pointer())
+ return fd.verityFlags(ctx, args[2].Pointer())
default:
// TODO(b/169682228): Investigate which ioctl commands should
// be allowed.
@@ -901,15 +1060,17 @@ func (fd *fileDescription) PRead(ctx context.Context, dst usermem.IOSequence, of
Ctx: ctx,
}
+ fd.d.hashMu.RLock()
n, err := merkletree.Verify(&merkletree.VerifyParams{
- Out: dst.Writer(ctx),
- File: &dataReader,
- Tree: &merkleReader,
- Size: int64(size),
- Name: fd.d.name,
- Mode: fd.d.mode,
- UID: fd.d.uid,
- GID: fd.d.gid,
+ Out: dst.Writer(ctx),
+ File: &dataReader,
+ Tree: &merkleReader,
+ Size: int64(size),
+ Name: fd.d.name,
+ Mode: fd.d.mode,
+ UID: fd.d.uid,
+ GID: fd.d.gid,
+ Children: fd.d.childrenNames,
//TODO(b/156980949): Support passing other hash algorithms.
HashAlgorithms: fd.d.fs.alg.toLinuxHashAlg(),
ReadOffset: offset,
@@ -917,6 +1078,7 @@ func (fd *fileDescription) PRead(ctx context.Context, dst usermem.IOSequence, of
Expected: fd.d.hash,
DataAndTreeInSameFile: false,
})
+ fd.d.hashMu.RUnlock()
if err != nil {
return 0, alertIntegrityViolation(fmt.Sprintf("Verification failed: %v", err))
}
diff --git a/pkg/sentry/fsimpl/verity/verity_test.go b/pkg/sentry/fsimpl/verity/verity_test.go
index b2da9dd96..7196e74eb 100644
--- a/pkg/sentry/fsimpl/verity/verity_test.go
+++ b/pkg/sentry/fsimpl/verity/verity_test.go
@@ -18,6 +18,7 @@ import (
"fmt"
"io"
"math/rand"
+ "strconv"
"testing"
"time"
@@ -307,6 +308,56 @@ func TestReopenUnmodifiedFileSucceeds(t *testing.T) {
}
}
+// TestOpenNonexistentFile ensures that opening a nonexistent file does not
+// trigger verification failure, even if the parent directory is verified.
+func TestOpenNonexistentFile(t *testing.T) {
+ vfsObj, root, ctx, err := newVerityRoot(t, SHA256)
+ if err != nil {
+ t.Fatalf("newVerityRoot: %v", err)
+ }
+
+ filename := "verity-test-file"
+ fd, _, err := newFileFD(ctx, vfsObj, root, filename, 0644)
+ if err != nil {
+ t.Fatalf("newFileFD: %v", err)
+ }
+
+ // Enable verity on the file and confirms a normal read succeeds.
+ var args arch.SyscallArguments
+ args[1] = arch.SyscallArgument{Value: linux.FS_IOC_ENABLE_VERITY}
+ if _, err := fd.Ioctl(ctx, nil /* uio */, args); err != nil {
+ t.Fatalf("Ioctl: %v", err)
+ }
+
+ // Enable verity on the parent directory.
+ parentFD, err := vfsObj.OpenAt(ctx, auth.CredentialsFromContext(ctx), &vfs.PathOperation{
+ Root: root,
+ Start: root,
+ }, &vfs.OpenOptions{
+ Flags: linux.O_RDONLY,
+ })
+ if err != nil {
+ t.Fatalf("OpenAt: %v", err)
+ }
+
+ if _, err := parentFD.Ioctl(ctx, nil /* uio */, args); err != nil {
+ t.Fatalf("Ioctl: %v", err)
+ }
+
+ // Ensure open an unexpected file in the parent directory fails with
+ // ENOENT rather than verification failure.
