1/*
2 * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
3 *
4 * Permission to use, copy, modify, and/or distribute this software for any
5 * purpose with or without fee is hereby granted, provided that the above
6 * copyright notice and this permission notice appear in all copies.
7 *
8 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
9 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
10 * AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
11 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
12 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
13 * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
14 * PERFORMANCE OF THIS SOFTWARE.
15 */
16
17/* $Id: base32.c,v 1.8 2020/09/14 08:40:44 florian Exp $ */
18
19/*! \file */
20
21#include <isc/base32.h>
22#include <isc/buffer.h>
23#include <isc/region.h>
24#include <string.h>
25#include <isc/util.h>
26
27#define RETERR(x) do { \
28	isc_result_t _r = (x); \
29	if (_r != ISC_R_SUCCESS) \
30		return (_r); \
31	} while (0)
32
33/*@}*/
34
35static const char base32hex[] =
36	"0123456789ABCDEFGHIJKLMNOPQRSTUV=0123456789abcdefghijklmnopqrstuv";
37
38static isc_result_t
39base32_totext(isc_region_t *source, int wordlength, const char *wordbreak,
40	      isc_buffer_t *target, const char base[], char pad)
41{
42	char buf[9];
43	unsigned int loops = 0;
44
45	if (wordlength >= 0 && wordlength < 8)
46		wordlength = 8;
47
48	memset(buf, 0, sizeof(buf));
49	while (source->length > 0) {
50		buf[0] = base[((source->base[0]>>3)&0x1f)];	/* 5 + */
51		if (source->length == 1) {
52			buf[1] = base[(source->base[0]<<2)&0x1c];
53			buf[2] = buf[3] = buf[4] = pad;
54			buf[5] = buf[6] = buf[7] = pad;
55			RETERR(isc_str_tobuffer(buf, target));
56			break;
57		}
58		buf[1] = base[((source->base[0]<<2)&0x1c)|	/* 3 = 8 */
59			      ((source->base[1]>>6)&0x03)];	/* 2 + */
60		buf[2] = base[((source->base[1]>>1)&0x1f)];	/* 5 + */
61		if (source->length == 2) {
62			buf[3] = base[(source->base[1]<<4)&0x10];
63			buf[4] = buf[5] = buf[6] = buf[7] = pad;
64			RETERR(isc_str_tobuffer(buf, target));
65			break;
66		}
67		buf[3] = base[((source->base[1]<<4)&0x10)|	/* 1 = 8 */
68			      ((source->base[2]>>4)&0x0f)];	/* 4 + */
69		if (source->length == 3) {
70			buf[4] = base[(source->base[2]<<1)&0x1e];
71			buf[5] = buf[6] = buf[7] = pad;
72			RETERR(isc_str_tobuffer(buf, target));
73			break;
74		}
75		buf[4] = base[((source->base[2]<<1)&0x1e)|	/* 4 = 8 */
76			      ((source->base[3]>>7)&0x01)];	/* 1 + */
77		buf[5] = base[((source->base[3]>>2)&0x1f)];	/* 5 + */
78		if (source->length == 4) {
79			buf[6] = base[(source->base[3]<<3)&0x18];
80			buf[7] = pad;
81			RETERR(isc_str_tobuffer(buf, target));
82			break;
83		}
84		buf[6] = base[((source->base[3]<<3)&0x18)|	/* 2 = 8 */
85			      ((source->base[4]>>5)&0x07)];	/* 3 + */
86		buf[7] = base[source->base[4]&0x1f];		/* 5 = 8 */
87		RETERR(isc_str_tobuffer(buf, target));
88		isc_region_consume(source, 5);
89
90		loops++;
91		if (source->length != 0 && wordlength >= 0 &&
92		    (int)((loops + 1) * 8) >= wordlength)
93		{
94			loops = 0;
95			RETERR(isc_str_tobuffer(wordbreak, target));
96		}
97	}
98	if (source->length > 0)
99		isc_region_consume(source, source->length);
100	return (ISC_R_SUCCESS);
101}
102
103isc_result_t
104isc_base32hexnp_totext(isc_region_t *source, int wordlength,
105		     const char *wordbreak, isc_buffer_t *target)
106{
107	return (base32_totext(source, wordlength, wordbreak, target,
108			      base32hex, 0));
109}
110
111/*%
112 * State of a base32 decoding process in progress.
