1 /*
2  * Poly1305 authenticator algorithm, RFC7539
3  *
4  * Copyright (C) 2015 Martin Willi
5  *
6  * Based on public domain code by Andrew Moon and Daniel J. Bernstein.
7  *
8  * This program is free software; you can redistribute it and/or modify
9  * it under the terms of the GNU General Public License as published by
10  * the Free Software Foundation; either version 2 of the License, or
11  * (at your option) any later version.
12  */
13 
14 #include <crypto/algapi.h>
15 #include <crypto/internal/hash.h>
16 #include <crypto/poly1305.h>
17 #include <linux/crypto.h>
18 #include <linux/kernel.h>
19 #include <linux/module.h>
20 #include <asm/unaligned.h>
21 
mlt(u64 a,u64 b)22 static inline u64 mlt(u64 a, u64 b)
23 {
24 	return a * b;
25 }
26 
sr(u64 v,u_char n)27 static inline u32 sr(u64 v, u_char n)
28 {
29 	return v >> n;
30 }
31 
and(u32 v,u32 mask)32 static inline u32 and(u32 v, u32 mask)
33 {
34 	return v & mask;
35 }
36 
crypto_poly1305_init(struct shash_desc * desc)37 int crypto_poly1305_init(struct shash_desc *desc)
38 {
39 	struct poly1305_desc_ctx *dctx = shash_desc_ctx(desc);
40 
41 	memset(dctx->h, 0, sizeof(dctx->h));
42 	dctx->buflen = 0;
43 	dctx->rset = false;
44 	dctx->sset = false;
45 
46 	return 0;
47 }
48 EXPORT_SYMBOL_GPL(crypto_poly1305_init);
49 
poly1305_setrkey(struct poly1305_desc_ctx * dctx,const u8 * key)50 static void poly1305_setrkey(struct poly1305_desc_ctx *dctx, const u8 *key)
51 {
52 	/* r &= 0xffffffc0ffffffc0ffffffc0fffffff */
53 	dctx->r[0] = (get_unaligned_le32(key +  0) >> 0) & 0x3ffffff;
54 	dctx->r[1] = (get_unaligned_le32(key +  3) >> 2) & 0x3ffff03;
55 	dctx->r[2] = (get_unaligned_le32(key +  6) >> 4) & 0x3ffc0ff;
56 	dctx->r[3] = (get_unaligned_le32(key +  9) >> 6) & 0x3f03fff;
57 	dctx->r[4] = (get_unaligned_le32(key + 12) >> 8) & 0x00fffff;
58 }
59 
poly1305_setskey(struct poly1305_desc_ctx * dctx,const u8 * key)60 static void poly1305_setskey(struct poly1305_desc_ctx *dctx, const u8 *key)
61 {
62 	dctx->s[0] = get_unaligned_le32(key +  0);
63 	dctx->s[1] = get_unaligned_le32(key +  4);
64 	dctx->s[2] = get_unaligned_le32(key +  8);
65 	dctx->s[3] = get_unaligned_le32(key + 12);
66 }
67 
68 /*
69  * Poly1305 requires a unique key for each tag, which implies that we can't set
70  * it on the tfm that gets accessed by multiple users simultaneously. Instead we
71  * expect the key as the first 32 bytes in the update() call.
72  */
crypto_poly1305_setdesckey(struct poly1305_desc_ctx * dctx,const u8 * src,unsigned int srclen)73 unsigned int crypto_poly1305_setdesckey(struct poly1305_desc_ctx *dctx,
74 					const u8 *src, unsigned int srclen)
75 {
76 	if (!dctx->sset) {
77 		if (!dctx->rset && srclen >= POLY1305_BLOCK_SIZE) {
78 			poly1305_setrkey(dctx, src);
79 			src += POLY1305_BLOCK_SIZE;
80 			srclen -= POLY1305_BLOCK_SIZE;
81 			dctx->rset = true;
82 		}
83 		if (srclen >= POLY1305_BLOCK_SIZE) {
84 			poly1305_setskey(dctx, src);
85 			src += POLY1305_BLOCK_SIZE;
86 			srclen -= POLY1305_BLOCK_SIZE;
87 			dctx->sset = true;
88 		}
89 	}
90 	return srclen;
91 }
92 EXPORT_SYMBOL_GPL(crypto_poly1305_setdesckey);
93 
poly1305_blocks(struct poly1305_desc_ctx * dctx,const u8 * src,unsigned int srclen,u32 hibit)94 static unsigned int poly1305_blocks(struct poly1305_desc_ctx *dctx,
