1/*	$NetBSD: base32.c,v 1.1 2024/02/18 20:57:48 christos Exp $	*/
2
3/*
4 * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
5 *
6 * SPDX-License-Identifier: MPL-2.0
7 *
8 * This Source Code Form is subject to the terms of the Mozilla Public
9 * License, v. 2.0. If a copy of the MPL was not distributed with this
10 * file, you can obtain one at https://mozilla.org/MPL/2.0/.
11 *
12 * See the COPYRIGHT file distributed with this work for additional
13 * information regarding copyright ownership.
14 */
15
16/*! \file */
17
18#include <stdbool.h>
19
20#include <isc/base32.h>
21#include <isc/buffer.h>
22#include <isc/lex.h>
23#include <isc/region.h>
24#include <isc/string.h>
25#include <isc/util.h>
26
27#define RETERR(x)                        \
28	do {                             \
29		isc_result_t _r = (x);   \
30		if (_r != ISC_R_SUCCESS) \
31			return ((_r));   \
32	} while (0)
33
34/*@{*/
35/*!
36 * These static functions are also present in lib/dns/rdata.c.  I'm not
37 * sure where they should go. -- bwelling
38 */
39static isc_result_t
40str_totext(const char *source, isc_buffer_t *target);
41
42static isc_result_t
43mem_tobuffer(isc_buffer_t *target, void *base, unsigned int length);
44
45/*@}*/
46
47static const char base32[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567="
48			     "abcdefghijklmnopqrstuvwxyz234567";
49static const char base32hex[] = "0123456789ABCDEFGHIJKLMNOPQRSTUV="
50				"0123456789abcdefghijklmnopqrstuv";
51
52static isc_result_t
53base32_totext(isc_region_t *source, int wordlength, const char *wordbreak,
54	      isc_buffer_t *target, const char base[], char pad) {
55	char buf[9];
56	unsigned int loops = 0;
57
58	if (wordlength >= 0 && wordlength < 8) {
59		wordlength = 8;
60	}
61
62	memset(buf, 0, sizeof(buf));
63	while (source->length > 0) {
64		buf[0] = base[((source->base[0] >> 3) & 0x1f)]; /* 5 + */
65		if (source->length == 1) {
66			buf[1] = base[(source->base[0] << 2) & 0x1c];
67			buf[2] = buf[3] = buf[4] = pad;
68			buf[5] = buf[6] = buf[7] = pad;
69			RETERR(str_totext(buf, target));
70			break;
71		}
72		buf[1] = base[((source->base[0] << 2) & 0x1c) | /* 3 = 8 */
73			      ((source->base[1] >> 6) & 0x03)]; /* 2 + */
74		buf[2] = base[((source->base[1] >> 1) & 0x1f)]; /* 5 + */
75		if (source->length == 2) {
76			buf[3] = base[(source->base[1] << 4) & 0x10];
77			buf[4] = buf[5] = buf[6] = buf[7] = pad;
78			RETERR(str_totext(buf, target));
79			break;
80		}
81		buf[3] = base[((source->base[1] << 4) & 0x10) | /* 1 = 8 */
82			      ((source->base[2] >> 4) & 0x0f)]; /* 4 + */
83		if (source->length == 3) {
84			buf[4] = base[(source->base[2] << 1) & 0x1e];
85			buf[5] = buf[6] = buf[7] = pad;
86			RETERR(str_totext(buf, target));
87			break;
88		}
89		buf[4] = base[((source->base[2] << 1) & 0x1e) | /* 4 = 8 */
90			      ((source->base[3] >> 7) & 0x01)]; /* 1 + */
91		buf[5] = base[((source->base[3] >> 2) & 0x1f)]; /* 5 + */
92		if (source->length == 4) {
93			buf[6] = base[(source->base[3] << 3) & 0x18];
94			buf[7] = pad;
95			RETERR(str_totext(buf, target));
