From: Eric Biggers <ebiggers@xxxxxxxxxx> Make fscrypt-crypt-util use an option --direct-key to specify the use of the DIRECT_KEY method for key derivation and IV generation. Previously, this method was implicitly detected via --mode-num being given without either --iv-ino-lblk-64 or --iv-ino-lblk-32. The benefit of this change is that it makes the various options to fscrypt-crypt-util behave more consistently. --direct-key, --iv-ino-lblk-64, and --iv-ino-lblk-32 now all work similarly (they select a key derivation and IV generation method); likewise, --mode-num, --file-nonce, --inode-number, and --fs-uuid now all work similarly (they provide information that key derivation and IV generation may need). Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx> --- common/encrypt | 10 ++++---- src/fscrypt-crypt-util.c | 52 ++++++++++++++++++++++++---------------- 2 files changed, 36 insertions(+), 26 deletions(-) diff --git a/common/encrypt b/common/encrypt index f90c4ef0..2cf02ca0 100644 --- a/common/encrypt +++ b/common/encrypt @@ -842,27 +842,25 @@ _verify_ciphertext_for_encryption_policy() set_encpolicy_args+=" -c $contents_mode_num" set_encpolicy_args+=" -n $filenames_mode_num" + crypt_util_contents_args+=" --mode-num=$contents_mode_num" + crypt_util_filename_args+=" --mode-num=$filenames_mode_num" if (( policy_version > 1 )); then set_encpolicy_args+=" -v 2" crypt_util_args+=" --kdf=HKDF-SHA512" if (( policy_flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY )); then - crypt_util_args+=" --mode-num=$contents_mode_num" + crypt_util_args+=" --direct-key" elif (( policy_flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64 )); then crypt_util_args+=" --iv-ino-lblk-64" - crypt_util_contents_args+=" --mode-num=$contents_mode_num" - crypt_util_filename_args+=" --mode-num=$filenames_mode_num" elif (( policy_flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32 )); then crypt_util_args+=" --iv-ino-lblk-32" - crypt_util_contents_args+=" --mode-num=$contents_mode_num" - crypt_util_filename_args+=" --mode-num=$filenames_mode_num" fi else if (( policy_flags & ~FSCRYPT_POLICY_FLAG_DIRECT_KEY )); then _fail "unsupported flags for v1 policy: $policy_flags" fi if (( policy_flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY )); then - crypt_util_args+=" --kdf=none" + crypt_util_args+=" --direct-key --kdf=none" else crypt_util_args+=" --kdf=AES-128-ECB" fi diff --git a/src/fscrypt-crypt-util.c b/src/fscrypt-crypt-util.c index 03cc3c4a..022ff7bd 100644 --- a/src/fscrypt-crypt-util.c +++ b/src/fscrypt-crypt-util.c @@ -64,6 +64,8 @@ static void usage(FILE *fp) " --block-size=BLOCK_SIZE Encrypt each BLOCK_SIZE bytes independently.\n" " Default: 4096 bytes\n" " --decrypt Decrypt instead of encrypt\n" +" --direct-key Use the format where the IVs include the file\n" +" nonce and the same key is shared across files.\n" " --file-nonce=NONCE File's nonce as a 32-character hex string\n" " --fs-uuid=UUID The filesystem UUID as a 32-character hex string.\n" " Required for --iv-ino-lblk-32 and\n" @@ -76,11 +78,10 @@ static void usage(FILE *fp) " 32-bit variant.\n" " --iv-ino-lblk-64 Use the format where the IVs include the inode\n" " number and the same key is shared across files.\n" -" Requires --kdf=HKDF-SHA512, --fs-uuid,\n" -" --inode-number, and --mode-num.\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" +" --mode-num=NUM The encryption mode number. This may be required\n" +" for key derivation, depending on other options.\n" " --padding=PADDING If last block is partial, zero-pad it to next\n" " PADDING-byte boundary. Default: BLOCK_SIZE\n" , fp); @@ -1790,6 +1791,7 @@ struct key_and_iv_params { u8 mode_num; u8 file_nonce[FILE_NONCE_SIZE]; bool file_nonce_specified; + bool direct_key; bool iv_ino_lblk_64; bool iv_ino_lblk_32; u64 block_number; @@ -1835,7 +1837,7 @@ static void get_key_and_iv(const struct key_and_iv_params *params, u8 *real_key, size_t real_key_size, union fscrypt_iv *iv) { - bool file_nonce_in_iv = false; + int iv_methods = 0; struct aes_key aes_key; u8 info[8 + 1 + 1 + UUID_SIZE] = "fscrypt"; size_t infolen = 