1 /***************************************************************************
2 * _ _ ____ _
3 * Project ___| | | | _ \| |
4 * / __| | | | |_) | |
5 * | (__| |_| | _ <| |___
6 * \___|\___/|_| \_\_____|
7 *
8 * Copyright (C) 1998 - 2016, Daniel Stenberg, <daniel@haxx.se>, et al.
9 *
10 * This software is licensed as described in the file COPYING, which
11 * you should have received as part of this distribution. The terms
12 * are also available at https://curl.haxx.se/docs/copyright.html.
13 *
14 * You may opt to use, copy, modify, merge, publish, distribute and/or sell
15 * copies of the Software, and permit persons to whom the Software is
16 * furnished to do so, under the terms of the COPYING file.
17 *
18 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
19 * KIND, either express or implied.
20 *
21 ***************************************************************************/
22
23 #include "curl_setup.h"
24
25 #include <curl/curl.h>
26
27 #include "dotdot.h"
28 #include "curl_memory.h"
29
30 /* The last #include file should be: */
31 #include "memdebug.h"
32
33 /*
34 * "Remove Dot Segments"
35 * https://tools.ietf.org/html/rfc3986#section-5.2.4
36 */
37
38 /*
39 * Curl_dedotdotify()
40 * @unittest: 1395
41 *
42 * This function gets a zero-terminated path with dot and dotdot sequences
43 * passed in and strips them off according to the rules in RFC 3986 section
44 * 5.2.4.
45 *
46 * The function handles a query part ('?' + stuff) appended but it expects
47 * that fragments ('#' + stuff) have already been cut off.
48 *
49 * RETURNS
50 *
51 * an allocated dedotdotified output string
52 */
Curl_dedotdotify(const char * input)53 char *Curl_dedotdotify(const char *input)
54 {
55 size_t inlen = strlen(input);
56 char *clone;
57 size_t clen = inlen; /* the length of the cloned input */
58 char *out = malloc(inlen+1);
59 char *outptr;
60 char *orgclone;
61 char *queryp;
62 if(!out)
63 return NULL; /* out of memory */
64
65 /* get a cloned copy of the input */
66 clone = strdup(input);
67 if(!clone) {
68 free(out);
69 return NULL;
70 }
71 orgclone = clone;
72 outptr = out;
73
74 if(!*clone) {
75 /* zero length string, return that */
76 free(out);
77 return clone;
78 }
79
80 /*
81 * To handle query-parts properly, we must find it and remove it during the
82 * dotdot-operation and then append it again at the end to the output
83 * string.
84 */
85 queryp = strchr(clone, '?');
86 if(queryp)
87 *queryp = 0;
88
89 do {
90
91 /* A. If the input buffer begins with a prefix of "../" or "./", then
92 remove that prefix from the input buffer; otherwise, */
93
94 if(!strncmp("./", clone, 2)) {
95 clone+=2;
96 clen-=2;
97 }
98 else if(!strncmp("../", clone, 3)) {
99 clone+=3;
100 clen-=3;
101 }
102
103 /* B. if the input buffer begins with a prefix of "/./" or "/.", where
104 "." is a complete path segment, then replace that prefix with "/" in
105 the input buffer; otherwise, */
106 else if(!strncmp("/./", clone, 3)) {
107 clone+=2;
108 clen-=2;
109 }
110 else if(!strcmp("/.", clone)) {
111 clone[1]='/';
112 clone++;
113 clen-=1;
114 }
115
116 /* C. if the input buffer begins with a prefix of "/../" or "/..", where
117 ".." is a complete path segment, then replace that prefix with "/" in
118 the input buffer and remove the last segment and its preceding "/" (if
119 any) from the output buffer; otherwise, */
120
121 else if(!strncmp("/../", clone, 4)) {
122 clone+=3;
123 clen-=3;
124 /* remove the last segment from the output buffer */
125 while(outptr > out) {
126 outptr--;
127 if(*outptr == '/')
128 break;
129 }
130 *outptr = 0; /* zero-terminate where it stops */
131 }
132 else if(!strcmp("/..", clone)) {
133 clone[2]='/';
134 clone+=2;
135 clen-=2;
136 /* remove the last segment from the output buffer */
137 while(outptr > out) {
138 outptr--;
139 if(*outptr == '/')
140 break;
141 }
142 *outptr = 0; /* zero-terminate where it stops */
143 }
144
145 /* D. if the input buffer consists only of "." or "..", then remove
146 that from the input buffer; otherwise, */
147
148 else if(!strcmp(".", clone) || !strcmp("..", clone)) {
149 *clone=0;
150 }
151
152 else {
153 /* E. move the first path segment in the input buffer to the end of
154 the output buffer, including the initial "/" character (if any) and
155 any subsequent characters up to, but not including, the next "/"
156 character or the end of the input buffer. */
157
158 do {
159 *outptr++ = *clone++;
160 clen--;
161 } while(*clone && (*clone != '/'));
162 *outptr = 0;
163 }
164
165 } while(*clone);
166
167 if(queryp) {
168 size_t qlen;
169 /* There was a query part, append that to the output. The 'clone' string
170 may now have been altered so we copy from the original input string
171 from the correct index. */
172 size_t oindex = queryp - orgclone;
173 qlen = strlen(&input[oindex]);
174 memcpy(outptr, &input[oindex], qlen+1); /* include the ending zero byte */
175 }
176
177 free(orgclone);
178 return out;
179 }
180