Revision 0620fddb56dfaf0e1034eeb69d79c73b361debbf authored by Eric Biggers on 08 June 2017, 13:49:26 UTC, committed by James Morris on 09 June 2017, 03:29:48 UTC
While a 'struct key' itself normally does not contain sensitive information, Documentation/security/keys.txt actually encourages this: "Having a payload is not required; and the payload can, in fact, just be a value stored in the struct key itself." In case someone has taken this advice, or will take this advice in the future, zero the key structure before freeing it. We might as well, and as a bonus this could make it a bit more difficult for an adversary to determine which keys have recently been in use. This is safe because the key_jar cache does not use a constructor. Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: James Morris <james.l.morris@oracle.com>
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chacha20_generic.c
/*
* ChaCha20 256-bit cipher algorithm, RFC7539
*
* Copyright (C) 2015 Martin Willi
*
* 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 <crypto/algapi.h>
#include <crypto/chacha20.h>
#include <crypto/internal/skcipher.h>
#include <linux/module.h>
static inline u32 le32_to_cpuvp(const void *p)
{
return le32_to_cpup(p);
}
static void chacha20_docrypt(u32 *state, u8 *dst, const u8 *src,
unsigned int bytes)
{
u8 stream[CHACHA20_BLOCK_SIZE];
if (dst != src)
memcpy(dst, src, bytes);
while (bytes >= CHACHA20_BLOCK_SIZE) {
chacha20_block(state, stream);
crypto_xor(dst, stream, CHACHA20_BLOCK_SIZE);
bytes -= CHACHA20_BLOCK_SIZE;
dst += CHACHA20_BLOCK_SIZE;
}
if (bytes) {
chacha20_block(state, stream);
crypto_xor(dst, stream, bytes);
}
}
void crypto_chacha20_init(u32 *state, struct chacha20_ctx *ctx, u8 *iv)
{
static const char constant[16] = "expand 32-byte k";
state[0] = le32_to_cpuvp(constant + 0);
state[1] = le32_to_cpuvp(constant + 4);
state[2] = le32_to_cpuvp(constant + 8);
state[3] = le32_to_cpuvp(constant + 12);
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] = le32_to_cpuvp(iv + 0);
state[13] = le32_to_cpuvp(iv + 4);
state[14] = le32_to_cpuvp(iv + 8);
state[15] = le32_to_cpuvp(iv + 12);
}
EXPORT_SYMBOL_GPL(crypto_chacha20_init);
int crypto_chacha20_setkey(struct crypto_skcipher *tfm, const u8 *key,
unsigned int keysize)
{
struct chacha20_ctx *ctx = crypto_skcipher_ctx(tfm);
int i;
if (keysize != CHACHA20_KEY_SIZE)
return -EINVAL;
for (i = 0; i < ARRAY_SIZE(ctx->key); i++)
ctx->key[i] = le32_to_cpuvp(key + i * sizeof(u32));
return 0;
}
EXPORT_SYMBOL_GPL(crypto_chacha20_setkey);
int crypto_chacha20_crypt(struct skcipher_request *req)
{
struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
struct chacha20_ctx *ctx = crypto_skcipher_ctx(tfm);
struct skcipher_walk walk;
u32 state[16];
int err;
err = skcipher_walk_virt(&walk, req, true);
crypto_chacha20_init(state, ctx, walk.iv);
while (walk.nbytes > 0) {
chacha20_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr,
walk.nbytes);
err = skcipher_walk_done(&walk, 0);
}
return err;
}
EXPORT_SYMBOL_GPL(crypto_chacha20_crypt);
static struct skcipher_alg alg = {
.base.cra_name = "chacha20",
.base.cra_driver_name = "chacha20-generic",
.base.cra_priority = 100,
.base.cra_blocksize = 1,
.base.cra_ctxsize = sizeof(struct chacha20_ctx),
.base.cra_alignmask = sizeof(u32) - 1,
.base.cra_module = THIS_MODULE,
.min_keysize = CHACHA20_KEY_SIZE,
.max_keysize = CHACHA20_KEY_SIZE,
.ivsize = CHACHA20_IV_SIZE,
.chunksize = CHACHA20_BLOCK_SIZE,
.setkey = crypto_chacha20_setkey,
.encrypt = crypto_chacha20_crypt,
.decrypt = crypto_chacha20_crypt,
};
static int __init chacha20_generic_mod_init(void)
{
return crypto_register_skcipher(&alg);
}
static void __exit chacha20_generic_mod_fini(void)
{
crypto_unregister_skcipher(&alg);
}
module_init(chacha20_generic_mod_init);
module_exit(chacha20_generic_mod_fini);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Martin Willi <martin@strongswan.org>");
MODULE_DESCRIPTION("chacha20 cipher algorithm");
MODULE_ALIAS_CRYPTO("chacha20");
MODULE_ALIAS_CRYPTO("chacha20-generic");
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