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linux/lib/crypto/sha256.c
Arvind Sankar 7a4295f6c9 crypto: lib/sha256 - Don't clear temporary variables 
The assignments to clear a through h and t1/t2 are optimized out by the
compiler because they are unused after the assignments.

Clearing individual scalar variables is unlikely to be useful, as they
may have been assigned to registers, and even if stack spilling was
required, there may be compiler-generated temporaries that are
impossible to clear in any case.

So drop the clearing of a through h and t1/t2.

Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2020-10-30 17:35:03 +11:00

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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* SHA-256, as specified in
* http://csrc.nist.gov/groups/STM/cavp/documents/shs/sha256-384-512.pdf
*
* SHA-256 code by Jean-Luc Cooke <jlcooke@certainkey.com>.
*
* Copyright (c) Jean-Luc Cooke <jlcooke@certainkey.com>
* Copyright (c) Andrew McDonald <andrew@mcdonald.org.uk>
* Copyright (c) 2002 James Morris <jmorris@intercode.com.au>
* Copyright (c) 2014 Red Hat Inc.
*/
#include <linux/bitops.h>
#include <linux/export.h>
#include <linux/module.h>
#include <linux/string.h>
#include <crypto/sha.h>
#include <asm/unaligned.h>
static inline u32 Ch(u32 x, u32 y, u32 z)
{
return z ^ (x & (y ^ z));
}
static inline u32 Maj(u32 x, u32 y, u32 z)
{
return (x & y) | (z & (x | y));
}
#define e0(x) (ror32(x, 2) ^ ror32(x, 13) ^ ror32(x, 22))
#define e1(x) (ror32(x, 6) ^ ror32(x, 11) ^ ror32(x, 25))
#define s0(x) (ror32(x, 7) ^ ror32(x, 18) ^ (x >> 3))
#define s1(x) (ror32(x, 17) ^ ror32(x, 19) ^ (x >> 10))
static inline void LOAD_OP(int I, u32 *W, const u8 *input)
{
W[I] = get_unaligned_be32((__u32 *)input + I);
}
static inline void BLEND_OP(int I, u32 *W)
{
W[I] = s1(W[I-2]) + W[I-7] + s0(W[I-15]) + W[I-16];
}
static void sha256_transform(u32 *state, const u8 *input)
{
u32 a, b, c, d, e, f, g, h, t1, t2;
u32 W[64];
int i;
/* load the input */
for (i = 0; i < 16; i++)
LOAD_OP(i, W, input);
/* now blend */
for (i = 16; i < 64; i++)
BLEND_OP(i, W);
/* load the state into our registers */
a = state[0]; b = state[1]; c = state[2]; d = state[3];
e = state[4]; f = state[5]; g = state[6]; h = state[7];
/* now iterate */
t1 = h + e1(e) + Ch(e, f, g) + 0x428a2f98 + W[0];
t2 = e0(a) + Maj(a, b, c); d += t1; h = t1 + t2;
t1 = g + e1(d) + Ch(d, e, f) + 0x71374491 + W[1];
t2 = e0(h) + Maj(h, a, b); c += t1; g = t1 + t2;
t1 = f + e1(c) + Ch(c, d, e) + 0xb5c0fbcf + W[2];
t2 = e0(g) + Maj(g, h, a); b += t1; f = t1 + t2;
t1 = e + e1(b) + Ch(b, c, d) + 0xe9b5dba5 + W[3];
t2 = e0(f) + Maj(f, g, h); a += t1; e = t1 + t2;
