From: Guus Sliepen <guus@tinc-vpn.org>
Date: Sun, 18 Feb 2018 15:51:06 +0000 (+0100)
Subject: Reduce memory allocations due to HMAC() and EVP_MD_*().
X-Git-Tag: release-1.1pre16~23
X-Git-Url: https://git.tinc-vpn.org/git/browse?a=commitdiff_plain;h=ecfef0eeb9b52f6d75b4aa936a1e11e6d8e678e3;p=tinc

Reduce memory allocations due to HMAC() and EVP_MD_*().

HMAC() allocates a temporary buffer on the heap each time it is called.
Similarly, we called EVP_MD_CTX_create() every time we wanted to
calculate a hash. Use HMAC_CTX and EVP_MD_CTX variables to store the
state so no (re)allocations are necessary. HMAC() was called for every
legacy packet sent and received.

This issue was found thanks to heaptrack.
---

diff --git a/src/openssl/digest.c b/src/openssl/digest.c
index 9c3ab1e8..d51dcaa9 100644
--- a/src/openssl/digest.c
+++ b/src/openssl/digest.c
@@ -66,9 +66,13 @@ digest_t *digest_open_by_nid(int nid, int maclength) {
 }
 
 bool digest_set_key(digest_t *digest, const void *key, size_t len) {
-	digest->key = xrealloc(digest->key, len);
-	memcpy(digest->key, key, len);
-	digest->keylength = len;
+	digest->hmac_ctx = HMAC_CTX_new();
+	HMAC_Init_ex(digest->hmac_ctx, key, len, digest->digest, NULL);
+
+	if(!digest->hmac_ctx) {
+		abort();
+	}
+
 	return true;
 }
 
@@ -77,7 +81,14 @@ void digest_close(digest_t *digest) {
 		return;
 	}
 
-	free(digest->key);
+	if(digest->md_ctx) {
+		EVP_MD_CTX_destroy(digest->md_ctx);
+	}
+
+	if(digest->hmac_ctx) {
+		HMAC_CTX_free(digest->hmac_ctx);
+	}
+
 	free(digest);
 }
 
@@ -85,27 +96,28 @@ bool digest_create(digest_t *digest, const void *indata, size_t inlen, void *out
 	size_t len = EVP_MD_size(digest->digest);
 	unsigned char tmpdata[len];
 
-	if(digest->key) {
-		if(!HMAC(digest->digest, digest->key, digest->keylength, indata, inlen, tmpdata, NULL)) {
+	if(digest->hmac_ctx) {
+		if(!HMAC_Init_ex(digest->hmac_ctx, NULL, 0, NULL, NULL)
+		                || !HMAC_Update(digest->hmac_ctx, indata, inlen)
+		                || !HMAC_Final(digest->hmac_ctx, tmpdata, NULL)) {
 			logger(DEBUG_ALWAYS, LOG_DEBUG, "Error creating digest: %s", ERR_error_string(ERR_get_error(), NULL));
 			return false;
 		}
 	} else {
-		EVP_MD_CTX *ctx = EVP_MD_CTX_create();
+		if(!digest->md_ctx) {
+			digest->md_ctx = EVP_MD_CTX_create();
+		}
 
-		if(!ctx) {
+		if(!digest->md_ctx) {
 			abort();
 		}
 
-		if(!EVP_DigestInit(ctx, digest->digest)
-		                || !EVP_DigestUpdate(ctx, indata, inlen)
-		                || !EVP_DigestFinal(ctx, tmpdata, NULL)) {
+		if(!EVP_DigestInit(digest->md_ctx, digest->digest)
+		                || !EVP_DigestUpdate(digest->md_ctx, indata, inlen)
+		                || !EVP_DigestFinal(digest->md_ctx, tmpdata, NULL)) {
 			logger(DEBUG_ALWAYS, LOG_DEBUG, "Error creating digest: %s", ERR_error_string(ERR_get_error(), NULL));
-			EVP_MD_CTX_destroy(ctx);
 			return false;
 		}
-
-		EVP_MD_CTX_destroy(ctx);
 	}
 
 	memcpy(outdata, tmpdata, digest->maclength);
diff --git a/src/openssl/digest.h b/src/openssl/digest.h
index 1b1389d1..d553977b 100644
--- a/src/openssl/digest.h
+++ b/src/openssl/digest.h
@@ -24,9 +24,9 @@
 
 struct digest {
 	const EVP_MD *digest;
+	HMAC_CTX *hmac_ctx;
+	EVP_MD_CTX *md_ctx;
 	int maclength;
-	int keylength;
-	char *key;
 };
 
 #endif