Test the FS_IOC_READ_VERITY_METADATA ioctl

index a8d3de06..9a182240 100644
@@ -48,12 +48,47 @@ _require_scratch_verity()
 	FSV_BLOCK_SIZE=$(get_page_size)
 }
 
-# Check for CONFIG_FS_VERITY_BUILTIN_SIGNATURES=y.
+# Check for CONFIG_FS_VERITY_BUILTIN_SIGNATURES=y, as well as the userspace
+# commands needed to generate certificates and add them to the kernel.
 _require_fsverity_builtin_signatures()
 {
 	if [ ! -e /proc/sys/fs/verity/require_signatures ]; then
 		_notrun "kernel doesn't support fs-verity builtin signatures"
 	fi
+	_require_command "$OPENSSL_PROG" openssl
+	_require_command "$KEYCTL_PROG" keyctl
+}
+
+# Use the openssl program to generate a private key and a X.509 certificate for
+# use with fs-verity built-in signature verification, and convert the
+# certificate to DER format.
+_fsv_generate_cert()
+{
+	local keyfile=$1
+	local certfile=$2
+	local certfileder=$3
+
+	if ! $OPENSSL_PROG req -newkey rsa:4096 -nodes -batch -x509 \
+			-keyout $keyfile -out $certfile &>> $seqres.full; then
+		_fail "Failed to generate certificate and private key (see $seqres.full)"
+	fi
+	$OPENSSL_PROG x509 -in $certfile -out $certfileder -outform der
+}
+
+# Clear the .fs-verity keyring.
+_fsv_clear_keyring()
+{
+	$KEYCTL_PROG clear %keyring:.fs-verity
+}
+
+# Load the given X.509 certificate in DER format into the .fs-verity keyring so
+# that the kernel can use it to verify built-in signatures.
+_fsv_load_cert()
+{
+	local certfileder=$1
+
+	$KEYCTL_PROG padd asymmetric '' %keyring:.fs-verity \
+		< $certfileder >> $seqres.full
 }
 
 # Disable mandatory signatures for fs-verity files, if they are supported.

index 0e945942..114463be 100755
@@ -34,8 +34,6 @@ rm -f $seqres.full
 _supported_fs generic
 _require_scratch_verity
 _require_fsverity_builtin_signatures
-_require_command "$OPENSSL_PROG" openssl
-_require_command "$KEYCTL_PROG" keyctl
 
 _scratch_mkfs_verity &>> $seqres.full
 _scratch_mount

@@ -53,21 +51,14 @@ othersigfile=$tmp.othersig
 
 echo -e "\n# Generating certificates and private keys"
 for suffix in '' '.2'; do
-	if ! $OPENSSL_PROG req -newkey rsa:4096 -nodes -batch -x509 \
-			-keyout $keyfile$suffix -out $certfile$suffix \
-			&>> $seqres.full; then
-		_fail "Failed to generate certificate and private key (see $seqres.full)"
-	fi
-	$OPENSSL_PROG x509 -in $certfile$suffix -out $certfileder$suffix \
-		-outform der
+	_fsv_generate_cert $keyfile$suffix $certfile$suffix $certfileder$suffix
 done
 
 echo -e "\n# Clearing fs-verity keyring"
-$KEYCTL_PROG clear %keyring:.fs-verity
+_fsv_clear_keyring
 
 echo -e "\n# Loading first certificate into fs-verity keyring"
-$KEYCTL_PROG padd asymmetric '' %keyring:.fs-verity \
-	< $certfileder >> $seqres.full
+_fsv_load_cert $certfileder
 
 echo -e "\n# Enabling fs.verity.require_signatures"
 _enable_fsverity_signatures

index 9a182240..38eea157 100644
@@ -120,6 +120,27 @@ _restore_fsverity_signatures()
         fi
 }
 
