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cryptfs: round down dm-crypt device size to crypto sector boundary

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This is needed to make adoptable storage volumes work with a 4K crypto
sector size when the block device size is not a multiple of 4K.

It is fine to do this because the filesystem ends on a 4K boundary
anyway and doesn't use any partial block at the end.

Bug: 123375298
Test: booted device configured to use FDE with sector size 4k, ran
      'sm set-virtual-disk true' and formatted the virtual SD card as
      adoptable storage.  Then did the same but with a temporary patch
      that changed kSizeVirtualDisk to be misaligned
Change-Id: I95ee6d7dcaaa8989c674aea9988c09116e830b0c
This commit is contained in:
Eric Biggers 2019-01-25 10:47:55 -08:00
parent aaac873faf
commit ed45ec3ae8
1 changed files with 29 additions and 6 deletions
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35
cryptfs.cpp
View file

@ -35,6 +35,7 @@
#include "VolumeManager.h"
#include "secontext.h"
#include <android-base/parseint.h>
#include <android-base/properties.h>
#include <android-base/stringprintf.h>
#include <bootloader_message/bootloader_message.h>
@ -75,6 +76,7 @@ extern "C" {
#include <crypto_scrypt.h>
}
using android::base::ParseUint;
using android::base::StringPrintf;
using namespace std::chrono_literals;
@ -1046,19 +1048,37 @@ static std::string extra_params_as_string(const std::vector<std::string>& extra_
return extra_params;
}
// Only adds parameters if the property is set.
static void add_sector_size_param(std::vector<std::string>* extra_params_vec) {
/*
* If the ro.crypto.fde_sector_size system property is set, append the
* parameters to make dm-crypt use the specified crypto sector size and round
* the crypto device size down to a crypto sector boundary.
*/
static int add_sector_size_param(std::vector<std::string>* extra_params_vec,
struct crypt_mnt_ftr* ftr) {
constexpr char DM_CRYPT_SECTOR_SIZE[] = "ro.crypto.fde_sector_size";
char sector_size[PROPERTY_VALUE_MAX];
char value[PROPERTY_VALUE_MAX];
if (property_get(DM_CRYPT_SECTOR_SIZE, sector_size, "") > 0) {
std::string param = StringPrintf("sector_size:%s", sector_size);
if (property_get(DM_CRYPT_SECTOR_SIZE, value, "") > 0) {
unsigned int sector_size;
if (!ParseUint(value, &sector_size) || sector_size < 512 || sector_size > 4096 ||
(sector_size & (sector_size - 1)) != 0) {
SLOGE("Invalid value for %s: %s. Must be >= 512, <= 4096, and a power of 2\n",
DM_CRYPT_SECTOR_SIZE, value);
return -1;
}
std::string param = StringPrintf("sector_size:%u", sector_size);
extra_params_vec->push_back(std::move(param));
// With this option, IVs will match the sector numbering, instead
// of being hard-coded to being based on 512-byte sectors.
extra_params_vec->emplace_back("iv_large_sectors");
// Round the crypto device size down to a crypto sector boundary.
ftr->fs_size &= ~((sector_size / 512) - 1);
}
return 0;
}
static int create_crypto_blk_dev(struct crypt_mnt_ftr* crypt_ftr, const unsigned char* master_key,
@ -1106,7 +1126,10 @@ static int create_crypto_blk_dev(struct crypt_mnt_ftr* crypt_ftr, const unsigned
if (flags & CREATE_CRYPTO_BLK_DEV_FLAGS_ALLOW_ENCRYPT_OVERRIDE) {
extra_params_vec.emplace_back("allow_encrypt_override");
}
add_sector_size_param(&extra_params_vec);
if (add_sector_size_param(&extra_params_vec, crypt_ftr)) {
SLOGE("Error processing dm-crypt sector size param\n");
goto errout;
}
load_count = load_crypto_mapping_table(crypt_ftr, master_key, real_blk_name, name, fd,
extra_params_as_string(extra_params_vec).c_str());
if (load_count < 0) {