[RFC PATCH 4/9] common/encrypt: support verifying ciphertext of v2 encryption policies

Eric Biggers
2019-08-12T17:58:48Z

Update _verify_ciphertext_for_encryption_policy() to support v2
encryption policies.

This also required adding HKDF-SHA512 support to fscrypt-crypt-util.

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
common/encrypt | 58 ++++++--
src/fscrypt-crypt-util.c | 304 ++++++++++++++++++++++++++++++++++-----
2 files changed, 316 insertions(+), 46 deletions(-)

diff --git a/common/encrypt b/common/encrypt
index fa6e2672..6a3c469d 100644
--- a/common/encrypt
+++ b/common/encrypt
@@ -379,9 +379,16 @@ _get_encryption_nonce()
# flags: 0x2
# master_key_descriptor: 0000000000000000
# nonce: EFBD18765DF6414EC0A2CD5F91297E12
+ #
+ # Also support the case where the whole xattr is printed as hex,
+ # as is the case for fscrypt_context_v2.
+ #
+ # xattr: e_name_index:9 e_name:c e_name_len:1 e_value_size:40 e_value:
+ # 020104020000000033809BFEBE68A4AD264079B30861DD5E6B9E72D07523C58794ACF52534BAA756
+ #
$DUMP_F2FS_PROG -i $inode $device | awk '
/\<e_name:c\>/ { found = 1 }
- /^nonce:/ && found {
+ (/^nonce:/ || /^[[:xdigit:]]+$/) && found {
print substr($0, length($0) - 31, 32);
found = 0;
}'
@@ -402,6 +409,11 @@ _require_get_encryption_nonce_support()
;;
f2fs)
_require_command "$DUMP_F2FS_PROG" dump.f2fs
+ # For fscrypt_context_v2, we actually need a f2fs-tools version
+ # that has the patch "f2fs-tools: improve xattr value printing"
+ # (https://sourceforge.net/p/linux-f2fs/mailman/message/36648640/).
+ # Otherwise the xattr is incorrectly parsed as v1. But just let
+ # the test fail in that case, as it was an f2fs-tools bug...
;;
*)
_notrun "_get_encryption_nonce() isn't implemented on $FSTYP"
@@ -551,7 +563,7 @@ _do_verify_ciphertext_for_encryption_policy()
local filenames_encryption_mode=$2
local policy_flags=$3
local set_encpolicy_args=$4
- local keydesc=$5
+ local keyspec=$5
local raw_key_hex=$6
local crypt_cmd="src/fscrypt-crypt-util $7"

@@ -573,7 +585,7 @@ _do_verify_ciphertext_for_encryption_policy()
done
dir=$SCRATCH_MNT/encdir
mkdir $dir
- _set_encpolicy $dir $keydesc $set_encpolicy_args -f $policy_flags
+ _set_encpolicy $dir $keyspec $set_encpolicy_args -f $policy_flags
for src in $tmp.testfile_*; do
dst=$dir/${src##*.}
cp $src $dst
@@ -593,7 +605,7 @@ _do_verify_ciphertext_for_encryption_policy()
dir=$SCRATCH_MNT/encdir.pad$padding
mkdir $dir
dir_inode=$(stat -c %i $dir)
- _set_encpolicy $dir $keydesc $set_encpolicy_args \
+ _set_encpolicy $dir $keyspec $set_encpolicy_args \
-f $((policy_flags | padding_flag))
for len in 1 3 15 16 17 32 100 254 255; do
name=$(tr -d -C a-zA-Z0-9 < /dev/urandom | head -c $len)
@@ -667,12 +679,14 @@ _fscrypt_mode_name_to_num()
# policy of the specified type is used.
#
# The first two parameters are the contents and filenames encryption modes to
-# test. Optionally, also specify 'direct' to test the DIRECT_KEY flag.
+# test. Optionally, also specify 'direct' to test the DIRECT_KEY flag, and/or
+# 'v2' to test v2 policies.
_verify_ciphertext_for_encryption_policy()
{
local contents_encryption_mode=$1
local filenames_encryption_mode=$2
local opt
+ local policy_version=1
local policy_flags=0
local set_encpolicy_args=""
local crypt_util_args=""
@@ -680,6 +694,9 @@ _verify_ciphertext_for_encryption_policy()
shift 2
for opt; do
case "$opt" in
+ v2)
+ policy_version=2
+ ;;
direct)
if [ $contents_encryption_mode != \
$filenames_encryption_mode ]; then
@@ -698,10 +715,18 @@ _verify_ciphertext_for_encryption_policy()
set_encpolicy_args+=" -c $contents_mode_num"
set_encpolicy_args+=" -n $filenames_mode_num"

