Re: [PATCH] Extract bch_crypt_update_passphrase function

Hongbo Li
2024-08-14T02:22:00Z

On 2024/8/14 1:37, Mae Kasza wrote:
> 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;
May be the helper like this is needed. But we could assign the
crypt->key outside, which seems more reasonable according to the helper
name. Just in my humble opinion.

Thanks,
Hongbo

> + 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 */