1 /*        $NetBSD: search.c,v 1.27 2020/04/22 23:54:32 joerg Exp $     */
2 
3 /*
4  * Copyright 1996 Matt Thomas <matt@3am-software.com>
5  * All rights reserved.
6  *
7  * Redistribution and use in source and binary forms, with or without
8  * modification, are permitted provided that the following conditions
9  * are met:
10  * 1. Redistributions of source code must retain the above copyright
11  *    notice, this list of conditions and the following disclaimer.
12  * 2. Redistributions in binary form must reproduce the above copyright
13  *    notice, this list of conditions and the following disclaimer in the
14  *    documentation and/or other materials provided with the distribution.
15  * 3. All advertising materials mentioning features or use of this software
16  *    must display the following acknowledgement:
17  *      This product includes software developed by John Polstra.
18  * 4. The name of the author may not be used to endorse or promote products
19  *    derived from this software without specific prior written permission.
20  *
21  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
22  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
23  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
24  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
25  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
26  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
27  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
28  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
29  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
30  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
31  */
32 
33 /*
34  * Dynamic linker for ELF.
35  *
36  * John Polstra <jdp@polstra.com>.
37  */
38 
39 #include <sys/cdefs.h>
40 #ifndef lint
41 __RCSID("$NetBSD: search.c,v 1.27 2020/04/22 23:54:32 joerg Exp $");
42 #endif /* not lint */
43 
44 #include <err.h>
45 #include <errno.h>
46 #include <fcntl.h>
47 #include <stdarg.h>
48 #include <stdio.h>
49 #include <stdlib.h>
50 #include <string.h>
51 #include <unistd.h>
52 #include <sys/types.h>
53 #include <sys/mman.h>
54 #include <sys/stat.h>
55 #include <dirent.h>
56 
57 #include "debug.h"
58 #include "rtld.h"
59 
60 /*
61  * Data declarations.
62  */
63 static Search_Path    *_rtld_invalid_paths;
64 
65 static Obj_Entry *_rtld_search_library_path(const char *, size_t,
66     const char *, size_t, int);
67 
68 static Obj_Entry *
_rtld_search_library_path(const char * name,size_t namelen,const char * dir,size_t dirlen,int flags)69 _rtld_search_library_path(const char *name, size_t namelen,
70     const char *dir, size_t dirlen, int flags)
71 {
72           char pathname[MAXPATHLEN];
73           size_t pathnamelen;
74           Obj_Entry *obj;
75           Search_Path *sp;
76 
77           pathnamelen = dirlen + 1 + namelen;
78           if (pathnamelen >= sizeof(pathname))
79                     return NULL;
80 
81           for (sp = _rtld_invalid_paths; sp != NULL; sp = sp->sp_next) {
82                     if (sp->sp_pathlen == pathnamelen &&
83                         sp->sp_path[dirlen] == '/' &&
84                         !memcmp(name, sp->sp_path + dirlen + 1, namelen) &&
85                         !memcmp(dir, sp->sp_path, dirlen)) {
86                               return NULL;
87                     }
88           }
89 
90           memcpy(pathname, dir, dirlen);
91           pathname[dirlen] = '/';
92           memcpy(pathname + dirlen + 1, name, namelen);
93           pathname[pathnamelen] = '\0';
94 
95           dbg(("  Trying \"%s\"", pathname));
96           obj = _rtld_load_object(pathname, flags);
97           if (obj == NULL) {
98                     Search_Path *path;
99 
100                     path = NEW(Search_Path);
101                     path->sp_pathlen = pathnamelen;
102                     path->sp_path = xstrdup(pathname);
103                     path->sp_next = _rtld_invalid_paths;
104                     _rtld_invalid_paths = path;
105           }
106           return obj;
107 }
108 
109 /*
110  * Find the library with the given name, and return its full pathname.
111  * The returned string is dynamically allocated.  Generates an error
112  * message and returns NULL if the library cannot be found.
113  *
114  * If the second argument is non-NULL, then it refers to an already-
115  * loaded shared object, whose library search path will be searched.
116  */
117 Obj_Entry *
_rtld_load_library(const char * name,const Obj_Entry * refobj,int flags)118 _rtld_load_library(const char *name, const Obj_Entry *refobj, int flags)
119 {
120           extern char *__progname;
121           char tmperror[512], *tmperrorp;
122           Search_Path *sp;
123           const char *pathname;
124           int namelen;
125           Obj_Entry *obj;
126 
127           if (strchr(name, '/') != NULL) {        /* Hard coded pathname */
128                     if (name[0] != '/' && !_rtld_trust) {
129                               _rtld_error(
130                               "absolute pathname required for shared object \"%s\"",
131                                   name);
132                               return NULL;
133                     }
134                     pathname = name;
135                     goto found;
136           }
137           dbg((" Searching for \"%s\" (%p)", name, refobj));
138 
139           tmperrorp = dlerror();
140           if (tmperrorp != NULL) {
141                     strlcpy(tmperror, tmperrorp, sizeof(tmperror));
142                     tmperrorp = tmperror;
143           }
144 
145           namelen = strlen(name);
146 
147           for (sp = _rtld_paths; sp != NULL; sp = sp->sp_next)
148                     if ((obj = _rtld_search_library_path(name, namelen,
149                         sp->sp_path, sp->sp_pathlen, flags)) != NULL)
150                               goto pathfound;
151 
152           if (refobj != NULL)
153                     for (sp = refobj->rpaths; sp != NULL; sp = sp->sp_next)
154                               if ((obj = _rtld_search_library_path(name,
155                                   namelen, sp->sp_path, sp->sp_pathlen, flags)) != NULL)
156                                         goto pathfound;
157 
158           for (sp = _rtld_default_paths; sp != NULL; sp = sp->sp_next)
159                     if ((obj = _rtld_search_library_path(name, namelen,
160                         sp->sp_path, sp->sp_pathlen, flags)) != NULL)
161                               goto pathfound;
162 
163           _rtld_error("%s: Shared object \"%s\" not found",
164               refobj ? refobj->path : __progname, name);
165           return NULL;
166 
167 pathfound:
168           /*
169            * The library has been found, but it couldn't be loaded for some
170            * reason.
171            */
172           if (obj == OBJ_ERR)
173                     return NULL;
174           /*
175            * Successfully found a library; restore the dlerror state as it was
176            * before _rtld_load_library() was called (any failed call to
177            * _rtld_search_library_path() will set the dlerror state, but if the
178            * library was eventually found, then the error state should not
179            * change.
180            */
181           if (tmperrorp)
182                     _rtld_error("%s", tmperror);
183           else
184                     (void)dlerror();
185           return obj;
186 
187 found:
188           obj = _rtld_load_object(pathname, flags);
189           if (obj == OBJ_ERR)
190                     return NULL;
191 
192           return obj;
193 }
194 
195