95 				    const u8 *src, unsigned int srclen,
96 				    u32 hibit)
97 {
98 	u32 r0, r1, r2, r3, r4;
99 	u32 s1, s2, s3, s4;
100 	u32 h0, h1, h2, h3, h4;
101 	u64 d0, d1, d2, d3, d4;
102 	unsigned int datalen;
103 
104 	if (unlikely(!dctx->sset)) {
105 		datalen = crypto_poly1305_setdesckey(dctx, src, srclen);
106 		src += srclen - datalen;
107 		srclen = datalen;
108 	}
109 
110 	r0 = dctx->r[0];
111 	r1 = dctx->r[1];
112 	r2 = dctx->r[2];
113 	r3 = dctx->r[3];
114 	r4 = dctx->r[4];
115 
116 	s1 = r1 * 5;
117 	s2 = r2 * 5;
118 	s3 = r3 * 5;
119 	s4 = r4 * 5;
120 
121 	h0 = dctx->h[0];
122 	h1 = dctx->h[1];
123 	h2 = dctx->h[2];
124 	h3 = dctx->h[3];
125 	h4 = dctx->h[4];
126 
127 	while (likely(srclen >= POLY1305_BLOCK_SIZE)) {
128 
129 		/* h += m[i] */
130 		h0 += (get_unaligned_le32(src +  0) >> 0) & 0x3ffffff;
131 		h1 += (get_unaligned_le32(src +  3) >> 2) & 0x3ffffff;
132 		h2 += (get_unaligned_le32(src +  6) >> 4) & 0x3ffffff;
133 		h3 += (get_unaligned_le32(src +  9) >> 6) & 0x3ffffff;
134 		h4 += (get_unaligned_le32(src + 12) >> 8) | hibit;
135 
136 		/* h *= r */
137 		d0 = mlt(h0, r0) + mlt(h1, s4) + mlt(h2, s3) +
138 		     mlt(h3, s2) + mlt(h4, s1);
139 		d1 = mlt(h0, r1) + mlt(h1, r0) + mlt(h2, s4) +
140 		     mlt(h3, s3) + mlt(h4, s2);
141 		d2 = mlt(h0, r2) + mlt(h1, r1) + mlt(h2, r0) +
142 		     mlt(h3, s4) + mlt(h4, s3);
143 		d3 = mlt(h0, r3) + mlt(h1, r2) + mlt(h2, r1) +
144 		     mlt(h3, r0) + mlt(h4, s4);
145 		d4 = mlt(h0, r4) + mlt(h1, r3) + mlt(h2, r2) +
146 		     mlt(h3, r1) + mlt(h4, r0);
147 
148 		/* (partial) h %= p */
149 		d1 += sr(d0, 26);     h0 = and(d0, 0x3ffffff);
150 		d2 += sr(d1, 26);     h1 = and(d1, 0x3ffffff);
151 		d3 += sr(d2, 26);     h2 = and(d2, 0x3ffffff);
152 		d4 += sr(d3, 26);     h3 = and(d3, 0x3ffffff);
153 		h0 += sr(d4, 26) * 5; h4 = and(d4, 0x3ffffff);
154 		h1 += h0 >> 26;       h0 = h0 & 0x3ffffff;
155 
156 		src += POLY1305_BLOCK_SIZE;
157 		srclen -= POLY1305_BLOCK_SIZE;
158 	}
159 
160 	dctx->h[0] = h0;
161 	dctx->h[1] = h1;
162 	dctx->h[2] = h2;
163 	dctx->h[3] = h3;
164 	dctx->h[4] = h4;
165 
166 	return srclen;
167 }
168 
crypto_poly1305_update(struct shash_desc * desc,const u8 * src,unsigned int srclen)169 int crypto_poly1305_update(struct shash_desc *desc,
170 			   const u8 *src, unsigned int srclen)
171 {
172 	struct poly1305_desc_ctx *dctx = shash_desc_ctx(desc);
173 	unsigned int bytes;
174 
175 	if (unlikely(dctx->buflen)) {
176 		bytes = min(srclen, POLY1305_BLOCK_SIZE - dctx->buflen);
177 		memcpy(dctx->buf + dctx->buflen, src, bytes);
178 		src += bytes;
179 		srclen -= bytes;
180 		dctx->buflen += bytes;
181 
182 		if (dctx->buflen == POLY1305_BLOCK_SIZE) {
183 			poly1305_blocks(dctx, dctx->buf,
184 					POLY1305_BLOCK_SIZE, 1 << 24);
185 			dctx->buflen = 0;
186 		}
187 	}
188 
189 	if (likely(srclen >= POLY1305_BLOCK_SIZE)) {
190 		bytes = poly1305_blocks(dctx, src, srclen, 1 << 24);
191 		src += srclen - bytes;
192 		srclen = bytes;
193 	}
194 
195 	if (unlikely(srclen)) {
196 		dctx->buflen = srclen;
197 		memcpy(dctx->buf, src, srclen);
198 	}
199 
200 	return 0;
201 }
202 EXPORT_SYMBOL_GPL(crypto_poly1305_update);