- if (( policy_flags & 0x04 )); then
- crypt_util_args+=" --kdf=none"
+ if (( policy_version > 1 )); then
+ set_encpolicy_args+=" -v 2"
+ crypt_util_args+=" --kdf=HKDF-SHA512"
+ if (( policy_flags & 0x04 )); then
+ crypt_util_args+=" --mode-num=$contents_mode_num"
+ fi
else
- crypt_util_args+=" --kdf=AES-128-ECB"
+ if (( policy_flags & 0x04 )); then
+ crypt_util_args+=" --kdf=none"
+ else
+ crypt_util_args+=" --kdf=AES-128-ECB"
+ fi
fi
set_encpolicy_args=${set_encpolicy_args# }

@@ -710,7 +735,9 @@ _verify_ciphertext_for_encryption_policy()
_require_xfs_io_command "fiemap"
_require_get_encryption_nonce_support
_require_get_ciphertext_filename_support
- _require_command "$KEYCTL_PROG" keyctl
+ if (( policy_version == 1 )); then
+ _require_command "$KEYCTL_PROG" keyctl
+ fi

echo "Creating encryption-capable filesystem" >> $seqres.full
_scratch_mkfs_encrypted &>> $seqres.full
@@ -718,9 +745,14 @@ _verify_ciphertext_for_encryption_policy()

echo "Generating encryption key" >> $seqres.full
local raw_key=$(_generate_raw_encryption_key)
- local keydesc=$(_generate_key_descriptor)
- _new_session_keyring
- _add_session_encryption_key $keydesc $raw_key
+ if (( policy_version > 1 )); then
+ local keyspec=$(_add_enckey $SCRATCH_MNT "$raw_key" \
+ | awk '{print $NF}')
+ else
+ local keyspec=$(_generate_key_descriptor)
+ _new_session_keyring
+ _add_session_encryption_key $keyspec $raw_key
+ fi
local raw_key_hex=$(echo "$raw_key" | tr -d '\\x')

echo
@@ -734,7 +766,7 @@ _verify_ciphertext_for_encryption_policy()
"$filenames_encryption_mode" \
"$policy_flags" \
"$set_encpolicy_args" \
- "$keydesc" \
+ "$keyspec" \
"$raw_key_hex" \
"$crypt_util_args"
}
diff --git a/src/fscrypt-crypt-util.c b/src/fscrypt-crypt-util.c
index 81574a55..f5fd8386 100644
--- a/src/fscrypt-crypt-util.c
+++ b/src/fscrypt-crypt-util.c
@@ -12,11 +12,11 @@
*
* All algorithms are implemented in portable C code to avoid depending on
* libcrypto (OpenSSL), and because some fscrypt-supported algorithms aren't
- * available in libcrypto anyway (e.g. Adiantum). For simplicity, all crypto
- * code here tries to follow the mathematical definitions directly, without
- * optimizing for performance or worrying about following security best
- * practices such as mitigating side-channel attacks. So, only use this program
- * for testing!
+ * available in libcrypto anyway (e.g. Adiantum), or are only supported in
+ * recent versions (e.g. HKDF-SHA512). For simplicity, all crypto code here
+ * tries to follow the mathematical definitions directly, without optimizing for
+ * performance or worrying about following security best practices such as
+ * mitigating side-channel attacks. So, only use this program for testing!
*/

