crypto: poly1305 - Add a generic Poly1305 authenticator implementation

Poly1305 is a fast message authenticator designed by Daniel J. Bernstein.
It is further defined in RFC7539 as a building block for the ChaCha20-Poly1305
AEAD for use in IETF protocols.

This is a portable C implementation of the algorithm without architecture
specific optimizations, based on public domain code by Daniel J. Bernstein and
Andrew Moon.

Signed-off-by: Martin Willi <martin@strongswan.org>
Acked-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

1 files changed, 300 insertions, 0 deletions

diff --git a/crypto/poly1305_generic.c b/crypto/poly1305_generic.c
new file mode 100644
index 0000000..9c1159b
--- /dev/null
+++ b/crypto/poly1305_generic.c
@@ -0,0 +1,300 @@
+/*
+ * Poly1305 authenticator algorithm, RFC7539
+ *
+ * Copyright (C) 2015 Martin Willi
+ *
+ * Based on public domain code by Andrew Moon and Daniel J. Bernstein.
+ *
+ * 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/internal/hash.h>
+#include <linux/crypto.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+
+#define POLY1305_BLOCK_SIZE	16
+#define POLY1305_KEY_SIZE	32
+#define POLY1305_DIGEST_SIZE	16
+
+struct poly1305_ctx {
+	/* key */
+	u32 r[5];
+	/* finalize key */
+	u32 s[4];
+};
+
+struct poly1305_desc_ctx {
+	/* accumulator */
+	u32 h[5];
+	/* partial buffer */
+	u8 buf[POLY1305_BLOCK_SIZE];
+	/* bytes used in partial buffer */
+	unsigned int buflen;
+};
+
+static inline u64 mlt(u64 a, u64 b)
+{
+	return a * b;
+}
+
+static inline u32 sr(u64 v, u_char n)
+{
+	return v >> n;
+}
+
+static inline u32 and(u32 v, u32 mask)
+{
+	return v & mask;
+}
+
+static inline u32 le32_to_cpuvp(const void *p)
+{
+	return le32_to_cpup(p);
+}
+
+static int poly1305_init(struct shash_desc *desc)
+{
+	struct poly1305_desc_ctx *dctx = shash_desc_ctx(desc);
+
+	memset(dctx->h, 0, sizeof(dctx->h));
+	dctx->buflen = 0;
+
+	return 0;
+}
+
+static int poly1305_setkey(struct crypto_shash *tfm,
+			   const u8 *key, unsigned int keylen)
+{
+	struct poly1305_ctx *ctx = crypto_shash_ctx(tfm);
+
+	if (keylen != POLY1305_KEY_SIZE) {
+		crypto_shash_set_flags(tfm, CRYPTO_TFM_RES_BAD_KEY_LEN);
+		return -EINVAL;
+	}
+
+	/* r &= 0xffffffc0ffffffc0ffffffc0fffffff */
+	ctx->r[0] = (le32_to_cpuvp(key +  0) >> 0) & 0x3ffffff;
+	ctx->r[1] = (le32_to_cpuvp(key +  3) >> 2) & 0x3ffff03;
+	ctx->r[2] = (le32_to_cpuvp(key +  6) >> 4) & 0x3ffc0ff;
+	ctx->r[3] = (le32_to_cpuvp(key +  9) >> 6) & 0x3f03fff;
+	ctx->r[4] = (le32_to_cpuvp(key + 12) >> 8) & 0x00fffff;
+
+	ctx->s[0] = le32_to_cpuvp(key + 16);
+	ctx->s[1] = le32_to_cpuvp(key + 20);
+	ctx->s[2] = le32_to_cpuvp(key + 24);
+	ctx->s[3] = le32_to_cpuvp(key + 28);
+
+	return 0;
+}
+
+static unsigned int poly1305_blocks(struct poly1305_desc_ctx *dctx,
