Re: [PATCH] cmd_set_passphrase: initialize KDF parameters

Hongbo Li
2024-08-12T02:50:42Z

On 2024/8/12 9:41, Kent Overstreet wrote:
> On Sun, Aug 11, 2024 at 11:40:38PM GMT, Mae Kasza wrote:
>> From: mae <git@badat.dev>
>>
>> The set-passphrase command failed to derive the key for disks initially
>> formatted with --encrypted and --no_passphrase.
>>
>> This happened because bch_sb_crypt_init only configures the KDF params
>> if a passphrase is specified.
>> This commit makes the command initialize the KDF with the same parameters
>> as bch_sb_crypt_init if the key wasn't encrypted before.
>>
>> Signed-off-by: Mae Kasza <git@badat.dev>
>
> This looks good to me, but I'm in the middle of a 20 hour drive and not
> feeling super confident to review crypto stuff tonight, so maybe someone
> else can go over it too before I pull it in..
>
>> ---
>> c_src/cmd_key.c | 9 +++++++--
>> c_src/crypto.c | 13 ++++++++-----
>> c_src/crypto.h | 1 +
>> 3 files changed, 16 insertions(+), 7 deletions(-)
>>
>> diff --git a/c_src/cmd_key.c b/c_src/cmd_key.c
>> index adb0ac8d..2da83758 100644
>> --- a/c_src/cmd_key.c
>> +++ b/c_src/cmd_key.c
>> @@ -104,7 +104,8 @@ 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");
>>
>> @@ -116,9 +117,13 @@ int cmd_set_passphrase(int argc, char *argv[])
>> die("Error getting current key");
>>
>> char *new_passphrase = read_passphrase_twice("Enter new passphrase: ");
>> + if (!bch2_key_is_encrypted(&crypt->key)) {
>> + bch_crypt_default_kdf_init(crypt);
It works, but using bch_sb_crypt_init to reinitialize crypt may be
better. In bch_sb_crypt_init, it has initialized the crypt and also
cleaned new_passphrase.

Thanks
Hongbo

>> + }
>> +
>> 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),
>> + if (bch2_chacha_encrypt_key(&passphrase_key, __bch2_sb_key_nonce(sb),
>> &new_key, sizeof(new_key)))
>> die("error encrypting key");
>> crypt->key = new_key;
>> diff --git a/c_src/crypto.c b/c_src/crypto.c
>> index 32671bd8..30ad92d4 100644
>> --- a/c_src/crypto.c
>> +++ b/c_src/crypto.c
>> @@ -180,11 +180,7 @@ void bch_sb_crypt_init(struct bch_sb *sb,
>> get_random_bytes(&crypt->key.key, sizeof(crypt->key.key));
>>
>> if (passphrase) {
>> -
>> - 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));
>> + bch_crypt_default_kdf_init(crypt);
>>
>> struct bch_key passphrase_key = derive_passphrase(crypt, passphrase);
>>
>> @@ -199,3 +195,10 @@ void bch_sb_crypt_init(struct bch_sb *sb,
>> memzero_explicit(&passphrase_key, sizeof(passphrase_key));
>> }
>> }
>> +
>> +void bch_crypt_default_kdf_init(struct bch_sb_field_crypt *crypt) {
>> + 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));
>> +}
>> diff --git a/c_src/crypto.h b/c_src/crypto.h
>> index baea6d86..846a8931 100644
>> --- a/c_src/crypto.h
>> +++ b/c_src/crypto.h
>> @@ -18,5 +18,6 @@ void bch2_passphrase_check(struct bch_sb *, const char *,
>> 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_default_kdf_init(struct bch_sb_field_crypt *);
>>
>> #endif /* _CRYPTO_H */
>> --
>> 2.45.2
>>
>
>