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1 | /// -*- mode: asm; asm-comment-char: ?/ -*- |
2 | /// | |
3 | /// ARM crypto-extension-based implementation of Rijndael | |
4 | /// | |
5 | /// (c) 2016 Straylight/Edgeware | |
6 | /// | |
7 | ||
8 | ///----- Licensing notice --------------------------------------------------- | |
9 | /// | |
10 | /// This file is part of Catacomb. | |
11 | /// | |
12 | /// Catacomb is free software; you can redistribute it and/or modify | |
13 | /// it under the terms of the GNU Library General Public License as | |
14 | /// published by the Free Software Foundation; either version 2 of the | |
15 | /// License, or (at your option) any later version. | |
16 | /// | |
17 | /// Catacomb is distributed in the hope that it will be useful, | |
18 | /// but WITHOUT ANY WARRANTY; without even the implied warranty of | |
19 | /// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
20 | /// GNU Library General Public License for more details. | |
21 | /// | |
22 | /// You should have received a copy of the GNU Library General Public | |
23 | /// License along with Catacomb; if not, write to the Free | |
24 | /// Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, | |
25 | /// MA 02111-1307, USA. | |
26 | ||
27 | ///-------------------------------------------------------------------------- | |
28 | /// External definitions. | |
29 | ||
30 | #include "config.h" | |
31 | #include "asm-common.h" | |
32 | ||
33 | .globl F(abort) | |
34 | .globl F(rijndael_rcon) | |
35 | ||
36 | ///-------------------------------------------------------------------------- | |
37 | /// Main code. | |
38 | ||
39 | .arch armv8-a | |
40 | .fpu crypto-neon-fp-armv8 | |
41 | ||
42 | /// The ARM crypto extension implements a little-endian version of AES | |
43 | /// (though the manual doesn't actually spell this out and you have to | |
44 | /// experiment), but Catacomb's internal interface presents as big-endian so | |
45 | /// as to work better with things like GCM. We therefore maintain the round | |
46 | /// keys in little-endian form, and have to end-swap blocks in and out. | |
47 | /// | |
48 | /// For added amusement, the crypto extension doesn't implement the larger- | |
49 | /// block versions of Rijndael, so we have to end-swap the keys if we're | |
50 | /// preparing for one of those. | |
51 | ||
52 | // Useful constants. | |
53 | .equ maxrounds, 16 // maximum number of rounds | |
54 | .equ maxblksz, 32 // maximum block size, in bytes | |
55 | .equ kbufsz, maxblksz*(maxrounds + 1) // size of a key-schedule buffer | |
56 | ||
57 | // Context structure. | |
58 | .equ nr, 0 // number of rounds | |
59 | .equ w, nr + 4 // encryption key words | |
60 | .equ wi, w + kbufsz // decryption key words | |
61 | ||
62 | ///-------------------------------------------------------------------------- | |
63 | /// Key setup. | |
64 | ||
65 | FUNC(rijndael_setup_arm_crypto) | |
66 | ||
67 | // Arguments: | |
68 | // r0 = pointer to context | |