#include <asm/byteorder.h>
@@ -63,8 +63,9 @@ static void usage(FILE *fp)
" --decrypt Decrypt instead of encrypt\n"
" --file-nonce=NONCE File's nonce as a 32-character hex string\n"
" --help Show this help\n"
-" --kdf=KDF Key derivation function to use: AES-128-ECB\n"
-" or none. Default: none\n"
+" --kdf=KDF Key derivation function to use: AES-128-ECB,\n"
+" HKDF-SHA512, or none. Default: none\n"
+" --mode-num=NUM Derive per-mode key using mode number NUM\n"
" --padding=PADDING If last block is partial, zero-pad it to next\n"
" PADDING-byte boundary. Default: BLOCK_SIZE\n"
, fp);
@@ -134,6 +135,11 @@ static inline u32 ror32(u32 v, int n)
return (v >> n) | (v << (32 - n));
}

+static inline u64 ror64(u64 v, int n)
+{
+ return (v >> n) | (v << (64 - n));
+}
+
static inline void xor(u8 *res, const u8 *a, const u8 *b, size_t count)
{
while (count--)
@@ -586,7 +592,7 @@ static void test_aes(void)
#endif /* ENABLE_ALG_TESTS */

/*----------------------------------------------------------------------------*
- * SHA-256 *
+ * SHA-512 and SHA-256 *
*----------------------------------------------------------------------------*/

/*
@@ -594,35 +600,104 @@ static void test_aes(void)
* https://csrc.nist.gov/csrc/media/publications/fips/180/2/archive/2002-08-01/documents/fips180-2withchangenotice.pdf
*/

+#define SHA512_DIGEST_SIZE 64
+#define SHA512_BLOCK_SIZE 128
+
#define SHA256_DIGEST_SIZE 32
#define SHA256_BLOCK_SIZE 64

#define Ch(x, y, z) (((x) & (y)) ^ (~(x) & (z)))
#define Maj(x, y, z) (((x) & (y)) ^ ((x) & (z)) ^ ((y) & (z)))
+
+#define Sigma512_0(x) (ror64((x), 28) ^ ror64((x), 34) ^ ror64((x), 39))
+#define Sigma512_1(x) (ror64((x), 14) ^ ror64((x), 18) ^ ror64((x), 41))
+#define sigma512_0(x) (ror64((x), 1) ^ ror64((x), 8) ^ ((x) >> 7))
+#define sigma512_1(x) (ror64((x), 19) ^ ror64((x), 61) ^ ((x) >> 6))
+
#define Sigma256_0(x) (ror32((x), 2) ^ ror32((x), 13) ^ ror32((x), 22))
#define Sigma256_1(x) (ror32((x), 6) ^ ror32((x), 11) ^ ror32((x), 25))
#define sigma256_0(x) (ror32((x), 7) ^ ror32((x), 18) ^ ((x) >> 3))
#define sigma256_1(x) (ror32((x), 17) ^ ror32((x), 19) ^ ((x) >> 10))

-static const u32 sha256_iv[8] = {
- 0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a, 0x510e527f, 0x9b05688c,
- 0x1f83d9ab, 0x5be0cd19,
+static const u64 sha512_iv[8] = {
+ 0x6a09e667f3bcc908, 0xbb67ae8584caa73b, 0x3c6ef372fe94f82b,
+ 0xa54ff53a5f1d36f1, 0x510e527fade682d1, 0x9b05688c2b3e6c1f,
+ 0x1f83d9abfb41bd6b, 0x5be0cd19137e2179,
};

