/*
* 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;
}
