/* * Copyright (C) 2009 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ #include #include #include #include #include #include #include #include "Retouch.h" #include "applypatch/applypatch.h" typedef struct { int32_t mmap_addr; char tag[4]; /* 'P', 'R', 'E', ' ' */ } prelink_info_t __attribute__((packed)); #define false 0 #define true 1 static int32_t offs_prev; static uint32_t cont_prev; static void init_compression_state(void) { offs_prev = 0; cont_prev = 0; } // For details on the encoding used for relocation lists, please // refer to build/tools/retouch/retouch-prepare.c. The intent is to // save space by removing most of the inherent redundancy. static void decode_bytes(uint8_t *encoded_bytes, int encoded_size, int32_t *dst_offset, uint32_t *dst_contents) { if (encoded_size == 2) { *dst_offset = offs_prev + (((encoded_bytes[0]&0x60)>>5)+1)*4; // if the original was negative, we need to 1-pad before applying delta int32_t tmp = (((encoded_bytes[0] & 0x0000001f) << 8) | encoded_bytes[1]); if (tmp & 0x1000) tmp = 0xffffe000 | tmp; *dst_contents = cont_prev + tmp; } else if (encoded_size == 3) { *dst_offset = offs_prev + (((encoded_bytes[0]&0x30)>>4)+1)*4; // if the original was negative, we need to 1-pad before applying delta int32_t tmp = (((encoded_bytes[0] & 0x0000000f) << 16) | (encoded_bytes[1] << 8) | encoded_bytes[2]); if (tmp & 0x80000) tmp = 0xfff00000 | tmp; *dst_contents = cont_prev + tmp; } else { *dst_offset = (encoded_bytes[0]<<24) | (encoded_bytes[1]<<16) | (encoded_bytes[2]<<8) | encoded_bytes[3]; if (*dst_offset == 0x3fffffff) *dst_offset = -1; *dst_contents = (encoded_bytes[4]<<24) | (encoded_bytes[5]<<16) | (encoded_bytes[6]<<8) | encoded_bytes[7]; } } static uint8_t *decode_in_memory(uint8_t *encoded_bytes, int32_t *offset, uint32_t *contents) { int input_size, charIx; uint8_t input[8]; input[0] = *(encoded_bytes++); if (input[0] & 0x80) input_size = 2; else if (input[0] & 0x40) input_size = 3; else input_size = 8; // we already read one byte.. charIx = 1; while (charIx < input_size) { input[charIx++] = *(encoded_bytes++); } // depends on the decoder state! decode_bytes(input, input_size, offset, contents); offs_prev = *offset; cont_prev = *contents; return encoded_bytes; } int retouch_mask_data(uint8_t *binary_object, int32_t binary_size, int32_t *desired_offset, int32_t *retouch_offset) { retouch_info_t *r_info; prelink_info_t *p_info; int32_t target_offset = 0; if (desired_offset) target_offset = *desired_offset; int32_t p_offs = binary_size-sizeof(prelink_info_t); // prelink_info_t int32_t r_offs = p_offs-sizeof(retouch_info_t); // retouch_info_t int32_t b_offs; // retouch data blob // If not retouched, we say it was a match. This might get invoked on // non-retouched binaries, so that's why we need to do this. if (retouch_offset != NULL) *retouch_offset = target_offset; if (r_offs < 0) return (desired_offset == NULL) ? RETOUCH_DATA_NOTAPPLICABLE : RETOUCH_DATA_MATCHED; p_info = (prelink_info_t *)(binary_object+p_offs); r_info = (retouch_info_t *)(binary_object+r_offs); if (strncmp(p_info->tag, "PRE ", 4) || strncmp(r_info->tag, "RETOUCH ", 8)) return (desired_offset == NULL) ? RETOUCH_DATA_NOTAPPLICABLE : RETOUCH_DATA_MATCHED; b_offs = r_offs-r_info->blob_size; if (b_offs < 0) { printf("negative binary offset: %d = %d - %d\n", b_offs, r_offs, r_info->blob_size); return RETOUCH_DATA_ERROR; } uint8_t *b_ptr = binary_object+b_offs; // Retouched: let's go through the work then. int32_t offset_candidate = target_offset; bool offset_set = false, offset_mismatch = false; init_compression_state(); while (b_ptr < (uint8_t *)r_info) { int32_t retouch_entry_offset; uint32_t *retouch_entry; uint32_t retouch_original_value; b_ptr = decode_in_memory(b_ptr, &retouch_entry_offset, &retouch_original_value); if (retouch_entry_offset < (-1) || retouch_entry_offset >= b_offs) { printf("bad retouch_entry_offset: %d", retouch_entry_offset); return RETOUCH_DATA_ERROR; } // "-1" means this is the value in prelink_info_t, which also gets // randomized. if (retouch_entry_offset == -1) retouch_entry = (uint32_t *)&(p_info->mmap_addr); else retouch_entry = (uint32_t *)(binary_object+retouch_entry_offset); if (desired_offset) *retouch_entry = retouch_original_value + target_offset; // Infer the randomization shift, compare to previously inferred. int32_t offset_of_this_entry = (int32_t)(*retouch_entry- retouch_original_value); if (!offset_set) { offset_candidate = offset_of_this_entry; offset_set = true; } else { if (offset_candidate != offset_of_this_entry) { offset_mismatch = true; printf("offset is mismatched: %d, this entry is %d," " original 0x%x @ 0x%x", offset_candidate, offset_of_this_entry, retouch_original_value, retouch_entry_offset); } } } if (b_ptr > (uint8_t *)r_info) { printf("b_ptr went too far: %p, while r_info is %p", b_ptr, r_info); return RETOUCH_DATA_ERROR; } if (offset_mismatch) return RETOUCH_DATA_MISMATCHED; if (retouch_offset != NULL) *retouch_offset = offset_candidate; return RETOUCH_DATA_MATCHED; } // On success, _override is set to the offset that was actually applied. // This implies that once we randomize to an offset we stick with it. // This in turn is necessary in order to guarantee recovery after crash. bool retouch_one_library(const char *binary_name, const char *binary_sha1, int32_t retouch_offset, int32_t *retouch_offset_override) { bool success = true; int result; FileContents file; file.data = NULL; char binary_name_atomic[strlen(binary_name)+10]; strcpy(binary_name_atomic, binary_name); strcat(binary_name_atomic, ".atomic"); // We need a path that exists for calling statfs() later. // // Assume that binary_name (eg "/system/app/Foo.apk") is located // on the same filesystem as its top-level directory ("/system"). char target_fs[strlen(binary_name)+1]; char* slash = strchr(binary_name+1, '/'); if (slash != NULL) { int count = slash - binary_name; strncpy(target_fs, binary_name, count); target_fs[count] = '\0'; } else { strcpy(target_fs, binary_name); } result = LoadFileContents(binary_name, &file, RETOUCH_DONT_MASK); if (result == 0) { // Figure out the *apparent* offset to which this file has been // retouched. If it looks good, we will skip processing (we might // have crashed and during this recovery pass we don't want to // overwrite a valuable saved file in /cache---which would happen // if we blindly retouch everything again). NOTE: This implies // that we might have to override the supplied retouch offset. We // can do the override only once though: everything should match // afterward. int32_t inferred_offset; int retouch_probe_result = retouch_mask_data(file.data, file.size, NULL, &inferred_offset); if (retouch_probe_result == RETOUCH_DATA_MATCHED) { if ((retouch_offset == inferred_offset) || ((retouch_offset != 0 && inferred_offset != 0) && (retouch_offset_override != NULL))) { // This file is OK already and we are allowed to override. // Let's just return the offset override value. It is critical // to skip regardless of override: a broken file might need // recovery down the list and we should not mess up the saved // copy by doing unnecessary retouching. // // NOTE: If retouching was already started with a different // value, we will not be allowed to override. This happens // if on the retouch list there is a patched binary (which is // masked in apply_patch()) before there is a non-patched // binary. if (retouch_offset_override != NULL) *retouch_offset_override = inferred_offset; success = true; goto out; } else { // Retouch to zero (mask the retouching), to make sure that // the SHA-1 check will pass below. int32_t zero = 