Pass volume key as a KeyBuffer

Not for security, but for consistency with the way we handle other
keys, and to move the length check to where it belongs.

Test: create private volume on Cuttlefish
Bug: 147814592
Change-Id: I10fc4896183d050ce25ff174faf78f525cf62930

cryptfs.cpp

@@ -71,6 +71,7 @@ extern "C" {
 using android::base::ParseUint;
 using android::base::StringPrintf;
 using android::fs_mgr::GetEntryForMountPoint;
+using android::vold::KeyBuffer;
 using namespace android::dm;
 using namespace std::chrono_literals;
 
@@ -1910,8 +1911,13 @@ errout:
  * as any metadata is been stored in a separate, small partition.  We
  * assume it must be using our same crypt type and keysize.
  */
-int cryptfs_setup_ext_volume(const char* label, const char* real_blkdev, const unsigned char* key,
+int cryptfs_setup_ext_volume(const char* label, const char* real_blkdev, const KeyBuffer& key,
                              std::string* out_crypto_blkdev) {
+    if (key.size() != cryptfs_get_keysize()) {
+        SLOGE("Raw keysize %zu does not match crypt keysize %" PRIu32, key.size(),
+              cryptfs_get_keysize());
+        return -1;
+    }
     uint64_t nr_sec = 0;
     if (android::vold::GetBlockDev512Sectors(real_blkdev, &nr_sec) != android::OK) {
         SLOGE("Failed to get size of %s: %s", real_blkdev, strerror(errno));
@@ -1929,7 +1935,8 @@ int cryptfs_setup_ext_volume(const char* label, const char* real_blkdev, const u
         android::base::GetBoolProperty("ro.crypto.allow_encrypt_override", false))
         flags |= CREATE_CRYPTO_BLK_DEV_FLAGS_ALLOW_ENCRYPT_OVERRIDE;
 
-    return create_crypto_blk_dev(&ext_crypt_ftr, key, real_blkdev, out_crypto_blkdev, label, flags);
+    return create_crypto_blk_dev(&ext_crypt_ftr, reinterpret_cast<const unsigned char*>(key.data()),
+                                 real_blkdev, out_crypto_blkdev, label, flags);
 }
 
 /*

cryptfs.h

@@ -25,6 +25,8 @@
 
 #include <cutils/properties.h>
 
+#include "KeyBuffer.h"
+
 #define CRYPT_FOOTER_OFFSET 0x4000
 
 /* Return values for cryptfs_crypto_complete */
@@ -62,8 +64,8 @@ int cryptfs_restart(void);
 int cryptfs_enable(int type, const char* passwd, int no_ui);
 int cryptfs_changepw(int type, const char* newpw);
 int cryptfs_enable_default(int no_ui);
-int cryptfs_setup_ext_volume(const char* label, const char* real_blkdev, const unsigned char* key,
-                             std::string* out_crypto_blkdev);
+int cryptfs_setup_ext_volume(const char* label, const char* real_blkdev,
+                             const android::vold::KeyBuffer& key, std::string* out_crypto_blkdev);
 int cryptfs_revert_ext_volume(const char* label);
 int cryptfs_getfield(const char* fieldname, char* value, int len);
 int cryptfs_setfield(const char* fieldname, const char* value);

model/Disk.cpp

@@ -216,7 +216,8 @@ void Disk::createPrivateVolume(dev_t device, const std::string& partGuid) {
 
     LOG(DEBUG) << "Found key for GUID " << normalizedGuid;
 
-    auto vol = std::shared_ptr<VolumeBase>(new PrivateVolume(device, keyRaw));
+    auto keyBuffer = KeyBuffer(keyRaw.begin(), keyRaw.end());
+    auto vol = std::shared_ptr<VolumeBase>(new PrivateVolume(device, keyBuffer));
     if (mJustPartitioned) {
         LOG(DEBUG) << "Device just partitioned; silently formatting";
         vol->setSilent(true);

model/PrivateVolume.cpp

@@ -43,7 +43,7 @@ namespace vold {
 
 static const unsigned int kMajorBlockMmc = 179;
 
-PrivateVolume::PrivateVolume(dev_t device, const std::string& keyRaw)
+PrivateVolume::PrivateVolume(dev_t device, const KeyBuffer& keyRaw)
     : VolumeBase(Type::kPrivate), mRawDevice(device), mKeyRaw(keyRaw) {
     setId(StringPrintf("private:%u,%u", major(device), minor(device)));
     mRawDevPath = StringPrintf("/dev/block/vold/%s", getId().c_str());
@@ -64,19 +64,13 @@ status_t PrivateVolume::doCreate() {
     if (CreateDeviceNode(mRawDevPath, mRawDevice)) {
         return -EIO;
     }
-    if (mKeyRaw.size() != cryptfs_get_keysize()) {
-        PLOG(ERROR) << getId() << " Raw keysize " << mKeyRaw.size()
-                    << " does not match crypt keysize " << cryptfs_get_keysize();
-        return -EIO;
-    }
 
     // Recover from stale vold by tearing down any old mappings
     cryptfs_revert_ext_volume(getId().c_str());
 
     // TODO: figure out better SELinux labels for private volumes
 
-    unsigned char* key = (unsigned char*)mKeyRaw.data();
-    int res = cryptfs_setup_ext_volume(getId().c_str(), mRawDevPath.c_str(), key, &mDmDevPath);
+    int res = cryptfs_setup_ext_volume(getId().c_str(), mRawDevPath.c_str(), mKeyRaw, &mDmDevPath);
     if (res != 0) {
         PLOG(ERROR) << getId() << " failed to setup cryptfs";
         return -EIO;

model/PrivateVolume.h

@@ -37,7 +37,7 @@ namespace vold {
  */
 class PrivateVolume : public VolumeBase {
   public:
-    PrivateVolume(dev_t device, const std::string& keyRaw);
+    PrivateVolume(dev_t device, const KeyBuffer& keyRaw);
     virtual ~PrivateVolume();
     const std::string& getFsType() const { return mFsType; };
     const std::string& getRawDevPath() const { return mRawDevPath; };
@@ -63,7 +63,7 @@ class PrivateVolume : public VolumeBase {
     std::string mPath;
 
     /* Encryption key as raw bytes */
-    std::string mKeyRaw;
+    KeyBuffer mKeyRaw;
 
     /* Filesystem type */
     std::string mFsType;