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crypto: ecdh - avoid buffer overflow in ecdh_set_secret()

Message ID 20210102135909.5637-1-ardb@kernel.org
State New
Headers show
Series crypto: ecdh - avoid buffer overflow in ecdh_set_secret() | expand

Commit Message

Ard Biesheuvel Jan. 2, 2021, 1:59 p.m. UTC 
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>
---
 crypto/ecdh.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
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Patch

diff --git a/crypto/ecdh.c b/crypto/ecdh.c
index d56b8603dec9..96f80c8f8e30 100644
--- a/crypto/ecdh.c
+++ b/crypto/ecdh.c
@@ -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);