| // Copyright (c) 2013, Facebook, Inc. |
| // All rights reserved. |
| // Redistribution and use in source and binary forms, with or without |
| // modification, are permitted provided that the following conditions are met: |
| // * Redistributions of source code must retain the above copyright notice, |
| // this list of conditions and the following disclaimer. |
| // * Redistributions in binary form must reproduce the above copyright notice, |
| // this list of conditions and the following disclaimer in the documentation |
| // and/or other materials provided with the distribution. |
| // * Neither the name Facebook nor the names of its contributors may be used to |
| // endorse or promote products derived from this software without specific |
| // prior written permission. |
| // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" |
| // AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| // IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE |
| // DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE |
| // FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
| // DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR |
| // SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER |
| // CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, |
| // OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| |
| #import "fishhook.h" |
| |
| #import <dlfcn.h> |
| #import <stdlib.h> |
| #import <string.h> |
| #import <sys/types.h> |
| #import <mach-o/dyld.h> |
| #import <mach-o/loader.h> |
| #import <mach-o/nlist.h> |
| |
| #ifdef __LP64__ |
| typedef struct mach_header_64 mach_header_t; |
| typedef struct segment_command_64 segment_command_t; |
| typedef struct section_64 section_t; |
| typedef struct nlist_64 nlist_t; |
| #define LC_SEGMENT_ARCH_DEPENDENT LC_SEGMENT_64 |
| #else |
| typedef struct mach_header mach_header_t; |
| typedef struct segment_command segment_command_t; |
| typedef struct section section_t; |
| typedef struct nlist nlist_t; |
| #define LC_SEGMENT_ARCH_DEPENDENT LC_SEGMENT |
| #endif |
| |
| #ifndef SEG_DATA_CONST |
| #define SEG_DATA_CONST "__DATA_CONST" |
| #endif |
| |
| struct rebindings_entry { |
| struct rebinding *rebindings; |
| uint8_t *dylib_ordinals; |
| size_t rebindings_nel; |
| struct rebindings_entry *next; |
| }; |
| |
| static struct rebindings_entry *_rebindings_head; |
| |
| static int prepend_rebindings(struct rebindings_entry **rebindings_head, |
| struct rebinding rebindings[], |
| size_t nel) { |
| struct rebindings_entry *new_entry = malloc(sizeof(struct rebindings_entry)); |
| if (!new_entry) { |
| return -1; |
| } |
| new_entry->rebindings = malloc(sizeof(struct rebinding) * nel); |
| if (!new_entry->rebindings) { |
| free(new_entry); |
| return -1; |
| } |
| new_entry->dylib_ordinals = malloc(sizeof(uint8_t) * nel); |
| if (!new_entry->dylib_ordinals) { |
| free(new_entry->rebindings); |
| free(new_entry); |
| return -1; |
| } |
| memcpy(new_entry->rebindings, rebindings, sizeof(struct rebinding) * nel); |
| new_entry->rebindings_nel = nel; |
| new_entry->next = *rebindings_head; |
| *rebindings_head = new_entry; |
| return 0; |
| } |
| |
| static void perform_rebinding_with_section(struct rebindings_entry *rebindings, |
| section_t *section, |
| intptr_t slide, |
| nlist_t *symtab, |
| char *strtab, |
| uint32_t *indirect_symtab) { |
