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1 /*
2  * lib/ext2fs/digest_encode.c
3  *
4  * A function to encode a digest using 64 characters that are valid in a
5  * filename per ext2fs rules.
6  *
7  * Written by Uday Savagaonkar, 2014.
8  *
9  * Copyright 2014 Google Inc.  All Rights Reserved.
10  *
11  * %Begin-Header%
12  * This file may be redistributed under the terms of the GNU Library
13  * General Public License, version 2.
14  * %End-Header%
15  */
16 
17 #include "config.h"
18 #if HAVE_SYS_TYPES_H
19 #include <sys/types.h>
20 #endif
21 #include "ext2fs.h"
22 
23 static const char *lookup_table =
24 	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";
25 
26 /**
27  * ext2fs_digest_encode() -
28  *
29  * Encodes the input digest using characters from the set [a-zA-Z0-9_+].
30  * The encoded string is roughly 4/3 times the size of the input string.
31  */
ext2fs_digest_encode(const char * src,int len,char * dst)32 int ext2fs_digest_encode(const char *src, int len, char *dst)
33 {
34 	int i = 0, bits = 0, ac = 0;
35 	char *cp = dst;
36 
37 	while (i < len) {
38 		ac += (((unsigned char) src[i]) << bits);
39 		bits += 8;
40 		do {
41 			*cp++ = lookup_table[ac & 0x3f];
42 			ac >>= 6;
43 			bits -= 6;
44 		} while (bits >= 6);
45 		i++;
46 	}
47 	if (bits)
48 		*cp++ = lookup_table[ac & 0x3f];
49 	return cp - dst;
50 }
51 
ext2fs_digest_decode(const char * src,int len,char * dst)52 int ext2fs_digest_decode(const char *src, int len, char *dst)
53 {
54 	int i = 0, bits = 0, ac = 0;
55 	const char *p;
56 	char *cp = dst;
57 
58 	while (i < len) {
59 		p = strchr(lookup_table, src[i]);
60 		if (p == NULL || src[i] == 0)
61 			return -1;
62 		ac += (p - lookup_table) << bits;
63 		bits += 6;
64 		if (bits >= 8) {
65 			*cp++ = ac & 0xff;
66 			ac >>= 8;
67 			bits -= 8;
68 		}
69 		i++;
70 	}
71 	if (ac)
72 		return -1;
73 	return cp - dst;
74 }
75 
76 
77 #ifdef UNITTEST
78 static const struct {
79 	unsigned char d[32];
80 	unsigned int len;
81 	const char *ed;
82 } tests[] = {
83 	{ { 0xe3, 0xb0, 0xc4, 0x42, 0x98, 0xfc, 0x1c, 0x14,
84 	    0x9a, 0xfb, 0xf4, 0xc8, 0x99, 0x6f, 0xb9, 0x24,
85 	    0x27, 0xae, 0x41, 0xe4, 0x64, 0x9b, 0x93, 0x4c,
86 	    0xa4, 0x95, 0x99, 0x1b, 0x78, 0x52, 0xb8, 0x55 }, 32,
87 	"jDLxChJ,cQhm7TPyZ+WukcirBROZbOJTkWZmbgnU4WF"
88 	},
89 	{ { 0xba, 0x78, 0x16, 0xbf, 0x8f, 0x01, 0xcf, 0xea,
90 	    0x41, 0x41, 0x40, 0xde, 0x5d, 0xae, 0x22, 0x23,
91 	    0xb0, 0x03, 0x61, 0xa3, 0x96, 0x17, 0x7a, 0x9c,
92 	    0xb4, 0x10, 0xff, 0x61, 0xf2, 0x00, 0x15, 0xad }, 32,
93 	"6inF,+YAPreQBBk3d5qIjA7AhNqlXoHn0Cx,hJPAV0K"
94 	},
