From 82abcc07227fb8f25394281c19c61053c7dd3f54 Mon Sep 17 00:00:00 2001
From: Andre Noll <maan@tuebingen.mpg.de>
Date: Tue, 2 May 2023 19:51:52 +0200
Subject: [PATCH] openssl: Kill rsa coefficient computations.

There's no need to pre-compute the two exponents for the Chinese
Remainder Theorem calculations as openssl will do that for us.
---
 openssl.c | 48 +++++-------------------------------------------
 1 file changed, 5 insertions(+), 43 deletions(-)

diff --git a/openssl.c b/openssl.c
index f696cd9e..09d11e1e 100644
--- a/openssl.c
+++ b/openssl.c
@@ -154,31 +154,15 @@ static int read_openssh_private_key(const unsigned char *blob,
 {
 	int ret;
 	RSA *rsa;
-	BN_CTX *ctx;
 	BIGNUM *n, *e, *d, *iqmp, *p, *q; /* stored in the key file */
-	BIGNUM *dmp1, *dmq1; /* these will be computed */
-	BIGNUM *tmp;
 	const unsigned char *cp = blob;
 
 	rsa = RSA_new();
 	if (!rsa)
 		return -E_BIGNUM;
-	ret = -E_BIGNUM;
-	tmp = BN_new();
-	if (!tmp)
-		goto free_rsa;
-	ctx = BN_CTX_new();
-	if (!ctx)
-		goto free_tmp;
-	dmp1 = BN_new();
-	if (!dmp1)
-		goto free_ctx;
-	dmq1 = BN_new();
-	if (!dmq1)
-		goto free_dmp1;
 	ret = read_bignum(cp, end - cp, &n);
 	if (ret < 0)
-		goto free_dmq1;
+		goto free_rsa;
 	cp += ret;
 	ret = read_bignum(cp, end - cp, &e);
 	if (ret < 0)
@@ -199,19 +183,11 @@ static int read_openssh_private_key(const unsigned char *blob,
 	ret = read_bignum(cp, end - cp, &q);
 	if (ret < 0)
 		goto free_p;
-	ret = -E_BIGNUM;
-	if (!BN_sub(tmp, q, BN_value_one()))
-		goto free_q;
-	if (!BN_mod(dmp1, d, tmp, ctx))
-		goto free_q;
-	if (!BN_sub(tmp, q, BN_value_one()))
-		goto free_q;
-	if (!BN_mod(dmq1, d, tmp, ctx))
-		goto free_q;
 #ifdef HAVE_RSA_SET0_KEY
 	RSA_set0_key(rsa, n, e, d);
 	RSA_set0_factors(rsa, p, q);
-	RSA_set0_crt_params(rsa, dmp1, dmq1, iqmp);
+	RSA_set0_crt_params(rsa, NULL, NULL, iqmp);
+
 #else
 	rsa->n = n;
 	rsa->e = e;
@@ -219,14 +195,9 @@ static int read_openssh_private_key(const unsigned char *blob,
 	rsa->iqmp = iqmp;
 	rsa->p = p;
 	rsa->q = q;
-	rsa->dmp1 = dmp1;
-	rsa->dmq1 = dmq1;
 #endif
 	*result = rsa;
-	ret = 1;
-	goto free_ctx;
-free_q:
-	BN_clear_free(q);
+	return 1;
 free_p:
 	BN_clear_free(p);
 free_iqmp:
@@ -237,17 +208,8 @@ free_e:
 	BN_free(e);
 free_n:
 	BN_free(n);
-free_dmq1:
-	BN_clear_free(dmq1);
-free_dmp1:
-	BN_clear_free(dmp1);
-free_ctx:
-	BN_CTX_free(ctx);
-free_tmp:
-	BN_clear_free(tmp);
 free_rsa:
-	if (ret < 0)
-		RSA_free(rsa);
+	RSA_free(rsa);
 	return ret;
 }
 
-- 
2.39.5