+				    struct poly1305_ctx *ctx, const u8 *src,
+				    unsigned int srclen, u32 hibit)
+{
+	u32 r0, r1, r2, r3, r4;
+	u32 s1, s2, s3, s4;
+	u32 h0, h1, h2, h3, h4;
+	u64 d0, d1, d2, d3, d4;
+
+	r0 = ctx->r[0];
+	r1 = ctx->r[1];
+	r2 = ctx->r[2];
+	r3 = ctx->r[3];
+	r4 = ctx->r[4];
+
+	s1 = r1 * 5;
+	s2 = r2 * 5;
+	s3 = r3 * 5;
+	s4 = r4 * 5;
+
+	h0 = dctx->h[0];
+	h1 = dctx->h[1];
+	h2 = dctx->h[2];
+	h3 = dctx->h[3];
+	h4 = dctx->h[4];
+
+	while (likely(srclen >= POLY1305_BLOCK_SIZE)) {
+
+		/* h += m[i] */
+		h0 += (le32_to_cpuvp(src +  0) >> 0) & 0x3ffffff;
+		h1 += (le32_to_cpuvp(src +  3) >> 2) & 0x3ffffff;
+		h2 += (le32_to_cpuvp(src +  6) >> 4) & 0x3ffffff;
+		h3 += (le32_to_cpuvp(src +  9) >> 6) & 0x3ffffff;
+		h4 += (le32_to_cpuvp(src + 12) >> 8) | hibit;
+
+		/* h *= r */
+		d0 = mlt(h0, r0) + mlt(h1, s4) + mlt(h2, s3) +
+		     mlt(h3, s2) + mlt(h4, s1);
+		d1 = mlt(h0, r1) + mlt(h1, r0) + mlt(h2, s4) +
+		     mlt(h3, s3) + mlt(h4, s2);
+		d2 = mlt(h0, r2) + mlt(h1, r1) + mlt(h2, r0) +
+		     mlt(h3, s4) + mlt(h4, s3);
+		d3 = mlt(h0, r3) + mlt(h1, r2) + mlt(h2, r1) +
+		     mlt(h3, r0) + mlt(h4, s4);
+		d4 = mlt(h0, r4) + mlt(h1, r3) + mlt(h2, r2) +
+		     mlt(h3, r1) + mlt(h4, r0);
+
+		/* (partial) h %= p */
+		d1 += sr(d0, 26);     h0 = and(d0, 0x3ffffff);
+		d2 += sr(d1, 26);     h1 = and(d1, 0x3ffffff);
+		d3 += sr(d2, 26);     h2 = and(d2, 0x3ffffff);
+		d4 += sr(d3, 26);     h3 = and(d3, 0x3ffffff);
+		h0 += sr(d4, 26) * 5; h4 = and(d4, 0x3ffffff);
+		h1 += h0 >> 26;       h0 = h0 & 0x3ffffff;
+
+		src += POLY1305_BLOCK_SIZE;
+		srclen -= POLY1305_BLOCK_SIZE;
+	}
+
+	dctx->h[0] = h0;
+	dctx->h[1] = h1;
+	dctx->h[2] = h2;
+	dctx->h[3] = h3;
+	dctx->h[4] = h4;
+
+	return srclen;
+}
+
+static int poly1305_update(struct shash_desc *desc,
+			   const u8 *src, unsigned int srclen)
+{
+	struct poly1305_desc_ctx *dctx = shash_desc_ctx(desc);
+	struct poly1305_ctx *ctx = crypto_shash_ctx(desc->tfm);
+	unsigned int bytes;
+
+	if (unlikely(dctx->buflen)) {
+		bytes = min(srclen, POLY1305_BLOCK_SIZE - dctx->buflen);
+		memcpy(dctx->buf + dctx->buflen, src, bytes);
+		src += bytes;
+		srclen -= bytes;
+		dctx->buflen += bytes;
+
+		if (dctx->buflen == POLY1305_BLOCK_SIZE) {
+			poly1305_blocks(dctx, ctx, dctx->buf,
+					POLY1305_BLOCK_SIZE, 1 << 24);
+			dctx->buflen = 0;
+		}
+	}
+
+	if (likely(srclen >= POLY1305_BLOCK_SIZE)) {
+		bytes = poly1305_blocks(dctx, ctx, src, srclen, 1 << 24);
+		src += srclen - bytes;
+		srclen = bytes;
+	}
+
+	if (unlikely(srclen)) {
+		dctx->buflen = srclen;
+		memcpy(dctx->buf, src, srclen);
+	}
+
+	return 0;
+}
+
+static int poly1305_final(struct shash_desc *desc, u8 *dst)
+{
+	struct poly1305_desc_ctx *dctx = shash_desc_ctx(desc);