+ if _, err = vfsObj.OpenAt(ctx, auth.CredentialsFromContext(ctx), &vfs.PathOperation{
+ Root: root,
+ Start: root,
+ Path: fspath.Parse(filename + "abc"),
+ }, &vfs.OpenOptions{
+ Flags: linux.O_RDONLY,
+ Mode: linux.ModeRegular,
+ }); err != syserror.ENOENT {
+ t.Errorf("OpenAt unexpected error: %v", err)
+ }
+}
+
// TestPReadModifiedFileFails ensures that read from a modified verity file
// fails.
func TestPReadModifiedFileFails(t *testing.T) {
@@ -439,10 +490,10 @@ func TestModifiedMerkleFails(t *testing.T) {
// Flip a random bit in the Merkle tree file.
stat, err := lowerMerkleFD.Stat(ctx, vfs.StatOptions{})
if err != nil {
- t.Fatalf("stat: %v", err)
+ t.Errorf("lowerMerkleFD.Stat: %v", err)
}
- merkleSize := int(stat.Size)
- if err := corruptRandomBit(ctx, lowerMerkleFD, merkleSize); err != nil {
+
+ if err := corruptRandomBit(ctx, lowerMerkleFD, int(stat.Size)); err != nil {
t.Fatalf("corruptRandomBit: %v", err)
}
@@ -510,11 +561,17 @@ func TestModifiedParentMerkleFails(t *testing.T) {
// This parent directory contains only one child, so any random
// modification in the parent Merkle tree should cause verification
// failure when opening the child file.
- stat, err := parentLowerMerkleFD.Stat(ctx, vfs.StatOptions{})
+ sizeString, err := parentLowerMerkleFD.GetXattr(ctx, &vfs.GetXattrOptions{
+ Name: childrenOffsetXattr,
+ Size: sizeOfStringInt32,
+ })
+ if err != nil {
+ t.Fatalf("parentLowerMerkleFD.GetXattr: %v", err)
+ }
+ parentMerkleSize, err := strconv.Atoi(sizeString)
if err != nil {
- t.Fatalf("stat: %v", err)
+ t.Fatalf("Failed convert size to int: %v", err)
}
- parentMerkleSize := int(stat.Size)
if err := corruptRandomBit(ctx, parentLowerMerkleFD, parentMerkleSize); err != nil {
t.Fatalf("corruptRandomBit: %v", err)
}
@@ -602,124 +659,165 @@ func TestModifiedStatFails(t *testing.T) {
}
}
-// TestOpenDeletedOrRenamedFileFails ensures that opening a deleted/renamed
-// verity enabled file or the corresponding Merkle tree file fails with the
-// verify error.
+// TestOpenDeletedFileFails ensures that opening a deleted verity enabled file
+// and/or the corresponding Merkle tree file fails with the verity error.
func TestOpenDeletedFileFails(t *testing.T) {
testCases := []struct {
- // Tests removing files is remove is true. Otherwise tests
- // renaming files.
- remove bool
- // The original file is removed/renamed if changeFile is true.
+ // The original file is removed if changeFile is true.
changeFile bool
- // The Merkle tree file is removed/renamed if changeMerkleFile
- // is true.
+ // The Merkle tree file is removed if changeMerkleFile is true.
changeMerkleFile bool
}{
{
- remove: true,
changeFile: true,
changeMerkleFile: false,
},
{
- remove: true,
changeFile: false,
changeMerkleFile: true,
},
{
- remove: false,
changeFile: true,
- changeMerkleFile: false,
+ changeMerkleFile: true,
},
+ }
+ for _, tc := range testCases {
+ t.Run(fmt.Sprintf("changeFile:%t, changeMerkleFile:%t", tc.changeFile, tc.changeMerkleFile), func(t *testing.T) {
+ vfsObj, root, ctx, err := newVerityRoot(t, SHA256)
+ if err != nil {
+ t.Fatalf("newVerityRoot: %v", err)
+ }
+
+ filename := "verity-test-file"
+ fd, _, err := newFileFD(ctx, vfsObj, root, filename, 0644)
+ if err != nil {
+ t.Fatalf("newFileFD: %v", err)
+ }
+
+ // Enable verity on the file.
