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crypto: ecdh - avoid buffer overflow in ecdh_set_secret()

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Pavel reports that commit 17858b140b ("crypto: ecdh - avoid unaligned
accesses in ecdh_set_secret()") fixes one problem but introduces another:
the unconditional memcpy() introduced by that commit may overflow the
target buffer if the source data is invalid, which could be the result of
intentional tampering.

So check params.key_size explicitly against the size of the target buffer
before validating the key further.

Fixes: 17858b140b ("crypto: ecdh - avoid unaligned accesses in ecdh_set_secret()")
Reported-by: Pavel Machek <pavel@denx.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Ard Biesheuvel 2021-01-02 14:59:09 +01:00 committed by Herbert Xu
parent fd16931a2f
commit 0aa171e9b2
1 changed files with 2 additions and 1 deletions
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3
crypto/ecdh.c
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@ -39,7 +39,8 @@ static int ecdh_set_secret(struct crypto_kpp *tfm, const void *buf,
struct ecdh params;
unsigned int ndigits;
if (crypto_ecdh_decode_key(buf, len, &params) < 0)
if (crypto_ecdh_decode_key(buf, len, &params) < 0 ||
params.key_size > sizeof(ctx->private_key))
return -EINVAL;
ndigits = ecdh_supported_curve(params.curve_id);