t1 = d + e1(a) + Ch(a, b, c) + 0x3956c25b + W[4];
t2 = e0(e) + Maj(e, f, g); h += t1; d = t1 + t2;
t1 = c + e1(h) + Ch(h, a, b) + 0x59f111f1 + W[5];
t2 = e0(d) + Maj(d, e, f); g += t1; c = t1 + t2;
t1 = b + e1(g) + Ch(g, h, a) + 0x923f82a4 + W[6];
t2 = e0(c) + Maj(c, d, e); f += t1; b = t1 + t2;
t1 = a + e1(f) + Ch(f, g, h) + 0xab1c5ed5 + W[7];
t2 = e0(b) + Maj(b, c, d); e += t1; a = t1 + t2;
t1 = h + e1(e) + Ch(e, f, g) + 0xd807aa98 + W[8];
t2 = e0(a) + Maj(a, b, c); d += t1; h = t1 + t2;
t1 = g + e1(d) + Ch(d, e, f) + 0x12835b01 + W[9];
t2 = e0(h) + Maj(h, a, b); c += t1; g = t1 + t2;
t1 = f + e1(c) + Ch(c, d, e) + 0x243185be + W[10];
t2 = e0(g) + Maj(g, h, a); b += t1; f = t1 + t2;
t1 = e + e1(b) + Ch(b, c, d) + 0x550c7dc3 + W[11];
t2 = e0(f) + Maj(f, g, h); a += t1; e = t1 + t2;
t1 = d + e1(a) + Ch(a, b, c) + 0x72be5d74 + W[12];
t2 = e0(e) + Maj(e, f, g); h += t1; d = t1 + t2;
t1 = c + e1(h) + Ch(h, a, b) + 0x80deb1fe + W[13];
t2 = e0(d) + Maj(d, e, f); g += t1; c = t1 + t2;
t1 = b + e1(g) + Ch(g, h, a) + 0x9bdc06a7 + W[14];
t2 = e0(c) + Maj(c, d, e); f += t1; b = t1 + t2;
t1 = a + e1(f) + Ch(f, g, h) + 0xc19bf174 + W[15];
t2 = e0(b) + Maj(b, c, d); e += t1; a = t1 + t2;
t1 = h + e1(e) + Ch(e, f, g) + 0xe49b69c1 + W[16];
t2 = e0(a) + Maj(a, b, c); d += t1; h = t1 + t2;
t1 = g + e1(d) + Ch(d, e, f) + 0xefbe4786 + W[17];
t2 = e0(h) + Maj(h, a, b); c += t1; g = t1 + t2;
t1 = f + e1(c) + Ch(c, d, e) + 0x0fc19dc6 + W[18];
t2 = e0(g) + Maj(g, h, a); b += t1; f = t1 + t2;
t1 = e + e1(b) + Ch(b, c, d) + 0x240ca1cc + W[19];
t2 = e0(f) + Maj(f, g, h); a += t1; e = t1 + t2;
t1 = d + e1(a) + Ch(a, b, c) + 0x2de92c6f + W[20];
t2 = e0(e) + Maj(e, f, g); h += t1; d = t1 + t2;
t1 = c + e1(h) + Ch(h, a, b) + 0x4a7484aa + W[21];
t2 = e0(d) + Maj(d, e, f); g += t1; c = t1 + t2;
t1 = b + e1(g) + Ch(g, h, a) + 0x5cb0a9dc + W[22];
t2 = e0(c) + Maj(c, d, e); f += t1; b = t1 + t2;
t1 = a + e1(f) + Ch(f, g, h) + 0x76f988da + W[23];
t2 = e0(b) + Maj(b, c, d); e += t1; a = t1 + t2;
t1 = h + e1(e) + Ch(e, f, g) + 0x983e5152 + W[24];
t2 = e0(a) + Maj(a, b, c); d += t1; h = t1 + t2;
t1 = g + e1(d) + Ch(d, e, f) + 0xa831c66d + W[25];
t2 = e0(h) + Maj(h, a, b); c += t1; g = t1 + t2;
t1 = f + e1(c) + Ch(c, d, e) + 0xb00327c8 + W[26];
t2 = e0(g) + Maj(g, h, a); b += t1; f = t1 + t2;
t1 = e + e1(b) + Ch(b, c, d) + 0xbf597fc7 + W[27];
t2 = e0(f) + Maj(f, g, h); a += t1; e = t1 + t2;
t1 = d + e1(a) + Ch(a, b, c) + 0xc6e00bf3 + W[28];
t2 = e0(e) + Maj(e, f, g); h += t1; d = t1 + t2;
t1 = c + e1(h) + Ch(h, a, b) + 0xd5a79147 + W[29];
t2 = e0(d) + Maj(d, e, f); g += t1; c = t1 + t2;
t1 = b + e1(g) + Ch(g, h, a) + 0x06ca6351 + W[30];
t2 = e0(c) + Maj(c, d, e); f += t1; b = t1 + t2;
