Re: [PATCH] cmd_set_passphrase: initialize KDF parameters

Mae Kasza
2024-08-13T13:16:43Z

On 8/12/24 04:50, Hongbo Li wrote:
>
>
> 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
>
bch_sb_crypt_init also reinitializes the crypt->key, so I can't just
reuse it here.

I could extract it into a bch_crypt_update_passphrase function.
Originally I wanted to avoid doing that to limit the scope of this
patchset, but I'll give it a shot

Thanks for the review!

Mae

>>> +    }
>>> +
>>>       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
>>>
>>
>>
>