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crypto: salsa20-generic - cleanup and convert to skcipher API
Convert salsa20-generic from the deprecated "blkcipher" API to the "skcipher" API, in the process fixing it up to be thread-safe (as the crypto API expects) by maintaining each request's state separately from the transform context. Also remove the unnecessary cra_alignmask and tighten validation of the key size by accepting only 16 or 32 bytes, not anything in between. These changes bring the code close to the way chacha20-generic does things, so hopefully it will be easier to maintain in the future. However, the way Salsa20 interprets the IV is still slightly different; that was not changed. Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Eric Biggers
Herbert Xu
parent
148b974dee
commit
b62b3db76f
@ -19,49 +19,27 @@
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*
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*/
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#include <linux/init.h>
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#include <asm/unaligned.h>
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#include <crypto/internal/skcipher.h>
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#include <linux/module.h>
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#include <linux/errno.h>
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#include <linux/crypto.h>
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#include <linux/types.h>
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#include <linux/bitops.h>
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#include <crypto/algapi.h>
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#include <asm/byteorder.h>
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#define SALSA20_IV_SIZE 8U
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#define SALSA20_MIN_KEY_SIZE 16U
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#define SALSA20_MAX_KEY_SIZE 32U
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#define SALSA20_IV_SIZE 8
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#define SALSA20_MIN_KEY_SIZE 16
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#define SALSA20_MAX_KEY_SIZE 32
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#define SALSA20_BLOCK_SIZE 64
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/*
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* Start of code taken from D. J. Bernstein's reference implementation.
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* With some modifications and optimizations made to suit our needs.
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*/
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/*
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salsa20-ref.c version 20051118
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D. J. Bernstein
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Public domain.
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*/
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#define U32TO8_LITTLE(p, v) \
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{ (p)[0] = (v >> 0) & 0xff; (p)[1] = (v >> 8) & 0xff; \
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(p)[2] = (v >> 16) & 0xff; (p)[3] = (v >> 24) & 0xff; }
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#define U8TO32_LITTLE(p) \
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(((u32)((p)[0]) ) | ((u32)((p)[1]) << 8) | \
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((u32)((p)[2]) << 16) | ((u32)((p)[3]) << 24) )
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struct salsa20_ctx
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{
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u32 input[16];
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struct salsa20_ctx {
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u32 initial_state[16];
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};
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static void salsa20_wordtobyte(u8 output[64], const u32 input[16])
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static void salsa20_block(u32 *state, __le32 *stream)
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{
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u32 x[16];
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int i;
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memcpy(x, input, sizeof(x));
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for (i = 20; i > 0; i -= 2) {
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memcpy(x, state, sizeof(x));
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for (i = 0; i < 20; i += 2) {
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x[ 4] ^= rol32((x[ 0] + x[12]), 7);
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x[ 8] ^= rol32((x[ 4] + x[ 0]), 9);
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x[12] ^= rol32((x[ 8] + x[ 4]), 13);
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@ -95,145 +73,135 @@ static void salsa20_wordtobyte(u8 output[64], const u32 input[16])
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x[14] ^= rol32((x[13] + x[12]), 13);
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x[15] ^= rol32((x[14] + x[13]), 18);
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}
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for (i = 0; i < 16; ++i)
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x[i] += input[i];
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for (i = 0; i < 16; ++i)
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U32TO8_LITTLE(output + 4 * i,x[i]);
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for (i = 0; i < 16; i++)
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stream[i] = cpu_to_le32(x[i] + state[i]);
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if (++state[8] == 0)
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state[9]++;
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}
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static const char sigma[16] = "expand 32-byte k";
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static const char tau[16] = "expand 16-byte k";
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static void salsa20_keysetup(struct salsa20_ctx *ctx, const u8 *k, u32 kbytes)
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static void salsa20_docrypt(u32 *state, u8 *dst, const u8 *src,
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unsigned int bytes)
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{
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const char *constants;
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ctx->input[1] = U8TO32_LITTLE(k + 0);
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ctx->input[2] = U8TO32_LITTLE(k + 4);
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ctx->input[3] = U8TO32_LITTLE(k + 8);
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ctx->input[4] = U8TO32_LITTLE(k + 12);
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if (kbytes == 32) { /* recommended */
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k += 16;
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constants = sigma;
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} else { /* kbytes == 16 */
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constants = tau;
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}