+# Require userspace and kernel support for 'fsverity dump_metadata'.
+# $1 must be a file with fs-verity enabled.
+_require_fsverity_dump_metadata()
+{
+	local verity_file=$1
+	local tmpfile=$tmp.require_fsverity_dump_metadata
+
+	if _fsv_dump_merkle_tree "$verity_file" 2>"$tmpfile" >/dev/null; then
+		return
+	fi
+	if grep -q "^ERROR: unrecognized command: 'dump_metadata'$" "$tmpfile"
+	then
+		_notrun "Missing 'fsverity dump_metadata' command"
+	fi
+	if grep -q "^ERROR: FS_IOC_READ_VERITY_METADATA failed on '.*': Inappropriate ioctl for device$" "$tmpfile"
+	then
+		_notrun "Kernel doesn't support FS_IOC_READ_VERITY_METADATA"
+	fi
+	_fail "Unexpected output from 'fsverity dump_metadata': $(<"$tmpfile")"
+}
+
 _scratch_mkfs_verity()
 {
 	case $FSTYP in

@@ -157,6 +178,21 @@ _fsv_scratch_begin_subtest()
 	echo -e "\n# $msg"
 }
 
+_fsv_dump_merkle_tree()
+{
+	$FSVERITY_PROG dump_metadata merkle_tree "$@"
+}
+
+_fsv_dump_descriptor()
+{
+	$FSVERITY_PROG dump_metadata descriptor "$@"
+}
+
+_fsv_dump_signature()
+{
+	$FSVERITY_PROG dump_metadata signature "$@"
+}
+
 _fsv_enable()
 {
 	$FSVERITY_PROG enable "$@"

new file mode 100755
index 00000000..24889d63
@@ -0,0 +1,79 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0-only
+# Copyright 2021 Google LLC
+#
+# FS QA Test No. 901
+#
+# Test retrieving the Merkle tree and fs-verity descriptor of a verity file
+# using FS_IOC_READ_VERITY_METADATA.
+#
+seq=`basename $0`
+seqres=$RESULT_DIR/$seq
+echo "QA output created by $seq"
+
+here=`pwd`
+tmp=/tmp/$$
+status=1	# failure is the default!
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+_cleanup()
+{
+	cd /
+	rm -f $tmp.*
+}
+
+. ./common/rc
+. ./common/filter
+. ./common/verity
+
+rm -f $seqres.full
+
+_supported_fs generic
+_require_scratch_verity
+_disable_fsverity_signatures
+# For the output of this test to always be the same, it has to use a specific
+# Merkle tree block size.
+if [ $FSV_BLOCK_SIZE != 4096 ]; then
+	_notrun "4096-byte verity block size not supported on this platform"
+fi
+
+_scratch_mkfs_verity &>> $seqres.full
+_scratch_mount
+
+echo -e "\n# Creating a verity file"
+fsv_file=$SCRATCH_MNT/file
+# Always use the same file contents, so that the output of the test is always
+# the same.  Also use a file that is large enough to have multiple Merkle tree
+# levels, so that the test verifies that the blocks are returned in the expected
+# order.  A 1 MB file with SHA-256 and a Merkle tree block size of 4096 will
+# have 3 Merkle tree blocks (3*4096 bytes): two at level 0 and one at level 1.
+head -c 1000000 /dev/zero > $fsv_file
+merkle_tree_size=$((3 * FSV_BLOCK_SIZE))
+fsverity_descriptor_size=256
+_fsv_enable $fsv_file --salt=abcd
+_require_fsverity_dump_metadata $fsv_file
+_fsv_measure $fsv_file
+
+echo -e "\n# Dumping Merkle tree"
+_fsv_dump_merkle_tree $fsv_file | sha256sum
+
+echo -e "\n# Dumping Merkle tree (in chunks)"
+# The above test may get the whole tree in one read, so also try reading it in
+# chunks.
+for (( i = 0; i < merkle_tree_size; i += 997 )); do
+	_fsv_dump_merkle_tree $fsv_file --offset=$i --length=997
+done | sha256sum
+
+echo -e "\n# Dumping descriptor"
+# Note that the hash that is printed here should be the same hash that was
+# printed by _fsv_measure above.
+_fsv_dump_descriptor $fsv_file | sha256sum
+
+echo -e "\n# Dumping descriptor (in chunks)"
+for (( i = 0; i < fsverity_descriptor_size; i += 13 )); do
+	_fsv_dump_descriptor $fsv_file --offset=$i --length=13
+done | sha256sum
+
+# success, all done
+status=0
+exit

