Merge changes from topic "fscrypt-key-mgmt-improvements"ndk-sysroot-r21

* changes:
  vold: support v2 encryption policies
  vold: use new ioctls to add/remove fscrypt keys when supported

4 files changed, 341 insertions, 52 deletions

diff --git a/FsCrypt.cpp b/FsCrypt.cpp
index 8d78473d..bea93289 100644
--- a/FsCrypt.cpp
+++ b/FsCrypt.cpp
@@ -57,6 +57,7 @@
 #include <android-base/logging.h>
 #include <android-base/properties.h>
 #include <android-base/stringprintf.h>
+#include <android-base/strings.h>
 #include <android-base/unique_fd.h>
 
 using android::base::StringPrintf;
@@ -70,7 +71,10 @@ namespace {
 struct PolicyKeyRef {
     std::string contents_mode;
     std::string filenames_mode;
+    int policy_version;
     std::string key_raw_ref;
+
+    PolicyKeyRef() : policy_version(0) {}
 };
 
 const std::string device_key_dir = std::string() + DATA_MNT_POINT + fscrypt_unencrypted_folder;
@@ -199,13 +203,66 @@ static bool read_and_fixate_user_ce_key(userid_t user_id,
     return false;
 }
 
+// Retrieve the options to use for encryption policies on the /data filesystem.
+static void get_data_file_encryption_options(PolicyKeyRef* key_ref) {
+    auto entry = GetEntryForMountPoint(&fstab_default, DATA_MNT_POINT);
+    if (entry == nullptr) {
+        return;
+    }
+    key_ref->contents_mode = entry->file_contents_mode;
+    key_ref->filenames_mode = entry->file_names_mode;
+    key_ref->policy_version = entry->file_policy_version;
+}
+
+// Retrieve the version to use for encryption policies on the /data filesystem.
+static int get_data_file_policy_version(void) {
+    auto entry = GetEntryForMountPoint(&fstab_default, DATA_MNT_POINT);
+    if (entry == nullptr) {
+        return 0;
+    }
+    return entry->file_policy_version;
+}
+
+// Retrieve the options to use for encryption policies on adoptable storage.
+static bool get_volume_file_encryption_options(PolicyKeyRef* key_ref) {
+    key_ref->contents_mode =
+            android::base::GetProperty("ro.crypto.volume.contents_mode", "aes-256-xts");
+    key_ref->filenames_mode =
+            android::base::GetProperty("ro.crypto.volume.filenames_mode", "aes-256-heh");
+    key_ref->policy_version = 1;
+
+    std::string raw_flags = android::base::GetProperty("ro.crypto.volume.flags", "");
+    auto flags = android::base::Split(raw_flags, "+");
+    for (const auto& flag : flags) {
+        if (flag == "v1") {
+            key_ref->policy_version = 1;
+        } else if (flag == "v2") {
+            key_ref->policy_version = 2;
+        } else {
+            LOG(ERROR) << "Unknown flag in ro.crypto.volume.flags: " << flag;
+            return false;
+        }
+    }
+    return true;
+}
+
+// Install a key for use by encrypted files on the /data filesystem.
+static bool install_data_key(const KeyBuffer& key, std::string* raw_ref) {
+    return android::vold::installKey(key, DATA_MNT_POINT, get_data_file_policy_version(), raw_ref);
+}
+
+// Evict a key for use by encrypted files on the /data filesystem.
+static bool evict_data_key(const std::string& raw_ref) {
+    return android::vold::evictKey(DATA_MNT_POINT, raw_ref, get_data_file_policy_version());
+}
+
 static bool read_and_install_user_ce_key(userid_t user_id,
                                          const android::vold::KeyAuthentication& auth) {
     if (s_ce_key_raw_refs.count(user_id) != 0) return true;
     KeyBuffer ce_key;
     if (!read_and_fixate_user_ce_key(user_id, auth, &ce_key)) return false;
     std::string ce_raw_ref;
-    if (!android::vold::installKey(ce_key, &ce_raw_ref)) return false;
+    if (!install_data_key(ce_key, &ce_raw_ref)) return false;
     s_ce_keys[user_id] = std::move(ce_key);
     s_ce_key_raw_refs[user_id] = ce_raw_ref;
     LOG(DEBUG) << "Installed ce key for user " << user_id;
@@ -255,10 +312,10 @@ static bool create_and_install_user_keys(userid_t user_id, bool create_ephemeral
             return false;
     }
     std::string de_raw_ref;
-    if (!android::vold::installKey(de_key, &de_raw_ref)) return false;
+    if (!install_data_key(de_key, &de_raw_ref)) return false;
     s_de_key_raw_refs[user_id] = de_raw_ref;
     std::string ce_raw_ref;
-    if (!android::vold::installKey(ce_key, &ce_raw_ref)) return false;
+    if (!install_data_key(ce_key, &ce_raw_ref)) return false;
     s_ce_keys[user_id] = ce_key;
     s_ce_key_raw_refs[user_id] = ce_raw_ref;
     LOG(DEBUG) << "Created keys for user " << user_id;
@@ -276,19 +333,10 @@ static bool lookup_key_ref(const std::map<userid_t, std::string>& key_map, useri
     return true;
 }
 
