summaryrefslogtreecommitdiff
path: root/ldso/util/ldd.c
blob: 68221faab7948b807052e6bc72ede879298c2eb8 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
/* vi: set sw=4 ts=4: */
/*
 * A small little ldd implementation for uClibc
 *
 * Copyright (C) 2000 by Lineo, inc.
 * Copyright (C) 2000,2001 Erik Andersen <andersee@debian.org>
 * Written by Erik Andersen <andersee@debian.org>
 *
 * Several functions in this file (specifically, elf_find_section_type(),
 * elf_find_phdr_type(), and elf_find_dynamic(), were stolen from elflib.c from
 * elfvector (http://www.BitWagon.com/elfvector.html) by John F. Reiser
 * <jreiser@BitWagon.com>, which is copyright 2000 BitWagon Software LLC
 * (GPL2).
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 *
 */


#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>
#include "elf.h"

struct library {
	char *name;
	int resolved;
	char *path;
	struct library *next;
};
struct library *lib_list = NULL;
char not_found[] = "not found";



Elf32_Shdr * elf_find_section_type( int key, Elf32_Ehdr *ehdr)
{
	int j;
	Elf32_Shdr *shdr = (Elf32_Shdr *)(ehdr->e_shoff + (char *)ehdr);
	for (j = ehdr->e_shnum; --j>=0; ++shdr) {
		if (shdr->sh_type == key) {
			return shdr;
		}
	}
	return NULL;
}

Elf32_Phdr * elf_find_phdr_type( int type, Elf32_Ehdr *ehdr)
{
	int j;
	Elf32_Phdr *phdr = (Elf32_Phdr *)(ehdr->e_phoff + (char *)ehdr);
	for (j = ehdr->e_phnum; --j>=0; ++phdr) {
		if (type==phdr->p_type) {
			return phdr;
		}
	}
	return NULL;
}

/* Returns value if return_val==1, ptr otherwise */ 
void * elf_find_dynamic(int const key, Elf32_Dyn *dynp, 
	Elf32_Ehdr *ehdr, int return_val)
{
	Elf32_Phdr *pt_text = elf_find_phdr_type(PT_LOAD, ehdr);
	unsigned tx_reloc = pt_text->p_vaddr - pt_text->p_offset;
	for (; DT_NULL!=dynp->d_tag; ++dynp) {
		if (dynp->d_tag == key) {
			if (return_val == 1)
				return (void *)dynp->d_un.d_val;
			else
				return (void *)(dynp->d_un.d_val - tx_reloc + (char *)ehdr );
		}
	}
	return NULL;
}

int check_elf_header(Elf32_Ehdr const *const ehdr)
{
	if (! ehdr || strncmp((void *)ehdr, ELFMAG, SELFMAG) != 0 ||  
			ehdr->e_ident[EI_CLASS] != ELFCLASS32 ||
			ehdr->e_ident[EI_VERSION] != EV_CURRENT) 
	{
		return 1;
	}
	return 0;
}

/* This function's behavior must exactly match that 
 * in uClibc/ldso/d-link/readelflib1.c */
static void search_for_named_library(char *name, char *result, const char *path_list)
{
	int i, count = 0;
	char *path, *path_n;
	struct stat filestat;

	/* We need a writable copy of this string */
	path = strdup(path_list);
	if (!path) {
		fprintf(stderr, "Out of memory!\n");
		exit(EXIT_FAILURE);
	}
	/* Eliminate all double //s */
	path_n=path;
	while((path_n=strstr(path_n, "//"))) {
		i = strlen(path_n);
		memmove(path_n, path_n+1, i-1);
	}

	/* Replace colons with zeros in path_list and count them */
	for(i=strlen(path); i > 0; i--) {
		if (path[i]==':') {
			path[i]=0;
			count++;
		}
	}

	path_n = path;
	for (i = 0; i < count; i++) {
		*result = '\0';
		strcat(result, path_n); 
		strcat(result, "/"); 
		strcat(result, name);
		if (stat (result, &filestat) == 0 && filestat.st_mode & S_IRUSR) {
			free(path);
			return;
		}
		path_n += (strlen(path_n) + 1);
	}
	free(path);
	*result = '\0';
}

void locate_library_file(Elf32_Ehdr* ehdr, Elf32_Dyn* dynamic, char *strtab, int is_suid, struct library *lib)
{
	char *buf;
	char *path;
	struct stat filestat;
	
	/* If this is a fully resolved name, our job is easy */
	if (stat (lib->name, &filestat) == 0) {
		lib->path = lib->name;
		return;
	}