| uint32_t *indirect_symbol_indices = indirect_symtab + section->reserved1; |
| void **indirect_symbol_bindings = (void **)((uintptr_t)slide + section->addr); |
| for (uint i = 0; i < section->size / sizeof(void *); i++) { |
| uint32_t symtab_index = indirect_symbol_indices[i]; |
| if (symtab_index == INDIRECT_SYMBOL_ABS || symtab_index == INDIRECT_SYMBOL_LOCAL || |
| symtab_index == (INDIRECT_SYMBOL_LOCAL | INDIRECT_SYMBOL_ABS)) { |
| continue; |
| } |
| uint32_t strtab_offset = symtab[symtab_index].n_un.n_strx; |
| char *symbol_name = strtab + strtab_offset; |
| if (strnlen(symbol_name, 2) < 2) { |
| continue; |
| } |
| int dylib_ordinal = GET_LIBRARY_ORDINAL(symtab[symtab_index].n_desc); |
| struct rebindings_entry *cur = rebindings; |
| while (cur) { |
| for (uint j = 0; j < cur->rebindings_nel; j++) { |
| if (cur->dylib_ordinals[j] != 0 && dylib_ordinal != cur->dylib_ordinals[j] && dylib_ordinal != SELF_LIBRARY_ORDINAL) { |
| continue; |
| } |
| |
| if (strcmp(&symbol_name[1], cur->rebindings[j].name) == 0) { |
| if (cur->rebindings[j].replaced != NULL && |
| indirect_symbol_bindings[i] != cur->rebindings[j].replacement) { |
| *(cur->rebindings[j].replaced) = indirect_symbol_bindings[i]; |
| } |
| indirect_symbol_bindings[i] = cur->rebindings[j].replacement; |
| goto symbol_loop; |
| } |
| } |
| cur = cur->next; |
| } |
| symbol_loop:; |
| } |
| } |
| |
| static void rebind_symbols_for_image(struct rebindings_entry *rebindings, |
| const struct mach_header *header, |
| intptr_t slide) { |
| Dl_info info; |
| if (dladdr(header, &info) == 0) { |
| return; |
| } |
| |
| struct load_command *cur_load_cmd; |
| segment_command_t *linkedit_segment = NULL; |
| struct symtab_command* symtab_cmd = NULL; |
| struct dysymtab_command* dysymtab_cmd = NULL; |
| |
| for (struct rebindings_entry *entry = rebindings; entry != NULL; entry = entry->next) { |
| bzero(entry->dylib_ordinals, sizeof(uint8_t) * entry->rebindings_nel); |
| } |
| |
| int cur_dylib_ordinal = 1; |
| bool image_has_dylibs_to_rebind = false; |
| |
| uintptr_t cur = (uintptr_t)header + sizeof(mach_header_t); |
| for (uint i = 0; i < header->ncmds; i++, cur += cur_load_cmd->cmdsize) { |
| cur_load_cmd = (struct load_command *)cur; |
| switch (cur_load_cmd->cmd) { |
| case LC_LOAD_DYLIB: |
| case LC_LOAD_WEAK_DYLIB: |
| case LC_REEXPORT_DYLIB: |
| case LC_LOAD_UPWARD_DYLIB: |
| case LC_LAZY_LOAD_DYLIB: { |
| if ((header->flags & MH_TWOLEVEL) == 0) { |
| break; |
| } |
| |
| struct dylib_command *dylib_cmd = (struct dylib_command *)cur_load_cmd; |
| char *dylib = (char *)(cur + dylib_cmd->dylib.name.offset); |
| for (struct rebindings_entry *entry = rebindings; entry != NULL; entry = entry->next) { |
| for (int el = 0; el < entry->rebindings_nel; ++el) { |
| struct rebinding *cur_rebinding = &entry->rebindings[el]; |
| if (cur_rebinding->dylib == NULL) { |
| image_has_dylibs_to_rebind = true; |
| } else if (strcmp(cur_rebinding->dylib, dylib) == 0) { |
| entry->dylib_ordinals[el] = cur_dylib_ordinal; |
| image_has_dylibs_to_rebind = true; |
| } |
| } |
| } |
| ++cur_dylib_ordinal; |
| break; |
| } |
| case LC_SEGMENT_ARCH_DEPENDENT: { |
| segment_command_t *seg_cmd = (segment_command_t *)cur_load_cmd; |
| if (strcmp(seg_cmd->segname, SEG_LINKEDIT) == 0) { |
| linkedit_segment = seg_cmd; |
| } |
| break; |
| } |
| case LC_SYMTAB: |
| symtab_cmd = (struct symtab_command*)cur_load_cmd; |
| break; |
| case LC_DYSYMTAB: |
