1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis */
2 /* SPDX-License-Identifier: Unlicense */
3
4 /* The implementation is based on:
5 * Public Domain poly1305 from Andrew Moon
6 * https://github.com/floodyberry/poly1305-donna
7 */
8
9 #include "tomcrypt_private.h"
10
11 #ifdef LTC_POLY1305
12
13 /* internal only */
s_poly1305_block(poly1305_state * st,const unsigned char * in,unsigned long inlen)14 static void s_poly1305_block(poly1305_state *st, const unsigned char *in, unsigned long inlen)
15 {
16 const unsigned long hibit = (st->final) ? 0 : (1UL << 24); /* 1 << 128 */
17 ulong32 r0,r1,r2,r3,r4;
18 ulong32 s1,s2,s3,s4;
19 ulong32 h0,h1,h2,h3,h4;
20 ulong32 tmp;
21 ulong64 d0,d1,d2,d3,d4;
22 ulong32 c;
23
24 r0 = st->r[0];
25 r1 = st->r[1];
26 r2 = st->r[2];
27 r3 = st->r[3];
28 r4 = st->r[4];
29
30 s1 = r1 * 5;
31 s2 = r2 * 5;
32 s3 = r3 * 5;
33 s4 = r4 * 5;
34
35 h0 = st->h[0];
36 h1 = st->h[1];
37 h2 = st->h[2];
38 h3 = st->h[3];
39 h4 = st->h[4];
40
41 while (inlen >= 16) {
42 /* h += in[i] */
43 LOAD32L(tmp, in+ 0); h0 += (tmp ) & 0x3ffffff;
44 LOAD32L(tmp, in+ 3); h1 += (tmp >> 2) & 0x3ffffff;
45 LOAD32L(tmp, in+ 6); h2 += (tmp >> 4) & 0x3ffffff;
46 LOAD32L(tmp, in+ 9); h3 += (tmp >> 6) & 0x3ffffff;
47 LOAD32L(tmp, in+12); h4 += (tmp >> 8) | hibit;
48
49 /* h *= r */
50 d0 = ((ulong64)h0 * r0) + ((ulong64)h1 * s4) + ((ulong64)h2 * s3) + ((ulong64)h3 * s2) + ((ulong64)h4 * s1);
51 d1 = ((ulong64)h0 * r1) + ((ulong64)h1 * r0) + ((ulong64)h2 * s4) + ((ulong64)h3 * s3) + ((ulong64)h4 * s2);
52 d2 = ((ulong64)h0 * r2) + ((ulong64)h1 * r1) + ((ulong64)h2 * r0) + ((ulong64)h3 * s4) + ((ulong64)h4 * s3);
53 d3 = ((ulong64)h0 * r3) + ((ulong64)h1 * r2) + ((ulong64)h2 * r1) + ((ulong64)h3 * r0) + ((ulong64)h4 * s4);
54 d4 = ((ulong64)h0 * r4) + ((ulong64)h1 * r3) + ((ulong64)h2 * r2) + ((ulong64)h3 * r1) + ((ulong64)h4 * r0);
55
56 /* (partial) h %= p */
57 c = (ulong32)(d0 >> 26); h0 = (ulong32)d0 & 0x3ffffff;
58 d1 += c; c = (ulong32)(d1 >> 26); h1 = (ulong32)d1 & 0x3ffffff;
59 d2 += c; c = (ulong32)(d2 >> 26); h2 = (ulong32)d2 & 0x3ffffff;
60 d3 += c; c = (ulong32)(d3 >> 26); h3 = (ulong32)d3 & 0x3ffffff;
61 d4 += c; c = (ulong32)(d4 >> 26); h4 = (ulong32)d4 & 0x3ffffff;
62 h0 += c * 5; c = (h0 >> 26); h0 = h0 & 0x3ffffff;
63 h1 += c;
64
65 in += 16;
66 inlen -= 16;
67 }
68
69 st->h[0] = h0;
70 st->h[1] = h1;
71 st->h[2] = h2;
72 st->h[3] = h3;
73 st->h[4] = h4;
