From ed282e9a463c068146c945984fdea7828e663861 Mon Sep 17 00:00:00 2001 From: Tobias Brunner 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