+	struct poly1305_ctx *ctx = crypto_shash_ctx(desc->tfm);
+	__le32 *mac = (__le32 *)dst;
+	u32 h0, h1, h2, h3, h4;
+	u32 g0, g1, g2, g3, g4;
+	u32 mask;
+	u64 f = 0;
+
+	if (unlikely(dctx->buflen)) {
+		dctx->buf[dctx->buflen++] = 1;
+		memset(dctx->buf + dctx->buflen, 0,
+		       POLY1305_BLOCK_SIZE - dctx->buflen);
+		poly1305_blocks(dctx, ctx, dctx->buf, POLY1305_BLOCK_SIZE, 0);
+	}
+
+	/* fully carry h */
+	h0 = dctx->h[0];
+	h1 = dctx->h[1];
+	h2 = dctx->h[2];
+	h3 = dctx->h[3];
+	h4 = dctx->h[4];
+
+	h2 += (h1 >> 26);     h1 = h1 & 0x3ffffff;
+	h3 += (h2 >> 26);     h2 = h2 & 0x3ffffff;
+	h4 += (h3 >> 26);     h3 = h3 & 0x3ffffff;
+	h0 += (h4 >> 26) * 5; h4 = h4 & 0x3ffffff;
+	h1 += (h0 >> 26);     h0 = h0 & 0x3ffffff;
+
+	/* compute h + -p */
+	g0 = h0 + 5;
+	g1 = h1 + (g0 >> 26);             g0 &= 0x3ffffff;
+	g2 = h2 + (g1 >> 26);             g1 &= 0x3ffffff;
+	g3 = h3 + (g2 >> 26);             g2 &= 0x3ffffff;
+	g4 = h4 + (g3 >> 26) - (1 << 26); g3 &= 0x3ffffff;
+
+	/* select h if h < p, or h + -p if h >= p */
+	mask = (g4 >> ((sizeof(u32) * 8) - 1)) - 1;
+	g0 &= mask;
+	g1 &= mask;
+	g2 &= mask;
+	g3 &= mask;
+	g4 &= mask;
+	mask = ~mask;
+	h0 = (h0 & mask) | g0;
+	h1 = (h1 & mask) | g1;
+	h2 = (h2 & mask) | g2;
+	h3 = (h3 & mask) | g3;
+	h4 = (h4 & mask) | g4;
+
+	/* h = h % (2^128) */
+	h0 = (h0 >>  0) | (h1 << 26);
+	h1 = (h1 >>  6) | (h2 << 20);
+	h2 = (h2 >> 12) | (h3 << 14);
+	h3 = (h3 >> 18) | (h4 <<  8);
+
+	/* mac = (h + s) % (2^128) */
+	f = (f >> 32) + h0 + ctx->s[0]; mac[0] = cpu_to_le32(f);
+	f = (f >> 32) + h1 + ctx->s[1]; mac[1] = cpu_to_le32(f);
+	f = (f >> 32) + h2 + ctx->s[2]; mac[2] = cpu_to_le32(f);
+	f = (f >> 32) + h3 + ctx->s[3]; mac[3] = cpu_to_le32(f);
+
+	return 0;
+}
+
+static struct shash_alg poly1305_alg = {
+	.digestsize	= POLY1305_DIGEST_SIZE,
+	.init		= poly1305_init,
+	.update		= poly1305_update,
+	.final		= poly1305_final,
+	.setkey		= poly1305_setkey,
+	.descsize	= sizeof(struct poly1305_desc_ctx),
+	.base		= {
+		.cra_name		= "poly1305",
+		.cra_driver_name	= "poly1305-generic",
+		.cra_priority		= 100,
+		.cra_flags		= CRYPTO_ALG_TYPE_SHASH,
+		.cra_alignmask		= sizeof(u32) - 1,
+		.cra_blocksize		= POLY1305_BLOCK_SIZE,
+		.cra_ctxsize		= sizeof(struct poly1305_ctx),
+		.cra_module		= THIS_MODULE,
+	},
+};
+
+static int __init poly1305_mod_init(void)
+{
+	return crypto_register_shash(&poly1305_alg);
+}
+
+static void __exit poly1305_mod_exit(void)
+{
+	crypto_unregister_shash(&poly1305_alg);
+}
+
+module_init(poly1305_mod_init);
+module_exit(poly1305_mod_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Martin Willi <martin@strongswan.org>");
+MODULE_DESCRIPTION("Poly1305 authenticator");
+MODULE_ALIAS_CRYPTO("poly1305");
+MODULE_ALIAS_CRYPTO("poly1305-generic");