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ctx->input[11] = U8TO32_LITTLE(k + 0);
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ctx->input[12] = U8TO32_LITTLE(k + 4);
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ctx->input[13] = U8TO32_LITTLE(k + 8);
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ctx->input[14] = U8TO32_LITTLE(k + 12);
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ctx->input[0] = U8TO32_LITTLE(constants + 0);
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ctx->input[5] = U8TO32_LITTLE(constants + 4);
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ctx->input[10] = U8TO32_LITTLE(constants + 8);
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ctx->input[15] = U8TO32_LITTLE(constants + 12);
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}
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static void salsa20_ivsetup(struct salsa20_ctx *ctx, const u8 *iv)
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{
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ctx->input[6] = U8TO32_LITTLE(iv + 0);
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ctx->input[7] = U8TO32_LITTLE(iv + 4);
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ctx->input[8] = 0;
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ctx->input[9] = 0;
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}
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static void salsa20_encrypt_bytes(struct salsa20_ctx *ctx, u8 *dst,
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const u8 *src, unsigned int bytes)
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{
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u8 buf[64];
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__le32 stream[SALSA20_BLOCK_SIZE / sizeof(__le32)];
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if (dst != src)
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memcpy(dst, src, bytes);
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while (bytes) {
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salsa20_wordtobyte(buf, ctx->input);
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ctx->input[8]++;
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if (!ctx->input[8])
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ctx->input[9]++;
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if (bytes <= 64) {
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crypto_xor(dst, buf, bytes);
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return;
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}
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crypto_xor(dst, buf, 64);
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bytes -= 64;
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dst += 64;
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while (bytes >= SALSA20_BLOCK_SIZE) {
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salsa20_block(state, stream);
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crypto_xor(dst, (const u8 *)stream, SALSA20_BLOCK_SIZE);
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bytes -= SALSA20_BLOCK_SIZE;
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dst += SALSA20_BLOCK_SIZE;
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}
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if (bytes) {
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salsa20_block(state, stream);
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crypto_xor(dst, (const u8 *)stream, bytes);
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}
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}
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/*
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* End of code taken from D. J. Bernstein's reference implementation.
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*/
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static int setkey(struct crypto_tfm *tfm, const u8 *key,
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unsigned int keysize)
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static void salsa20_init(u32 *state, const struct salsa20_ctx *ctx,
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const u8 *iv)
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{
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struct salsa20_ctx *ctx = crypto_tfm_ctx(tfm);
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salsa20_keysetup(ctx, key, keysize);
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memcpy(state, ctx->initial_state, sizeof(ctx->initial_state));
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state[6] = get_unaligned_le32(iv + 0);
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state[7] = get_unaligned_le32(iv + 4);
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}
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static int salsa20_setkey(struct crypto_skcipher *tfm, const u8 *key,
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unsigned int keysize)
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{
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static const char sigma[16] = "expand 32-byte k";
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static const char tau[16] = "expand 16-byte k";
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struct salsa20_ctx *ctx = crypto_skcipher_ctx(tfm);
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const char *constants;
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if (keysize != SALSA20_MIN_KEY_SIZE &&
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keysize != SALSA20_MAX_KEY_SIZE)
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return -EINVAL;
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ctx->initial_state[1] = get_unaligned_le32(key + 0);
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ctx->initial_state[2] = get_unaligned_le32(key + 4);
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ctx->initial_state[3] = get_unaligned_le32(key + 8);
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ctx->initial_state[4] = get_unaligned_le32(key + 12);
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if (keysize == 32) { /* recommended */
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key += 16;
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constants = sigma;
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} else { /* keysize == 16 */
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constants = tau;
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}
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ctx->initial_state[11] = get_unaligned_le32(key + 0);
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ctx->initial_state[12] = get_unaligned_le32(key + 4);
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ctx->initial_state[13] = get_unaligned_le32(key + 8);
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ctx->initial_state[14] = get_unaligned_le32(key + 12);
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ctx->initial_state[0] = get_unaligned_le32(constants + 0);
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ctx->initial_state[5] = get_unaligned_le32(constants + 4);
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ctx->initial_state[10] = get_unaligned_le32(constants + 8);
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ctx->initial_state[15] = get_unaligned_le32(constants + 12);
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/* space for the nonce; it will be overridden for each request */
