Fix Timing Oracle in RSA decryption

A timing based side channel exists in the OpenSSL RSA Decryption
implementation which could be sufficient to recover a plaintext across
a network in a Bleichenbacher style attack. To achieve a successful
decryption an attacker would have to be able to send a very large number
of trial messages for decryption. The vulnerability affects all RSA
padding modes: PKCS#1 v1.5, RSA-OEAP and RSASVE.

Patch written by Dmitry Belyavsky and Hubert Kario

CVE-2022-4304

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>

Author: beldmit

crypto/bn/bn_blind.c

@@ -13,20 +13,6 @@
 
 #define BN_BLINDING_COUNTER     32
 
-struct bn_blinding_st {
-    BIGNUM *A;
-    BIGNUM *Ai;
-    BIGNUM *e;
-    BIGNUM *mod;                /* just a reference */
-    CRYPTO_THREAD_ID tid;
-    int counter;
-    unsigned long flags;
-    BN_MONT_CTX *m_ctx;
-    int (*bn_mod_exp) (BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
-                       const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx);
-    CRYPTO_RWLOCK *lock;
-};
-
 BN_BLINDING *BN_BLINDING_new(const BIGNUM *A, const BIGNUM *Ai, BIGNUM *mod)
 {
     BN_BLINDING *ret = NULL;

crypto/bn/bn_local.h

@@ -290,6 +290,20 @@ struct bn_gencb_st {
     } cb;
 };
 
+struct bn_blinding_st {
+    BIGNUM *A;
+    BIGNUM *Ai;
+    BIGNUM *e;
+    BIGNUM *mod;                /* just a reference */
+    CRYPTO_THREAD_ID tid;
+    int counter;
+    unsigned long flags;
+    BN_MONT_CTX *m_ctx;
+    int (*bn_mod_exp) (BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
+                       const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx);
+    CRYPTO_RWLOCK *lock;
+};
+
 /*-
  * BN_window_bits_for_exponent_size -- macro for sliding window mod_exp functions
  *

crypto/bn/build.info

@@ -105,7 +105,7 @@ $COMMON=bn_add.c bn_div.c bn_exp.c bn_lib.c bn_ctx.c bn_mul.c \
         bn_mod.c bn_conv.c bn_rand.c bn_shift.c bn_word.c bn_blind.c \
         bn_kron.c bn_sqrt.c bn_gcd.c bn_prime.c bn_sqr.c \
         bn_recp.c bn_mont.c bn_mpi.c bn_exp2.c bn_gf2m.c bn_nist.c \
-        bn_intern.c bn_dh.c bn_rsa_fips186_4.c bn_const.c
+        bn_intern.c bn_dh.c bn_rsa_fips186_4.c bn_const.c rsa_sup_mul.c
 SOURCE[../../libcrypto]=$COMMON $BNASM bn_print.c bn_err.c bn_srp.c
 DEFINE[../../libcrypto]=$BNDEF
 IF[{- !$disabled{'deprecated-0.9.8'} -}]