[PATCH 5.4 49/92] crypto: ecdh - avoid buffer overflow in ecdh_set_secret()

From: Ard Biesheuvel ardb@kernel.org

commit 0aa171e9b267ce7c52d3a3df7bc9c1fc0203dec5 upstream.

Pavel reports that commit 17858b140bf4 ("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: 17858b140bf4 ("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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- crypto/ecdh.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/crypto/ecdh.c +++ b/crypto/ecdh.c @@ -39,7 +39,8 @@ static int ecdh_set_secret(struct crypto 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);