96			break;
97		}
98		buf[6] = base[((source->base[3] << 3) & 0x18) | /* 2 = 8 */
99			      ((source->base[4] >> 5) & 0x07)]; /* 3 + */
100		buf[7] = base[source->base[4] & 0x1f];		/* 5 = 8 */
101		RETERR(str_totext(buf, target));
102		isc_region_consume(source, 5);
103
104		loops++;
105		if (source->length != 0 && wordlength >= 0 &&
106		    (int)((loops + 1) * 8) >= wordlength)
107		{
108			loops = 0;
109			RETERR(str_totext(wordbreak, target));
110		}
111	}
112	if (source->length > 0) {
113		isc_region_consume(source, source->length);
114	}
115	return (ISC_R_SUCCESS);
116}
117
118isc_result_t
119isc_base32_totext(isc_region_t *source, int wordlength, const char *wordbreak,
120		  isc_buffer_t *target) {
121	return (base32_totext(source, wordlength, wordbreak, target, base32,
122			      '='));
123}
124
125isc_result_t
126isc_base32hex_totext(isc_region_t *source, int wordlength,
127		     const char *wordbreak, isc_buffer_t *target) {
128	return (base32_totext(source, wordlength, wordbreak, target, base32hex,
129			      '='));
130}
131
132isc_result_t
133isc_base32hexnp_totext(isc_region_t *source, int wordlength,
134		       const char *wordbreak, isc_buffer_t *target) {
135	return (base32_totext(source, wordlength, wordbreak, target, base32hex,
136			      0));
137}
138
139/*%
140 * State of a base32 decoding process in progress.
141 */
142typedef struct {
143	int length;	      /*%< Desired length of binary data or -1 */
144	isc_buffer_t *target; /*%< Buffer for resulting binary data */
145	int digits;	      /*%< Number of buffered base32 digits */
146	bool seen_end;	      /*%< True if "=" end marker seen */
147	int val[8];
148	const char *base; /*%< Which encoding we are using */
149	int seen_32;	  /*%< Number of significant bytes if non
150			   * zero */
151	bool pad;	  /*%< Expect padding */
152} base32_decode_ctx_t;
153
154static void
155base32_decode_init(base32_decode_ctx_t *ctx, int length, const char base[],
156		   bool pad, isc_buffer_t *target) {
157	ctx->digits = 0;
158	ctx->seen_end = false;
159	ctx->seen_32 = 0;
160	ctx->length = length;
161	ctx->target = target;
162	ctx->base = base;
163	ctx->pad = pad;
164}
165
166static isc_result_t
167base32_decode_char(base32_decode_ctx_t *ctx, int c) {
168	const char *s;
169	unsigned int last;
170
171	if (ctx->seen_end) {
172		return (ISC_R_BADBASE32);
173	}
174	if ((s = strchr(ctx->base, c)) == NULL) {
175		return (ISC_R_BADBASE32);
176	}
177	last = (unsigned int)(s - ctx->base);
178
179	/*
180	 * Handle lower case.
181	 */
182	if (last > 32) {
183		last -= 33;
184	}
185
186	/*
187	 * Check that padding is contiguous.
188	 */
189	if (last != 32 && ctx->seen_32 != 0) {
190		return (ISC_R_BADBASE32);
191	}
192
193	/*
194	 * If padding is not permitted flag padding as a error.
195	 */
196	if (last == 32 && !ctx->pad) {
197		return (ISC_R_BADBASE32);
198	}
199
200	/*
201	 * Check that padding starts at the right place and that
202	 * bits that should be zero are.
203	 * Record how many significant bytes in answer (seen_32).