74 }
75
76 /**
77 Initialize an POLY1305 context.
78 @param st The POLY1305 state
79 @param key The secret key
80 @param keylen The length of the secret key (octets)
81 @return CRYPT_OK if successful
82 */
poly1305_init(poly1305_state * st,const unsigned char * key,unsigned long keylen)83 int poly1305_init(poly1305_state *st, const unsigned char *key, unsigned long keylen)
84 {
85 LTC_ARGCHK(st != NULL);
86 LTC_ARGCHK(key != NULL);
87 LTC_ARGCHK(keylen == 32);
88
89 /* r &= 0xffffffc0ffffffc0ffffffc0fffffff */
90 LOAD32L(st->r[0], key + 0); st->r[0] = (st->r[0] ) & 0x3ffffff;
91 LOAD32L(st->r[1], key + 3); st->r[1] = (st->r[1] >> 2) & 0x3ffff03;
92 LOAD32L(st->r[2], key + 6); st->r[2] = (st->r[2] >> 4) & 0x3ffc0ff;
93 LOAD32L(st->r[3], key + 9); st->r[3] = (st->r[3] >> 6) & 0x3f03fff;
94 LOAD32L(st->r[4], key + 12); st->r[4] = (st->r[4] >> 8) & 0x00fffff;
95
96 /* h = 0 */
97 st->h[0] = 0;
98 st->h[1] = 0;
99 st->h[2] = 0;
100 st->h[3] = 0;
101 st->h[4] = 0;
102
103 /* save pad for later */
104 LOAD32L(st->pad[0], key + 16);
105 LOAD32L(st->pad[1], key + 20);
106 LOAD32L(st->pad[2], key + 24);
107 LOAD32L(st->pad[3], key + 28);
108
109 st->leftover = 0;
110 st->final = 0;
111 return CRYPT_OK;
112 }
113
114 /**
115 Process data through POLY1305
116 @param st The POLY1305 state
117 @param in The data to send through HMAC
118 @param inlen The length of the data to HMAC (octets)
119 @return CRYPT_OK if successful
120 */
poly1305_process(poly1305_state * st,const unsigned char * in,unsigned long inlen)121 int poly1305_process(poly1305_state *st, const unsigned char *in, unsigned long inlen)
122 {
123 unsigned long i;
124
125 if (inlen == 0) return CRYPT_OK; /* nothing to do */
126 LTC_ARGCHK(st != NULL);
127 LTC_ARGCHK(in != NULL);
128
129 /* handle leftover */
130 if (st->leftover) {
131 unsigned long want = (16 - st->leftover);
132 if (want > inlen) want = inlen;
133 for (i = 0; i < want; i++) st->buffer[st->leftover + i] = in[i];
134 inlen -= want;
135 in += want;
136 st->leftover += want;
137 if (st->leftover < 16) return CRYPT_OK;
138 s_poly1305_block(st, st->buffer, 16);
139 st->leftover = 0;
140 }
141
142 /* process full blocks */
143 if (inlen >= 16) {
144 unsigned long want = (inlen & ~(16 - 1));
145 s_poly1305_block(st, in, want);
146 in += want;
147 inlen -= want;
148 }
149
150 /* store leftover */
151 if (inlen) {
152 for (i = 0; i < inlen; i++) st->buffer[st->leftover + i] = in[i];
153 st->leftover += inlen;
154 }
155 return CRYPT_OK;
156 }
157
158 /**
159 Terminate a POLY1305 session
160 @param st The POLY1305 state
161 @param mac [out] The destination of the POLY1305 authentication tag