203 
crypto_poly1305_final(struct shash_desc * desc,u8 * dst)204 int crypto_poly1305_final(struct shash_desc *desc, u8 *dst)
205 {
206 	struct poly1305_desc_ctx *dctx = shash_desc_ctx(desc);
207 	u32 h0, h1, h2, h3, h4;
208 	u32 g0, g1, g2, g3, g4;
209 	u32 mask;
210 	u64 f = 0;
211 
212 	if (unlikely(!dctx->sset))
213 		return -ENOKEY;
214 
215 	if (unlikely(dctx->buflen)) {
216 		dctx->buf[dctx->buflen++] = 1;
217 		memset(dctx->buf + dctx->buflen, 0,
218 		       POLY1305_BLOCK_SIZE - dctx->buflen);
219 		poly1305_blocks(dctx, dctx->buf, POLY1305_BLOCK_SIZE, 0);
220 	}
221 
222 	/* fully carry h */
223 	h0 = dctx->h[0];
224 	h1 = dctx->h[1];
225 	h2 = dctx->h[2];
226 	h3 = dctx->h[3];
227 	h4 = dctx->h[4];
228 
229 	h2 += (h1 >> 26);     h1 = h1 & 0x3ffffff;
230 	h3 += (h2 >> 26);     h2 = h2 & 0x3ffffff;
231 	h4 += (h3 >> 26);     h3 = h3 & 0x3ffffff;
232 	h0 += (h4 >> 26) * 5; h4 = h4 & 0x3ffffff;
233 	h1 += (h0 >> 26);     h0 = h0 & 0x3ffffff;
234 
235 	/* compute h + -p */
236 	g0 = h0 + 5;
237 	g1 = h1 + (g0 >> 26);             g0 &= 0x3ffffff;
238 	g2 = h2 + (g1 >> 26);             g1 &= 0x3ffffff;
239 	g3 = h3 + (g2 >> 26);             g2 &= 0x3ffffff;
240 	g4 = h4 + (g3 >> 26) - (1 << 26); g3 &= 0x3ffffff;
241 
242 	/* select h if h < p, or h + -p if h >= p */
243 	mask = (g4 >> ((sizeof(u32) * 8) - 1)) - 1;
244 	g0 &= mask;
245 	g1 &= mask;
246 	g2 &= mask;
247 	g3 &= mask;
248 	g4 &= mask;
249 	mask = ~mask;
250 	h0 = (h0 & mask) | g0;
251 	h1 = (h1 & mask) | g1;
252 	h2 = (h2 & mask) | g2;
253 	h3 = (h3 & mask) | g3;
254 	h4 = (h4 & mask) | g4;
255 
256 	/* h = h % (2^128) */
257 	h0 = (h0 >>  0) | (h1 << 26);
258 	h1 = (h1 >>  6) | (h2 << 20);
259 	h2 = (h2 >> 12) | (h3 << 14);
260 	h3 = (h3 >> 18) | (h4 <<  8);
261 
262 	/* mac = (h + s) % (2^128) */
263 	f = (f >> 32) + h0 + dctx->s[0]; put_unaligned_le32(f, dst +  0);
264 	f = (f >> 32) + h1 + dctx->s[1]; put_unaligned_le32(f, dst +  4);
265 	f = (f >> 32) + h2 + dctx->s[2]; put_unaligned_le32(f, dst +  8);
266 	f = (f >> 32) + h3 + dctx->s[3]; put_unaligned_le32(f, dst + 12);
267 
268 	return 0;
269 }
270 EXPORT_SYMBOL_GPL(crypto_poly1305_final);
271 
272 static struct shash_alg poly1305_alg = {
273 	.digestsize	= POLY1305_DIGEST_SIZE,
274 	.init		= crypto_poly1305_init,
275 	.update		= crypto_poly1305_update,
276 	.final		= crypto_poly1305_final,
277 	.descsize	= sizeof(struct poly1305_desc_ctx),
278 	.base		= {
279 		.cra_name		= "poly1305",
280 		.cra_driver_name	= "poly1305-generic",
281 		.cra_priority		= 100,
282 		.cra_blocksize		= POLY1305_BLOCK_SIZE,
283 		.cra_module		= THIS_MODULE,
284 	},
285 };
286 
poly1305_mod_init(void)287 static int __init poly1305_mod_init(void)
288 {
289 	return crypto_register_shash(&poly1305_alg);
290 }
291 
poly1305_mod_exit(void)292 static void __exit poly1305_mod_exit(void)
293 {
294 	crypto_unregister_shash(&poly1305_alg);
295 }
296 
297 module_init(poly1305_mod_init);
298 module_exit(poly1305_mod_exit);
299 
300 MODULE_LICENSE("GPL");
301 MODULE_AUTHOR("Martin Willi <martin@strongswan.org>");
302 MODULE_DESCRIPTION("Poly1305 authenticator");
303 MODULE_ALIAS_CRYPTO("poly1305");
304 MODULE_ALIAS_CRYPTO("poly1305-generic");
305