diff options
Diffstat (limited to 'pkg/sentry/fsimpl/verity')
| -rw-r--r-- | pkg/sentry/fsimpl/verity/BUILD | 2 | ||||
| -rw-r--r-- | pkg/sentry/fsimpl/verity/verity.go | 128 |
2 files changed, 130 insertions, 0 deletions
diff --git a/pkg/sentry/fsimpl/verity/BUILD b/pkg/sentry/fsimpl/verity/BUILD index 326c4ed90..d28450e53 100644 --- a/pkg/sentry/fsimpl/verity/BUILD +++ b/pkg/sentry/fsimpl/verity/BUILD @@ -14,11 +14,13 @@ go_library( "//pkg/context", "//pkg/fspath", "//pkg/merkletree", + "//pkg/sentry/arch", "//pkg/sentry/fs/lock", "//pkg/sentry/kernel/auth", "//pkg/sentry/socket/unix/transport", "//pkg/sentry/vfs", "//pkg/sync", "//pkg/syserror", + "//pkg/usermem", ], ) diff --git a/pkg/sentry/fsimpl/verity/verity.go b/pkg/sentry/fsimpl/verity/verity.go index eedb5f484..0bac8e938 100644 --- a/pkg/sentry/fsimpl/verity/verity.go +++ b/pkg/sentry/fsimpl/verity/verity.go @@ -22,16 +22,21 @@ package verity import ( + "strconv" "sync/atomic" "gvisor.dev/gvisor/pkg/abi/linux" "gvisor.dev/gvisor/pkg/context" "gvisor.dev/gvisor/pkg/fspath" + + "gvisor.dev/gvisor/pkg/merkletree" + "gvisor.dev/gvisor/pkg/sentry/arch" fslock "gvisor.dev/gvisor/pkg/sentry/fs/lock" "gvisor.dev/gvisor/pkg/sentry/kernel/auth" "gvisor.dev/gvisor/pkg/sentry/vfs" "gvisor.dev/gvisor/pkg/sync" "gvisor.dev/gvisor/pkg/syserror" + "gvisor.dev/gvisor/pkg/usermem" ) // Name is the default filesystem name. @@ -471,6 +476,129 @@ func (fd *fileDescription) SetStat(ctx context.Context, opts vfs.SetStatOptions) return syserror.EPERM } +// 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 root +// 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 root hahes of its children, written +// to the Merkle tree file. +func (fd *fileDescription) generateMerkle(ctx context.Context) ([]byte, uint64, error) { + fdReader := vfs.FileReadWriteSeeker{ + FD: fd.lowerFD, + Ctx: ctx, + } + merkleReader := vfs.FileReadWriteSeeker{ + FD: fd.merkleReader, + Ctx: ctx, + } + merkleWriter := vfs.FileReadWriteSeeker{ + FD: fd.merkleWriter, + Ctx: ctx, + } + var rootHash []byte + var dataSize uint64 + + switch atomic.LoadUint32(&fd.d.mode) & linux.S_IFMT { + case linux.S_IFREG: + // For a regular file, generate a Merkle tree based on its + // content. + var err error + stat, err := fd.lowerFD.Stat(ctx, vfs.StatOptions{}) + if err != nil { + return nil, 0, err + } + dataSize = stat.Size + + rootHash, err = merkletree.Generate(&fdReader, int64(dataSize), &merkleReader, &merkleWriter, false /* dataAndTreeInSameFile */) + if err != nil { + return nil, 0, err + } + case linux.S_IFDIR: + // For a directory, generate a Merkle tree based on the root + // hashes of its children that has already been written to the + // Merkle tree file. + merkleStat, err := fd.merkleReader.Stat(ctx, vfs.StatOptions{}) + if err != nil { + return nil, 0, err + } + dataSize = merkleStat.Size + + rootHash, err = merkletree.Generate(&merkleReader, int64(dataSize), &merkleReader, &merkleWriter, true /* dataAndTreeInSameFile */) + if err != nil { + return nil, 0, err + } + default: + // TODO(b/167728857): Investigate whether and how we should + // enable other types of file. + return nil, 0, syserror.EINVAL + } + return rootHash, dataSize, nil +} + +// enableVerity enables verity features on fd by generating a Merkle tree file +// and stores its root hash in its parent directory's Merkle tree. +func (fd *fileDescription) enableVerity(ctx context.Context, uio usermem.IO, args arch.SyscallArguments) (uintptr, error) { + if !fd.d.fs.allowRuntimeEnable { + return 0, syserror.EPERM + } + + // Lock to prevent other threads performing enable or access the file + // while it's being enabled. + verityMu.Lock() + defer verityMu.Unlock() + + if fd.lowerFD == nil || fd.merkleReader == nil || fd.merkleWriter == nil || fd.parentMerkleWriter == nil { + panic("Unexpected verity fd: missing expected underlying fds") + } + + rootHash, dataSize, err := fd.generateMerkle(ctx) + if err != nil { + return 0, err + } + + stat, err := fd.parentMerkleWriter.Stat(ctx, vfs.StatOptions{}) + if err != nil { + return 0, err + } + + // Write the root hash of fd to the parent directory's Merkle tree + // file, as it should be part of the parent Merkle tree data. + // parentMerkleWriter is open with O_APPEND, so it should write + // directly to the end of the file. + if _, err = fd.parentMerkleWriter.Write(ctx, usermem.BytesIOSequence(rootHash), vfs.WriteOptions{}); err != nil { + return 0, err + } + + // Record the offset of the root hash of fd in parent directory's + // Merkle tree file. + if err := fd.merkleWriter.SetXattr(ctx, &vfs.SetXattrOptions{ + Name: merkleOffsetInParentXattr, + Value: strconv.Itoa(int(stat.Size)), + }); err != nil { + return 0, err + } + + // Record the size of the data being hashed for fd. + if err := fd.merkleWriter.SetXattr(ctx, &vfs.SetXattrOptions{ + Name: merkleSizeXattr, + Value: strconv.Itoa(int(dataSize)), + }); err != nil { + return 0, err + } + fd.d.rootHash = append(fd.d.rootHash, rootHash...) + return 0, nil +} + +// Ioctl implements vfs.FileDescriptionImpl.Ioctl. +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, args) + default: + return fd.lowerFD.Ioctl(ctx, uio, args) + } +} + // 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) |