204	 */
205	if (last == 32 && ctx->seen_32 == 0) {
206		switch (ctx->digits) {
207		case 0:
208		case 1:
209			return (ISC_R_BADBASE32);
210		case 2:
211			if ((ctx->val[1] & 0x03) != 0) {
212				return (ISC_R_BADBASE32);
213			}
214			ctx->seen_32 = 1;
215			break;
216		case 3:
217			return (ISC_R_BADBASE32);
218		case 4:
219			if ((ctx->val[3] & 0x0f) != 0) {
220				return (ISC_R_BADBASE32);
221			}
222			ctx->seen_32 = 2;
223			break;
224		case 5:
225			if ((ctx->val[4] & 0x01) != 0) {
226				return (ISC_R_BADBASE32);
227			}
228			ctx->seen_32 = 3;
229			break;
230		case 6:
231			return (ISC_R_BADBASE32);
232		case 7:
233			if ((ctx->val[6] & 0x07) != 0) {
234				return (ISC_R_BADBASE32);
235			}
236			ctx->seen_32 = 4;
237			break;
238		}
239	}
240
241	/*
242	 * Zero fill pad values.
243	 */
244	ctx->val[ctx->digits++] = (last == 32) ? 0 : last;
245
246	if (ctx->digits == 8) {
247		int n = 5;
248		unsigned char buf[5];
249
250		if (ctx->seen_32 != 0) {
251			ctx->seen_end = true;
252			n = ctx->seen_32;
253		}
254		buf[0] = (ctx->val[0] << 3) | (ctx->val[1] >> 2);
255		buf[1] = (ctx->val[1] << 6) | (ctx->val[2] << 1) |
256			 (ctx->val[3] >> 4);
257		buf[2] = (ctx->val[3] << 4) | (ctx->val[4] >> 1);
258		buf[3] = (ctx->val[4] << 7) | (ctx->val[5] << 2) |
259			 (ctx->val[6] >> 3);
260		buf[4] = (ctx->val[6] << 5) | (ctx->val[7]);
261		RETERR(mem_tobuffer(ctx->target, buf, n));
262		if (ctx->length >= 0) {
263			if (n > ctx->length) {
264				return (ISC_R_BADBASE32);
265			} else {
266				ctx->length -= n;
267			}
268		}
269		ctx->digits = 0;
270	}
271	return (ISC_R_SUCCESS);
272}
273
274static isc_result_t
275base32_decode_finish(base32_decode_ctx_t *ctx) {
276	if (ctx->length > 0) {
277		return (ISC_R_UNEXPECTEDEND);
278	}
279	/*
280	 * Add missing padding if required.
281	 */
282	if (!ctx->pad && ctx->digits != 0) {
283		ctx->pad = true;
284		do {
285			RETERR(base32_decode_char(ctx, '='));
286		} while (ctx->digits != 0);
287	}
288	if (ctx->digits != 0) {
289		return (ISC_R_BADBASE32);
290	}
291	return (ISC_R_SUCCESS);
292}
293
294static isc_result_t
295base32_tobuffer(isc_lex_t *lexer, const char base[], bool pad,
296		isc_buffer_t *target, int length) {
297	unsigned int before, after;
298	base32_decode_ctx_t ctx;
299	isc_textregion_t *tr;
300	isc_token_t token;
301	bool eol;
302
303	REQUIRE(length >= -2);
304
305	base32_decode_init(&ctx, length, base, pad, target);
306
307	before = isc_buffer_usedlength(target);
308	while (!ctx.seen_end && (ctx.length != 0)) {
309		unsigned int i;
310
311		if (length > 0) {
312			eol = false;
313		} else {
314			eol = true;
315		}
316		RETERR(isc_lex_getmastertoken(lexer, &token,
317					      isc_tokentype_string, eol));
318		if (token.type != isc_tokentype_string) {
319			break;
320		}
321		tr = &token.value.as_textregion;
322		for (i = 0; i < tr->length; i++) {
323			RETERR(base32_decode_char(&ctx, tr->base[i]));
324		}
325	}
326	after = isc_buffer_usedlength(target);
327	if (ctx.length < 0 && !ctx.seen_end) {
328		isc_lex_ungettoken(lexer, &token);
329	}
330	RETERR(base32_decode_finish(&ctx));
331	if (length == -2 && before == after) {
332		return (ISC_R_UNEXPECTEDEND);
333	}
