From c0702fc30a3d9f0431d964210ef27dadb2c89f3c Mon Sep 17 00:00:00 2001
From: Eric Biggers <ebiggers@google.com>
Date: Fri, 27 Nov 2020 11:28:50 -0800
Subject: sys/linux: add some sample fscrypt keys

Add some sample keys with their precomputed fscrypt key identifiers, and
add some sample fscrypt key descriptors.

This hopefully makes it much more likely that syzkaller will generate
programs that both add an encryption key to the kernel
(FS_IOC_ADD_ENCRYPTION_KEY or add_key$fscrypt_v1) *and* create a
directory that is encrypted using that key (mkdir() +
FS_IOC_SET_ENCRYPTION_POLICY).  Doing this requires matching up the
value of the fscrypt key identifier or the fscrypt key descriptor.
---
 sys/linux/fs_ioctl_fscrypt.txt | 61 +++++++++++++++++++++++++++++++++++++-----
 1 file changed, 55 insertions(+), 6 deletions(-)

(limited to 'sys/linux')

diff --git a/sys/linux/fs_ioctl_fscrypt.txt b/sys/linux/fs_ioctl_fscrypt.txt
index 87c0c6f33..f9e1c7619 100644
--- a/sys/linux/fs_ioctl_fscrypt.txt
+++ b/sys/linux/fs_ioctl_fscrypt.txt
@@ -16,8 +16,55 @@ ioctl$FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS(fd fd_dir, cmd const[FS_IOC_REMOVE_
 ioctl$FS_IOC_GET_ENCRYPTION_KEY_STATUS(fd fd_dir, cmd const[FS_IOC_GET_ENCRYPTION_KEY_STATUS], arg ptr[inout, fscrypt_get_key_status_arg])
 ioctl$FS_IOC_GET_ENCRYPTION_NONCE(fd fd, cmd const[FS_IOC_GET_ENCRYPTION_NONCE], arg ptr[out, array[int8, 16]])
 
-type fscrypt_key_descriptor array[int8, FSCRYPT_KEY_DESCRIPTOR_SIZE]
-type fscrypt_key_identifier array[int8, FSCRYPT_KEY_IDENTIFIER_SIZE]
+# Define the types for fscrypt raw keys, key identifiers, and key descriptors.
+#
+# "Key identifiers" are the new way to identify fscrypt keys.  They are 16-byte
+# values that must be computed in a specific way from the raw key.  The
+# FS_IOC_ADD_ENCRYPTION_KEY ioctl will do this computation and return the
+# identifier to userspace, as a side effect of adding a key.  But it's unclear
+# that syzkaller can understand this flow yet (as arrays can't be resources), so
+# we also define some sample keys with precomputed identifiers to use.
+#
+# "Key descriptors" are the old way to identify fscrypt keys.  They are 8-byte
+# values arbitrarily assigned by userspace.
+
+fscrypt_raw_key [
+	auto	array[int8[16:64]]
+# 64-byte keys (usable with aes256, aes128, adiantum)
+	a	stringnoz[`0102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f202122232425262728292a2b2c2d2e2f303132333435363738393a3b3c3d3e3f40`]
+	b	stringnoz["aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa11111111111111111111111111111111"]
+# 32-byte key (usable with aes128, adiantum)
+	c	stringnoz["abcdefghijklmnopqrstuvwxyz0123456"]
+# 16-byte key (usable with aes128 only)
+	d	stringnoz["abcdefghijklmnop"]
+] [varlen]
+
+fscrypt_key_identifier [
+	auto	array[int8, FSCRYPT_KEY_IDENTIFIER_SIZE]
+# These 16-byte values are computed from the raw keys listed above.
+	a	stringnoz[`69b2f6edeee720cce0577937eb8a6751`]
+	b	stringnoz[`912ae510a458723a839a9fad701538ac`]
+	c	stringnoz[`1c2d6754b6cc7daacb599875d7faf9bb`]
+	d	stringnoz[`7eb80af3f24ef086726a4cea3a154ce0`]
+]
+
+fscrypt_key_descriptor [
+	auto	array[int8, FSCRYPT_KEY_DESCRIPTOR_SIZE]
+# These are arbitrary 8-byte values.
+	desc1	stringnoz[`0000111122223333`]
+	desc2	stringnoz[`e355a76a11a1be18`]
+	desc3	stringnoz[`e8dab99234bb312e`]
+	desc4	stringnoz[`85baa174f0cb1142`]
+]
+
+# fscrypt_key_descriptor translated into a hex string
+fscrypt_key_descriptor_hex [
+	auto	array[flags[hex_chars, int8], 16]
+	desc1	stringnoz["0000111122223333"]
+	desc2	stringnoz["e355a76a11a1be18"]
+	desc3	stringnoz["e8dab99234bb312e"]
+	desc4	stringnoz["85baa174f0cb1142"]
+]
 
 # Below are the data structures needed to put keys for fscrypt_policy_v1 in the
 # regular Linux keyrings via the add_key() syscall.  Note that this part of the
@@ -25,12 +72,14 @@ type fscrypt_key_identifier array[int8, FSCRYPT_KEY_IDENTIFIER_SIZE]
 
 fscrypt_v1_key_description {
 	prefix		stringnoz["fscrypt:"]
-	descriptor	array[flags[hex_chars, int8], 16]
+	descriptor	fscrypt_key_descriptor_hex
 	nil		const[0, int8]
 }
 
 fscrypt_v1_key_payload {
 	mode	const[0, int32]
+# This really should be fscrypt_raw_key, but that has the varlen attribute so it
+# doesn't work in this struct.
 	raw	array[int8, 64]
 	size	int32[16:64]
 }
@@ -96,15 +145,15 @@ fscrypt_key_specifier_payload [
 fscrypt_provisioning_key_payload {
 	type		flags[fscrypt_key_specifier_type, int32]
 	reserved	const[0, int32]
-	raw		array[int8]
+	raw		fscrypt_raw_key
 }
 
 fscrypt_add_key_arg {
 	key_spec	fscrypt_key_specifier
-	raw_size	len[raw, int32]
+	raw_size	bytesize[raw, int32]
 	key_id		fscrypt_provisioning_key[opt]	(in)
 	reserved	array[const[0, int32], 8]
-	raw		array[int8]
+	raw		fscrypt_raw_key
 }
 
 fscrypt_remove_key_arg {
-- 
cgit mrf-deployment