113 */
114typedef struct {
115	int length;		/*%< Desired length of binary data or -1 */
116	isc_buffer_t *target;	/*%< Buffer for resulting binary data */
117	int digits;		/*%< Number of buffered base32 digits */
118	int seen_end;	/*%< True if "=" end marker seen */
119	int val[8];
120	const char *base;	/*%< Which encoding we are using */
121	int seen_32;		/*%< Number of significant bytes if non zero */
122	int pad;	/*%< Expect padding */
123} base32_decode_ctx_t;
124
125static inline void
126base32_decode_init(base32_decode_ctx_t *ctx, int length, const char base[],
127		   int pad, isc_buffer_t *target)
128{
129	ctx->digits = 0;
130	ctx->seen_end = 0;
131	ctx->seen_32 = 0;
132	ctx->length = length;
133	ctx->target = target;
134	ctx->base = base;
135	ctx->pad = pad;
136}
137
138static inline isc_result_t
139base32_decode_char(base32_decode_ctx_t *ctx, int c) {
140	const char *s;
141	unsigned int last;
142
143	if (ctx->seen_end)
144		return (ISC_R_BADBASE32);
145	if ((s = strchr(ctx->base, c)) == NULL)
146		return (ISC_R_BADBASE32);
147	last = (unsigned int)(s - ctx->base);
148
149	/*
150	 * Handle lower case.
151	 */
152	if (last > 32)
153		last -= 33;
154
155	/*
156	 * Check that padding is contiguous.
157	 */
158	if (last != 32 && ctx->seen_32 != 0)
159		return (ISC_R_BADBASE32);
160
161	/*
162	 * If padding is not permitted flag padding as a error.
163	 */
164	if (last == 32 && !ctx->pad)
165		return (ISC_R_BADBASE32);
166
167	/*
168	 * Check that padding starts at the right place and that
169	 * bits that should be zero are.
170	 * Record how many significant bytes in answer (seen_32).
171	 */
172	if (last == 32 && ctx->seen_32 == 0)
173		switch (ctx->digits) {
174		case 0:
175		case 1:
176			return (ISC_R_BADBASE32);
177		case 2:
178			if ((ctx->val[1]&0x03) != 0)
179				return (ISC_R_BADBASE32);
180			ctx->seen_32 = 1;
181			break;
182		case 3:
183			return (ISC_R_BADBASE32);
184		case 4:
185			if ((ctx->val[3]&0x0f) != 0)
186				return (ISC_R_BADBASE32);
187			ctx->seen_32 = 3;
188			break;
189		case 5:
190			if ((ctx->val[4]&0x01) != 0)
191				return (ISC_R_BADBASE32);
192			ctx->seen_32 = 3;
193			break;
194		case 6:
195			return (ISC_R_BADBASE32);
196		case 7:
197			if ((ctx->val[6]&0x07) != 0)
198				return (ISC_R_BADBASE32);
199			ctx->seen_32 = 4;
200			break;
201		}
202
203	/*
204	 * Zero fill pad values.
205	 */
206	ctx->val[ctx->digits++] = (last == 32) ? 0 : last;
207
208	if (ctx->digits == 8) {
209		int n = 5;
210		unsigned char buf[5];
211
212		if (ctx->seen_32 != 0) {
213			ctx->seen_end = 1;
214			n = ctx->seen_32;
215		}
216		buf[0] = (ctx->val[0]<<3)|(ctx->val[1]>>2);
217		buf[1] = (ctx->val[1]<<6)|(ctx->val[2]<<1)|(ctx->val[3]>>4);
218		buf[2] = (ctx->val[3]<<4)|(ctx->val[4]>>1);
219		buf[3] = (ctx->val[4]<<7)|(ctx->val[5]<<2)|(ctx->val[6]>>3);
220		buf[4] = (ctx->val[6]<<5)|(ctx->val[7]);
221		RETERR(isc_mem_tobuffer(ctx->target, buf, n));
222		if (ctx->length >= 0) {
223			if (n > ctx->length)
224				return (ISC_R_BADBASE32);
225			else
226				ctx->length -= n;
227		}
228		ctx->digits = 0;
229	}
230	return (ISC_R_SUCCESS);
231}
232
233static inline isc_result_t
234base32_decode_finish(base32_decode_ctx_t *ctx) {
235
236	if (ctx->length > 0)
237		return (ISC_R_UNEXPECTEDEND);
238	/*
239	 * Add missing padding if required.
240	 */
241	if (!ctx->pad && ctx->digits != 0) {
242		ctx->pad = 1;
243		do {
244			RETERR(base32_decode_char(ctx, '='));
245		} while (ctx->digits != 0);
246	}
247	if (ctx->digits != 0)
248		return (ISC_R_BADBASE32);
249	return (ISC_R_SUCCESS);
250}
251
252static isc_result_t
253base32_decoderegion(isc_region_t *source, const char base[],
254		    int pad, isc_buffer_t *target)
255{
256	base32_decode_ctx_t ctx;
257
258	base32_decode_init(&ctx, -1, base, pad, target);
259	while (source->length != 0) {
260		int c = *source->base;
261		RETERR(base32_decode_char(&ctx, c));
262		isc_region_consume(source, 1);
263	}
264	RETERR(base32_decode_finish(&ctx));
265	return (ISC_R_SUCCESS);
266}
267
268isc_result_t
269isc_base32hexnp_decoderegion(isc_region_t *source, isc_buffer_t *target) {
270	return (base32_decoderegion(source, base32hex, 0, target));
271}
272