+ var args arch.SyscallArguments
+ args[1] = arch.SyscallArgument{Value: linux.FS_IOC_ENABLE_VERITY}
+ if _, err := fd.Ioctl(ctx, nil /* uio */, args); err != nil {
+ t.Fatalf("Ioctl: %v", err)
+ }
+
+ rootLowerVD := root.Dentry().Impl().(*dentry).lowerVD
+ if tc.changeFile {
+ if err := vfsObj.UnlinkAt(ctx, auth.CredentialsFromContext(ctx), &vfs.PathOperation{
+ Root: rootLowerVD,
+ Start: rootLowerVD,
+ Path: fspath.Parse(filename),
+ }); err != nil {
+ t.Fatalf("UnlinkAt: %v", err)
+ }
+ }
+ if tc.changeMerkleFile {
+ if err := vfsObj.UnlinkAt(ctx, auth.CredentialsFromContext(ctx), &vfs.PathOperation{
+ Root: rootLowerVD,
+ Start: rootLowerVD,
+ Path: fspath.Parse(merklePrefix + filename),
+ }); err != nil {
+ t.Fatalf("UnlinkAt: %v", err)
+ }
+ }
+
+ // Ensure reopening the verity enabled file fails.
+ if _, err = vfsObj.OpenAt(ctx, auth.CredentialsFromContext(ctx), &vfs.PathOperation{
+ Root: root,
+ Start: root,
+ Path: fspath.Parse(filename),
+ }, &vfs.OpenOptions{
+ Flags: linux.O_RDONLY,
+ Mode: linux.ModeRegular,
+ }); err != syserror.EIO {
+ t.Errorf("got OpenAt error: %v, expected EIO", err)
+ }
+ })
+ }
+}
+
+// TestOpenRenamedFileFails ensures that opening a renamed verity enabled file
+// and/or the corresponding Merkle tree file fails with the verity error.
+func TestOpenRenamedFileFails(t *testing.T) {
+ testCases := []struct {
+ // The original file is renamed if changeFile is true.
+ changeFile bool
+ // The Merkle tree file is renamed if changeMerkleFile is true.
+ changeMerkleFile bool
+ }{
{
- remove: false,
changeFile: true,
changeMerkleFile: false,
},
+ {
+ changeFile: false,
+ changeMerkleFile: true,
+ },
+ {
+ changeFile: true,
+ changeMerkleFile: true,
+ },
}
for _, tc := range testCases {
- t.Run(fmt.Sprintf("remove:%t", tc.remove), func(t *testing.T) {
- for _, alg := range hashAlgs {
- vfsObj, root, ctx, err := newVerityRoot(t, alg)
- if err != nil {
- t.Fatalf("newVerityRoot: %v", err)
- }
-
- filename := "verity-test-file"
- fd, _, err := newFileFD(ctx, vfsObj, root, filename, 0644)
- if err != nil {
- t.Fatalf("newFileFD: %v", err)
- }
+ t.Run(fmt.Sprintf("changeFile:%t, changeMerkleFile:%t", tc.changeFile, tc.changeMerkleFile), func(t *testing.T) {
+ vfsObj, root, ctx, err := newVerityRoot(t, SHA256)
+ if err != nil {
+ t.Fatalf("newVerityRoot: %v", err)
+ }
- // Enable verity on the file.
