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From ed282e9a463c068146c945984fdea7828e663861 Mon Sep 17 00:00:00 2001
From: Tobias Brunner <tobias@strongswan.org>
Date: Mon, 29 May 2017 11:59:34 +0200
Subject: [PATCH] gmp: Fix RSA signature verification for m >= n
By definition, m must be <= n-1, we didn't enforce that and because
mpz_export() returns NULL if the passed value is zero a crash could have
been triggered with m == n.
Fixes CVE-2017-11185.
---
src/libstrongswan/plugins/gmp/gmp_rsa_public_key.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/src/libstrongswan/plugins/gmp/gmp_rsa_public_key.c b/src/libstrongswan/plugins/gmp/gmp_rsa_public_key.c
index 32a72ac9600b..a741f85d4f62 100644
--- a/src/libstrongswan/plugins/gmp/gmp_rsa_public_key.c
+++ b/src/libstrongswan/plugins/gmp/gmp_rsa_public_key.c
@@ -78,11 +78,17 @@ static chunk_t rsaep(private_gmp_rsa_public_key_t *this, chunk_t data)
mpz_t m, c;
chunk_t encrypted;
- mpz_init(c);
mpz_init(m);
-
mpz_import(m, data.len, 1, 1, 1, 0, data.ptr);
+ if (mpz_cmp_ui(m, 0) <= 0 || mpz_cmp(m, this->n) >= 0)
+ { /* m must be <= n-1, but 0 is a valid value, doesn't really make sense
+ * here, though */
+ mpz_clear(m);
+ return chunk_empty;
+ }
+
+ mpz_init(c);
mpz_powm(c, m, this->e, this->n);
encrypted.len = this->k;
@@ -150,7 +156,7 @@ static bool verify_emsa_pkcs1_signature(private_gmp_rsa_public_key_t *this,
*/
/* check magic bytes */
- if (*(em.ptr) != 0x00 || *(em.ptr+1) != 0x01)
+ if (em.len < 2 || *(em.ptr) != 0x00 || *(em.ptr+1) != 0x01)
{
goto end;
}
--
2.7.4
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