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38 lines
1.5 KiB
38 lines
1.5 KiB
From 129ab919a8c3abfc17bea776f0774e0ccf33ca09 Mon Sep 17 00:00:00 2001
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From: Tobias Brunner <tobias@strongswan.org>
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Date: Tue, 25 Sep 2018 14:50:08 +0200
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Subject: [PATCH] gmp: Fix buffer overflow with very small RSA keys
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Because `keylen` is unsigned the subtraction results in an integer
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underflow if the key length is < 11 bytes.
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This is only a problem when verifying signatures with a public key (for
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private keys the plugin enforces a minimum modulus length) and to do so
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we usually only use trusted keys. However, the x509 plugin actually
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calls issued_by() on a parsed certificate to check if it is self-signed,
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which is the reason this issue was found by OSS-Fuzz in the first place.
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So, unfortunately, this can be triggered by sending an invalid client
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cert to a peer.
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Fixes: 5955db5b124a ("gmp: Don't parse PKCS1 v1.5 RSA signatures to verify them")
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Fixes: CVE-2018-17540
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---
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src/libstrongswan/plugins/gmp/gmp_rsa_private_key.c | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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diff --git a/src/libstrongswan/plugins/gmp/gmp_rsa_private_key.c b/src/libstrongswan/plugins/gmp/gmp_rsa_private_key.c
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index e9a83fdf49a1..a255a40abce2 100644
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--- a/src/libstrongswan/plugins/gmp/gmp_rsa_private_key.c
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+++ b/src/libstrongswan/plugins/gmp/gmp_rsa_private_key.c
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@@ -301,7 +301,7 @@ bool gmp_emsa_pkcs1_signature_data(hash_algorithm_t hash_algorithm,
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data = digestInfo;
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}
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- if (data.len > keylen - 11)
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+ if (keylen < 11 || data.len > keylen - 11)
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{
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chunk_free(&digestInfo);
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DBG1(DBG_LIB, "signature value of %zu bytes is too long for key of "
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--
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2.7.4
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