summaryrefslogtreecommitdiff
path: root/libbb/uuencode.c
blob: 23e2123bcb90d309492240de94943a1119c59c4c (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
/* vi: set sw=4 ts=4: */
/*
 * Copyright 2003, Glenn McGrath
 * Copyright 2006, Rob Landley <rob@landley.net>
 * Copyright 2010, Denys Vlasenko
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 */

#include "libbb.h"

/* Conversion table.  for base 64 */
const char bb_uuenc_tbl_base64[65 + 2] ALIGN1 = {
	'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',
	'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
	'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
	'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
	'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
	'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
	'w', 'x', 'y', 'z', '0', '1', '2', '3',
	'4', '5', '6', '7', '8', '9', '+', '/',
	'=' /* termination character */,
	'\n', '\0' /* needed for uudecode.c */
};

const char bb_uuenc_tbl_std[65] ALIGN1 = {
	'`', '!', '"', '#', '$', '%', '&', '\'',
	'(', ')', '*', '+', ',', '-', '.', '/',
	'0', '1', '2', '3', '4', '5', '6', '7',
	'8', '9', ':', ';', '<', '=', '>', '?',
	'@', 'A', 'B', 'C', 'D', 'E', 'F', 'G',
	'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O',
	'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W',
	'X', 'Y', 'Z', '[', '\\', ']', '^', '_',
	'`' /* termination character */
};

/*
 * Encode bytes at S of length LENGTH to uuencode or base64 format and place it
 * to STORE.  STORE will be 0-terminated, and must point to a writable
 * buffer of at least 1+BASE64_LENGTH(length) bytes.
 * where BASE64_LENGTH(len) = (4 * ((LENGTH + 2) / 3))
 */
void FAST_FUNC bb_uuencode(char *p, const void *src, int length, const char *tbl)
{
	const unsigned char *s = src;

	/* Transform the 3x8 bits to 4x6 bits */
	while (length > 0) {
		unsigned s1, s2;

		/* Are s[1], s[2] valid or should be assumed 0? */
		s1 = s2 = 0;
		length -= 3; /* can be >=0, -1, -2 */
		if (length >= -1) {
			s1 = s[1];
			if (length >= 0)
				s2 = s[2];
		}
		*p++ = tbl[s[0] >> 2];
		*p++ = tbl[((s[0] & 3) << 4) + (s1 >> 4)];
		*p++ = tbl[((s1 & 0xf) << 2) + (s2 >> 6)];
		*p++ = tbl[s2 & 0x3f];
		s += 3;
	}
	/* Zero-terminate */
	*p = '\0';
	/* If length is -2 or -1, pad last char or two */
	while (length) {
		*--p = tbl[64];
		length++;
	}
}

/*
 * Decode base64 encoded string. Stops on '\0'.
 *
 * Returns: pointer to the undecoded part of source.
 * If points to '\0', then the source was fully decoded.
 * (*dst): advanced past the last written byte.
 */
const char* FAST_FUNC decode_base64(char **pp_dst, const char *src)
{
	char *dst = *pp_dst;
	const char *src_tail;

	while (1) {
		unsigned char translated[4];
		int count = 0;

		/* Process one group of 4 chars */
		src_tail = src;
		while (count < 4) {
			char *table_ptr;
			int ch;

			/* Get next _valid_ character.
			 * bb_uuenc_tbl_base64[] contains this string:
			 *  0         1         2         3         4         5         6
			 *  012345678901234567890123456789012345678901234567890123456789012345
			 * "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=\n"
			 */
			do {
				ch = *src;
				if (ch == '\0') {
					if (count == 0) {
						/* Example:
						 * If we decode "QUJD <NUL>", we want
						 * to return ptr to NUL, not to ' ',
						 * because we did fully decode
						 * the string (to "ABC").
						 */
						src_tail = src;
					}
					goto ret;
				}
				src++;
				table_ptr = strchr(bb_uuenc_tbl_base64, ch);
//TODO: add BASE64_FLAG_foo to die on bad char?
//Note that then we may need to still allow '\r' (for mail processing)
			} while (!table_ptr);

			/* Convert encoded character to decimal */
			ch = table_ptr - bb_uuenc_tbl_base64;

			if (ch == 65) {  /* '\n' */
				continue;
			}
			/* ch is 64 if char was '=', otherwise 0..63 */
			translated[count] = ch & 63; /* 64 -> 0 */
			if (ch == 64) {  /* '=' */
				break;
			}
			count++;
		}

		/* Merge 6 bit chars to 8 bit.
		 * count can be < 4 when we decode the tail:
		 * "eQ==" -> "y", not "y NUL NUL"
		 */
		if (count > 1)
			*dst++ = translated[0] << 2 | translated[1] >> 4;
		if (count > 2)
			*dst++ = translated[1] << 4 | translated[2] >> 2;
		if (count > 3)
			*dst++ = translated[2] << 6 | translated[3];
	} /* while (1) */
 ret:
	*pp_dst = dst;
	return src_tail;
}

/*
 * Decode base64 encoded stream.
 * Can stop on EOF, specified char, or on uuencode-style "====" line:
 * flags argument controls it.
 */
void FAST_FUNC read_base64(FILE *src_stream, FILE *dst_stream, int flags)
{
/* Note that EOF _can_ be passed as exit_char too */
#define exit_char    ((int)(signed char)flags)
#define uu_style_end (flags & BASE64_FLAG_UU_STOP)

	/* uuencoded files have 61 byte lines. Use 64 byte buffer
	 * to process line at a time.
	 */
	enum { BUFFER_SIZE = 64 };

	char in_buf[BUFFER_SIZE + 2];
	char out_buf[BUFFER_SIZE / 4 * 3 + 2];
	char *out_tail;
	const char *in_tail;
	int term_seen = 0;
	int in_count = 0;

	while (1) {
		while (in_count < BUFFER_SIZE) {
			int ch = fgetc(src_stream);
			if (ch == exit_char) {
				if (in_count == 0)
					return;
				term_seen = 1;
				break;
			}
			if (ch == EOF) {
				term_seen = 1;
				break;
			}
			/* Prevent "====" line to be split: stop if we see '\n'.
			 * We can also skip other whitespace and skirt the problem
			 * of files with NULs by stopping on any control char or space:
			 */
			if (ch <= ' ')
				break;
			in_buf[in_count++] = ch;
		}
		in_buf[in_count] = '\0';

		/* Did we encounter "====" line? */
		if (uu_style_end && strcmp(in_buf, "====") == 0)
			return;

		out_tail = out_buf;
		in_tail = decode_base64(&out_tail, in_buf);

                fwrite(out_buf, (out_tail - out_buf), 1, dst_stream);

		if (term_seen) {
			/* Did we consume ALL characters? */
			if (*in_tail == '\0')
				return;
			/* No */
			bb_error_msg_and_die("truncated base64 input");
		}

		/* It was partial decode */
		in_count = strlen(in_tail);
		memmove(in_buf, in_tail, in_count);
	}
}