162 @param maclen [in/out] The max size and resulting size of the POLY1305 authentication tag
163 @return CRYPT_OK if successful
164 */
poly1305_done(poly1305_state * st,unsigned char * mac,unsigned long * maclen)165 int poly1305_done(poly1305_state *st, unsigned char *mac, unsigned long *maclen)
166 {
167 ulong32 h0,h1,h2,h3,h4,c;
168 ulong32 g0,g1,g2,g3,g4;
169 ulong64 f;
170 ulong32 mask;
171
172 LTC_ARGCHK(st != NULL);
173 LTC_ARGCHK(mac != NULL);
174 LTC_ARGCHK(maclen != NULL);
175 LTC_ARGCHK(*maclen >= 16);
176
177 /* process the remaining block */
178 if (st->leftover) {
179 unsigned long i = st->leftover;
180 st->buffer[i++] = 1;
181 for (; i < 16; i++) st->buffer[i] = 0;
182 st->final = 1;
183 s_poly1305_block(st, st->buffer, 16);
184 }
185
186 /* fully carry h */
187 h0 = st->h[0];
188 h1 = st->h[1];
189 h2 = st->h[2];
190 h3 = st->h[3];
191 h4 = st->h[4];
192
193 c = h1 >> 26; h1 = h1 & 0x3ffffff;
194 h2 += c; c = h2 >> 26; h2 = h2 & 0x3ffffff;
195 h3 += c; c = h3 >> 26; h3 = h3 & 0x3ffffff;
196 h4 += c; c = h4 >> 26; h4 = h4 & 0x3ffffff;
197 h0 += c * 5; c = h0 >> 26; h0 = h0 & 0x3ffffff;
198 h1 += c;
199
200 /* compute h + -p */
201 g0 = h0 + 5; c = g0 >> 26; g0 &= 0x3ffffff;
202 g1 = h1 + c; c = g1 >> 26; g1 &= 0x3ffffff;
203 g2 = h2 + c; c = g2 >> 26; g2 &= 0x3ffffff;
204 g3 = h3 + c; c = g3 >> 26; g3 &= 0x3ffffff;
205 g4 = h4 + c - (1UL << 26);
206
207 /* select h if h < p, or h + -p if h >= p */
208 mask = (g4 >> 31) - 1;
209 g0 &= mask;
210 g1 &= mask;
211 g2 &= mask;
212 g3 &= mask;
213 g4 &= mask;
214 mask = ~mask;
215 h0 = (h0 & mask) | g0;
216 h1 = (h1 & mask) | g1;
217 h2 = (h2 & mask) | g2;
218 h3 = (h3 & mask) | g3;
219 h4 = (h4 & mask) | g4;
220
221 /* h = h % (2^128) */
222 h0 = ((h0 ) | (h1 << 26)) & 0xffffffff;
223 h1 = ((h1 >> 6) | (h2 << 20)) & 0xffffffff;
224 h2 = ((h2 >> 12) | (h3 << 14)) & 0xffffffff;
225 h3 = ((h3 >> 18) | (h4 << 8)) & 0xffffffff;
226
227 /* mac = (h + pad) % (2^128) */
228 f = (ulong64)h0 + st->pad[0] ; h0 = (ulong32)f;
229 f = (ulong64)h1 + st->pad[1] + (f >> 32); h1 = (ulong32)f;
230 f = (ulong64)h2 + st->pad[2] + (f >> 32); h2 = (ulong32)f;
231 f = (ulong64)h3 + st->pad[3] + (f >> 32); h3 = (ulong32)f;
232
233 STORE32L(h0, mac + 0);
234 STORE32L(h1, mac + 4);
235 STORE32L(h2, mac + 8);
236 STORE32L(h3, mac + 12);
237
238 /* zero out the state */
239 st->h[0] = 0;
240 st->h[1] = 0;
241 st->h[2] = 0;
242 st->h[3] = 0;
243 st->h[4] = 0;
244 st->r[0] = 0;
245 st->r[1] = 0;
246 st->r[2] = 0;
247 st->r[3] = 0;
248 st->r[4] = 0;
249 st->pad[0] = 0;
250 st->pad[1] = 0;
251 st->pad[2] = 0;
252 st->pad[3] = 0;
253
254 *maclen = 16;
255 return CRYPT_OK;
256 }
257
258 #endif
259