-static void get_data_file_encryption_modes(PolicyKeyRef* key_ref) {
-    auto entry = GetEntryForMountPoint(&fstab_default, DATA_MNT_POINT);
-    if (entry == nullptr) {
-        return;
-    }
-    key_ref->contents_mode = entry->file_contents_mode;
-    key_ref->filenames_mode = entry->file_names_mode;
-}
-
 static bool ensure_policy(const PolicyKeyRef& key_ref, const std::string& path) {
     return fscrypt_policy_ensure(path.c_str(), key_ref.key_raw_ref.data(),
                                  key_ref.key_raw_ref.size(), key_ref.contents_mode.c_str(),
-                                 key_ref.filenames_mode.c_str()) == 0;
+                                 key_ref.filenames_mode.c_str(), key_ref.policy_version) == 0;
 }
 
 static bool is_numeric(const char* name) {
@@ -325,7 +373,7 @@ static bool load_all_de_keys() {
             KeyBuffer key;
             if (!android::vold::retrieveKey(key_path, kEmptyAuthentication, &key)) return false;
             std::string raw_ref;
-            if (!android::vold::installKey(key, &raw_ref)) return false;
+            if (!install_data_key(key, &raw_ref)) return false;
             s_de_key_raw_refs[user_id] = raw_ref;
             LOG(DEBUG) << "Installed de key for user " << user_id;
         }
@@ -344,14 +392,18 @@ bool fscrypt_initialize_systemwide_keys() {
     }
 
     PolicyKeyRef device_ref;
+    get_data_file_encryption_options(&device_ref);
+
     if (!android::vold::retrieveAndInstallKey(true, kEmptyAuthentication, device_key_path,
-                                              device_key_temp, &device_ref.key_raw_ref))
+                                              device_key_temp, "", device_ref.policy_version,
+                                              &device_ref.key_raw_ref))
         return false;
-    get_data_file_encryption_modes(&device_ref);
 
-    std::string modestring = device_ref.contents_mode + ":" + device_ref.filenames_mode;
-    std::string mode_filename = std::string("/data") + fscrypt_key_mode;
-    if (!android::vold::writeStringToFile(modestring, mode_filename)) return false;
+    std::string options_string =
+            StringPrintf("%s:%s:v%d", device_ref.contents_mode.c_str(),
+                         device_ref.filenames_mode.c_str(), device_ref.policy_version);
+    std::string options_filename = std::string("/data") + fscrypt_key_mode;
+    if (!android::vold::writeStringToFile(options_string, options_filename)) return false;
 
     std::string ref_filename = std::string("/data") + fscrypt_key_ref;
     if (!android::vold::writeStringToFile(device_ref.key_raw_ref, ref_filename)) return false;
@@ -360,7 +412,7 @@ bool fscrypt_initialize_systemwide_keys() {
     KeyBuffer per_boot_key;
     if (!android::vold::randomKey(&per_boot_key)) return false;
     std::string per_boot_raw_ref;
-    if (!android::vold::installKey(per_boot_key, &per_boot_raw_ref)) return false;
+    if (!install_data_key(per_boot_key, &per_boot_raw_ref)) return false;
     std::string per_boot_ref_filename = std::string("/data") + fscrypt_key_per_boot_ref;
     if (!android::vold::writeStringToFile(per_boot_raw_ref, per_boot_ref_filename)) return false;
     LOG(INFO) << "Wrote per boot key reference to:" << per_boot_ref_filename;
@@ -419,15 +471,20 @@ bool fscrypt_vold_create_user_key(userid_t user_id, int serial, bool ephemeral)
 }
 
