xref: /freebsd/crypto/openssh/openbsd-compat/getcwd.c (revision 3e8eb5c7f4909209c042403ddee340b2ee7003a5)
1 /*	$OpenBSD: getcwd.c,v 1.14 2005/08/08 08:05:34 espie Exp */
2 /*
3  * Copyright (c) 1989, 1991, 1993
4  *	The Regents of the University of California.  All rights reserved.
5  *
6  * Redistribution and use in source and binary forms, with or without
7  * modification, are permitted provided that the following conditions
8  * are met:
9  * 1. Redistributions of source code must retain the above copyright
10  *    notice, this list of conditions and the following disclaimer.
11  * 2. Redistributions in binary form must reproduce the above copyright
12  *    notice, this list of conditions and the following disclaimer in the
13  *    documentation and/or other materials provided with the distribution.
14  * 3. Neither the name of the University nor the names of its contributors
15  *    may be used to endorse or promote products derived from this software
16  *    without specific prior written permission.
17  *
18  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
19  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
22  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
24  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
25  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
26  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
27  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28  * SUCH DAMAGE.
29  */
30 
31 /* OPENBSD ORIGINAL: lib/libc/gen/getcwd.c */
32 
33 #include "includes.h"
34 
35 #if !defined(HAVE_GETCWD)
36 
37 #include <sys/stat.h>
38 #include <errno.h>
39 #include <dirent.h>
40 #include <sys/dir.h>
41 #include <stdio.h>
42 #include <stdlib.h>
43 #include <string.h>
44 #include "includes.h"
45 
46 #define	ISDOT(dp) \
47 	(dp->d_name[0] == '.' && (dp->d_name[1] == '\0' || \
48 	    (dp->d_name[1] == '.' && dp->d_name[2] == '\0')))
49 
50 char *
51 getcwd(char *pt, size_t size)
52 {
53 	struct dirent *dp;
54 	DIR *dir = NULL;
55 	dev_t dev;
56 	ino_t ino;
57 	int first;
58 	char *bpt, *bup;
59 	struct stat s;
60 	dev_t root_dev;
61 	ino_t root_ino;
62 	size_t ptsize, upsize;
63 	int save_errno;
64 	char *ept, *eup, *up;
65 
66 	/*
67 	 * If no buffer specified by the user, allocate one as necessary.
68 	 * If a buffer is specified, the size has to be non-zero.  The path
69 	 * is built from the end of the buffer backwards.
70 	 */
71 	if (pt) {
72 		ptsize = 0;
73 		if (!size) {
74 			errno = EINVAL;
75 			return (NULL);
76 		}
77 		ept = pt + size;
78 	} else {
79 		if ((pt = malloc(ptsize = MAXPATHLEN)) == NULL)
80 			return (NULL);
81 		ept = pt + ptsize;
82 	}
83 	bpt = ept - 1;
84 	*bpt = '\0';
85 
86 	/*
87 	 * Allocate bytes for the string of "../"'s.
88 	 * Should always be enough (it's 340 levels).  If it's not, allocate
89 	 * as necessary.  Special * case the first stat, it's ".", not "..".
90 	 */
91 	if ((up = malloc(upsize = MAXPATHLEN)) == NULL)
92 		goto err;
93 	eup = up + upsize;
94 	bup = up;
95 	up[0] = '.';
96 	up[1] = '\0';
97 
98 	/* Save root values, so know when to stop. */
99 	if (stat("/", &s))
100 		goto err;
101 	root_dev = s.st_dev;
102 	root_ino = s.st_ino;
103 
104 	errno = 0;			/* XXX readdir has no error return. */
105 
106 	for (first = 1;; first = 0) {
107 		/* Stat the current level. */
108 		if (lstat(up, &s))
109 			goto err;
110 
111 		/* Save current node values. */
112 		ino = s.st_ino;
113 		dev = s.st_dev;
114 
115 		/* Check for reaching root. */
116 		if (root_dev == dev && root_ino == ino) {
117 			*--bpt = '/';
118 			/*
119 			 * It's unclear that it's a requirement to copy the
120 			 * path to the beginning of the buffer, but it's always
121 			 * been that way and stuff would probably break.
