Replacing strncpy with strlcpy to avoid strings that lacks null terminate.
Signed-off-by: Rickard Strandqvist <[email protected]>
---
crypto/rng.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/crypto/rng.c b/crypto/rng.c
index e0a25c2..c3d4fb3 100644
--- a/crypto/rng.c
+++ b/crypto/rng.c
@@ -65,7 +65,7 @@ static int crypto_rng_report(struct sk_buff *skb, struct crypto_alg *alg)
{
struct crypto_report_rng rrng;
- strncpy(rrng.type, "rng", sizeof(rrng.type));
+ strlcpy(rrng.type, "rng", sizeof(rrng.type));
rrng.seedsize = alg->cra_rng.seedsize;
--
1.7.10.4
Rickard,
On Jul 26, 2014, at 7:18 AM, Rickard Strandqvist <[email protected]> wrote:
> Replacing strncpy with strlcpy to avoid strings that lacks null terminate.
>
> Signed-off-by: Rickard Strandqvist <[email protected]>
> ---
> crypto/rng.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/crypto/rng.c b/crypto/rng.c
> index e0a25c2..c3d4fb3 100644
> --- a/crypto/rng.c
> +++ b/crypto/rng.c
> @@ -65,7 +65,7 @@ static int crypto_rng_report(struct sk_buff *skb, struct crypto_alg *alg)
> {
> struct crypto_report_rng rrng;
>
> - strncpy(rrng.type, "rng", sizeof(rrng.type));
> + strlcpy(rrng.type, "rng", sizeof(rrng.type));
>
> rrng.seedsize = alg->cra_rng.seedsize;
Not to pick on this patch in particular, but you need to be careful about changing strncpy to strlcpy. Although strlcpy ensures termination, it does not prevent information leakage - strncpy ensures that the entire destination buffer is written. When leakage is a concern, it is better to use strncpy and then to store a zero in the last location of the buffer to ensure termination.
These "simple" transformations can be risky - and many of these do not represent any sort of problem when the source is smaller than the destination. I hope information leakage is being considered.
--
Mark Rustad, [email protected]
2014-07-27 4:35 GMT+02:00 Mark D Rustad <[email protected]>:
> Rickard,
>
> On Jul 26, 2014, at 7:18 AM, Rickard Strandqvist <[email protected]> wrote:
>
>> Replacing strncpy with strlcpy to avoid strings that lacks null terminate.
>>
>> Signed-off-by: Rickard Strandqvist <[email protected]>
>> ---
>> crypto/rng.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/crypto/rng.c b/crypto/rng.c
>> index e0a25c2..c3d4fb3 100644
>> --- a/crypto/rng.c
>> +++ b/crypto/rng.c
>> @@ -65,7 +65,7 @@ static int crypto_rng_report(struct sk_buff *skb, struct crypto_alg *alg)
>> {
>> struct crypto_report_rng rrng;
>>
>> - strncpy(rrng.type, "rng", sizeof(rrng.type));
>> + strlcpy(rrng.type, "rng", sizeof(rrng.type));
>>
>> rrng.seedsize = alg->cra_rng.seedsize;
>
> Not to pick on this patch in particular, but you need to be careful about changing strncpy to strlcpy. Although strlcpy ensures termination, it does not prevent information leakage - strncpy ensures that the entire destination buffer is written. When leakage is a concern, it is better to use strncpy and then to store a zero in the last location of the buffer to ensure termination.
>
> These "simple" transformations can be risky - and many of these do not represent any sort of problem when the source is smaller than the destination. I hope information leakage is being considered.
>
Hi Mark
You clearly have a point there! Information leakage is not something I
think about very often otherwise.
It is really unbelievable that C messed up when trying to make a
better solution to strcpy. strncpy doing something completely new with
zeroes whole size but still does not guarantee a terminating null
character. And strlcpy that works great as a replacement for strcpy,
but really can not replace strncpy in all cases. Incredibly stupid!
:-(
But ok, I'll submit a [Patch V2] with foo[sizeof(foo) - 1] = '\ 0'
on all under crypto/ then ?
Kind regards
Rickard Strandqvist