From: Guus Sliepen <guus@tinc-vpn.org>
Date: Sun, 18 Mar 2012 15:41:13 +0000 (+0100)
Subject: Allow CTR mode counter to be set to a specific value.
X-Git-Tag: release-1.1pre3~141
X-Git-Url: https://tinc-vpn.org/git/browse?a=commitdiff_plain;h=03e06fd43aff73b4a5c9d367968a1279371ae252;p=tinc

Allow CTR mode counter to be set to a specific value.
---

diff --git a/src/openssl/cipher.c b/src/openssl/cipher.c
index 9b9e3446..1ca15abb 100644
--- a/src/openssl/cipher.c
+++ b/src/openssl/cipher.c
@@ -105,6 +105,19 @@ bool cipher_set_key_from_rsa(cipher_t *cipher, void *key, size_t len, bool encry
 	return false;
 }
 
+bool cipher_set_counter(cipher_t *cipher, const void *counter, size_t len) {
+	if(len > cipher->cipher->block_size - 4) {
+		logger(DEBUG_ALWAYS, LOG_ERR, "Counter too long");
+		abort();
+	}
+
+	memcpy(cipher->counter->counter + cipher->cipher->block_size - len, counter, len);
+	memset(cipher->counter->counter, 0, 4);
+	cipher->counter->n = 0;
+
+	return true;
+}
+
 bool cipher_set_counter_key(cipher_t *cipher, void *key) {
 	int result = EVP_EncryptInit_ex(&cipher->ctx, cipher->cipher, NULL, (unsigned char *)key, NULL);
 	if(!result) {
diff --git a/src/openssl/cipher.h b/src/openssl/cipher.h
index 589ec4c4..9b6221bc 100644
--- a/src/openssl/cipher.h
+++ b/src/openssl/cipher.h
@@ -39,6 +39,7 @@ extern void cipher_close(cipher_t *);
 extern size_t cipher_keylength(const cipher_t *);
 extern bool cipher_set_key(cipher_t *, void *, bool);
 extern bool cipher_set_key_from_rsa(cipher_t *, void *, size_t, bool);
+extern bool cipher_set_counter(cipher_t *, const void *, size_t);
 extern bool cipher_set_counter_key(cipher_t *, void *);
 extern bool cipher_encrypt(cipher_t *, const void *indata, size_t inlen, void *outdata, size_t *outlen, bool);
 extern bool cipher_decrypt(cipher_t *, const void *indata, size_t inlen, void *outdata, size_t *outlen, bool);