-static const u32 sha256_round_constants[64] = {
- 0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1,
- 0x923f82a4, 0xab1c5ed5, 0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3,
- 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174, 0xe49b69c1, 0xefbe4786,
- 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
- 0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147,
- 0x06ca6351, 0x14292967, 0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13,
- 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85, 0xa2bfe8a1, 0xa81a664b,
- 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
- 0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a,
- 0x5b9cca4f, 0x682e6ff3, 0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208,
- 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2,
+static const u64 sha512_round_constants[80] = {
+ 0x428a2f98d728ae22, 0x7137449123ef65cd, 0xb5c0fbcfec4d3b2f,
+ 0xe9b5dba58189dbbc, 0x3956c25bf348b538, 0x59f111f1b605d019,
+ 0x923f82a4af194f9b, 0xab1c5ed5da6d8118, 0xd807aa98a3030242,
+ 0x12835b0145706fbe, 0x243185be4ee4b28c, 0x550c7dc3d5ffb4e2,
+ 0x72be5d74f27b896f, 0x80deb1fe3b1696b1, 0x9bdc06a725c71235,
+ 0xc19bf174cf692694, 0xe49b69c19ef14ad2, 0xefbe4786384f25e3,
+ 0x0fc19dc68b8cd5b5, 0x240ca1cc77ac9c65, 0x2de92c6f592b0275,
+ 0x4a7484aa6ea6e483, 0x5cb0a9dcbd41fbd4, 0x76f988da831153b5,
+ 0x983e5152ee66dfab, 0xa831c66d2db43210, 0xb00327c898fb213f,
+ 0xbf597fc7beef0ee4, 0xc6e00bf33da88fc2, 0xd5a79147930aa725,
+ 0x06ca6351e003826f, 0x142929670a0e6e70, 0x27b70a8546d22ffc,
+ 0x2e1b21385c26c926, 0x4d2c6dfc5ac42aed, 0x53380d139d95b3df,
+ 0x650a73548baf63de, 0x766a0abb3c77b2a8, 0x81c2c92e47edaee6,
+ 0x92722c851482353b, 0xa2bfe8a14cf10364, 0xa81a664bbc423001,
+ 0xc24b8b70d0f89791, 0xc76c51a30654be30, 0xd192e819d6ef5218,
+ 0xd69906245565a910, 0xf40e35855771202a, 0x106aa07032bbd1b8,
+ 0x19a4c116b8d2d0c8, 0x1e376c085141ab53, 0x2748774cdf8eeb99,
+ 0x34b0bcb5e19b48a8, 0x391c0cb3c5c95a63, 0x4ed8aa4ae3418acb,
+ 0x5b9cca4f7763e373, 0x682e6ff3d6b2b8a3, 0x748f82ee5defb2fc,
+ 0x78a5636f43172f60, 0x84c87814a1f0ab72, 0x8cc702081a6439ec,
+ 0x90befffa23631e28, 0xa4506cebde82bde9, 0xbef9a3f7b2c67915,
+ 0xc67178f2e372532b, 0xca273eceea26619c, 0xd186b8c721c0c207,
+ 0xeada7dd6cde0eb1e, 0xf57d4f7fee6ed178, 0x06f067aa72176fba,
+ 0x0a637dc5a2c898a6, 0x113f9804bef90dae, 0x1b710b35131c471b,
+ 0x28db77f523047d84, 0x32caab7b40c72493, 0x3c9ebe0a15c9bebc,
+ 0x431d67c49c100d4c, 0x4cc5d4becb3e42b6, 0x597f299cfc657e2a,
+ 0x5fcb6fab3ad6faec, 0x6c44198c4a475817,
};

