Re: [PATCH] cmd_set_passphrase: initialize KDF parameters

[Hongbo Li <lihongbo22@huawei.com>]

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
>>
> 
>