95 	{ { 0x24, 0x8d, 0x6a, 0x61, 0xd2, 0x06, 0x38, 0xb8,
96 	    0xe5, 0xc0, 0x26, 0x93, 0x0c, 0x3e, 0x60, 0x39,
97 	    0xa3, 0x3c, 0xe4, 0x59, 0x64, 0xff, 0x21, 0x67,
98 	    0xf6, 0xec, 0xed, 0xd4, 0x19, 0xdb, 0x06, 0xc1 }, 32,
99 	"k0oahJtB4gb5AbykM4DY5MKPknFZ,HyZ2ze7Unx2GEM"
100 	},
101 	{ { 0x00, }, 1,
102 	"AA"
103 	},
104 	{ { 0x01, }, 1,
105 	"BA"
106 	},
107 	{ { 0x01, 0x02 }, 2,
108 	"BIA"
109 	},
110 	{ { 0x01, 0x02, 0x03 }, 3,
111 	"BIwA"
112 	},
113 	{ { 0x01, 0x02, 0x03, 0x04 }, 4,
114 	"BIwAEA"
115 	},
116 	{ { 0x01, 0x02, 0x03, 0x04, 0xff }, 5,
117 	"BIwAE8P"
118 	},
119 	{ { 0x01, 0x02, 0x03, 0x04, 0xff, 0xfe }, 6,
120 	"BIwAE8v,"
121 	},
122 	{ { 0x01, 0x02, 0x03, 0x04, 0xff, 0xfe, 0xfd }, 7,
123 	"BIwAE8v,9D"
124 	},
125 };
126 
main(int argc,char ** argv)127 int main(int argc, char **argv)
128 {
129 	int i, ret, len;
130 	int errors = 0;
131 	char tmp[1024], tmp2[1024];
132 
133 	if (argc == 3 && !strcmp(argv[1], "encode")) {
134 		memset(tmp, 0, sizeof(tmp));
135 		ext2fs_digest_encode(argv[2], strlen(argv[2]), tmp);
136 		puts(tmp);
137 		exit(0);
138 	}
139 	if (argc == 3 && !strcmp(argv[1], "decode")) {
140 		memset(tmp, 0, sizeof(tmp));
141 		ret = ext2fs_digest_decode(argv[2], strlen(argv[2]), tmp);
142 		puts(tmp);
143 		fprintf(stderr, "returned %d\n", ret);
144 		exit(0);
145 	}
146 	for (i = 0; i < (int)(sizeof(tests) / sizeof(tests[0])); i++) {
147 		memset(tmp, 0, sizeof(tmp));
148 		ret = ext2fs_digest_encode((const char *) tests[i].d,
149 					   tests[i].len, tmp);
150 		len = strlen(tmp);
151 		printf("Test Digest %d (returned %d): ", i, ret);
152 		if (ret != len) {
153 			printf("FAILED returned %d, string length was %d\n",
154 			       ret, len);
155 			errors++;
156 			continue;
157 		} else if (strcmp(tmp, tests[i].ed) != 0) {
158 			printf("FAILED: got %s, expected %s\n", tmp,
159 			       tests[i].ed);
160 			errors++;
161 			continue;
162 		}
163 		ret = ext2fs_digest_decode(tmp, len, tmp2);
164 		if (ret != tests[i].len) {
165 			printf("FAILED decode returned %d, expected %d\n",
166 			       ret, tests[i].len);
167 			errors++;
168 			continue;
169 		}
170 		if (memcmp(tmp2, tests[i].d, ret) != 0) {
171 			puts("FAILED: decode mismatched");
172 			errors++;
173 			continue;
174 		}
175 		printf("OK\n");
176 	}
177 	for (i = 1; i < argc; i++) {
178 		memset(tmp, 0, sizeof(tmp));
179 		ret = ext2fs_digest_encode(argv[i], strlen(argv[i]), tmp);
180 		len = strlen(tmp);
181 		printf("Digest of '%s' is '%s' (returned %d, length %d)\n",
182 		       argv[i], tmp, ret, len);
183 	}
184 	return errors;
185 }
186 
187 #endif /* UNITTEST */
188