| dysymtab_cmd = (struct dysymtab_command*)cur_load_cmd; |
| break; |
| default: |
| break; |
| } |
| } |
| |
| // This optimization is enabled by two-level namespaces. |
| // |
| // There are two sets of dylibs: |
| // 1. The set of dylibs associated with the rebindings |
| // 2. The set of dylibs loaded by an image (i.e executable or library) |
| // |
| // When there is no overlap between these two sets of dylibs, then it becomes |
| // unnecessary to scan the symbol table of given image. However, if any |
| // rebinding has no target dylib (NULL), then all images are searched. |
| if (!image_has_dylibs_to_rebind) { |
| return; |
| } |
| |
| if (!symtab_cmd || !dysymtab_cmd || !linkedit_segment || |
| !dysymtab_cmd->nindirectsyms) { |
| return; |
| } |
| |
| // Find base symbol/string table addresses |
| uintptr_t linkedit_base = (uintptr_t)slide + linkedit_segment->vmaddr - linkedit_segment->fileoff; |
| nlist_t *symtab = (nlist_t *)(linkedit_base + symtab_cmd->symoff); |
| char *strtab = (char *)(linkedit_base + symtab_cmd->stroff); |
| |
| // Get indirect symbol table (array of uint32_t indices into symbol table) |
| uint32_t *indirect_symtab = (uint32_t *)(linkedit_base + dysymtab_cmd->indirectsymoff); |
| |
| cur = (uintptr_t)header + sizeof(mach_header_t); |
| for (uint i = 0; i < header->ncmds; i++, cur += cur_load_cmd->cmdsize) { |
| cur_load_cmd = (struct load_command *)cur; |
| if (cur_load_cmd->cmd == LC_SEGMENT_ARCH_DEPENDENT) { |
| segment_command_t *seg_cmd = (segment_command_t *)cur_load_cmd; |
| if (strcmp(seg_cmd->segname, SEG_DATA) != 0 && |
| strcmp(seg_cmd->segname, SEG_DATA_CONST) != 0) { |
| continue; |
| } |
| for (uint j = 0; j < seg_cmd->nsects; j++) { |
| section_t *sect = |
| (section_t *)(cur + sizeof(segment_command_t)) + j; |
| if ((sect->flags & SECTION_TYPE) == S_LAZY_SYMBOL_POINTERS) { |
| perform_rebinding_with_section(rebindings, sect, slide, symtab, strtab, indirect_symtab); |
| } |
| if ((sect->flags & SECTION_TYPE) == S_NON_LAZY_SYMBOL_POINTERS) { |
| perform_rebinding_with_section(rebindings, sect, slide, symtab, strtab, indirect_symtab); |
| } |
| } |
| } |
| } |
| } |
| |
| static void _rebind_symbols_for_image(const struct mach_header *header, |
| intptr_t slide) { |
| rebind_symbols_for_image(_rebindings_head, header, slide); |
| } |
| |
| int rebind_symbols_image(void *header, |
| intptr_t slide, |
| struct rebinding rebindings[], |
| size_t rebindings_nel) { |
| struct rebindings_entry *rebindings_head = NULL; |
| int retval = prepend_rebindings(&rebindings_head, rebindings, rebindings_nel); |
| rebind_symbols_for_image(rebindings_head, header, slide); |
| free(rebindings_head); |
| return retval; |
| } |
| |
| int rebind_symbols(struct rebinding rebindings[], size_t rebindings_nel) { |
| int retval = prepend_rebindings(&_rebindings_head, rebindings, rebindings_nel); |
| if (retval < 0) { |
| return retval; |
| } |
| // If this was the first call, register callback for image additions (which is also invoked for |
| // existing images, otherwise, just run on existing images |
| if (!_rebindings_head->next) { |
| _dyld_register_func_for_add_image(_rebind_symbols_for_image); |
| } else { |
| uint32_t c = _dyld_image_count(); |
| for (uint32_t i = 0; i < c; i++) { |
| _rebind_symbols_for_image(_dyld_get_image_header(i), _dyld_get_image_vmaddr_slide(i)); |
| } |
| } |
| return retval; |
| } |