69 | // r1 = block size in words | |
70 | // r2 = pointer to key material | |
71 | // r3 = key size in words | |
72 | ||
73 | stmfd sp!, {r4-r9, r14} | |
74 | ||
75 | // The initial round key material is taken directly from the input | |
76 | // key, so copy it over. Unfortunately, the key material is not | |
77 | // guaranteed to be aligned in any especially useful way, so we must | |
78 | // sort this out. | |
79 | add r9, r0, #w | |
80 | mov r14, r3 | |
c82543b7 | 81 | ands r6, r2, #3 |
26e182fc | 82 | beq 1f |
c82543b7 MW |
83 | mov r6, r6, lsl #3 |
84 | rsb r7, r6, #32 | |
26e182fc | 85 | bic r2, r2, #3 |
c82543b7 | 86 | ldr r4, [r2], #4 |
26e182fc | 87 | |
c82543b7 MW |
88 | 0: ldr r5, [r2], #4 |
89 | mov r4, r4, lsr r6 | |
90 | orr r4, r5, lsl r7 | |
91 | str r4, [r9], #4 | |
26e182fc | 92 | subs r14, r14, #1 |
c82543b7 | 93 | movhi r4, r5 |
26e182fc MW |
94 | bhi 0b |
95 | b 9f | |
96 | ||
c82543b7 MW |
97 | 1: ldr r4, [r2], #4 |
98 | str r4, [r9], #4 | |
26e182fc MW |
99 | subs r14, r14, #1 |
100 | bhi 1b | |
101 | ||
102 | // Find out other useful things and prepare for the main loop. | |
aec6bc36 | 103 | 9: ldr r7, [r0, #nr] // number of rounds |
26e182fc | 104 | mla r2, r1, r7, r1 // total key size in words |
26e182fc MW |
105 | leaextq r5, rijndael_rcon // round constants |
106 | sub r8, r2, r3 // minus what we've copied already | |
107 | veor q1, q1 // all-zero register for the key | |
108 | add r8, r9, r8, lsl #2 // limit of the key buffer | |
16021451 | 109 | mov r12, #0 // position in current cycle |
26e182fc | 110 | |
16021451 MW |
111 | // Main key expansion loop. Dispatch according to the position in |
112 | // the cycle. | |
113 | 0: ldr r6, [r9, -r3, lsl #2] // word from previous cycle | |
114 | cmp r12, #0 // first word of the cycle? | |
115 | beq 1f | |
116 | cmp r12, #4 // fourth word of the cycle? | |
117 | bne 2f | |
118 | cmp r3, #7 // seven or eight words of key? | |
119 | bcc 2f | |
120 | ||
121 | // Fourth word of the cycle, seven or eight words of key. We must do | |
122 | // the byte substitution. | |
26e182fc MW |
123 | vdup.32 q0, r4 |
124 | aese.8 q0, q1 // effectively, just SubBytes | |
125 | vmov.32 r4, d0[0] | |
16021451 | 126 | b 2f |
26e182fc | 127 | |
16021451 MW |
128 | // First word of the cycle. Byte substitution, rotation, and round |
129 | // constant. | |
130 | 1: ldrb r14, [r5], #1 // next round constant | |
26e182fc | 131 | ldr r6, [r9, -r3, lsl #2] |
26e182fc MW |
132 | vdup.32 q0, r4 |
133 | aese.8 q0, q1 // effectively, just SubBytes | |
134 | vmov.32 r4, d0[0] | |
16021451 | 135 | eor r4, r14, r4, ror #8 |
26e182fc | 136 | |
16021451 MW |
137 | // Common ending: mix in the word from the previous cycle and store. |
138 | 2: eor r4, r4, r6 | |
26e182fc | 139 | str r4, [r9], #4 |
26e182fc | 140 | |
16021451 MW |
141 | // Prepare for the next iteration. If we're done, then stop; if |
142 | // we've finished a cycle then reset the counter. | |
143 | add r12, r12, #1 | |
26e182fc | 144 | cmp r9, r8 |
