linux-kernel - Re: [PATCH v2] crypto: ecc - Prevent ecc_digits_from

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Date: Mon, 29 Apr 2024 12:57:21 -0400
From: Stefan Berger <stefanb@...ux.ibm.com>
To: Jarkko Sakkinen <jarkko@...nel.org>, keyrings@...r.kernel.org,
        linux-crypto@...r.kernel.org, herbert@...dor.apana.org.au,
        davem@...emloft.net
Cc: linux-kernel@...r.kernel.org, lukas@...ner.de
Subject: Re: [PATCH v2] crypto: ecc - Prevent ecc_digits_from_bytes from
 reading too many bytes



On 4/29/24 12:47, Jarkko Sakkinen wrote:
> On Mon Apr 29, 2024 at 7:13 PM EEST, Stefan Berger wrote:
>> Prevent ecc_digits_from_bytes from reading too many bytes from the input
>> byte array in case an insufficient number of bytes is provided to fill the
>> output digit array of ndigits. Therefore, initialize the most significant
>> digits with 0 to avoid trying to read too many bytes later on. Convert the
>> function into a regular function since it is getting too big for an inline
>> function.
>>
>> If too many bytes are provided on the input byte array the extra bytes
>> are ignored since the input variable 'ndigits' limits the number of digits
>> that will be filled.
>>
>> Fixes: d67c96fb97b5 ("crypto: ecdsa - Convert byte arrays with key coordinates to digits")
>> Signed-off-by: Stefan Berger <stefanb@...ux.ibm.com>
>>
>> ---
>>
>> v2:
>>   - un-inline function
>>   - use memset
>> ---
>>   crypto/ecc.c                  | 22 ++++++++++++++++++++++
>>   include/crypto/internal/ecc.h | 15 ++-------------
>>   2 files changed, 24 insertions(+), 13 deletions(-)
>>
>> diff --git a/crypto/ecc.c b/crypto/ecc.c
>> index c1d2e884be1e..fe761256e335 100644
>> --- a/crypto/ecc.c
>> +++ b/crypto/ecc.c
>> @@ -68,6 +68,28 @@ const struct ecc_curve *ecc_get_curve(unsigned int curve_id)
>>   }
>>   EXPORT_SYMBOL(ecc_get_curve);
>>   
> 
> Just a minor nit:
> 
> For exported symbol you need to document the function,including
> the parameters [1].

Like other functions, the ecc_digits_from_bytes also still/already has 
the documentation in the header file:

/**
  * ecc_digits_from_bytes() - Create ndigits-sized digits array from 
byte array
  * @in:       Input byte array
  * @nbytes    Size of input byte array
  * @out       Output digits array
  * @ndigits:  Number of digits to create from byte array
  */
void ecc_digits_from_bytes(const u8 *in, unsigned int nbytes,
                            u64 *out, unsigned int ndigits);

  Should be ok?