1 /*-------------------------------------------------------------------------
2 *
3 * base64.c
4 * Encoding and decoding routines for base64 without whitespace.
5 *
6 * Copyright (c) 2001-2020, PostgreSQL Global Development Group
7 *
8 *
9 * IDENTIFICATION
10 * src/common/base64.c
11 *
12 *-------------------------------------------------------------------------
13 */
14
15 #ifndef FRONTEND
16 #include "postgres.h"
17 #else
18 #include "postgres_fe.h"
19 #endif
20
21 #include "common/base64.h"
22
23 /*
24 * BASE64
25 */
26
27 static const char _base64[] =
28 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
29
30 static const int8 b64lookup[128] = {
31 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
32 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
33 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,
34 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1,
35 -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
36 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,
37 -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
38 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1,
39 };
40
41 /*
42 * pg_b64_encode
43 *
44 * Encode into base64 the given string. Returns the length of the encoded
45 * string, and -1 in the event of an error with the result buffer zeroed
46 * for safety.
47 */
48 int
pg_b64_encode(const char * src,int len,char * dst,int dstlen)49 pg_b64_encode(const char *src, int len, char *dst, int dstlen)
50 {
51 char *p;
52 const char *s,
53 *end = src + len;
54 int pos = 2;
55 uint32 buf = 0;
56
57 s = src;
58 p = dst;
59
60 while (s < end)
61 {
62 buf |= (unsigned char) *s << (pos << 3);
63 pos--;
64 s++;
65
66 /* write it out */
67 if (pos < 0)
68 {
69 /*
70 * Leave if there is an overflow in the area allocated for the
71 * encoded string.
72 */
73 if ((p - dst + 4) > dstlen)
74 goto error;
75
76 *p++ = _base64[(buf >> 18) & 0x3f];
77 *p++ = _base64[(buf >> 12) & 0x3f];
78 *p++ = _base64[(buf >> 6) & 0x3f];
79 *p++ = _base64[buf & 0x3f];
80
81 pos = 2;
82 buf = 0;
83 }
84 }
85 if (pos != 2)
86 {
87 /*
88 * Leave if there is an overflow in the area allocated for the encoded
89 * string.
90 */
91 if ((p - dst + 4) > dstlen)
92 goto error;
93
94 *p++ = _base64[(buf >> 18) & 0x3f];
95 *p++ = _base64[(buf >> 12) & 0x3f];
96 *p++ = (pos == 0) ? _base64[(buf >> 6) & 0x3f] : '=';
97 *p++ = '=';
98 }
99
100 Assert((p - dst) <= dstlen);
101 return p - dst;
102
103 error:
104 memset(dst, 0, dstlen);
105 return -1;
106 }
107
108 /*
109 * pg_b64_decode
110 *
111 * Decode the given base64 string. Returns the length of the decoded
112 * string on success, and -1 in the event of an error with the result
113 * buffer zeroed for safety.
114 */
115 int
pg_b64_decode(const char * src,int len,char * dst,int dstlen)116 pg_b64_decode(const char *src, int len, char *dst, int dstlen)
117 {
118 const char *srcend = src + len,
119 *s = src;
120 char *p = dst;
121 char c;
122 int b = 0;
123 uint32 buf = 0;
124 int pos = 0,
125 end = 0;
126
127 while (s < srcend)
128 {
129 c = *s++;
130
131 /* Leave if a whitespace is found */
132 if (c == ' ' || c == '\t' || c == '\n' || c == '\r')
133 goto error;
134
135 if (c == '=')
136 {
137 /* end sequence */
138 if (!end)
139 {
140 if (pos == 2)
141 end = 1;
142 else if (pos == 3)
143 end = 2;
144 else
145 {
146 /*
147 * Unexpected "=" character found while decoding base64
148 * sequence.
149 */
150 goto error;
151 }
152 }
153 b = 0;
154 }
155 else
156 {
157 b = -1;
158 if (c > 0 && c < 127)
159 b = b64lookup[(unsigned char) c];
160 if (b < 0)
161 {
162 /* invalid symbol found */
163 goto error;
164 }
165 }
166 /* add it to buffer */
167 buf = (buf << 6) + b;
168 pos++;
169 if (pos == 4)
170 {
171 /*
172 * Leave if there is an overflow in the area allocated for the
173 * decoded string.
174 */
175 if ((p - dst + 1) > dstlen)
176 goto error;
177 *p++ = (buf >> 16) & 255;
178
179 if (end == 0 || end > 1)
180 {
181 /* overflow check */
182 if ((p - dst + 1) > dstlen)
183 goto error;
184 *p++ = (buf >> 8) & 255;
185 }
186 if (end == 0 || end > 2)
187 {
188 /* overflow check */
189 if ((p - dst + 1) > dstlen)
190 goto error;
191 *p++ = buf & 255;
192 }
193 buf = 0;
194 pos = 0;
195 }
196 }
197
198 if (pos != 0)
199 {
200 /*
201 * base64 end sequence is invalid. Input data is missing padding, is
202 * truncated or is otherwise corrupted.
203 */
204 goto error;
205 }
206
207 Assert((p - dst) <= dstlen);
208 return p - dst;
209
210 error:
211 memset(dst, 0, dstlen);
212 return -1;
213 }
214
215 /*
216 * pg_b64_enc_len
217 *
218 * Returns to caller the length of the string if it were encoded with
219 * base64 based on the length provided by caller. This is useful to
220 * estimate how large a buffer allocation needs to be done before doing
221 * the actual encoding.
222 */
223 int
pg_b64_enc_len(int srclen)224 pg_b64_enc_len(int srclen)
225 {
226 /* 3 bytes will be converted to 4 */
227 return (srclen + 2) * 4 / 3;
228 }
229
230 /*
231 * pg_b64_dec_len
232 *
233 * Returns to caller the length of the string if it were to be decoded
234 * with base64, based on the length given by caller. This is useful to
235 * estimate how large a buffer allocation needs to be done before doing
236 * the actual decoding.
237 */
238 int
pg_b64_dec_len(int srclen)239 pg_b64_dec_len(int srclen)
240 {
241 return (srclen * 3) >> 2;
242 }
243