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ctx->initial_state[6] = 0;
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ctx->initial_state[7] = 0;
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/* initial block number */
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ctx->initial_state[8] = 0;
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ctx->initial_state[9] = 0;
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return 0;
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}
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static int encrypt(struct blkcipher_desc *desc,
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struct scatterlist *dst, struct scatterlist *src,
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unsigned int nbytes)
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static int salsa20_crypt(struct skcipher_request *req)
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{
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struct blkcipher_walk walk;
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struct crypto_blkcipher *tfm = desc->tfm;
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struct salsa20_ctx *ctx = crypto_blkcipher_ctx(tfm);
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struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
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const struct salsa20_ctx *ctx = crypto_skcipher_ctx(tfm);
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struct skcipher_walk walk;
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u32 state[16];
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int err;
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blkcipher_walk_init(&walk, dst, src, nbytes);
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err = blkcipher_walk_virt_block(desc, &walk, 64);
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err = skcipher_walk_virt(&walk, req, true);
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salsa20_ivsetup(ctx, walk.iv);
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salsa20_init(state, ctx, walk.iv);
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while (walk.nbytes >= 64) {
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salsa20_encrypt_bytes(ctx, walk.dst.virt.addr,
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walk.src.virt.addr,
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walk.nbytes - (walk.nbytes % 64));
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err = blkcipher_walk_done(desc, &walk, walk.nbytes % 64);
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}
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while (walk.nbytes > 0) {
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unsigned int nbytes = walk.nbytes;
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if (walk.nbytes) {
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salsa20_encrypt_bytes(ctx, walk.dst.virt.addr,
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walk.src.virt.addr, walk.nbytes);
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err = blkcipher_walk_done(desc, &walk, 0);
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if (nbytes < walk.total)
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nbytes = round_down(nbytes, walk.stride);
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salsa20_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr,
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nbytes);
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err = skcipher_walk_done(&walk, walk.nbytes - nbytes);
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}
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return err;
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}
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static struct crypto_alg alg = {
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.cra_name = "salsa20",
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.cra_driver_name = "salsa20-generic",
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.cra_priority = 100,
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.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER,
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.cra_type = &crypto_blkcipher_type,
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.cra_blocksize = 1,
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.cra_ctxsize = sizeof(struct salsa20_ctx),
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.cra_alignmask = 3,
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.cra_module = THIS_MODULE,
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.cra_u = {
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.blkcipher = {
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.setkey = setkey,
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.encrypt = encrypt,
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.decrypt = encrypt,
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.min_keysize = SALSA20_MIN_KEY_SIZE,
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.max_keysize = SALSA20_MAX_KEY_SIZE,
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.ivsize = SALSA20_IV_SIZE,
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}
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}
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static struct skcipher_alg alg = {
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.base.cra_name = "salsa20",
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.base.cra_driver_name = "salsa20-generic",
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.base.cra_priority = 100,
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.base.cra_blocksize = 1,
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.base.cra_ctxsize = sizeof(struct salsa20_ctx),
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.base.cra_module = THIS_MODULE,
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.min_keysize = SALSA20_MIN_KEY_SIZE,
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.max_keysize = SALSA20_MAX_KEY_SIZE,
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.ivsize = SALSA20_IV_SIZE,
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.chunksize = SALSA20_BLOCK_SIZE,
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.setkey = salsa20_setkey,
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.encrypt = salsa20_crypt,
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.decrypt = salsa20_crypt,
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};
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static int __init salsa20_generic_mod_init(void)
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{
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return crypto_register_alg(&alg);
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return crypto_register_skcipher(&alg);
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}
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static void __exit salsa20_generic_mod_fini(void)
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{
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crypto_unregister_alg(&alg);
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crypto_unregister_skcipher(&alg);
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}
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module_init(salsa20_generic_mod_init);
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