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authorEric Biggers <ebiggers@google.com>2018-11-16 17:26:21 -0800
committerHerbert Xu <herbert@gondor.apana.org.au>2018-11-20 14:26:55 +0800
commit1ca1b917940c24ca3d1f490118c5474168622953 (patch)
tree26cde5a85d0792a8dd709a6f5316f76af8801a35 /crypto/chacha_generic.c
parentde61d7ae5d3789dcba3749a418f76613fbee8414 (diff)
crypto: chacha20-generic - refactor to allow varying number of rounds
In preparation for adding XChaCha12 support, rename/refactor chacha20-generic to support different numbers of rounds. The justification for needing XChaCha12 support is explained in more detail in the patch "crypto: chacha - add XChaCha12 support". The only difference between ChaCha{8,12,20} are the number of rounds itself; all other parts of the algorithm are the same. Therefore, remove the "20" from all definitions, structures, functions, files, etc. that will be shared by all ChaCha versions. Also make ->setkey() store the round count in the chacha_ctx (previously chacha20_ctx). The generic code then passes the round count through to chacha_block(). There will be a ->setkey() function for each explicitly allowed round count; the encrypt/decrypt functions will be the same. I decided not to do it the opposite way (same ->setkey() function for all round counts, with different encrypt/decrypt functions) because that would have required more boilerplate code in architecture-specific implementations of ChaCha and XChaCha. Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Acked-by: Martin Willi <martin@strongswan.org> Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Diffstat (limited to 'crypto/chacha_generic.c')
-rw-r--r--crypto/chacha_generic.c193
1 files changed, 193 insertions, 0 deletions
diff --git a/crypto/chacha_generic.c b/crypto/chacha_generic.c
new file mode 100644
index 000000000000..438f15a14054
--- /dev/null
+++ b/crypto/chacha_generic.c
@@ -0,0 +1,193 @@
+/*
+ * ChaCha20 (RFC7539) and XChaCha20 stream cipher algorithms
+ *
+ * Copyright (C) 2015 Martin Willi
+ * Copyright (C) 2018 Google LLC
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include <asm/unaligned.h>
+#include <crypto/algapi.h>
+#include <crypto/chacha.h>
+#include <crypto/internal/skcipher.h>
+#include <linux/module.h>
+
+static void chacha_docrypt(u32 *state, u8 *dst, const u8 *src,
+ unsigned int bytes, int nrounds)
+{
+ /* aligned to potentially speed up crypto_xor() */
+ u8 stream[CHACHA_BLOCK_SIZE] __aligned(sizeof(long));
+
+ if (dst != src)
+ memcpy(dst, src, bytes);
+
+ while (bytes >= CHACHA_BLOCK_SIZE) {
+ chacha_block(state, stream, nrounds);
+ crypto_xor(dst, stream, CHACHA_BLOCK_SIZE);
+ bytes -= CHACHA_BLOCK_SIZE;
+ dst += CHACHA_BLOCK_SIZE;
+ }
+ if (bytes) {
+ chacha_block(state, stream, nrounds);
+ crypto_xor(dst, stream, bytes);
+ }
+}
+
+static int chacha_stream_xor(struct skcipher_request *req,
+ struct chacha_ctx *ctx, u8 *iv)
+{
+ struct skcipher_walk walk;
+ u32 state[16];
+ int err;
+
+ err = skcipher_walk_virt(&walk, req, false);
+
+ crypto_chacha_init(state, ctx, iv);
+
+ while (walk.nbytes > 0) {
+ unsigned int nbytes = walk.nbytes;
+
+ if (nbytes < walk.total)
+ nbytes = round_down(nbytes, walk.stride);
+
+ chacha_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr,
+ nbytes, ctx->nrounds);
+ err = skcipher_walk_done(&walk, walk.nbytes - nbytes);
+ }
+
+ return err;
+}
+
+void crypto_chacha_init(u32 *state, struct chacha_ctx *ctx, u8 *iv)
+{
+ state[0] = 0x61707865; /* "expa" */
+ state[1] = 0x3320646e; /* "nd 3" */
+ state[2] = 0x79622d32; /* "2-by" */
+ state[3] = 0x6b206574; /* "te k" */