- var args arch.SyscallArguments
- args[1] = arch.SyscallArgument{Value: linux.FS_IOC_ENABLE_VERITY}
- if _, err := fd.Ioctl(ctx, nil /* uio */, args); err != nil {
- t.Fatalf("Ioctl: %v", err)
- }
+ filename := "verity-test-file"
+ fd, _, err := newFileFD(ctx, vfsObj, root, filename, 0644)
+ if err != nil {
+ t.Fatalf("newFileFD: %v", err)
+ }
- rootLowerVD := root.Dentry().Impl().(*dentry).lowerVD
- if tc.remove {
- if tc.changeFile {
- if err := vfsObj.UnlinkAt(ctx, auth.CredentialsFromContext(ctx), &vfs.PathOperation{
- Root: rootLowerVD,
- Start: rootLowerVD,
- Path: fspath.Parse(filename),
- }); err != nil {
- t.Fatalf("UnlinkAt: %v", err)
- }
- }
- if tc.changeMerkleFile {
- if err := vfsObj.UnlinkAt(ctx, auth.CredentialsFromContext(ctx), &vfs.PathOperation{
- Root: rootLowerVD,
- Start: rootLowerVD,
- Path: fspath.Parse(merklePrefix + filename),
- }); err != nil {
- t.Fatalf("UnlinkAt: %v", err)
- }
- }
- } else {
- newFilename := "renamed-test-file"
- if tc.changeFile {
- if err := vfsObj.RenameAt(ctx, auth.CredentialsFromContext(ctx), &vfs.PathOperation{
- Root: rootLowerVD,
- Start: rootLowerVD,
- Path: fspath.Parse(filename),
- }, &vfs.PathOperation{
- Root: rootLowerVD,
- Start: rootLowerVD,
- Path: fspath.Parse(newFilename),
- }, &vfs.RenameOptions{}); err != nil {
- t.Fatalf("RenameAt: %v", err)
- }
- }
- if tc.changeMerkleFile {
- if err := vfsObj.RenameAt(ctx, auth.CredentialsFromContext(ctx), &vfs.PathOperation{
- Root: rootLowerVD,
- Start: rootLowerVD,
- Path: fspath.Parse(merklePrefix + filename),
- }, &vfs.PathOperation{
- Root: rootLowerVD,
- Start: rootLowerVD,
- Path: fspath.Parse(merklePrefix + newFilename),
- }, &vfs.RenameOptions{}); err != nil {
- t.Fatalf("UnlinkAt: %v", err)
- }
- }
- }
+ // Enable verity on the file.
+ var args arch.SyscallArguments
+ args[1] = arch.SyscallArgument{Value: linux.FS_IOC_ENABLE_VERITY}
+ if _, err := fd.Ioctl(ctx, nil /* uio */, args); err != nil {
+ t.Fatalf("Ioctl: %v", err)
+ }
- // Ensure reopening the verity enabled file fails.
- if _, err = vfsObj.OpenAt(ctx, auth.CredentialsFromContext(ctx), &vfs.PathOperation{
- Root: root,
- Start: root,
+ rootLowerVD := root.Dentry().Impl().(*dentry).lowerVD
+ newFilename := "renamed-test-file"
+ if tc.changeFile {
+ if err := vfsObj.RenameAt(ctx, auth.CredentialsFromContext(ctx), &vfs.PathOperation{
+ Root: rootLowerVD,
+ Start: rootLowerVD,
Path: fspath.Parse(filename),
- }, &vfs.OpenOptions{
- Flags: linux.O_RDONLY,
- Mode: linux.ModeRegular,
- }); err != syserror.EIO {
- t.Errorf("got OpenAt error: %v, expected EIO", err)
+ }, &vfs.PathOperation{
+ Root: rootLowerVD,
+ Start: rootLowerVD,
+ Path: fspath.Parse(newFilename),
+ }, &vfs.RenameOptions{}); err != nil {
+ t.Fatalf("RenameAt: %v", err)
}
}
+ if tc.changeMerkleFile {
+ if err := vfsObj.RenameAt(ctx, auth.CredentialsFromContext(ctx), &vfs.PathOperation{
+ Root: rootLowerVD,
+ Start: rootLowerVD,
+ Path: fspath.Parse(merklePrefix + filename),
+ }, &vfs.PathOperation{
+ Root: rootLowerVD,
+ Start: rootLowerVD,
+ Path: fspath.Parse(merklePrefix + newFilename),
+ }, &vfs.RenameOptions{}); err != nil {
+ t.Fatalf("UnlinkAt: %v", err)
+ }
+ }
+
+ // Ensure reopening the verity enabled file fails.
+ if _, err = vfsObj.OpenAt(ctx, auth.CredentialsFromContext(ctx), &vfs.PathOperation{
+ Root: root,
+ Start: root,
+ Path: fspath.Parse(filename),
+ }, &vfs.OpenOptions{
+ Flags: linux.O_RDONLY,
+ Mode: linux.ModeRegular,
+ }); err != syserror.EIO {
+ t.Errorf("got OpenAt error: %v, expected EIO", err)
+ }
})
}
}
generated by cgit v1.2.3 (git 2.39.1) at 2025-01-11 13:59:37 +0000