xref: /titanic_50/usr/src/lib/libast/common/path/pathcanon.c (revision ff17c8bf86c3e567734be83f90267edee20f580f)
1 /***********************************************************************
2 *                                                                      *
3 *               This software is part of the ast package               *
4 *           Copyright (c) 1985-2007 AT&T Knowledge Ventures            *
5 *                      and is licensed under the                       *
6 *                  Common Public License, Version 1.0                  *
7 *                      by AT&T Knowledge Ventures                      *
8 *                                                                      *
9 *                A copy of the License is available at                 *
10 *            http://www.opensource.org/licenses/cpl1.0.txt             *
11 *         (with md5 checksum 059e8cd6165cb4c31e351f2b69388fd9)         *
12 *                                                                      *
13 *              Information and Software Systems Research               *
14 *                            AT&T Research                             *
15 *                           Florham Park NJ                            *
16 *                                                                      *
17 *                 Glenn Fowler <gsf@research.att.com>                  *
18 *                  David Korn <dgk@research.att.com>                   *
19 *                   Phong Vo <kpv@research.att.com>                    *
20 *                                                                      *
21 ***********************************************************************/
22 #pragma prototyped
23 /*
24  * Glenn Fowler
25  * AT&T Research
26  *
27  * in-place path name canonicalization -- preserves the logical view
28  * pointer to trailing 0 in path returned
29  *
30  *	remove redundant .'s and /'s
31  *	move ..'s to the front
32  *	/.. preserved (for pdu and newcastle hacks)
33  *	FS_3D handles ...
34  *	if (flags&PATH_PHYSICAL) then symlinks resolved at each component
35  *	if (flags&PATH_DOTDOT) then each .. checked for access
36  *	if (flags&PATH_EXISTS) then path must exist at each component
37  *	if (flags&PATH_VERIFIED(n)) then first n chars of path exist
38  *
39  * longer pathname possible if (flags&PATH_PHYSICAL) or FS_3D ... involved
40  * 0 returned on error and if (flags&(PATH_DOTDOT|PATH_EXISTS)) then path
41  * will contain the components following the failure point
42  */
43 
44 #include <ast.h>
45 #include <ls.h>
46 #include <fs3d.h>
47 #include <error.h>
48 
49 char*
50 pathcanon(char* path, int flags)
51 {
52 	register char*	p;
53 	register char*	r;
54 	register char*	s;
55 	register char*	t;
56 	register int	dots;
57 	char*		phys;
58 	char*		v;
59 	int		loop;
60 	int		oerrno;
61 #if defined(FS_3D)
62 	long		visits = 0;
63 #endif
64 
65 	oerrno = errno;
66 	dots = loop = 0;
67 	phys = path;
68 	v = path + ((flags >> 5) & 01777);
69 	if (*path == '/' && *(path + 1) == '/' && *astconf("PATH_LEADING_SLASHES", NiL, NiL) == '1')
70 		do path++; while (*path == '/' && *(path + 1) == '/');
71 	p = r = s = t = path;
72 	for (;;) switch (*t++ = *s++)
73 	{
74 	case '.':
75 		dots++;
76 		break;
77 	case 0:
78 		s--;
79 		/*FALLTHROUGH*/
80 	case '/':
81 		while (*s == '/') s++;
82 		switch (dots)
83 		{
84 		case 1:
85 			t -= 2;
86 			break;
87 		case 2:
88 			if ((flags & (PATH_DOTDOT|PATH_EXISTS)) == PATH_DOTDOT && (t - 2) >= v)
89 			{
90 				struct stat	st;
91 
92 				*(t - 2) = 0;
93 				if (stat(phys, &st))
94 				{
95 					strcpy(path, s);
96 					return 0;
97 				}
98 				*(t - 2) = '.';
99 			}
100 #if PRESERVE_TRAILING_SLASH
101 			if (t - 5 < r) r = t;
102 #else
103 			if (t - 5 < r)
104 			{
105 				if (t - 4 == r) t = r + 1;
106 				else r = t;
107 			}
108 #endif
109 			else for (t -= 5; t > r && *(t - 1) != '/'; t--);
110 			break;
111 		case 3:
112 #if defined(FS_3D)
113 			{
114 				char*		x;
115 				char*		o;
116 				int		c;
117 
118 				o = t;
119 				if ((t -= 5) <= path) t = path + 1;
120 				c = *t;
121 				*t = 0;
122 				if (x = pathnext(phys, s - (*s != 0), &visits))
123 				{
124 					r = path;
125 					if (t == r + 1) x = r;
126 					v = s = t = x;
127 				}
128 				else
129 				{
130 					*t = c;
131 					t = o;
132 				}
133 			}
134 #else
135 			r = t;
136 #endif
137 			break;
138 		default:
139 			if ((flags & PATH_PHYSICAL) && loop < 32 && (t - 1) > path)
140 			{
141 				int	c;
142 				char	buf[PATH_MAX];
143 
144 				c = *(t - 1);
145 				*(t - 1) = 0;
146 				dots = pathgetlink(phys, buf, sizeof(buf));
147 				*(t - 1) = c;
148 				if (dots > 0)
149 				{
150 					loop++;
151 					strcpy(buf + dots, s - (*s != 0));
152 					if (*buf == '/') p = r = path;
153 					v = s = t = p;
154 					strcpy(p, buf);
155 				}
156 				else if (dots < 0 && errno == ENOENT)
157 				{
158 					if (flags & PATH_EXISTS)
159 					{
160 						strcpy(path, s);
161 						return 0;
162 					}
163 					flags &= ~(PATH_PHYSICAL|PATH_DOTDOT);
164 				}
165 				dots = 4;
166 			}
167 			break;
168 		}
169 		if (dots >= 4 && (flags & PATH_EXISTS) && (t - 1) >= v && (t > path + 1 || t > path && *(t - 1) && *(t - 1) != '/'))
170 		{
171 			struct stat	st;
172 
173 			*(t - 1) = 0;
174 			if (stat(phys, &st))
175 			{
176 				strcpy(path, s);
177 				return 0;
178 			}
179 			v = t;
180 			if (*s) *(t - 1) = '/';
181 		}
182 		if (!*s)
183 		{
184 			if (t > path && !*(t - 1)) t--;
185 			if (t == path) *t++ = '.';
186 #if DONT_PRESERVE_TRAILING_SLASH
187 			else if (t > path + 1 && *(t - 1) == '/') t--;
188 #else
189 			else if ((s <= path || *(s - 1) != '/') && t > path + 1 && *(t - 1) == '/') t--;
190 #endif
191 			*t = 0;
192 			errno = oerrno;
193 			return t;
194 		}
195 		dots = 0;
196 		p = t;
197 		break;
198 	default:
199 		dots = 4;
200 		break;
201 	}
202 }
203