diff options
Diffstat (limited to 'minelf/Retouch.c')
| -rw-r--r-- | minelf/Retouch.c | 406 |
1 files changed, 406 insertions, 0 deletions
diff --git a/minelf/Retouch.c b/minelf/Retouch.c new file mode 100644 index 000000000..33809cd6d --- /dev/null +++ b/minelf/Retouch.c @@ -0,0 +1,406 @@ +/* + * 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 <errno.h> +#include <sys/stat.h> +#include <fcntl.h> +#include <stdio.h> +#include <unistd.h> +#include <string.h> +#include <strings.h> +#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; +} |