+ state[4] = ctx->key[0];
+ state[5] = ctx->key[1];
+ state[6] = ctx->key[2];
+ state[7] = ctx->key[3];
+ state[8] = ctx->key[4];
+ state[9] = ctx->key[5];
+ state[10] = ctx->key[6];
+ state[11] = ctx->key[7];
+ state[12] = get_unaligned_le32(iv + 0);
+ state[13] = get_unaligned_le32(iv + 4);
+ state[14] = get_unaligned_le32(iv + 8);
+ state[15] = get_unaligned_le32(iv + 12);
+}
+EXPORT_SYMBOL_GPL(crypto_chacha_init);
+
+static int chacha_setkey(struct crypto_skcipher *tfm, const u8 *key,
+ unsigned int keysize, int nrounds)
+{
+ struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm);
+ int i;
+
+ if (keysize != CHACHA_KEY_SIZE)
+ return -EINVAL;
+
+ for (i = 0; i < ARRAY_SIZE(ctx->key); i++)
+ ctx->key[i] = get_unaligned_le32(key + i * sizeof(u32));
+
+ ctx->nrounds = nrounds;
+ return 0;
+}
+
+int crypto_chacha20_setkey(struct crypto_skcipher *tfm, const u8 *key,
+ unsigned int keysize)
+{
+ return chacha_setkey(tfm, key, keysize, 20);
+}
+EXPORT_SYMBOL_GPL(crypto_chacha20_setkey);
+
+int crypto_chacha_crypt(struct skcipher_request *req)
+{
+ struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
+ struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm);
+
+ return chacha_stream_xor(req, ctx, req->iv);
+}
+EXPORT_SYMBOL_GPL(crypto_chacha_crypt);
+
+int crypto_xchacha_crypt(struct skcipher_request *req)
+{
+ struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
+ struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm);
+ struct chacha_ctx subctx;
+ u32 state[16];
+ u8 real_iv[16];
+
+ /* Compute the subkey given the original key and first 128 nonce bits */
+ crypto_chacha_init(state, ctx, req->iv);
+ hchacha_block(state, subctx.key, ctx->nrounds);
+ subctx.nrounds = ctx->nrounds;
+
+ /* Build the real IV */
+ memcpy(&real_iv[0], req->iv + 24, 8); /* stream position */
+ memcpy(&real_iv[8], req->iv + 16, 8); /* remaining 64 nonce bits */
+
+ /* Generate the stream and XOR it with the data */
+ return chacha_stream_xor(req, &subctx, real_iv);
+}
+EXPORT_SYMBOL_GPL(crypto_xchacha_crypt);
+
+static struct skcipher_alg algs[] = {
+ {
+ .base.cra_name = "chacha20",
+ .base.cra_driver_name = "chacha20-generic",
+ .base.cra_priority = 100,
+ .base.cra_blocksize = 1,
+ .base.cra_ctxsize = sizeof(struct chacha_ctx),
+ .base.cra_module = THIS_MODULE,
+
+ .min_keysize = CHACHA_KEY_SIZE,
+ .max_keysize = CHACHA_KEY_SIZE,
+ .ivsize = CHACHA_IV_SIZE,
+ .chunksize = CHACHA_BLOCK_SIZE,
+ .setkey = crypto_chacha20_setkey,
+ .encrypt = crypto_chacha_crypt,
+ .decrypt = crypto_chacha_crypt,
+ }, {
+ .base.cra_name = "xchacha20",
+ .base.cra_driver_name = "xchacha20-generic",
+ .base.cra_priority = 100,
+ .base.cra_blocksize = 1,
+ .base.cra_ctxsize = sizeof(struct chacha_ctx),
+ .base.cra_module = THIS_MODULE,
+
+ .min_keysize = CHACHA_KEY_SIZE,
+ .max_keysize = CHACHA_KEY_SIZE,
+ .ivsize = XCHACHA_IV_SIZE,
+ .chunksize = CHACHA_BLOCK_SIZE,
+ .setkey = crypto_chacha20_setkey,
+ .encrypt = crypto_xchacha_crypt,
+ .decrypt = crypto_xchacha_crypt,
+ }
+};
+
+static int __init chacha_generic_mod_init(void)
+{
+ return crypto_register_skciphers(algs, ARRAY_SIZE(algs));
+}
+
+static void __exit chacha_generic_mod_fini(void)
+{
+ crypto_unregister_skciphers(algs, ARRAY_SIZE(algs));
+}
+
+module_init(chacha_generic_mod_init);
+module_exit(chacha_generic_mod_fini);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Martin Willi <martin@strongswan.org>");
+MODULE_DESCRIPTION("ChaCha and XChaCha stream ciphers (generic)");
+MODULE_ALIAS_CRYPTO("chacha20");
+MODULE_ALIAS_CRYPTO("chacha20-generic");
+MODULE_ALIAS_CRYPTO("xchacha20");
+MODULE_ALIAS_CRYPTO("xchacha20-generic");