[PATCH stable] crypto: chacha20poly1305 - prevent integer overflow on large input

[PATCH stable] crypto: chacha20poly1305 - prevent integer overflow on large input

[Jason A. Donenfeld]

This code assigns src_len (size_t) to sl (int), which causes problems
when src_len is very large. Probably nobody in the kernel should be
passing this much data to chacha20poly1305 all in one go anyway, so I
don't think we need to change the algorithm or introduce larger types
or anything. But we should at least error out early in this case and
print a warning so that we get reports if this does happen and can look
into why anybody is possibly passing it that much data or if they're
accidently passing -1 or similar.

Fixes: d95312a3ccc0 ("crypto: lib/chacha20poly1305 - reimplement crypt_from_sg() routine")
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: stable@vger.kernel.org # 5.5+
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
 lib/crypto/chacha20poly1305.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/lib/crypto/chacha20poly1305.c b/lib/crypto/chacha20poly1305.c
index 6d83cafebc69..ad0699ce702f 100644
--- a/lib/crypto/chacha20poly1305.c
+++ b/lib/crypto/chacha20poly1305.c
@@ -235,6 +235,9 @@ bool chacha20poly1305_crypt_sg_inplace(struct scatterlist *src,
 		__le64 lens[2];
 	} b __aligned(16);
 
+	if (WARN_ON(src_len > INT_MAX))
+		return false;
+
 	chacha_load_key(b.k, key);
 
 	b.iv[0] = 0;
-- 
2.25.0

Re: [PATCH stable] crypto: chacha20poly1305 - prevent integer overflow on large input

[Ard Biesheuvel]

On Thu, 6 Feb 2020 at 11:42, Jason A. Donenfeld <Jason@zx2c4.com> wrote:
>
> This code assigns src_len (size_t) to sl (int), which causes problems
> when src_len is very large. Probably nobody in the kernel should be
> passing this much data to chacha20poly1305 all in one go anyway, so I
> don't think we need to change the algorithm or introduce larger types
> or anything. But we should at least error out early in this case and
> print a warning so that we get reports if this does happen and can look
> into why anybody is possibly passing it that much data or if they're
> accidently passing -1 or similar.
>
> Fixes: d95312a3ccc0 ("crypto: lib/chacha20poly1305 - reimplement crypt_from_sg() routine")
> Cc: Ard Biesheuvel <ardb@kernel.org>
> Cc: stable@vger.kernel.org # 5.5+
> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

Acked-by: Ard Biesheuvel <ardb@kernel.org>

> ---
>  lib/crypto/chacha20poly1305.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/lib/crypto/chacha20poly1305.c b/lib/crypto/chacha20poly1305.c
> index 6d83cafebc69..ad0699ce702f 100644
> --- a/lib/crypto/chacha20poly1305.c
> +++ b/lib/crypto/chacha20poly1305.c
> @@ -235,6 +235,9 @@ bool chacha20poly1305_crypt_sg_inplace(struct scatterlist *src,
>                 __le64 lens[2];
>         } b __aligned(16);
>
> +       if (WARN_ON(src_len > INT_MAX))
> +               return false;
> +
>         chacha_load_key(b.k, key);
>
>         b.iv[0] = 0;
> --
> 2.25.0
>

Re: [PATCH stable] crypto: chacha20poly1305 - prevent integer overflow on large input

[Herbert Xu]

Jason A. Donenfeld <Jason@zx2c4.com> wrote:
> This code assigns src_len (size_t) to sl (int), which causes problems
> when src_len is very large. Probably nobody in the kernel should be
> passing this much data to chacha20poly1305 all in one go anyway, so I
> don't think we need to change the algorithm or introduce larger types
> or anything. But we should at least error out early in this case and
> print a warning so that we get reports if this does happen and can look
> into why anybody is possibly passing it that much data or if they're
> accidently passing -1 or similar.
> 
> Fixes: d95312a3ccc0 ("crypto: lib/chacha20poly1305 - reimplement crypt_from_sg() routine")
> Cc: Ard Biesheuvel <ardb@kernel.org>
> Cc: stable@vger.kernel.org # 5.5+
> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
> ---
> lib/crypto/chacha20poly1305.c | 3 +++
> 1 file changed, 3 insertions(+)

Patch applied.  Thanks.
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt