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[4/4] crypto: dh - don't permit 'key' or 'g' size longer than 'p'

Message ID 20171101222517.41602-5-ebiggers3@gmail.com (mailing list archive)
State Superseded
Delegated to: Herbert Xu
Headers show

Commit Message

Eric Biggers Nov. 1, 2017, 10:25 p.m. UTC 
From: Eric Biggers <ebiggers@google.com>

The "qat-dh" DH implementation assumes that 'key' and 'g' can be copied
into a buffer with size 'p_size'.  However it was never checked that
that was actually the case, which allowed users to cause a buffer
underflow via KEYCTL_DH_COMPUTE.

Fix this by updating crypto_dh_decode_key() to verify this precondition
for all DH implementations.

Fixes: c9839143ebbf ("crypto: qat - Add DH support")
Cc: <stable@vger.kernel.org> # v4.8+
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 crypto/dh_helper.c | 8 ++++++++
 1 file changed, 8 insertions(+)
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Patch

diff --git a/crypto/dh_helper.c b/crypto/dh_helper.c
index 708ae20d2d3c..7f00c771fe8d 100644
--- a/crypto/dh_helper.c
+++ b/crypto/dh_helper.c
@@ -83,6 +83,14 @@  int crypto_dh_decode_key(const char *buf, unsigned int len, struct dh *params)
 	if (secret.len != crypto_dh_key_len(params))
 		return -EINVAL;
 
+	/*
+	 * Don't permit the buffer for 'key' or 'g' to be larger than 'p', since
+	 * some drivers assume otherwise.
+	 */
+	if (params->key_size > params->p_size ||
+	    params->g_size > params->p_size)
+		return -EINVAL;
+
 	/* Don't allocate memory. Set pointers to data within
 	 * the given buffer
 	 */