Initial code.

src/lib/crypto/crypto_aesctr.c

+/*-
+ * Copyright 2007-2009 Colin Percival
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * This file was originally written by Colin Percival as part of the Tarsnap
+ * online backup system.
+ */
+#include "scrypt_platform.h"
+
+#include <stdint.h>
+#include <stdlib.h>
+
+#include <openssl/aes.h>
+
+#include "sysendian.h"
+
+#include "crypto_aesctr.h"
+
+struct crypto_aesctr {
+        AES_KEY * key;
+        uint64_t nonce;
+        uint64_t bytectr;
+        uint8_t buf[16];
+};
+
+/**
+ * crypto_aesctr_init(key, nonce):
+ * Prepare to encrypt/decrypt data with AES in CTR mode, using the provided
+ * expanded key and nonce.  The key provided must remain valid for the
+ * lifetime of the stream.
+ */
+struct crypto_aesctr *
+crypto_aesctr_init(AES_KEY * key, uint64_t nonce)
+{
+        struct crypto_aesctr * stream;
+
+        /* Allocate memory. */
+        if ((stream = malloc(sizeof(struct crypto_aesctr))) == NULL)
+                goto err0;
+
+        /* Initialize values. */
+        stream->key = key;
+        stream->nonce = nonce;
+        stream->bytectr = 0;
+
+        /* Success! */
+        return (stream);
+
+err0:
+        /* Failure! */
+        return (NULL);
+}
+
+/**
+ * crypto_aesctr_stream(stream, inbuf, outbuf, buflen):
+ * Generate the next ${buflen} bytes of the AES-CTR stream and xor them with
+ * bytes from ${inbuf}, writing the result into ${outbuf}.  If the buffers
+ * ${inbuf} and ${outbuf} overlap, they must be identical.
+ */
+void
+crypto_aesctr_stream(struct crypto_aesctr * stream, const uint8_t * inbuf,
+    uint8_t * outbuf, size_t buflen)
+{
+        uint8_t pblk[16];
+        size_t pos;
+        int bytemod;
+
+        for (pos = 0; pos < buflen; pos++) {
+                /* How far through the buffer are we? */
+                bytemod = stream->bytectr % 16;
+
+                /* Generate a block of cipherstream if needed. */
+                if (bytemod == 0) {
+                        be64enc(pblk, stream->nonce);
+                        be64enc(pblk + 8, stream->bytectr / 16);
+                        AES_encrypt(pblk, stream->buf, stream->key);
+                }
+
+                /* Encrypt a byte. */
+                outbuf[pos] = inbuf[pos] ^ stream->buf[bytemod];
+
+                /* Move to the next byte of cipherstream. */
+                stream->bytectr += 1;
+        }
+}
+
+/**
+ * crypto_aesctr_free(stream):
+ * Free the provided stream object.
+ */
+void
+crypto_aesctr_free(struct crypto_aesctr * stream)
+{
+        int i;
+
+        /* Zero potentially sensitive information. */
+        for (i = 0; i < 16; i++)
+                stream->buf[i] = 0;
+        stream->bytectr = stream->nonce = 0;
+
+        /* Free the stream. */
+        free(stream);
+}