 // "Lock" all encrypted directories whose key has been removed.  This is needed
-// because merely removing the keyring key doesn't affect inodes in the kernel's
-// inode cache whose per-file key was already set up.  So to remove the per-file
-// keys and make the files "appear encrypted", these inodes must be evicted.
+// in the case where the keys are being put in the session keyring (rather in
+// the newer filesystem-level keyrings), because removing a key from the session
+// keyring doesn't affect inodes in the kernel's inode cache whose per-file key
+// was already set up.  So to remove the per-file keys and make the files
+// "appear encrypted", these inodes must be evicted.
 //
 // To do this, sync() to clean all dirty inodes, then drop all reclaimable slab
 // objects systemwide.  This is overkill, but it's the best available method
 // currently.  Don't use drop_caches mode "3" because that also evicts pagecache
 // for in-use files; all files relevant here are already closed and sync'ed.
-static void drop_caches() {
+static void drop_caches_if_needed() {
+    if (android::vold::isFsKeyringSupported()) {
+        return;
+    }
     sync();
     if (!writeStringToFile("2", "/proc/sys/vm/drop_caches")) {
         PLOG(ERROR) << "Failed to drop caches during key eviction";
@@ -440,8 +497,8 @@ static bool evict_ce_key(userid_t user_id) {
     std::string raw_ref;
     // If we haven't loaded the CE key, no need to evict it.
     if (lookup_key_ref(s_ce_key_raw_refs, user_id, &raw_ref)) {
-        success &= android::vold::evictKey(raw_ref);
-        drop_caches();
+        success &= evict_data_key(raw_ref);
+        drop_caches_if_needed();
     }
     s_ce_key_raw_refs.erase(user_id);
     return success;
@@ -455,8 +512,7 @@ bool fscrypt_destroy_user_key(userid_t user_id) {
     bool success = true;
     std::string raw_ref;
     success &= evict_ce_key(user_id);
-    success &=
-        lookup_key_ref(s_de_key_raw_refs, user_id, &raw_ref) && android::vold::evictKey(raw_ref);
+    success &= lookup_key_ref(s_de_key_raw_refs, user_id, &raw_ref) && evict_data_key(raw_ref);
     s_de_key_raw_refs.erase(user_id);
     auto it = s_ephemeral_users.find(user_id);
     if (it != s_ephemeral_users.end()) {
@@ -546,14 +602,12 @@ static bool read_or_create_volkey(const std::string& misc_path, const std::strin
         return false;
     }
     android::vold::KeyAuthentication auth("", secdiscardable_hash);
-    if (!android::vold::retrieveAndInstallKey(true, auth, key_path, key_path + "_tmp",
-                                              &key_ref->key_raw_ref))
-        return false;
-    key_ref->contents_mode =
-        android::base::GetProperty("ro.crypto.volume.contents_mode", "aes-256-xts");
-    key_ref->filenames_mode =
-        android::base::GetProperty("ro.crypto.volume.filenames_mode", "aes-256-heh");
-    return true;
+
+    if (!get_volume_file_encryption_options(key_ref)) return false;
+
+    return android::vold::retrieveAndInstallKey(true, auth, key_path, key_path + "_tmp",
+                                                volume_uuid, key_ref->policy_version,
+                                                &key_ref->key_raw_ref);
 }
 
 static bool destroy_volkey(const std::string& misc_path, const std::string& volume_uuid) {
@@ -701,7 +755,7 @@ bool fscrypt_prepare_user_storage(const std::string& volume_uuid, userid_t user_
             PolicyKeyRef de_ref;
             if (volume_uuid.empty()) {
                 if (!lookup_key_ref(s_de_key_raw_refs, user_id, &de_ref.key_raw_ref)) return false;
-                get_data_file_encryption_modes(&de_ref);
+                get_data_file_encryption_options(&de_ref);
                 if (!ensure_policy(de_ref, system_de_path)) return false;
                 if (!ensure_policy(de_ref, misc_de_path)) return false;
                 if (!ensure_policy(de_ref, vendor_de_path)) return false;
@@ -732,7 +786,7 @@ bool fscrypt_prepare_user_storage(const std::string& volume_uuid, userid_t user_
             PolicyKeyRef ce_ref;
             if (volume_uuid.empty()) {
                 if (!lookup_key_ref(s_ce_key_raw_refs, user_id, &ce_ref.key_raw_ref)) return false;
-                get_data_file_encryption_modes(&ce_ref);
+                get_data_file_encryption_options(&ce_ref);
                 if (!ensure_policy(ce_ref, system_ce_path)) return false;
                 if (!ensure_policy(ce_ref, misc_ce_path)) return false;
                 if (!ensure_policy(ce_ref, vendor_ce_path)) return false;
diff --git a/KeyUtil.cpp b/KeyUtil.cpp
index 12cae9b7..f8223772 100644
--- a/KeyUtil.cpp
+++ b/KeyUtil.cpp
@@ -16,12 +16,14 @@
 
