common/verity: add common functions for testing fs-verity
authorEric Biggers <ebiggers@google.com>
Mon, 30 Sep 2019 21:15:47 +0000 (14:15 -0700)
committerEryu Guan <guaneryu@gmail.com>
Sun, 13 Oct 2019 13:01:30 +0000 (21:01 +0800)
Add common functions for setting up and testing fs-verity.  fs-verity is
an ext4 and f2fs filesystem feature which provides Merkle tree based
hashing (similar to dm-verity) for individual read-only files, mainly
for the purpose of efficient authenticity verification.  Other
filesystems may add fs-verity support later, using the same API.

Running the fs-verity tests will require:

- Kernel v5.4-rc1 or later configured with CONFIG_FS_VERITY=y

- The 'fsverity' utility program from
  https://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/fsverity-utils.git

- e2fsprogs v1.45.2 or later for ext4 tests, or f2fs-tools v1.11.0 or
  later for f2fs tests

Some individual tests will have additional requirements.

For more information about fs-verity, see
https://www.kernel.org/doc/html/latest/filesystems/fsverity.html

Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>
common/config
common/verity [new file with mode: 0644]

index 4eda36c7aaeb16b16d1473a7ad752d36ecafba81..1ff3b950bf3b8138ee7bc5ca479a1d3f810b9413 100644 (file)
@@ -213,6 +213,7 @@ export CHECKBASHISMS_PROG="$(type -P checkbashisms)"
 export XFS_INFO_PROG="$(type -P xfs_info)"
 export DUPEREMOVE_PROG="$(type -P duperemove)"
 export CC_PROG="$(type -P cc)"
+export FSVERITY_PROG="$(type -P fsverity)"
 