+/* Compute the SHA-512 digest of the given buffer */
+static void sha512(const u8 *in, size_t inlen, u8 out[SHA512_DIGEST_SIZE])
+{
+ const size_t msglen = ROUND_UP(inlen + 17, SHA512_BLOCK_SIZE);
+ u8 * const msg = xmalloc(msglen);
+ u64 H[8];
+ int i;
+
+ /* super naive way of handling the padding */
+ memcpy(msg, in, inlen);
+ memset(&msg[inlen], 0, msglen - inlen);
+ msg[inlen] = 0x80;
+ put_unaligned_be64((u64)inlen * 8, &msg[msglen - sizeof(__be64)]);
+ in = msg;
+
+ memcpy(H, sha512_iv, sizeof(H));
+ do {
+ u64 a = H[0], b = H[1], c = H[2], d = H[3],
+ e = H[4], f = H[5], g = H[6], h = H[7];
+ u64 W[80];
+
+ for (i = 0; i < 16; i++)
+ W[i] = get_unaligned_be64(&in[i * sizeof(__be64)]);
+ for (; i < ARRAY_SIZE(W); i++)
+ W[i] = sigma512_1(W[i - 2]) + W[i - 7] +
+ sigma512_0(W[i - 15]) + W[i - 16];
+ for (i = 0; i < ARRAY_SIZE(W); i++) {
+ u64 T1 = h + Sigma512_1(e) + Ch(e, f, g) +
+ sha512_round_constants[i] + W[i];
+ u64 T2 = Sigma512_0(a) + Maj(a, b, c);
+
+ h = g; g = f; f = e; e = d + T1;
+ d = c; c = b; b = a; a = T1 + T2;
+ }
+ H[0] += a; H[1] += b; H[2] += c; H[3] += d;
+ H[4] += e; H[5] += f; H[6] += g; H[7] += h;
+ } while ((in += SHA512_BLOCK_SIZE) != &msg[msglen]);
+
+ for (i = 0; i < ARRAY_SIZE(H); i++)
+ put_unaligned_be64(H[i], &out[i * sizeof(__be64)]);
+ free(msg);
+}
+
/* Compute the SHA-256 digest of the given buffer */
static void sha256(const u8 *in, size_t inlen, u8 out[SHA256_DIGEST_SIZE])
{
@@ -638,7 +713,8 @@ static void sha256(const u8 *in, size_t inlen, u8 out[SHA256_DIGEST_SIZE])
put_unaligned_be64((u64)inlen * 8, &msg[msglen - sizeof(__be64)]);
in = msg;

- memcpy(H, sha256_iv, sizeof(H));
+ for (i = 0; i < ARRAY_SIZE(H); i++)
+ H[i] = (u32)(sha512_iv[i] >> 32);
do {
u32 a = H[0], b = H[1], c = H[2], d = H[3],
e = H[4], f = H[5], g = H[6], h = H[7];
@@ -651,7 +727,7 @@ static void sha256(const u8 *in, size_t inlen, u8 out[SHA256_DIGEST_SIZE])
sigma256_0(W[i - 15]) + W[i - 16];
for (i = 0; i < ARRAY_SIZE(W); i++) {
u32 T1 = h + Sigma256_1(e) + Ch(e, f, g) +
- sha256_round_constants[i] + W[i];
+ (u32)(sha512_round_constants[i] >> 32) + W[i];
u32 T2 = Sigma256_0(a) + Maj(a, b, c);

h = g; g = f; f = e; e = d + T1;
@@ -674,8 +750,8 @@ static void test_sha2(void)

while (num_tests--) {
u8 in[4096];
- u8 digest[SHA256_DIGEST_SIZE];
- u8 ref_digest[SHA256_DIGEST_SIZE];
+ u8 digest[SHA512_DIGEST_SIZE];
+ u8 ref_digest[SHA512_DIGEST_SIZE];
const size_t inlen = rand() % (1 + sizeof(in));