t1 = a + e1(f) + Ch(f, g, h) + 0x14292967 + W[31];
t2 = e0(b) + Maj(b, c, d); e += t1; a = t1 + t2;
t1 = h + e1(e) + Ch(e, f, g) + 0x27b70a85 + W[32];
t2 = e0(a) + Maj(a, b, c); d += t1; h = t1 + t2;
t1 = g + e1(d) + Ch(d, e, f) + 0x2e1b2138 + W[33];
t2 = e0(h) + Maj(h, a, b); c += t1; g = t1 + t2;
t1 = f + e1(c) + Ch(c, d, e) + 0x4d2c6dfc + W[34];
t2 = e0(g) + Maj(g, h, a); b += t1; f = t1 + t2;
t1 = e + e1(b) + Ch(b, c, d) + 0x53380d13 + W[35];
t2 = e0(f) + Maj(f, g, h); a += t1; e = t1 + t2;
t1 = d + e1(a) + Ch(a, b, c) + 0x650a7354 + W[36];
t2 = e0(e) + Maj(e, f, g); h += t1; d = t1 + t2;
t1 = c + e1(h) + Ch(h, a, b) + 0x766a0abb + W[37];
t2 = e0(d) + Maj(d, e, f); g += t1; c = t1 + t2;
t1 = b + e1(g) + Ch(g, h, a) + 0x81c2c92e + W[38];
t2 = e0(c) + Maj(c, d, e); f += t1; b = t1 + t2;
t1 = a + e1(f) + Ch(f, g, h) + 0x92722c85 + W[39];
t2 = e0(b) + Maj(b, c, d); e += t1; a = t1 + t2;
t1 = h + e1(e) + Ch(e, f, g) + 0xa2bfe8a1 + W[40];
t2 = e0(a) + Maj(a, b, c); d += t1; h = t1 + t2;
t1 = g + e1(d) + Ch(d, e, f) + 0xa81a664b + W[41];
t2 = e0(h) + Maj(h, a, b); c += t1; g = t1 + t2;
t1 = f + e1(c) + Ch(c, d, e) + 0xc24b8b70 + W[42];
t2 = e0(g) + Maj(g, h, a); b += t1; f = t1 + t2;
t1 = e + e1(b) + Ch(b, c, d) + 0xc76c51a3 + W[43];
t2 = e0(f) + Maj(f, g, h); a += t1; e = t1 + t2;
t1 = d + e1(a) + Ch(a, b, c) + 0xd192e819 + W[44];
t2 = e0(e) + Maj(e, f, g); h += t1; d = t1 + t2;
t1 = c + e1(h) + Ch(h, a, b) + 0xd6990624 + W[45];
t2 = e0(d) + Maj(d, e, f); g += t1; c = t1 + t2;
t1 = b + e1(g) + Ch(g, h, a) + 0xf40e3585 + W[46];
t2 = e0(c) + Maj(c, d, e); f += t1; b = t1 + t2;
t1 = a + e1(f) + Ch(f, g, h) + 0x106aa070 + W[47];
t2 = e0(b) + Maj(b, c, d); e += t1; a = t1 + t2;
t1 = h + e1(e) + Ch(e, f, g) + 0x19a4c116 + W[48];
t2 = e0(a) + Maj(a, b, c); d += t1; h = t1 + t2;
t1 = g + e1(d) + Ch(d, e, f) + 0x1e376c08 + W[49];
t2 = e0(h) + Maj(h, a, b); c += t1; g = t1 + t2;
t1 = f + e1(c) + Ch(c, d, e) + 0x2748774c + W[50];
t2 = e0(g) + Maj(g, h, a); b += t1; f = t1 + t2;
t1 = e + e1(b) + Ch(b, c, d) + 0x34b0bcb5 + W[51];
t2 = e0(f) + Maj(f, g, h); a += t1; e = t1 + t2;
t1 = d + e1(a) + Ch(a, b, c) + 0x391c0cb3 + W[52];
t2 = e0(e) + Maj(e, f, g); h += t1; d = t1 + t2;
t1 = c + e1(h) + Ch(h, a, b) + 0x4ed8aa4a + W[53];
t2 = e0(d) + Maj(d, e, f); g += t1; c = t1 + t2;
t1 = b + e1(g) + Ch(g, h, a) + 0x5b9cca4f + W[54];
t2 = e0(c) + Maj(c, d, e); f += t1; b = t1 + t2;
t1 = a + e1(f) + Ch(f, g, h) + 0x682e6ff3 + W[55];
t2 = e0(b) + Maj(b, c, d); e += t1; a = t1 + t2;
t1 = h + e1(e) + Ch(e, f, g) + 0x748f82ee + W[56];
t2 = e0(a) + Maj(a, b, c); d += t1; h = t1 + t2;
t1 = g + e1(d) + Ch(d, e, f) + 0x78a5636f + W[57];