8; @@ -1848,11 +1850,22 @@ static void get_key_and_iv(const struct key_and_iv_params *params, /* Overridden later for iv_ino_lblk_{64,32} */ iv->block_number = cpu_to_le64(params->block_number); - if (params->iv_ino_lblk_64 || params->iv_ino_lblk_32) { + iv_methods += params->direct_key; + iv_methods += params->iv_ino_lblk_64; + iv_methods += params->iv_ino_lblk_32; + if (iv_methods > 1) + die("Conflicting IV methods specified"); + if (iv_methods != 0 && params->kdf == KDF_AES_128_ECB) + die("--kdf=AES-128-ECB is incompatible with IV method options"); + + if (params->direct_key) { + if (!params->file_nonce_specified) + die("--direct-key requires file nonce"); + if (params->kdf != KDF_NONE && params->mode_num == 0) + die("--direct-key with KDF requires --mode-num"); + } else if (params->iv_ino_lblk_64 || params->iv_ino_lblk_32) { const char *opt = params->iv_ino_lblk_64 ? "--iv-ino-lblk-64" : "--iv-ino-lblk-32"; - if (params->iv_ino_lblk_64 && params->iv_ino_lblk_32) - die("--iv-ino-lblk-64 and --iv-ino-lblk-32 are mutually exclusive"); if (params->kdf != KDF_HKDF_SHA512) die("%s requires --kdf=HKDF-SHA512", opt); if (!params->fs_uuid_specified) @@ -1869,16 +1882,11 @@ static void get_key_and_iv(const struct key_and_iv_params *params, switch (params->kdf) { case KDF_NONE: - if (params->mode_num != 0) - die("--mode-num isn't supported with --kdf=none"); memcpy(real_key, params->master_key, real_key_size); - file_nonce_in_iv = true; break; case KDF_AES_128_ECB: if (!params->file_nonce_specified) - die("--file-nonce is required with --kdf=AES-128-ECB"); - if (params->mode_num != 0) - die("--mode-num isn't supported with --kdf=AES-128-ECB"); + die("--kdf=AES-128-ECB requires --file-nonce"); STATIC_ASSERT(FILE_NONCE_SIZE == AES_128_KEY_SIZE); ASSERT(real_key_size % AES_BLOCK_SIZE == 0); aes_setkey(&aes_key, params->file_nonce, AES_128_KEY_SIZE); @@ -1887,7 +1895,10 @@ static void get_key_and_iv(const struct key_and_iv_params *params, &real_key[i]); break; case KDF_HKDF_SHA512: - if (params->iv_ino_lblk_64) { + if (params->direct_key) { + info[infolen++] = HKDF_CONTEXT_DIRECT_KEY; + info[infolen++] = params->mode_num; + } else if (params->iv_ino_lblk_64) { info[infolen++] = HKDF_CONTEXT_IV_INO_LBLK_64_KEY; info[infolen++] = params->mode_num; memcpy(&info[infolen], params->fs_uuid, UUID_SIZE); @@ -1903,17 +1914,13 @@ static void get_key_and_iv(const struct key_and_iv_params *params, cpu_to_le32(hash_inode_number(params) + params->block_number); iv->inode_number = 0; - } else if (params->mode_num != 0) { - info[infolen++] = HKDF_CONTEXT_DIRECT_KEY; - info[infolen++] = params->mode_num; - file_nonce_in_iv = true; } else if (params->file_nonce_specified) { info[infolen++] = HKDF_CONTEXT_PER_FILE_ENC_KEY; memcpy(&info[infolen], params->file_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"); + die("--kdf=HKDF-SHA512 requires --file-nonce or --iv-ino-lblk-*"); } hkdf_sha512(params->master_key, params->master_key_size, NULL, 0, info, infolen, real_key, real_key_size); @@ -1922,7 +1929,7 @@ static void get_key_and_iv(const struct key_and_iv_params *params, ASSERT(0); } - if (file_nonce_in_iv && params->file_nonce_specified) + if (params->direct_key) memcpy(iv->nonce, params->file_nonce, FILE_NONCE_SIZE); } @@ -1930,6 +1937,7 @@ enum { OPT_BLOCK_NUMBER, OPT_BLOCK_SIZE, OPT_DECRYPT, + OPT_DIRECT_KEY, OPT_FILE_NONCE, OPT_FS_UUID, OPT_HELP, @@ -1945,6 +1953,7 @@ static const struct option longopts[] = { { "block-number", required_argument, NULL, OPT_BLOCK_NUMBER }, { "block-size", required_argument, NULL, OPT_BLOCK_SIZE }, { "decrypt", no_argument, NULL, OPT_DECRYPT }, + { "direct-key", no_argument, NULL, OPT_DIRECT_KEY }, { "file-nonce", required_argument, NULL, OPT_FILE_NONCE }, { "fs-uuid", required_argument, NULL, OPT_FS_UUID }, { "help", no_argument, NULL, OPT_HELP }, @@ -1999,6 +2008,9 @@ int main(int argc, char *argv[]) case OPT_DECRYPT: decrypting = true; break; + case OPT_DIRECT_KEY: + params.direct_key = true; + break; case OPT_FILE_NONCE: if (hex2bin(optarg, params.file_nonce, FILE_NONCE_SIZE) != FILE_NONCE_SIZE) -- 2.35.1
![]() |