 #include "KeyUtil.h"
 
-#include <linux/fs.h>
 #include <iomanip>
 #include <sstream>
 #include <string>
 
+#include <fcntl.h>
+#include <linux/fs.h>
 #include <openssl/sha.h>
+#include <sys/ioctl.h>
 
 #include <android-base/file.h>
 #include <android-base/logging.h>
@@ -29,6 +31,7 @@
 
 #include "KeyStorage.h"
 #include "Utils.h"
+#include "fscrypt_uapi.h"
 
 namespace android {
 namespace vold {
@@ -45,6 +48,42 @@ bool randomKey(KeyBuffer* key) {
     return true;
 }
 
+// Return true if the kernel supports the ioctls to add/remove fscrypt keys
+// directly to/from the filesystem.
+bool isFsKeyringSupported(void) {
+    static bool initialized = false;
+    static bool supported;
+
+    if (!initialized) {
+        android::base::unique_fd fd(open("/data", O_RDONLY | O_DIRECTORY | O_CLOEXEC));
+
+        // FS_IOC_ADD_ENCRYPTION_KEY with a NULL argument will fail with ENOTTY
+        // if the ioctl isn't supported.  Otherwise it will fail with another
+        // error code such as EFAULT.
+        errno = 0;
+        (void)ioctl(fd, FS_IOC_ADD_ENCRYPTION_KEY, NULL);
+        if (errno == ENOTTY) {
+            LOG(INFO) << "Kernel doesn't support FS_IOC_ADD_ENCRYPTION_KEY.  Falling back to "
+                         "session keyring";
+            supported = false;
+        } else {
+            if (errno != EFAULT) {
+                PLOG(WARNING) << "Unexpected error from FS_IOC_ADD_ENCRYPTION_KEY";
+            }
+            LOG(DEBUG) << "Detected support for FS_IOC_ADD_ENCRYPTION_KEY";
+            supported = true;
+        }
+        // There's no need to check for FS_IOC_REMOVE_ENCRYPTION_KEY, since it's
+        // guaranteed to be available if FS_IOC_ADD_ENCRYPTION_KEY is.  There's
+        // also no need to check for support on external volumes separately from
+        // /data, since either the kernel supports the ioctls on all
+        // fscrypt-capable filesystems or it doesn't.
+
+        initialized = true;
+    }
+    return supported;
+}
+
 // Get raw keyref - used to make keyname and to pass to ioctl
 static std::string generateKeyRef(const uint8_t* key, int length) {
     SHA512_CTX c;
@@ -78,16 +117,20 @@ static bool fillKey(const KeyBuffer& key, fscrypt_key* fs_key) {
 
 static char const* const NAME_PREFIXES[] = {"ext4", "f2fs", "fscrypt", nullptr};
 
-static std::string keyname(const std::string& prefix, const std::string& raw_ref) {
+static std::string keyrefstring(const std::string& raw_ref) {
     std::ostringstream o;
-    o << prefix << ":";
     for (unsigned char i : raw_ref) {
         o << std::hex << std::setw(2) << std::setfill('0') << (int)i;
     }
     return o.str();
 }
 
-// Get the keyring we store all keys in
+static std::string buildLegacyKeyName(const std::string& prefix, const std::string& raw_ref) {
+    return prefix + ":" + keyrefstring(raw_ref);
+}
+
+// Get the ID of the keyring we store all fscrypt keys in when the kernel is too
+// old to support FS_IOC_ADD_ENCRYPTION_KEY and FS_IOC_REMOVE_ENCRYPTION_KEY.
 static bool fscryptKeyring(key_serial_t* device_keyring) {
     *device_keyring = keyctl_search(KEY_SPEC_SESSION_KEYRING, "keyring", "fscrypt", 0);
     if (*device_keyring == -1) {
@@ -97,19 +140,17 @@ static bool fscryptKeyring(key_serial_t* device_keyring) {
     return true;
 }
 
