diff options
Diffstat (limited to 'pkg/sentry/fsimpl/verity/verity.go')
| -rw-r--r-- | pkg/sentry/fsimpl/verity/verity.go | 75 |
1 files changed, 65 insertions, 10 deletions
diff --git a/pkg/sentry/fsimpl/verity/verity.go b/pkg/sentry/fsimpl/verity/verity.go index 249cc1341..96b5bd87f 100644 --- a/pkg/sentry/fsimpl/verity/verity.go +++ b/pkg/sentry/fsimpl/verity/verity.go @@ -22,6 +22,7 @@ package verity import ( + "fmt" "strconv" "sync/atomic" @@ -29,7 +30,6 @@ import ( "gvisor.dev/gvisor/pkg/context" "gvisor.dev/gvisor/pkg/fspath" "gvisor.dev/gvisor/pkg/marshal/primitive" - "gvisor.dev/gvisor/pkg/merkletree" "gvisor.dev/gvisor/pkg/sentry/arch" fslock "gvisor.dev/gvisor/pkg/sentry/fs/lock" @@ -135,6 +135,16 @@ func (FilesystemType) Name() string { return Name } +// alertIntegrityViolation alerts a violation of integrity, which usually means +// unexpected modification to the file system is detected. In +// noCrashOnVerificationFailure mode, it returns an error, otherwise it panic. +func alertIntegrityViolation(err error, msg string) error { + if noCrashOnVerificationFailure { + return err + } + panic(msg) +} + // GetFilesystem implements vfs.FilesystemType.GetFilesystem. func (fstype FilesystemType) GetFilesystem(ctx context.Context, vfsObj *vfs.VirtualFilesystem, creds *auth.Credentials, source string, opts vfs.GetFilesystemOptions) (*vfs.Filesystem, *vfs.Dentry, error) { iopts, ok := opts.InternalData.(InternalFilesystemOptions) @@ -204,15 +214,12 @@ func (fstype FilesystemType) GetFilesystem(ctx context.Context, vfsObj *vfs.Virt return nil, nil, err } } else if err != nil { - // Failed to get dentry for the root Merkle file. This indicates - // an attack that removed/renamed the root Merkle file, or it's - // never generated. - if noCrashOnVerificationFailure { - fs.vfsfs.DecRef(ctx) - d.DecRef(ctx) - return nil, nil, err - } - panic("Failed to find root Merkle file") + // Failed to get dentry for the root Merkle file. This + // indicates an unexpected modification that removed/renamed + // the root Merkle file, or it's never generated. + fs.vfsfs.DecRef(ctx) + d.DecRef(ctx) + return nil, nil, alertIntegrityViolation(err, "Failed to find root Merkle file") } d.lowerMerkleVD = lowerMerkleVD @@ -618,6 +625,54 @@ func (fd *fileDescription) Ioctl(ctx context.Context, uio usermem.IO, args arch. } } +// PRead implements vfs.FileDescriptionImpl.PRead. +func (fd *fileDescription) PRead(ctx context.Context, dst usermem.IOSequence, offset int64, opts vfs.ReadOptions) (int64, error) { + // No need to verify if the file is not enabled yet in + // allowRuntimeEnable mode. + if fd.d.fs.allowRuntimeEnable && len(fd.d.rootHash) == 0 { + return fd.lowerFD.PRead(ctx, dst, offset, opts) + } + + // dataSize is the size of the whole file. + dataSize, err := fd.merkleReader.GetXattr(ctx, &vfs.GetXattrOptions{ + Name: merkleSizeXattr, + Size: sizeOfInt32, + }) + + // The Merkle tree file for the child should have been created and + // contains the expected xattrs. If the xattr does not exist, it + // indicates unexpected modifications to the file system. + if err == syserror.ENODATA { + return 0, alertIntegrityViolation(err, fmt.Sprintf("Failed to get xattr %s: %v", merkleSizeXattr, err)) + } + if err != nil { + return 0, err + } + + // The dataSize xattr should be an integer. If it's not, it indicates + // unexpected modifications to the file system. + size, err := strconv.Atoi(dataSize) + if err != nil { + return 0, alertIntegrityViolation(err, fmt.Sprintf("Failed to convert xattr %s to int: %v", merkleSizeXattr, err)) + } + + dataReader := vfs.FileReadWriteSeeker{ + FD: fd.lowerFD, + Ctx: ctx, + } + + merkleReader := vfs.FileReadWriteSeeker{ + FD: fd.merkleReader, + Ctx: ctx, + } + + n, err := merkletree.Verify(dst.Writer(ctx), &dataReader, &merkleReader, int64(size), offset, dst.NumBytes(), fd.d.rootHash, false /* dataAndTreeInSameFile */) + if err != nil { + return 0, alertIntegrityViolation(syserror.EINVAL, fmt.Sprintf("Verification failed: %v", err)) + } + return n, err +} + // LockPOSIX implements vfs.FileDescriptionImpl.LockPOSIX. func (fd *fileDescription) LockPOSIX(ctx context.Context, uid fslock.UniqueID, t fslock.LockType, start, length uint64, whence int16, block fslock.Blocker) error { return fd.Locks().LockPOSIX(ctx, &fd.vfsfd, uid, t, start, length, whence, block) |