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