rand_bytes(in, inlen);
@@ -683,6 +759,124 @@ static void test_sha2(void)
sha256(in, inlen, digest);
SHA256(in, inlen, ref_digest);
ASSERT(memcmp(digest, ref_digest, SHA256_DIGEST_SIZE) == 0);
+
+ sha512(in, inlen, digest);
+ SHA512(in, inlen, ref_digest);
+ ASSERT(memcmp(digest, ref_digest, SHA512_DIGEST_SIZE) == 0);
+ }
+}
+#endif /* ENABLE_ALG_TESTS */
+
+/*----------------------------------------------------------------------------*
+ * HKDF implementation *
+ *----------------------------------------------------------------------------*/
+
+static void hmac_sha512(const u8 *key, size_t keylen, const u8 *msg,
+ size_t msglen, u8 mac[SHA512_DIGEST_SIZE])
+{
+ u8 *ibuf = xmalloc(SHA512_BLOCK_SIZE + msglen);
+ u8 obuf[SHA512_BLOCK_SIZE + SHA512_DIGEST_SIZE];
+
+ ASSERT(keylen <= SHA512_BLOCK_SIZE); /* keylen > bs not implemented */
+
+ memset(ibuf, 0x36, SHA512_BLOCK_SIZE);
+ xor(ibuf, ibuf, key, keylen);
+ memcpy(&ibuf[SHA512_BLOCK_SIZE], msg, msglen);
+
+ memset(obuf, 0x5c, SHA512_BLOCK_SIZE);
+ xor(obuf, obuf, key, keylen);
+ sha512(ibuf, SHA512_BLOCK_SIZE + msglen, &obuf[SHA512_BLOCK_SIZE]);
+ sha512(obuf, sizeof(obuf), mac);
+
+ free(ibuf);
+}
+
+static void hkdf_sha512(const u8 *ikm, size_t ikmlen,
+ const u8 *salt, size_t saltlen,
+ const u8 *info, size_t infolen,
+ u8 *output, size_t outlen)
+{
+ static const u8 default_salt[SHA512_DIGEST_SIZE];
+ u8 prk[SHA512_DIGEST_SIZE]; /* pseudorandom key */
+ u8 *buf = xmalloc(1 + infolen + SHA512_DIGEST_SIZE);
+ u8 counter = 1;
+ size_t i;
+
+ if (saltlen == 0) {
+ salt = default_salt;
+ saltlen = sizeof(default_salt);
+ }
+
+ /* HKDF-Extract */
+ ASSERT(ikmlen > 0);
+ hmac_sha512(salt, saltlen, ikm, ikmlen, prk);
+
+ /* HKDF-Expand */
+ for (i = 0; i < outlen; i += SHA512_DIGEST_SIZE) {
+ u8 *p = buf;
+ u8 tmp[SHA512_DIGEST_SIZE];
+
+ ASSERT(counter != 0);
+ if (i > 0) {
+ memcpy(p, &output[i - SHA512_DIGEST_SIZE],
+ SHA512_DIGEST_SIZE);
+ p += SHA512_DIGEST_SIZE;
+ }
+ memcpy(p, info, infolen);
+ p += infolen;
+ *p++ = counter++;
+ hmac_sha512(prk, sizeof(prk), buf, p - buf, tmp);
+ memcpy(&output[i], tmp, MIN(sizeof(tmp), outlen - i));
+ }
+ free(buf);
+}
+
+#ifdef ENABLE_ALG_TESTS
+#include <openssl/evp.h>
+#include <openssl/kdf.h>
+static void openssl_hkdf_sha512(const u8 *ikm, size_t ikmlen,
+ const u8 *salt, size_t saltlen,
+ const u8 *info, size_t infolen,
+ u8 *output, size_t outlen)
+{
+ EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_HKDF, NULL);
+ size_t actual_outlen = outlen;
+
+ ASSERT(pctx != NULL);
+ ASSERT(EVP_PKEY_derive_init(pctx) > 0);
+ ASSERT(EVP_PKEY_CTX_set_hkdf_md(pctx, EVP_sha512()) > 0);
+ ASSERT(EVP_PKEY_CTX_set1_hkdf_key(pctx, ikm, ikmlen) > 0);
+ ASSERT(EVP_PKEY_CTX_set1_hkdf_salt(pctx, salt, saltlen) > 0);
+ ASSERT(EVP_PKEY_CTX_add1_hkdf_info(pctx, info, infolen) > 0);
+ ASSERT(EVP_PKEY_derive(pctx, output, &actual_outlen) > 0);
+ ASSERT(actual_outlen == outlen);
+ EVP_PKEY_CTX_free(pctx);
+}
+
+static void test_hkdf_sha512(void)
+{
+ unsigned long num_tests = NUM_ALG_TEST_ITERATIONS;
+
+ while (num_tests--) {
+ u8 ikm[SHA512_DIGEST_SIZE];
+ u8 salt[SHA512_DIGEST_SIZE];
+ u8 info[128];
+ u8 actual_output[512];
+ u8 expected_output[sizeof(actual_output)];
+ size_t ikmlen = 1 + (rand() % sizeof(ikm));
+ size_t saltlen = rand() % (1 + sizeof(salt));
+ size_t infolen = rand() % (1 + sizeof(info));
+ size_t outlen = rand() % (1 + sizeof(actual_output));
+
+ rand_bytes(ikm, ikmlen);
+ rand_bytes(salt, saltlen);
+ rand_bytes(info, infolen);
+
+ hkdf_sha512(ikm, ikmlen, salt, saltlen, info, infolen,
+ actual_output, outlen);
+ openssl_hkdf_sha512(ikm, ikmlen, salt, saltlen, info, infolen,
+ expected_output, outlen);
+ ASSERT(memcmp(actual_output, expected_output, outlen) == 0);
}
}
#endif /* ENABLE_ALG_TESTS */
@@ -1476,6 +1670,7 @@ static void crypt_loop(const struct fscrypt_cipher *cipher, const u8 *key,
enum kdf_algorithm {
KDF_NONE,
KDF_AES_128_ECB,
+ KDF_HKDF_SHA512,
};

