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 000000000000..9c1159b991f4
--- /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");