	/* We need some elbow room here.  Make some room...*/
	buf = malloc(1024);
	if (!buf) {
		fprintf(stderr, "Out of memory!\n");
		exit(EXIT_FAILURE);
	}

	/* This function must match the behavior of _dl_load_shared_library
	 * in readelflib1.c or things won't work out as expected... */

	/* The ABI specifies that RPATH is searched first, so do that now.  */
	path = (char *)elf_find_dynamic(DT_RPATH, dynamic, ehdr, 0);
	if (path) {
		search_for_named_library(lib->name, buf, path);
		if (*buf != '\0') {
			lib->path = buf;
			return;
		}
	}

	/* Next check LD_{ELF_}LIBRARY_PATH if specified and allowed.
	 * Since this app doesn't actually run an executable I will skip
	 * the suid check, and just use LD_{ELF_}LIBRARY_PATH if set */
	if (is_suid==1)
		path = NULL;
	else
		path = getenv("LD_LIBRARY_PATH");
	if (path) {
		search_for_named_library(lib->name, buf, path);
		if (*buf != '\0') {
			lib->path = buf;
			return;
		}
	}

#ifdef USE_CACHE
	/* FIXME -- add code to check the Cache here */ 
#endif

	/* Lastly, search the standard list of paths for the library.
	   This list must exactly match the list in uClibc/ldso/d-link/readelflib1.c */
	path =	UCLIBC_TARGET_PREFIX "/usr/lib:"
			UCLIBC_TARGET_PREFIX "/lib:"
			UCLIBC_DEVEL_PREFIX "/lib:"
			UCLIBC_BUILD_DIR "/lib:"
			"/usr/lib:"
			"/lib";
	search_for_named_library(lib->name, buf, path);
	if (*buf != '\0') {
		lib->path = buf;
	} else { 
		free(buf);
		lib->path = not_found;
	}
}

static int add_library(Elf32_Ehdr* ehdr, Elf32_Dyn* dynamic, char *strtab, int is_setuid, char *s)
{
	char *tmp, *tmp1, *tmp2;
	struct library *cur, *newlib=lib_list;

	if (!s || !strlen(s))
		return 1;

	/* We add libc.so.0 elsewhere */
	if (strcmp(s, UCLIBC_LDSO)==0)
		return 1;

	tmp = s; 
	while (*tmp) {
		if (*tmp == '/')
			s = tmp + 1;
		tmp++;
	}

	for (cur = lib_list; cur; cur=cur->next) {
		/* Check if this library is already in the list */
		tmp1 = tmp2 = cur->name; 
		while (*tmp1) {
			if (*tmp1 == '/')
				tmp2 = tmp1 + 1;
			tmp1++;
		}
		if(strcmp(tmp2, s)==0) {
			//printf("find_elf_interpreter is skipping '%s' (already in list)\n", cur->name);
			return 0;
		}
	}

	/* Ok, this lib needs to be added to the list */
	newlib = malloc(sizeof(struct library));
	if (!newlib)
		return 1;
	newlib->name = malloc(strlen(s));
	strcpy(newlib->name, s);
	newlib->resolved = 0;
	newlib->path = NULL;
	newlib->next = NULL;

	/* Now try and locate where this library might be living... */
	locate_library_file(ehdr, dynamic, strtab, is_setuid, newlib);

	//printf("add_library is adding '%s' to '%s'\n", newlib->name, newlib->path);
	if (!lib_list) {
		lib_list = newlib;
	} else {
		for (cur = lib_list;  cur->next; cur=cur->next); /* nothing */
		cur->next = newlib;
	}
	return 0;
}


static void find_needed_libraries(Elf32_Ehdr* ehdr, Elf32_Dyn* dynamic, char *strtab, int is_setuid)
{
	Elf32_Dyn  *dyns;

	for (dyns=dynamic; dyns->d_tag!=DT_NULL; ++dyns) {
		if (dyns->d_tag == DT_NEEDED) {
			add_library(ehdr, dynamic, strtab, is_setuid, (char*)strtab + dyns->d_un.d_val);
		}
	}
}
    
static void find_elf_interpreter(Elf32_Ehdr* ehdr, Elf32_Dyn* dynamic, char *strtab, int is_setuid)
{
	static int been_there_done_that=0;
	Elf32_Phdr *phdr;

	if (been_there_done_that==1)
		return;
	been_there_done_that=1;
	phdr = elf_find_phdr_type(PT_INTERP, ehdr);
	if (phdr) {
		struct library *cur, *newlib=NULL;
		char *s = (char*)ehdr + phdr->p_offset;
	