-// Install password into global keyring
-// Return raw key reference for use in policy
-bool installKey(const KeyBuffer& key, std::string* raw_ref) {
+// Add an encryption key to the legacy global session keyring.
+static bool installKeyLegacy(const KeyBuffer& key, const std::string& raw_ref) {
     // Place fscrypt_key into automatically zeroing buffer.
     KeyBuffer fsKeyBuffer(sizeof(fscrypt_key));
     fscrypt_key& fs_key = *reinterpret_cast<fscrypt_key*>(fsKeyBuffer.data());
 
     if (!fillKey(key, &fs_key)) return false;
-    *raw_ref = generateKeyRef(fs_key.raw, fs_key.size);
     key_serial_t device_keyring;
     if (!fscryptKeyring(&device_keyring)) return false;
     for (char const* const* name_prefix = NAME_PREFIXES; *name_prefix != nullptr; name_prefix++) {
-        auto ref = keyname(*name_prefix, *raw_ref);
+        auto ref = buildLegacyKeyName(*name_prefix, raw_ref);
         key_serial_t key_id =
             add_key("logon", ref.c_str(), (void*)&fs_key, sizeof(fs_key), device_keyring);
         if (key_id == -1) {
@@ -122,12 +163,110 @@ bool installKey(const KeyBuffer& key, std::string* raw_ref) {
     return true;
 }
 
-bool evictKey(const std::string& raw_ref) {
+// Build a struct fscrypt_key_specifier for use in the key management ioctls.
+static bool buildKeySpecifier(fscrypt_key_specifier* spec, const std::string& raw_ref,
+                              int policy_version) {
+    switch (policy_version) {
+        case 1:
+            if (raw_ref.size() != FSCRYPT_KEY_DESCRIPTOR_SIZE) {
+                LOG(ERROR) << "Invalid key specifier size for v1 encryption policy: "
+                           << raw_ref.size();
+                return false;
+            }
+            spec->type = FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR;
+            memcpy(spec->u.descriptor, raw_ref.c_str(), FSCRYPT_KEY_DESCRIPTOR_SIZE);
+            return true;
+        case 2:
+            if (raw_ref.size() != FSCRYPT_KEY_IDENTIFIER_SIZE) {
+                LOG(ERROR) << "Invalid key specifier size for v2 encryption policy: "
+                           << raw_ref.size();
+                return false;
+            }
+            spec->type = FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER;
+            memcpy(spec->u.identifier, raw_ref.c_str(), FSCRYPT_KEY_IDENTIFIER_SIZE);
+            return true;
+        default:
+            LOG(ERROR) << "Invalid encryption policy version: " << policy_version;
+            return false;
+    }
+}
+
+// Install a file-based encryption key to the kernel, for use by encrypted files
+// on the specified filesystem using the specified encryption policy version.
+//
+// For v1 policies, we use FS_IOC_ADD_ENCRYPTION_KEY if the kernel supports it.
+// Otherwise we add the key to the legacy global session keyring.
+//
+// For v2 policies, we always use FS_IOC_ADD_ENCRYPTION_KEY; it's the only way
+// the kernel supports.
+//
+// Returns %true on success, %false on failure.  On success also sets *raw_ref
+// to the raw key reference for use in the encryption policy.
+bool installKey(const KeyBuffer& key, const std::string& mountpoint, int policy_version,
+                std::string* raw_ref) {
+    // Put the fscrypt_add_key_arg in an automatically-zeroing buffer, since we
+    // have to copy the raw key into it.
+    KeyBuffer arg_buf(sizeof(struct fscrypt_add_key_arg) + key.size(), 0);
+    struct fscrypt_add_key_arg* arg = (struct fscrypt_add_key_arg*)arg_buf.data();
+
+    // Initialize the "key specifier", which is like a name for the key.
+    switch (policy_version) {
+        case 1:
+            // A key for a v1 policy is specified by an arbitrary 8-byte
+            // "descriptor", which must be provided by userspace.  We use the
+            // first 8 bytes from the double SHA-512 of the key itself.
+            *raw_ref = generateKeyRef((const uint8_t*)key.data(), key.size());
+            if (!isFsKeyringSupported()) {
+                return installKeyLegacy(key, *raw_ref);
+            }
+            if (!buildKeySpecifier(&arg->key_spec, *raw_ref, policy_version)) {
+                return false;
+            }
+            break;
+        case 2:
+            // A key for a v2 policy is specified by an 16-byte "identifier",
+            // which is a cryptographic hash of the key itself which the kernel
+            // computes and returns.  Any user-provided value is ignored; we
+            // just need to set the specifier type to indicate that we're adding
+            // this type of key.
+            arg->key_spec.type = FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER;
+            break;
+        default:
+            LOG(ERROR) << "Invalid encryption policy version: " << policy_version;
+            return false;
+    }
+
+    // Provide the raw key.
+    arg->raw_size = key.size();
+    memcpy(arg->raw, key.data(), key.size());
+
+    android::base::unique_fd fd(open(mountpoint.c_str(), O_RDONLY | O_DIRECTORY | O_CLOEXEC));
+    if (fd == -1) {
+        PLOG(ERROR) << "Failed to open " << mountpoint << " to install key";
+        return false;
+    }
+
+    if (ioctl(fd, FS_IOC_ADD_ENCRYPTION_KEY, arg) != 0) {
+        PLOG(ERROR) << "Failed to install fscrypt key to " << mountpoint;
+        return false;
+    }
+
+    if (arg->key_spec.type == FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER) {
+        // Retrieve the key identifier that the kernel computed.
+        *raw_ref = std::string((char*)arg->key_spec.u.identifier, FSCRYPT_KEY_IDENTIFIER_SIZE);
+    }
+    LOG(DEBUG) << "Installed fscrypt key with ref " << keyrefstring(*raw_ref) << " to "
+               << mountpoint;
+    return true;
+}
+
+// Remove an encryption key from the legacy global session keyring.
+static bool evictKeyLegacy(const std::string& raw_ref) {
     key_serial_t device_keyring;
     if (!fscryptKeyring(&device_keyring)) return false;
     bool success = true;
     for (char const* const* name_prefix = NAME_PREFIXES; *name_prefix != nullptr; name_prefix++) {
-        auto ref = keyname(*name_prefix, raw_ref);
+        auto ref = buildLegacyKeyName(*name_prefix, raw_ref);
         auto key_serial = keyctl_search(device_keyring, "logon", ref.c_str(), 0);
 