 # use 'udevadm settle' or 'udevsettle' to wait for lv to be settled.
 # newer systems have udevadm command but older systems like RHEL5 don't.
diff --git a/common/verity b/common/verity
new file mode 100644 (file)
index 0000000..a8aae51
--- /dev/null
@@ -0,0 +1,199 @@
+# SPDX-License-Identifier: GPL-2.0
+# Copyright 2018 Google LLC
+#
+# Functions for setting up and testing fs-verity
+
+_require_scratch_verity()
+{
+       _require_scratch
+       _require_command "$FSVERITY_PROG" fsverity
+
+       if ! _scratch_mkfs_verity &>>$seqres.full; then
+               # ext4: need e2fsprogs v1.44.5 or later (but actually v1.45.2+
+               #       is needed for some tests to pass, due to an e2fsck bug)
+               # f2fs: need f2fs-tools v1.11.0 or later
+               _notrun "$FSTYP userspace tools don't support fs-verity"
+       fi
+
+       # Try to mount the filesystem.  If this fails then either the kernel
+       # isn't aware of fs-verity, or the mkfs options were not compatible with
+       # verity (e.g. ext4 with block size != PAGE_SIZE).
+       if ! _try_scratch_mount &>>$seqres.full; then
+               _notrun "kernel is unaware of $FSTYP verity feature," \
+                       "or mkfs options are not compatible with verity"
+       fi
+
+       # The filesystem may be aware of fs-verity but have it disabled by
+       # CONFIG_FS_VERITY=n.  Detect support via sysfs.
+       if [ ! -e /sys/fs/$FSTYP/features/verity ]; then
+               _notrun "kernel $FSTYP isn't configured with verity support"
+       fi
+
+       # The filesystem may have fs-verity enabled but not actually usable by
+       # default.  E.g., ext4 only supports verity on extent-based files, so it
+       # doesn't work on ext3-style filesystems.  So, try actually using it.
+       echo foo > $SCRATCH_MNT/tmpfile
+       if ! _fsv_enable $SCRATCH_MNT/tmpfile; then
+               _notrun "$FSTYP verity isn't usable by default with these mkfs options"
+       fi
+       rm -f $SCRATCH_MNT/tmpfile
+
+       _scratch_unmount
+
+       # Merkle tree block size.  Currently all filesystems only support
+       # PAGE_SIZE for this.  This is also the default for 'fsverity enable'.
+       FSV_BLOCK_SIZE=$(get_page_size)
+}
+
+_scratch_mkfs_verity()
+{
+       case $FSTYP in
+       ext4|f2fs)
+               _scratch_mkfs -O verity
+               ;;
+       *)
+               _notrun "No verity support for $FSTYP"
+               ;;
+       esac
+}
+
+_scratch_mkfs_encrypted_verity()
+{
+       case $FSTYP in
+       ext4)
+               _scratch_mkfs -O encrypt,verity
+               ;;
+       f2fs)
+               # f2fs-tools as of v1.11.0 doesn't allow comma-separated
+               # features with -O.  Instead -O must be supplied multiple times.
+               _scratch_mkfs -O encrypt -O verity
+               ;;
+       *)
+               _notrun "$FSTYP not supported in _scratch_mkfs_encrypted_verity"
+               ;;
+       esac
+}
+
+_fsv_scratch_begin_subtest()
+{
+       local msg=$1
+
+       rm -rf "${SCRATCH_MNT:?}"/*
+       echo -e "\n# $msg"
+}
+
+_fsv_enable()
+{
+       $FSVERITY_PROG enable "$@"
+}
+
+_fsv_measure()
+{
+        $FSVERITY_PROG measure "$@" | awk '{print $1}'
+}
+
+# Generate a file, then enable verity on it.
+_fsv_create_enable_file()
+{
+       local file=$1
+       shift
+
+       head -c $((FSV_BLOCK_SIZE * 2)) /dev/zero > "$file"
+       _fsv_enable "$file" "$@"
+}
+
+_fsv_have_hash_algorithm()
+{
+       local hash_alg=$1
+       local test_file=$2
+
+       rm -f $test_file
+       head -c 4096 /dev/zero > $test_file
+       if ! _fsv_enable --hash-alg=$hash_alg $test_file &>> $seqres.full; then
+               # no kernel support
+               return 1
+       fi
+       rm -f $test_file
+       return 0
+}
+
+#
+# _fsv_scratch_corrupt_bytes - Write some bytes to a file, bypassing the filesystem
+#
+# Write the bytes sent on stdin to the given offset in the given file, but do so
+# by writing directly to the extents on the block device, with the filesystem
+# unmounted.  This can be used to corrupt a verity file for testing purposes,
+# bypassing the restrictions imposed by the filesystem.
+#
+# The file is assumed to be located on $SCRATCH_DEV.
+#
+_fsv_scratch_corrupt_bytes()
+{
+       local file=$1
+       local offset=$2
+       local lstart lend pstart pend
+       local dd_cmds=()
+       local cmd
+
+       sync    # Sync to avoid unwritten extents
+
+       cat > $tmp.bytes
+       local end=$(( offset + $(stat -c %s $tmp.bytes ) ))
+
+       # For each extent that intersects the requested range in order, add a
+       # command that writes the next part of the data to that extent.
+       while read -r lstart lend pstart pend; do
+               lstart=$((lstart * 512))
+               lend=$(((lend + 1) * 512))
+               pstart=$((pstart * 512))
+               pend=$(((pend + 1) * 512))
+
+               if (( lend - lstart != pend - pstart )); then
+                       _fail "Logical and physical extent lengths differ for file '$file'"
+               elif (( offset < lstart )); then
+                       _fail "Hole in file '$file' at byte $offset.  Next extent begins at byte $lstart"
+               elif (( offset < lend )); then
+                       local len=$((lend - offset))
+                       local seek=$((pstart + (offset - lstart)))
+                       dd_cmds+=("head -c $len | dd of=$SCRATCH_DEV oflag=seek_bytes seek=$seek status=none")
+                       (( offset += len ))
+               fi
+       done < <($XFS_IO_PROG -r -c "fiemap $offset $((end - offset))" "$file" \
+                | _filter_xfs_io_fiemap)
+
+       if (( offset < end )); then
+               _fail "Extents of file '$file' ended at byte $offset, but needed until $end"
+       fi
+
+       # Execute the commands to write the data
+       _scratch_unmount
+       for cmd in "${dd_cmds[@]}"; do
+               eval "$cmd"
+       done < $tmp.bytes
+       sync    # Sync to flush the block device's pagecache
+       _scratch_mount
+}
+
+#
+# _fsv_scratch_corrupt_merkle_tree - Corrupt a file's Merkle tree
+#
+# Like _fsv_scratch_corrupt_bytes(), but this corrupts the file's fs-verity
+# Merkle tree.  The offset is given as a byte offset into the Merkle tree.
+#
+_fsv_scratch_corrupt_merkle_tree()
+{
+       local file=$1
+       local offset=$2
+
+       case $FSTYP in
+       ext4|f2fs)
+               # ext4 and f2fs store the Merkle tree after the file contents
+               # itself, starting at the next 65536-byte aligned boundary.
+               (( offset += ($(stat -c %s $file) + 65535) & ~65535 ))
+               _fsv_scratch_corrupt_bytes $file $offset
+               ;;
+       *)
+               _fail "_fsv_scratch_corrupt_merkle_tree() unimplemented on $FSTYP"
+               ;;
+       esac
+}