static enum kdf_algorithm parse_kdf_algorithm(const char *arg)
@@ -1484,21 +1679,36 @@ static enum kdf_algorithm parse_kdf_algorithm(const char *arg)
return KDF_NONE;
if (strcmp(arg, "AES-128-ECB") == 0)
return KDF_AES_128_ECB;
+ if (strcmp(arg, "HKDF-SHA512") == 0)
+ return KDF_HKDF_SHA512;
die("Unknown KDF: %s", arg);
}

+static u8 parse_mode_number(const char *arg)
+{
+ char *tmp;
+ long num = strtol(arg, &tmp, 10);
+
+ if (num <= 0 || *tmp || (u8)num != num)
+ die("Invalid mode number: %s", arg);
+ return num;
+}
+
/*
* Get the key and starting IV with which the encryption will actually be done.
- * If a KDF was specified, a subkey is derived from the master key and file
- * nonce. Otherwise, the master key is used directly.
+ * If a KDF was specified, a subkey is derived from the master key and the mode
+ * number or file nonce. Otherwise, the master key is used directly.
*/
static void get_key_and_iv(const u8 *master_key, size_t master_key_size,
enum kdf_algorithm kdf,
- const u8 nonce[FILE_NONCE_SIZE],
+ u8 mode_num, const u8 nonce[FILE_NONCE_SIZE],
u8 *real_key, size_t real_key_size,
struct fscrypt_iv *iv)
{
+ bool nonce_in_iv = false;
struct aes_key aes_key;
+ u8 info[8 + 1 + FILE_NONCE_SIZE] = "fscrypt";
+ size_t infolen = 8;
size_t i;