         // Unlink the key from the keyring.  Prefer unlinking to revoking or
@@ -144,8 +283,51 @@ bool evictKey(const std::string& raw_ref) {
     return success;
 }
 
+// Evict a file-based encryption key from the kernel.
+//
+// We use FS_IOC_REMOVE_ENCRYPTION_KEY if the kernel supports it.  Otherwise we
+// remove the key from the legacy global session keyring.
+//
+// In the latter case, the caller is responsible for dropping caches.
+bool evictKey(const std::string& mountpoint, const std::string& raw_ref, int policy_version) {
+    if (policy_version == 1 && !isFsKeyringSupported()) {
+        return evictKeyLegacy(raw_ref);
+    }
+
+    android::base::unique_fd fd(open(mountpoint.c_str(), O_RDONLY | O_DIRECTORY | O_CLOEXEC));
+    if (fd == -1) {
+        PLOG(ERROR) << "Failed to open " << mountpoint << " to evict key";
+        return false;
+    }
+
+    struct fscrypt_remove_key_arg arg;
+    memset(&arg, 0, sizeof(arg));
+
+    if (!buildKeySpecifier(&arg.key_spec, raw_ref, policy_version)) {
+        return false;
+    }
+
+    std::string ref = keyrefstring(raw_ref);
+
+    if (ioctl(fd, FS_IOC_REMOVE_ENCRYPTION_KEY, &arg) != 0) {
+        PLOG(ERROR) << "Failed to evict fscrypt key with ref " << ref << " from " << mountpoint;
+        return false;
+    }
+
+    LOG(DEBUG) << "Evicted fscrypt key with ref " << ref << " from " << mountpoint;
+    if (arg.removal_status_flags & FSCRYPT_KEY_REMOVAL_STATUS_FLAG_OTHER_USERS) {
+        // Should never happen because keys are only added/removed as root.
+        LOG(ERROR) << "Unexpected case: key with ref " << ref << " is still added by other users!";
+    } else if (arg.removal_status_flags & FSCRYPT_KEY_REMOVAL_STATUS_FLAG_FILES_BUSY) {
+        LOG(ERROR) << "Files still open after removing key with ref " << ref
+                   << ".  These files were not locked!";
+    }
+    return true;
+}
+
 bool retrieveAndInstallKey(bool create_if_absent, const KeyAuthentication& key_authentication,
                            const std::string& key_path, const std::string& tmp_path,
+                           const std::string& volume_uuid, int policy_version,
                            std::string* key_ref) {
     KeyBuffer key;
     if (pathExists(key_path)) {
@@ -161,7 +343,7 @@ bool retrieveAndInstallKey(bool create_if_absent, const KeyAuthentication& key_a
         if (!storeKeyAtomically(key_path, tmp_path, key_authentication, key)) return false;
     }
 