new file mode 100644
index 00000000..ab018052
@@ -0,0 +1,16 @@
+QA output created by 901
+
+# Creating a verity file
+sha256:11e4f886bf2d70a6ef3a8b6ce8e8c62c9e5d3263208b9f120ae46791f124be73
+
+# Dumping Merkle tree
+db88cdad554734cd648a1bfbb5be7f86646c54397847aab0b3f42a28829fed17  -
+
+# Dumping Merkle tree (in chunks)
+db88cdad554734cd648a1bfbb5be7f86646c54397847aab0b3f42a28829fed17  -
+
+# Dumping descriptor
+11e4f886bf2d70a6ef3a8b6ce8e8c62c9e5d3263208b9f120ae46791f124be73  -
+
+# Dumping descriptor (in chunks)
+11e4f886bf2d70a6ef3a8b6ce8e8c62c9e5d3263208b9f120ae46791f124be73  -

index b10fdea4..3cc40795 100644
@@ -625,3 +625,4 @@
 620 auto mount quick
 621 auto quick encrypt
 622 auto shutdown metadata atime
+901 auto quick verity

new file mode 100755
index 00000000..ee1096df
@@ -0,0 +1,66 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0-only
+# Copyright 2021 Google LLC
+#
+# FS QA Test No. 902
+#
+# Test retrieving the built-in signature of a verity file using
+# FS_IOC_READ_VERITY_METADATA.
+#
+# This is separate from the other tests for FS_IOC_READ_VERITY_METADATA because
+# the fs-verity built-in signature support is optional.
+#
+seq=`basename $0`
+seqres=$RESULT_DIR/$seq
+echo "QA output created by $seq"
+
+here=`pwd`
+tmp=/tmp/$$
+status=1	# failure is the default!
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+_cleanup()
+{
+	cd /
+	rm -f $tmp.*
+}
+
+. ./common/rc
+. ./common/filter
+. ./common/verity
+
+rm -f $seqres.full
+
+_supported_fs generic
+_require_scratch_verity
+_require_fsverity_builtin_signatures
+
+_scratch_mkfs_verity &>> $seqres.full
+_scratch_mount
+
+echo -e "\n# Setting up signed verity file"
+_fsv_generate_cert $tmp.key $tmp.cert $tmp.cert.der
+_fsv_clear_keyring
+_fsv_load_cert $tmp.cert.der
+fsv_file=$SCRATCH_MNT/file
+echo foo > $fsv_file
+_fsv_sign $fsv_file $tmp.sig --key=$tmp.key --cert=$tmp.cert >> $seqres.full
+_fsv_enable $fsv_file --signature=$tmp.sig
+_require_fsverity_dump_metadata $fsv_file
+
+echo -e "\n# Dumping and comparing signature"
+_fsv_dump_signature $fsv_file > $tmp.sig2
+# The signature returned by FS_IOC_READ_VERITY_METADATA should exactly match the
+# one we passed to FS_IOC_ENABLE_VERITY earlier.
+cmp $tmp.sig $tmp.sig2
+
+echo -e "\n# Dumping and comparing signature (in chunks)"
+sig_size=$(stat -c %s $tmp.sig)
+for (( i = 0; i < sig_size; i += 13 )); do
+	_fsv_dump_signature $fsv_file --offset=$i --length=13
+done > $tmp.sig2
+cmp $tmp.sig $tmp.sig2
+
+# success, all done
+status=0
+exit

new file mode 100644
index 00000000..4b8d9f6e
@@ -0,0 +1,7 @@
+QA output created by 902
+
+# Setting up signed verity file
+
+# Dumping and comparing signature
+
+# Dumping and comparing signature (in chunks)

index 3cc40795..ce9aa950 100644
@@ -626,3 +626,4 @@
 621 auto quick encrypt
 622 auto shutdown metadata atime
 901 auto quick verity
+902 auto quick verity