122 			 */
123 			memmove(pt, bpt, ept - bpt);
124 			free(up);
125 			return (pt);
126 		}
127 
128 		/*
129 		 * Build pointer to the parent directory, allocating memory
130 		 * as necessary.  Max length is 3 for "../", the largest
131 		 * possible component name, plus a trailing NUL.
132 		 */
133 		if (bup + 3  + MAXNAMLEN + 1 >= eup) {
134 			char *nup;
135 
136 			if ((nup = realloc(up, upsize *= 2)) == NULL)
137 				goto err;
138 			bup = nup + (bup - up);
139 			up = nup;
140 			eup = up + upsize;
141 		}
142 		*bup++ = '.';
143 		*bup++ = '.';
144 		*bup = '\0';
145 
146 		/* Open and stat parent directory. */
147 		if (!(dir = opendir(up)) || fstat(dirfd(dir), &s))
148 			goto err;
149 
150 		/* Add trailing slash for next directory. */
151 		*bup++ = '/';
152 
153 		/*
154 		 * If it's a mount point, have to stat each element because
155 		 * the inode number in the directory is for the entry in the
156 		 * parent directory, not the inode number of the mounted file.
157 		 */
158 		save_errno = 0;
159 		if (s.st_dev == dev) {
160 			for (;;) {
161 				if (!(dp = readdir(dir)))
162 					goto notfound;
163 				if (dp->d_fileno == ino)
164 					break;
165 			}
166 		} else
167 			for (;;) {
168 				if (!(dp = readdir(dir)))
169 					goto notfound;
170 				if (ISDOT(dp))
171 					continue;
172 				memcpy(bup, dp->d_name, dp->d_namlen + 1);
173 
174 				/* Save the first error for later. */
175 				if (lstat(up, &s)) {
176 					if (!save_errno)
177 						save_errno = errno;
178 					errno = 0;
179 					continue;
180 				}
181 				if (s.st_dev == dev && s.st_ino == ino)
182 					break;
183 			}
184 
185 		/*
186 		 * Check for length of the current name, preceding slash,
187 		 * leading slash.
188 		 */
189 		if (bpt - pt < dp->d_namlen + (first ? 1 : 2)) {
190 			size_t len;
191 			char *npt;
192 
193 			if (!ptsize) {
194 				errno = ERANGE;
195 				goto err;
196 			}
197 			len = ept - bpt;
198 			if ((npt = realloc(pt, ptsize *= 2)) == NULL)
199 				goto err;
200 			bpt = npt + (bpt - pt);
201 			pt = npt;
202 			ept = pt + ptsize;
203 			memmove(ept - len, bpt, len);
204 			bpt = ept - len;
205 		}
206 		if (!first)
207 			*--bpt = '/';
208 		bpt -= dp->d_namlen;
209 		memcpy(bpt, dp->d_name, dp->d_namlen);
210 		(void)closedir(dir);
211 
212 		/* Truncate any file name. */
213 		*bup = '\0';
214 	}
215 
216 notfound:
217 	/*
218 	 * If readdir set errno, use it, not any saved error; otherwise,
219 	 * didn't find the current directory in its parent directory, set
220 	 * errno to ENOENT.
221 	 */
222 	if (!errno)
223 		errno = save_errno ? save_errno : ENOENT;
224 	/* FALLTHROUGH */
225 err:
226 	save_errno = errno;
227 
228 	if (ptsize)
229 		free(pt);
230 	free(up);
231 	if (dir)
232 		(void)closedir(dir);
233 
234 	errno = save_errno;
235 
236 	return (NULL);
237 }
238 
239 #endif /* !defined(HAVE_GETCWD) */
240