-    if (!installKey(key, key_ref)) {
+    if (!installKey(key, BuildDataPath(volume_uuid), policy_version, key_ref)) {
         LOG(ERROR) << "Failed to install key in " << key_path;
         return false;
     }
diff --git a/KeyUtil.h b/KeyUtil.h
index 7ee67254..f6799d9a 100644
--- a/KeyUtil.h
+++ b/KeyUtil.h
@@ -27,10 +27,15 @@ namespace android {
 namespace vold {
 
 bool randomKey(KeyBuffer* key);
-bool installKey(const KeyBuffer& key, std::string* raw_ref);
-bool evictKey(const std::string& raw_ref);
+
+bool isFsKeyringSupported(void);
+
+bool installKey(const KeyBuffer& key, const std::string& mountpoint, int policy_version,
+                std::string* raw_ref);
+bool evictKey(const std::string& mountpoint, const std::string& raw_ref, int policy_version);
 bool retrieveAndInstallKey(bool create_if_absent, const KeyAuthentication& key_authentication,
                            const std::string& key_path, const std::string& tmp_path,
+                           const std::string& volume_uuid, int policy_version,
                            std::string* key_ref);
 bool retrieveKey(bool create_if_absent, const std::string& key_path, const std::string& tmp_path,
                  KeyBuffer* key, bool keepOld = true);
diff --git a/fscrypt_uapi.h b/fscrypt_uapi.h
new file mode 100644
index 00000000..3999036a
--- /dev/null
+++ b/fscrypt_uapi.h
@@ -0,0 +1,48 @@
+#ifndef _UAPI_LINUX_FSCRYPT_H
+#define _UAPI_LINUX_FSCRYPT_H
+
+// Definitions for FS_IOC_ADD_ENCRYPTION_KEY and FS_IOC_REMOVE_ENCRYPTION_KEY
+
+// TODO: switch to <linux/fscrypt.h> once it's in Bionic
+
+#ifndef FS_IOC_ADD_ENCRYPTION_KEY
+
+#include <linux/types.h>
+
+#define FSCRYPT_KEY_DESCRIPTOR_SIZE 8
+#define FSCRYPT_KEY_IDENTIFIER_SIZE 16
+
+#define FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR 1
+#define FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER 2
+
+struct fscrypt_key_specifier {
+    __u32 type;
+    __u32 __reserved;
+    union {
+        __u8 __reserved[32];
+        __u8 descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
+        __u8 identifier[FSCRYPT_KEY_IDENTIFIER_SIZE];
+    } u;
+};
+
+struct fscrypt_add_key_arg {
+    struct fscrypt_key_specifier key_spec;
+    __u32 raw_size;
+    __u32 __reserved[9];
+    __u8 raw[];
+};
+
+struct fscrypt_remove_key_arg {
+    struct fscrypt_key_specifier key_spec;
+#define FSCRYPT_KEY_REMOVAL_STATUS_FLAG_FILES_BUSY 0x00000001
+#define FSCRYPT_KEY_REMOVAL_STATUS_FLAG_OTHER_USERS 0x00000002
+    __u32 removal_status_flags;
+    __u32 __reserved[5];
+};
+
+#define FS_IOC_ADD_ENCRYPTION_KEY _IOWR('f', 23, struct fscrypt_add_key_arg)
+#define FS_IOC_REMOVE_ENCRYPTION_KEY _IOWR('f', 24, struct fscrypt_remove_key_arg)
+
+#endif /* FS_IOC_ADD_ENCRYPTION_KEY */
+
+#endif /* _UAPI_LINUX_FSCRYPT_H */