/* vi: set sw=4 ts=4: */ /* * A small little ldd implementation for uClibc * * Copyright (C) 2000 by Lineo, inc and Erik Andersen * Copyright (C) 2000-2002 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 * */ #define _GNU_SOURCE #include <stdlib.h> #include <stdio.h> #include <fcntl.h> #include <string.h> #include <unistd.h> #include <sys/mman.h> #include <sys/stat.h> #include <sys/types.h> #include "bswap.h" #if defined (sun) #include "link.h" #else #include "elf.h" #endif #ifdef DMALLOC #include <dmalloc.h> #endif struct library { char *name; int resolved; char *path; struct library *next; }; struct library *lib_list = NULL; char not_found[] = "not found"; char *interp = NULL; char *interp_dir = NULL; int byteswap; inline uint32_t byteswap32_to_host(uint32_t value) { if (byteswap==1) { return(bswap_32(value)); } else { return(value); } } Elf32_Shdr * elf_find_section_type( int key, Elf32_Ehdr *ehdr) { int j; Elf32_Shdr *shdr; shdr = (Elf32_Shdr *)(ehdr->e_shoff + (char *)ehdr); for (j = ehdr->e_shnum; --j>=0; ++shdr) { if (key==byteswap32_to_host(shdr->sh_type)) { 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==byteswap32_to_host(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 = byteswap32_to_host(pt_text->p_vaddr) - byteswap32_to_host(pt_text->p_offset); for (; DT_NULL!=byteswap32_to_host(dynp->d_tag); ++dynp) { if (key == byteswap32_to_host(dynp->d_tag)) { if (return_val == 1) return (void *)(intptr_t)byteswap32_to_host(dynp->d_un.d_val); else return (void *)(byteswap32_to_host(dynp->d_un.d_val) - tx_reloc + (char *)ehdr ); } } return NULL; } int check_elf_header(Elf32_Ehdr *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; } /* Check if the target endianness matches the host's endianness */ byteswap = 0; #if __BYTE_ORDER == __LITTLE_ENDIAN if (ehdr->e_ident[5] == ELFDATA2MSB) { /* Ick -- we will have to byte-swap everything */ byteswap = 1; } #elif __BYTE_ORDER == __BIG_ENDIAN if (ehdr->e_ident[5] == ELFDATA2LSB) { byteswap = 1; } #else #error Unknown host byte order! #endif /* Be vary lazy, and only byteswap the stuff we use */ if (byteswap==1) { ehdr->e_type=bswap_16(ehdr->e_type); ehdr->e_phoff=bswap_32(ehdr->e_phoff); ehdr->e_shoff=bswap_32(ehdr->e_shoff); ehdr->e_phnum=bswap_16(ehdr->e_phnum); ehdr->e_shnum=bswap_16(ehdr->e_shnum); } 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 = 1; 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++) { strcpy(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 /* Next look for libraries wherever the shared library * loader was installed -- this is usually where we * should find things... */ if (interp_dir) { search_for_named_library(lib->name, buf, interp_dir); if (*buf != '\0') { lib->path = buf; return; } } /* 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; tmp = s; while (*tmp) { if (*tmp == '/') s = tmp + 1; tmp++; } /* We add libc.so.0 elsewhere */ if ((tmp=strrchr(interp, '/')) != NULL) { int len = strlen(interp_dir); if (strcmp(s, interp+1+len)==0) return 1; } 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)+1); 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; byteswap32_to_host(dyns->d_tag)!=DT_NULL; ++dyns) { if (DT_NEEDED == byteswap32_to_host(dyns->d_tag)) { add_library(ehdr, dynamic, strtab, is_setuid, (char*)strtab + byteswap32_to_host(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 + byteswap32_to_host(phdr->p_offset); char *tmp, *tmp1; interp = strdup(s); interp_dir = strdup(s); tmp = strrchr(interp_dir, '/'); if (*tmp) *tmp = '\0'; else { free(interp_dir); interp_dir = interp; } 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)+1); strcpy(newlib->name, s); newlib->path = newlib->name; newlib->resolved = 1; newlib->next = NULL; #if 0 //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; } #endif } } /* 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); find_elf_interpreter(ehdr, dynamic, dynstr, is_suid); if (dynsec) { dynamic = (Elf32_Dyn*)(byteswap32_to_host(dynsec->sh_offset) + (intptr_t)ehdr); dynstr = (char *)elf_find_dynamic(DT_STRTAB, dynamic, ehdr, 0); find_needed_libraries(ehdr, dynamic, dynstr, is_suid); } return 0; } int main( int argc, char** argv) { int multi=0; int got_em_all=1; char *filename = NULL; struct library *cur; if (argc < 2) { fprintf(stderr, "ldd: missing file arguments\n"); fprintf(stderr, "Try `ldd --help' for more information.\n"); exit(EXIT_FAILURE); } if (argc > 2) { multi++; } while (--argc > 0) { ++argv; if(strcmp(*argv, "--")==0) { /* Ignore "--" */ continue; } if(strcmp(*argv, "--help")==0) { fprintf(stderr, "Usage: ldd [OPTION]... FILE...\n"); fprintf(stderr, "\t--help\t\tprint this help and exit\n"); exit(EXIT_FAILURE); } filename=*argv; 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; if (multi) { printf("%s:\n", *argv); } for (cur = lib_list; cur; cur=cur->next) { got_em_all=1; printf("\t%s => %s (0x00000000)\n", cur->name, cur->path); } if (interp_dir && got_em_all==1) printf("\t%s => %s (0x00000000)\n", interp, interp); if (got_em_all==0) printf("\tnot a dynamic executable\n"); } return 0; }