Messages in this thread | | | Subject | Re: [PATCH] crypto: rng.c: Cleaning up missing null-terminate in conjunction with strncpy | From | Mark D Rustad <> | Date | Sat, 26 Jul 2014 19:35:22 -0700 |
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Rickard,
On Jul 26, 2014, at 7:18 AM, Rickard Strandqvist <rickard_strandqvist@spectrumdigital.se> wrote:
> Replacing strncpy with strlcpy to avoid strings that lacks null terminate. > > Signed-off-by: Rickard Strandqvist <rickard_strandqvist@spectrumdigital.se> > --- > 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, MRustad@gmail.com
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