t2 = e0(h) + Maj(h, a, b); c += t1; g = t1 + t2;
t1 = f + e1(c) + Ch(c, d, e) + 0x84c87814 + W[58];
t2 = e0(g) + Maj(g, h, a); b += t1; f = t1 + t2;
t1 = e + e1(b) + Ch(b, c, d) + 0x8cc70208 + W[59];
t2 = e0(f) + Maj(f, g, h); a += t1; e = t1 + t2;
t1 = d + e1(a) + Ch(a, b, c) + 0x90befffa + W[60];
t2 = e0(e) + Maj(e, f, g); h += t1; d = t1 + t2;
t1 = c + e1(h) + Ch(h, a, b) + 0xa4506ceb + W[61];
t2 = e0(d) + Maj(d, e, f); g += t1; c = t1 + t2;
t1 = b + e1(g) + Ch(g, h, a) + 0xbef9a3f7 + W[62];
t2 = e0(c) + Maj(c, d, e); f += t1; b = t1 + t2;
t1 = a + e1(f) + Ch(f, g, h) + 0xc67178f2 + W[63];
t2 = e0(b) + Maj(b, c, d); e += t1; a = t1 + t2;
state[0] += a; state[1] += b; state[2] += c; state[3] += d;
state[4] += e; state[5] += f; state[6] += g; state[7] += h;
/* clear any sensitive info... */
memzero_explicit(W, 64 * sizeof(u32));
}
void sha256_update(struct sha256_state *sctx, const u8 *data, unsigned int len)
{
unsigned int partial, done;
const u8 *src;
partial = sctx->count & 0x3f;
sctx->count += len;
done = 0;
src = data;
if ((partial + len) > 63) {
if (partial) {
done = -partial;
memcpy(sctx->buf + partial, data, done + 64);
src = sctx->buf;
}
do {
sha256_transform(sctx->state, src);
done += 64;
src = data + done;
} while (done + 63 < len);
partial = 0;
}
memcpy(sctx->buf + partial, src, len - done);
}
EXPORT_SYMBOL(sha256_update);
void sha224_update(struct sha256_state *sctx, const u8 *data, unsigned int len)
{
sha256_update(sctx, data, len);
}
EXPORT_SYMBOL(sha224_update);
static void __sha256_final(struct sha256_state *sctx, u8 *out, int digest_words)
{
__be32 *dst = (__be32 *)out;
__be64 bits;
unsigned int index, pad_len;
int i;
static const u8 padding[64] = { 0x80, };
/* Save number of bits */
bits = cpu_to_be64(sctx->count << 3);
/* Pad out to 56 mod 64. */
index = sctx->count & 0x3f;
pad_len = (index < 56) ? (56 - index) : ((64+56) - index);
sha256_update(sctx, padding, pad_len);
/* Append length (before padding) */
sha256_update(sctx, (const u8 *)&bits, sizeof(bits));
/* Store state in digest */
for (i = 0; i < digest_words; i++)
put_unaligned_be32(sctx->state[i], &dst[i]);
/* Zeroize sensitive information. */
memzero_explicit(sctx, sizeof(*sctx));
}
void sha256_final(struct sha256_state *sctx, u8 *out)
{
__sha256_final(sctx, out, 8);
}
EXPORT_SYMBOL(sha256_final);
void sha224_final(struct sha256_state *sctx, u8 *out)
{
__sha256_final(sctx, out, 7);
}
EXPORT_SYMBOL(sha224_final);
void sha256(const u8 *data, unsigned int len, u8 *out)
{
struct sha256_state sctx;
sha256_init(&sctx);
sha256_update(&sctx, data, len);
sha256_final(&sctx, out);
}
EXPORT_SYMBOL(sha256);
MODULE_LICENSE("GPL");
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