ASSERT(real_key_size <= master_key_size);
@@ -1507,22 +1717,43 @@ static void get_key_and_iv(const u8 *master_key, size_t master_key_size,

switch (kdf) {
case KDF_NONE:
+ if (mode_num != 0)
+ die("--mode-num isn't supported with --kdf=none");
memcpy(real_key, master_key, real_key_size);
- if (nonce != NULL)
- memcpy(&iv->bytes[8], nonce, FILE_NONCE_SIZE);
+ nonce_in_iv = true;
break;
case KDF_AES_128_ECB:
if (nonce == NULL)
die("--file-nonce is required with --kdf=AES-128-ECB");
+ if (mode_num != 0)
+ die("--mode-num isn't supported with --kdf=AES-128-ECB");
STATIC_ASSERT(FILE_NONCE_SIZE == AES_128_KEY_SIZE);
ASSERT(real_key_size % AES_BLOCK_SIZE == 0);
aes_setkey(&aes_key, nonce, AES_128_KEY_SIZE);
for (i = 0; i < real_key_size; i += AES_BLOCK_SIZE)
aes_encrypt(&aes_key, &master_key[i], &real_key[i]);
break;
+ case KDF_HKDF_SHA512:
+ if (mode_num != 0) {
+ info[infolen++] = 3; /* HKDF_CONTEXT_PER_MODE_KEY */
+ info[infolen++] = mode_num;
+ nonce_in_iv = true;
+ } else if (nonce != NULL) {
+ info[infolen++] = 2; /* HKDF_CONTEXT_PER_FILE_KEY */
+ memcpy(&info[infolen], nonce, FILE_NONCE_SIZE);
+ infolen += FILE_NONCE_SIZE;
+ } else {
+ die("With --kdf=HKDF-SHA512, at least one of --file-nonce and --mode-num must be specified");
+ }
+ hkdf_sha512(master_key, master_key_size, NULL, 0,
+ info, infolen, real_key, real_key_size);
+ break;
default:
ASSERT(0);
}
+
+ if (nonce_in_iv && nonce != NULL)
+ memcpy(&iv->bytes[8], nonce, FILE_NONCE_SIZE);
}

enum {
@@ -1531,6 +1762,7 @@ enum {
OPT_FILE_NONCE,
OPT_HELP,
OPT_KDF,
+ OPT_MODE_NUM,
OPT_PADDING,
};

@@ -1540,6 +1772,7 @@ static const struct option longopts[] = {
{ "file-nonce", required_argument, NULL, OPT_FILE_NONCE },
{ "help", no_argument, NULL, OPT_HELP },
{ "kdf", required_argument, NULL, OPT_KDF },
+ { "mode-num", required_argument, NULL, OPT_MODE_NUM },
{ "padding", required_argument, NULL, OPT_PADDING },
{ NULL, 0, NULL, 0 },
};
@@ -1551,6 +1784,7 @@ int main(int argc, char *argv[])
u8 _file_nonce[FILE_NONCE_SIZE];
u8 *file_nonce = NULL;
enum kdf_algorithm kdf = KDF_NONE;
+ u8 mode_num = 0;
size_t padding = 0;
const struct fscrypt_cipher *cipher;
u8 master_key[MAX_KEY_SIZE];
@@ -1565,6 +1799,7 @@ int main(int argc, char *argv[])
#ifdef ENABLE_ALG_TESTS
test_aes();
test_sha2();
+ test_hkdf_sha512();
test_aes_256_xts();
test_aes_256_cts_cbc();
test_adiantum();
@@ -1592,6 +1827,9 @@ int main(int argc, char *argv[])
case OPT_KDF:
kdf = parse_kdf_algorithm(optarg);
break;
+ case OPT_MODE_NUM:
+ mode_num = parse_mode_number(optarg);
+ break;
case OPT_PADDING:
padding = strtoul(optarg, &tmp, 10);
if (padding <= 0 || *tmp || !is_power_of_2(padding) ||
@@ -1625,7 +1863,7 @@ int main(int argc, char *argv[])
if (master_key_size < cipher->keysize)
die("Master key is too short for cipher %s", cipher->name);

- get_key_and_iv(master_key, master_key_size, kdf, file_nonce,
+ get_key_and_iv(master_key, master_key_size, kdf, mode_num, file_nonce,
real_key, cipher->keysize, &iv);

crypt_loop(cipher, real_key, &iv, decrypting, block_size, padding);