f71eed58 | 145 | bcs 9f |
16021451 MW |
146 | cmp r12, r3 |
147 | movcs r12, #0 | |
f71eed58 | 148 | b 0b |
26e182fc MW |
149 | |
150 | // Next job is to construct the decryption keys. The keys for the | |
151 | // first and last rounds don't need to be mangled, but the remaining | |
152 | // ones do -- and they all need to be reordered too. | |
153 | // | |
154 | // The plan of action, then, is to copy the final encryption round's | |
155 | // keys into place first, then to do each of the intermediate rounds | |
156 | // in reverse order, and finally do the first round. | |
157 | // | |
158 | // Do all the heavy lifting with NEON registers. The order we're | |
159 | // doing this in means that it's OK if we read or write too much, and | |
160 | // there's easily enough buffer space for the over-enthusiastic reads | |
161 | // and writes because the context has space for 32-byte blocks, which | |
162 | // is our maximum and an exact fit for two Q-class registers. | |
f71eed58 | 163 | 9: add r5, r0, #wi |
26e182fc MW |
164 | add r4, r0, #w |
165 | add r4, r4, r2, lsl #2 | |
166 | sub r4, r4, r1, lsl #2 // last round's keys | |
167 | ||
168 | // Copy the last encryption round's keys. | |
169 | teq r1, #4 | |
170 | vldmiaeq r4, {d0, d1} | |
171 | vldmiane r4, {d0-d3} | |
172 | vstmiaeq r5, {d0, d1} | |
173 | vstmiane r5, {d0-d3} | |
174 | ||
175 | // Update the loop variables and stop if we've finished. | |
f71eed58 | 176 | 0: sub r4, r4, r1, lsl #2 |
26e182fc MW |
177 | add r5, r5, r1, lsl #2 |
178 | subs r7, r7, #1 | |
f71eed58 | 179 | beq 9f |
26e182fc MW |
180 | |
181 | // Do another middle round's keys... | |
182 | teq r1, #4 | |
183 | vldmiaeq r4, {d0, d1} | |
184 | vldmiane r4, {d0-d3} | |
185 | aesimc.8 q0, q0 | |
186 | vstmiaeq r5, {d0, d1} | |
f71eed58 | 187 | beq 0b |
26e182fc MW |
188 | aesimc.8 q1, q1 |
189 | vstmia r5, {d0-d3} | |
f71eed58 | 190 | b 0b |
26e182fc MW |
191 | |
192 | // Finally do the first encryption round. | |
f71eed58 | 193 | 9: teq r1, #4 |
26e182fc MW |
194 | vldmiaeq r4, {d0, d1} |
195 | vldmiane r4, {d0-d3} | |
196 | vstmiaeq r5, {d0, d1} | |
197 | vstmiane r5, {d0-d3} | |
198 | ||
199 | // If the block size is not exactly four words then we must end-swap | |
200 | // everything. We can use fancy NEON toys for this. | |
f71eed58 | 201 | beq 9f |
26e182fc MW |
202 | |
203 | // End-swap the encryption keys. | |
204 | add r1, r0, #w | |
205 | bl endswap_block | |
206 | ||
207 | // And the decryption keys | |
208 | add r1, r0, #wi | |
209 | bl endswap_block | |
210 | ||
211 | // All done. | |
f71eed58 | 212 | 9: ldmfd sp!, {r4-r9, pc} |
26e182fc MW |
213 | |
214 | endswap_block: | |
215 | // End-swap R2 words starting at R1. R1 is clobbered; R2 is not. | |
216 | // It's OK to work in 16-byte chunks. | |
217 | mov r4, r2 | |
218 | 0: vldmia r1, {d0, d1} | |
219 | vrev32.8 q0, q0 | |
220 | vstmia r1!, {d0, d1} | |
221 | subs r4, r4, #4 | |
222 | bhi 0b | |
223 | bx r14 | |
224 | ||
225 | ENDFUNC | |
226 | ||