0; retouch_mask_data(file.data, file.size, &zero, NULL); SHA(file.data, file.size, file.sha1); } } if (retouch_probe_result == RETOUCH_DATA_NOTAPPLICABLE) { // In the case of not retouchable, fake it. We do not want // to do the normal processing and overwrite the backup file: // we might be recovering! // // We return a zero override, which tells the caller that we // simply skipped the file. if (retouch_offset_override != NULL) *retouch_offset_override = 0; success = true; goto out; } // If we get here, either there was a mismatch in the offset, or // the file has not been processed yet. Continue with normal // processing. } if (result != 0 || FindMatchingPatch(file.sha1, &binary_sha1, 1) < 0) { free(file.data); printf("Attempting to recover source from '%s' ...\n", CACHE_TEMP_SOURCE); result = LoadFileContents(CACHE_TEMP_SOURCE, &file, RETOUCH_DO_MASK); if (result != 0 || FindMatchingPatch(file.sha1, &binary_sha1, 1) < 0) { printf(" failed.\n"); success = false; goto out; } printf(" succeeded.\n"); } // Retouch in-memory before worrying about backing up the original. // // Recovery steps will be oblivious to the actual retouch offset used, // so might as well write out the already-retouched copy. Then, in the // usual case, we will just swap the file locally, with no more writes // needed. In the no-free-space case, we will then write the same to the // original location. result = retouch_mask_data(file.data, file.size, &retouch_offset, NULL); if (result != RETOUCH_DATA_MATCHED) { success = false; goto out; } if (retouch_offset_override != NULL) *retouch_offset_override = retouch_offset; // How much free space do we need? bool enough_space = false; size_t free_space = FreeSpaceForFile(target_fs); // 50% margin when estimating the space needed. enough_space = (free_space > (file.size * 3 / 2)); // The experts say we have to allow for a retry of the // whole process to avoid filesystem weirdness. int retry = 1; bool made_copy = false; do { // First figure out where to store a copy of the original. // Ideally leave the original itself intact until the // atomic swap. If no room on the same partition, fall back // to the cache partition and remove the original. if (!enough_space) { printf("Target is %ldB; free space is %ldB: not enough.\n", (long)file.size, (long)free_space); retry = 0; if (MakeFreeSpaceOnCache(file.size) < 0) { printf("Not enough free space on '/cache'.\n"); success = false; goto out; } if (SaveFileContents(CACHE_TEMP_SOURCE, file) < 0) { printf("Failed to back up source file.\n"); success = false; goto out; } made_copy = true; unlink(binary_name); size_t free_space = FreeSpaceForFile(target_fs); printf("(now %ld bytes free for target)\n", (long)free_space); } result = SaveFileContents(binary_name_atomic, file); if (result != 0) { // Maybe the filesystem was optimistic: retry. enough_space = false; unlink(binary_name_atomic); printf("Saving the retouched contents failed; retrying.\n"); continue; } // Succeeded; no need to retry. break; } while (retry-- > 0); // Give the .atomic file the same owner, group, and mode of the // original source file. if (chmod(binary_name_atomic, file.st.st_mode) != 0) { printf("chmod of \"%s\" failed: %s\n", binary_name_atomic, strerror(errno)); success = false; goto out; } if (chown(binary_name_atomic, file.st.st_uid, file.st.st_gid) != 0) { printf("chown of \"%s\" failed: %s\n", binary_name_atomic, strerror(errno)); success = false; goto out; } // Finally, rename the .atomic file to replace the target file. if (rename(binary_name_atomic, binary_name) != 0) { printf("rename of .atomic to \"%s\" failed: %s\n", binary_name, strerror(errno)); success = false; goto out; } // If this run created a copy, and we're here, we can delete it. if (made_copy) unlink(CACHE_TEMP_SOURCE); out: // clean up free(file.data); unlink(binary_name_atomic); return success; }