[PATCH] Extract bch_crypt_update_passphrase function

Mae Kasza
2024-08-13T17:38:28Z

This also fixes a bug where the set-passphrase
command failed to derive the key for disks initially
formatted with --encrypted and --no_passphrase, due to
bch_sb_crypt_init not configuring the KDF params if
the passphrase wasn't specified during formatting.

Signed-off-by: Mae Kasza <git@badat.dev>
---
c_src/cmd_key.c | 26 ++++++++++----------------
c_src/crypto.c | 43 ++++++++++++++++++++++++++++++++-----------
c_src/crypto.h | 3 +++
3 files changed, 45 insertions(+), 27 deletions(-)

diff --git a/c_src/cmd_key.c b/c_src/cmd_key.c
index adb0ac8d..ac8a94a8 100644
--- a/c_src/cmd_key.c
+++ b/c_src/cmd_key.c
@@ -104,24 +104,19 @@ int cmd_set_passphrase(int argc, char *argv[])
if (IS_ERR(c))
die("Error opening %s: %s", argv[1], bch2_err_str(PTR_ERR(c)));

- struct bch_sb_field_crypt *crypt = bch2_sb_field_get(c->disk_sb.sb, crypt);
+ struct bch_sb *sb = c->disk_sb.sb;
+ struct bch_sb_field_crypt *crypt = bch2_sb_field_get(sb, crypt);
if (!crypt)
die("Filesystem does not have encryption enabled");

- struct bch_encrypted_key new_key;
- new_key.magic = BCH_KEY_MAGIC;
-
- int ret = bch2_decrypt_sb_key(c, crypt, &new_key.key);
+ struct bch_key key;
+ int ret = bch2_decrypt_sb_key(c, crypt, &key);
if (ret)
die("Error getting current key");

char *new_passphrase = read_passphrase_twice("Enter new passphrase: ");
- struct bch_key passphrase_key = derive_passphrase(crypt, new_passphrase);

- if (bch2_chacha_encrypt_key(&passphrase_key, __bch2_sb_key_nonce(c->disk_sb.sb),
- &new_key, sizeof(new_key)))
- die("error encrypting key");
- crypt->key = new_key;
+ bch_crypt_update_passphrase(sb, crypt, &key, new_passphrase);

bch2_revoke_key(c->disk_sb.sb);
bch2_write_super(c);
@@ -142,18 +137,17 @@ int cmd_remove_passphrase(int argc, char *argv[])
if (IS_ERR(c))
die("Error opening %s: %s", argv[1], bch2_err_str(PTR_ERR(c)));

- struct bch_sb_field_crypt *crypt = bch2_sb_field_get(c->disk_sb.sb, crypt);
+ struct bch_sb *sb = c->disk_sb.sb;
+ struct bch_sb_field_crypt *crypt = bch2_sb_field_get(sb, crypt);
if (!crypt)
die("Filesystem does not have encryption enabled");

- struct bch_encrypted_key new_key;
- new_key.magic = BCH_KEY_MAGIC;
-
- int ret = bch2_decrypt_sb_key(c, crypt, &new_key.key);
+ struct bch_key key;
+ int ret = bch2_decrypt_sb_key(c, crypt, &key);
if (ret)
die("Error getting current key");

- crypt->key = new_key;
+ bch_crypt_update_passphrase(sb, crypt, &key, NULL);

bch2_write_super(c);
bch2_fs_stop(c);
diff --git a/c_src/crypto.c b/c_src/crypto.c
index 32671bd8..301dbebe 100644
--- a/c_src/crypto.c
+++ b/c_src/crypto.c
@@ -176,26 +176,47 @@ void bch_sb_crypt_init(struct bch_sb *sb,
struct bch_sb_field_crypt *crypt,
const char *passphrase)
{
+ struct bch_key key;
+ get_random_bytes(&key, sizeof(key));
+
crypt->key.magic = BCH_KEY_MAGIC;
- get_random_bytes(&crypt->key.key, sizeof(crypt->key.key));
+ crypt->key.key = key;

- if (passphrase) {
+ bch_crypt_update_passphrase(sb, crypt, &key, passphrase);
+}

+void bch_crypt_update_passphrase(
+ struct bch_sb *sb,
+ struct bch_sb_field_crypt *crypt,
+ struct bch_key *key,
+ const char *new_passphrase)
+{
+
+ struct bch_encrypted_key new_key;
+ new_key.magic = BCH_KEY_MAGIC;
+ new_key.key = *key;
+
+ if(!new_passphrase) {
+ crypt->key = new_key;
+ return;
+ }
+
+ // If crypt already has an encrypted key reuse it's encryption params
+ if (!bch2_key_is_encrypted(&crypt->key)) {
SET_BCH_CRYPT_KDF_TYPE(crypt, BCH_KDF_SCRYPT);
SET_BCH_KDF_SCRYPT_N(crypt, ilog2(16384));
SET_BCH_KDF_SCRYPT_R(crypt, ilog2(8));
SET_BCH_KDF_SCRYPT_P(crypt, ilog2(16));
+ }

- struct bch_key passphrase_key = derive_passphrase(crypt, passphrase);
-
- assert(!bch2_key_is_encrypted(&crypt->key));
+ struct bch_key passphrase_key = derive_passphrase(crypt, new_passphrase);

- if (bch2_chacha_encrypt_key(&passphrase_key, __bch2_sb_key_nonce(sb),
- &crypt->key, sizeof(crypt->key)))
- die("error encrypting key");
+ if (bch2_chacha_encrypt_key(&passphrase_key, __bch2_sb_key_nonce(sb),
+ &new_key, sizeof(new_key)))
+ die("error encrypting key");

- assert(bch2_key_is_encrypted(&crypt->key));
+ memzero_explicit(&passphrase_key, sizeof(passphrase_key));

- memzero_explicit(&passphrase_key, sizeof(passphrase_key));
- }
+ crypt->key = new_key;
+ assert(bch2_key_is_encrypted(&crypt->key));
}
diff --git a/c_src/crypto.h b/c_src/crypto.h
index baea6d86..cd3baac8 100644
--- a/c_src/crypto.h
+++ b/c_src/crypto.h
@@ -19,4 +19,7 @@ void bch2_add_key(struct bch_sb *, const char *, const char *, const char *);
void bch_sb_crypt_init(struct bch_sb *sb, struct bch_sb_field_crypt *,
const char *);

+void bch_crypt_update_passphrase(struct bch_sb *sb, struct bch_sb_field_crypt *crypt,
+ struct bch_key *key, const char *new_passphrase);
+
#endif /* _CRYPTO_H */
--
2.45.2