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

[tinc] / src / openssl / cipher.c

diff --git a/src/openssl/cipher.c b/src/openssl/cipher.c
index 9b9e344..1ca15ab 100644 (file)
--- 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) {