334	return (ISC_R_SUCCESS);
335}
336
337isc_result_t
338isc_base32_tobuffer(isc_lex_t *lexer, isc_buffer_t *target, int length) {
339	return (base32_tobuffer(lexer, base32, true, target, length));
340}
341
342isc_result_t
343isc_base32hex_tobuffer(isc_lex_t *lexer, isc_buffer_t *target, int length) {
344	return (base32_tobuffer(lexer, base32hex, true, target, length));
345}
346
347isc_result_t
348isc_base32hexnp_tobuffer(isc_lex_t *lexer, isc_buffer_t *target, int length) {
349	return (base32_tobuffer(lexer, base32hex, false, target, length));
350}
351
352static isc_result_t
353base32_decodestring(const char *cstr, const char base[], bool pad,
354		    isc_buffer_t *target) {
355	base32_decode_ctx_t ctx;
356
357	base32_decode_init(&ctx, -1, base, pad, target);
358	for (;;) {
359		int c = *cstr++;
360		if (c == '\0') {
361			break;
362		}
363		if (c == ' ' || c == '\t' || c == '\n' || c == '\r') {
364			continue;
365		}
366		RETERR(base32_decode_char(&ctx, c));
367	}
368	RETERR(base32_decode_finish(&ctx));
369	return (ISC_R_SUCCESS);
370}
371
372isc_result_t
373isc_base32_decodestring(const char *cstr, isc_buffer_t *target) {
374	return (base32_decodestring(cstr, base32, true, target));
375}
376
377isc_result_t
378isc_base32hex_decodestring(const char *cstr, isc_buffer_t *target) {
379	return (base32_decodestring(cstr, base32hex, true, target));
380}
381
382isc_result_t
383isc_base32hexnp_decodestring(const char *cstr, isc_buffer_t *target) {
384	return (base32_decodestring(cstr, base32hex, false, target));
385}
386
387static isc_result_t
388base32_decoderegion(isc_region_t *source, const char base[], bool pad,
389		    isc_buffer_t *target) {
390	base32_decode_ctx_t ctx;
391
392	base32_decode_init(&ctx, -1, base, pad, target);
393	while (source->length != 0) {
394		int c = *source->base;
395		RETERR(base32_decode_char(&ctx, c));
396		isc_region_consume(source, 1);
397	}
398	RETERR(base32_decode_finish(&ctx));
399	return (ISC_R_SUCCESS);
400}
401
402isc_result_t
403isc_base32_decoderegion(isc_region_t *source, isc_buffer_t *target) {
404	return (base32_decoderegion(source, base32, true, target));
405}
406
407isc_result_t
408isc_base32hex_decoderegion(isc_region_t *source, isc_buffer_t *target) {
409	return (base32_decoderegion(source, base32hex, true, target));
410}
411
412isc_result_t
413isc_base32hexnp_decoderegion(isc_region_t *source, isc_buffer_t *target) {
414	return (base32_decoderegion(source, base32hex, false, target));
415}
416
417static isc_result_t
418str_totext(const char *source, isc_buffer_t *target) {
419	unsigned int l;
420	isc_region_t region;
421
422	isc_buffer_availableregion(target, &region);
423	l = strlen(source);
424
425	if (l > region.length) {
426		return (ISC_R_NOSPACE);
427	}
428
429	memmove(region.base, source, l);
430	isc_buffer_add(target, l);
431	return (ISC_R_SUCCESS);
432}
433
434static isc_result_t
435mem_tobuffer(isc_buffer_t *target, void *base, unsigned int length) {
436	isc_region_t tr;
437
438	isc_buffer_availableregion(target, &tr);
439	if (length > tr.length) {
440		return (ISC_R_NOSPACE);
441	}
442	memmove(tr.base, base, length);
443	isc_buffer_add(target, length);
444	return (ISC_R_SUCCESS);
445}
446