		char *tmp, *tmp1;
		tmp1 = tmp = s;
		while (*tmp) {
			if (*tmp == '/')
				tmp1 = tmp + 1;
			tmp++;
		}
		for (cur = lib_list; cur; cur=cur->next) {
			/* Check if this library is already in the list */
			if(strcmp(cur->name, tmp1)==0) {
				//printf("find_elf_interpreter is replacing '%s' (already in list)\n", cur->name);
				newlib = cur;
				free(newlib->name);
				free(newlib->path);
				return;
			}
		}
		if (newlib == NULL)
			newlib = malloc(sizeof(struct library));
		if (!newlib)
			return;
		newlib->name = malloc(strlen(s));
		strcpy(newlib->name, s);
		newlib->path = newlib->name;
		newlib->resolved = 1;
		newlib->next = NULL;
	
		//printf("find_elf_interpreter is adding '%s' to '%s'\n", newlib->name, newlib->path);
		if (!lib_list) {
			lib_list = newlib;
		} else {
			for (cur = lib_list;  cur->next; cur=cur->next); /* nothing */
			cur->next = newlib;
		}
	}
}

/* map the .so, and locate interesting pieces */
int find_dependancies(char* filename)
{
	int is_suid = 0;
	FILE *thefile;
	struct stat statbuf;
	char *dynstr=NULL;
	Elf32_Ehdr *ehdr = NULL;
	Elf32_Shdr *dynsec = NULL;
	Elf32_Dyn *dynamic = NULL;

	if (filename == not_found)
		return 0;

	if (!filename) {
		fprintf(stderr, "No filename specified.\n");
		exit(EXIT_FAILURE);
	}
	if (!(thefile = fopen(filename, "r"))) {
		perror(filename);
		exit(EXIT_FAILURE);
	}
	if (fstat(fileno(thefile), &statbuf) < 0) {
		perror(filename);
		exit(EXIT_FAILURE);
	}

	if (statbuf.st_size < sizeof(Elf32_Ehdr))
		goto foo;

	/* mmap the file to make reading stuff from it effortless */
	ehdr = (Elf32_Ehdr *)mmap(0, statbuf.st_size, 
			PROT_READ|PROT_WRITE, MAP_PRIVATE, fileno(thefile), 0);

foo:
	/* Check if this looks like a legit ELF file */
	if (check_elf_header(ehdr)) {
		fprintf(stderr, "%s: not an ELF file.\n", filename);
		exit(EXIT_FAILURE);
	}
	/* Check if this is the right kind of ELF file */
	if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN) {
		fprintf(stderr, "%s: not a dynamic executable\n", filename);
		exit(EXIT_FAILURE);
	}
	if (ehdr->e_type == ET_EXEC) {
		if (statbuf.st_mode & S_ISUID)
			is_suid = 1;
		if ((statbuf.st_mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP))
			is_suid = 1;
		/* FIXME */
		if (is_suid)
			fprintf(stderr, "%s: is setuid\n", filename);
	}

	dynsec = elf_find_section_type(SHT_DYNAMIC, ehdr);
	if (dynsec) {
		dynamic = (Elf32_Dyn*)(dynsec->sh_offset + (int)ehdr);
		dynstr = (char *)elf_find_dynamic(DT_STRTAB, dynamic, ehdr, 0);
		find_needed_libraries(ehdr, dynamic, dynstr, is_suid);
	}
	find_elf_interpreter(ehdr, dynamic, dynstr, is_suid);
	
	return 0;
}



int main( int argc, char** argv)
{
	int got_em_all=1;
	char *filename = argv[1];
	struct library *cur;


	if (!filename) {
		fprintf(stderr, "No filename specified.\n");
		exit(EXIT_FAILURE);
	}

	find_dependancies(filename);
	
	while(got_em_all) {
		got_em_all=0;
		/* Keep walking the list till everybody is resolved */
		for (cur = lib_list; cur; cur=cur->next) {
			if (cur->resolved == 0 && cur->path) {
				got_em_all=1;
				//printf("checking sub-depends for '%s\n", cur->path);
				find_dependancies(cur->path);
				cur->resolved = 1;
			}
		}
	}

	
	/* Print the list */
	got_em_all=0;
	for (cur = lib_list; cur; cur=cur->next) {
		got_em_all=1;
		printf("\t%s => %s\n", cur->name, cur->path);
	}
	if (got_em_all==0)
		printf("\tnot a dynamic executable\n");

	return 0;
}