227 | ///-------------------------------------------------------------------------- | |
228 | /// Encrypting and decrypting blocks. | |
229 | ||
6717fd12 MW |
230 | .macro encdec op, aes, mc, koff |
231 | FUNC(rijndael_\op\()_arm_crypto) | |
26e182fc MW |
232 | |
233 | // Arguments: | |
234 | // r0 = pointer to context | |
235 | // r1 = pointer to input block | |
236 | // r2 = pointer to output block | |
237 | ||
238 | // Set things up ready. | |
239 | ldr r3, [r0, #nr] | |
6717fd12 | 240 | add r0, r0, #\koff |
26e182fc MW |
241 | vldmia r1, {d0, d1} |
242 | vrev32.8 q0, q0 | |
243 | ||
6717fd12 MW |
244 | // Check the number of rounds and dispatch. |
245 | sub r3, r3, #10 | |
246 | cmp r3, #5 | |
247 | addlo pc, pc, r3, lsl #2 | |
26e182fc MW |
248 | callext F(abort) |
249 | ||
6717fd12 MW |
250 | b 10f |
251 | b 11f | |
252 | b 12f | |
253 | b 13f | |
254 | b 14f | |
255 | ||
256 | // Eleven rounds. | |
257 | 11: vldmia r0!, {d16, d17} | |
258 | \aes\().8 q0, q8 | |
259 | \mc\().8 q0, q0 | |
260 | b 10f | |
261 | ||
262 | // Twelve rounds. | |
263 | 12: vldmia r0!, {d16-d19} | |
264 | \aes\().8 q0, q8 | |
265 | \mc\().8 q0, q0 | |
266 | \aes\().8 q0, q9 | |
267 | \mc\().8 q0, q0 | |
268 | b 10f | |
269 | ||
270 | // Thirteen rounds. | |
271 | 13: vldmia r0!, {d16-d21} | |
272 | \aes\().8 q0, q8 | |
273 | \mc\().8 q0, q0 | |
274 | \aes\().8 q0, q9 | |
275 | \mc\().8 q0, q0 | |
276 | \aes\().8 q0, q10 | |
277 | \mc\().8 q0, q0 | |
278 | b 10f | |
279 | ||
280 | // Fourteen rounds. (Drops through to the ten round case because | |
281 | // this is the next most common.) | |
282 | 14: vldmia r0!, {d16-d23} | |
283 | \aes\().8 q0, q8 | |
284 | \mc\().8 q0, q0 | |
285 | \aes\().8 q0, q9 | |
286 | \mc\().8 q0, q0 | |
287 | \aes\().8 q0, q10 | |
288 | \mc\().8 q0, q0 | |
289 | \aes\().8 q0, q11 | |
290 | \mc\().8 q0, q0 | |
291 | // Drop through... | |
292 | ||
293 | // Ten rounds. | |
294 | 10: vldmia r0!, {d16-d25} | |
295 | \aes\().8 q0, q8 | |
296 | \mc\().8 q0, q0 | |
297 | \aes\().8 q0, q9 | |
298 | \mc\().8 q0, q0 | |
299 | \aes\().8 q0, q10 | |
300 | \mc\().8 q0, q0 | |
301 | \aes\().8 q0, q11 | |
302 | \mc\().8 q0, q0 | |
303 | \aes\().8 q0, q12 | |
304 | \mc\().8 q0, q0 | |
305 | ||
306 | vldmia r0!, {d16-d27} | |
307 | \aes\().8 q0, q8 | |
308 | \mc\().8 q0, q0 | |
309 | \aes\().8 q0, q9 | |
310 | \mc\().8 q0, q0 | |
311 | \aes\().8 q0, q10 | |
312 | \mc\().8 q0, q0 | |
313 | \aes\().8 q0, q11 | |
314 | \mc\().8 q0, q0 | |
315 | ||
316 | // Final round has no MixColumns, but is followed by final whitening. | |
317 | \aes\().8 q0, q12 | |
318 | veor q0, q0, q13 | |
26e182fc MW |
319 | |
320 | // All done. | |
321 | vrev32.8 q0, q0 | |
322 | vstmia r2, {d0, d1} | |
323 | bx r14 | |
324 | ||
6717fd12 MW |
325 | ENDFUNC |
326 | .endm | |
26e182fc | 327 | |
6717fd12 MW |
328 | encdec eblk, aese, aesmc, w |
329 | encdec dblk, aesd, aesimc, wi | |
26e182fc MW |
330 | |
331 | ///----- That's all, folks -------------------------------------------------- |