vold: use new ioctls to add/remove fscrypt keys when supported am: f3dc4203dd am: 12a9212ac1

am: 20c8b122bb

Change-Id: Ib5be791fd0eb99ac637e8528c3eee3684787d348

FsCrypt.cpp

@@ -199,13 +199,23 @@ static bool read_and_fixate_user_ce_key(userid_t user_id,
     return false;
 }
 
+// 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, 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);
+}
+
 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 +265,10 @@ 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;
@@ -325,7 +335,7 @@ 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;
         }
@@ -345,7 +355,7 @@ bool fscrypt_initialize_systemwide_keys() {
 
     PolicyKeyRef device_ref;
     if (!android::vold::retrieveAndInstallKey(true, kEmptyAuthentication, device_key_path,
-                                              device_key_temp, &device_ref.key_raw_ref))
+                                              device_key_temp, "", &device_ref.key_raw_ref))
         return false;
     get_data_file_encryption_modes(&device_ref);
 
@@ -360,7 +370,7 @@ 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 +429,20 @@ 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
+// in the case where the keys are being put in the session keyring (rather in
-// inode cache whose per-file key was already set up.  So to remove the per-file
+// the newer filesystem-level keyrings), because removing a key from the session
-// keys and make the files "appear encrypted", these inodes must be evicted.
+// 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 +455,8 @@ 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);
+        success &= evict_data_key(raw_ref);
-        drop_caches();
+        drop_caches_if_needed();
     }
     s_ce_key_raw_refs.erase(user_id);
     return success;
@@ -455,8 +470,7 @@ bool fscrypt_destroy_user_key(userid_t user_id) {
     bool success = true;
     std::string raw_ref;
     success &= evict_ce_key(user_id);
-    success &=
+    success &= lookup_key_ref(s_de_key_raw_refs, user_id, &raw_ref) && evict_data_key(raw_ref);
-        lookup_key_ref(s_de_key_raw_refs, user_id, &raw_ref) && android::vold::evictKey(raw_ref);
     s_de_key_raw_refs.erase(user_id);
     auto it = s_ephemeral_users.find(user_id);
     if (it != s_ephemeral_users.end()) {
@@ -546,7 +560,7 @@ 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",
+    if (!android::vold::retrieveAndInstallKey(true, auth, key_path, key_path + "_tmp", volume_uuid,
                                               &key_ref->key_raw_ref))
         return false;
     key_ref->contents_mode =

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
+// Add an encryption key to the legacy global session keyring.
-// Return raw key reference for use in policy
+static bool installKeyLegacy(const KeyBuffer& key, const std::string& raw_ref) {
-bool installKey(const KeyBuffer& key, 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 +163,55 @@ bool installKey(const KeyBuffer& key, std::string* raw_ref) {
     return true;
 }
 
-bool evictKey(const std::string& raw_ref) {
+// Install a file-based encryption key to the kernel, for use by encrypted files
+// on the specified filesystem.
+//
+// We use FS_IOC_ADD_ENCRYPTION_KEY if the kernel supports it.  Otherwise we add
+// the key to the legacy global session keyring.
+//
+// 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, std::string* raw_ref) {
+    *raw_ref = generateKeyRef((const uint8_t*)key.data(), key.size());
+    if (!isFsKeyringSupported()) {
+        return installKeyLegacy(key, *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();
+
+    arg->key_spec.type = FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR;
+    memcpy(arg->key_spec.u.descriptor, raw_ref.c_str(), FSCRYPT_KEY_DESCRIPTOR_SIZE);
+
+    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 with ref " << keyrefstring(*raw_ref) << " to "
+                    << mountpoint;
+        return false;
+    }
+
+    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
@@ -144,9 +228,50 @@ 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) {
+    if (!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));
+
+    arg.key_spec.type = FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR;
+    memcpy(arg.key_spec.u.descriptor, raw_ref.c_str(), FSCRYPT_KEY_DESCRIPTOR_SIZE);
+
+    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,
-                           std::string* key_ref) {
+                           const std::string& volume_uuid, std::string* key_ref) {
     KeyBuffer key;
     if (pathExists(key_path)) {
         LOG(DEBUG) << "Key exists, using: " << key_path;
@@ -161,7 +286,7 @@ 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), key_ref)) {
         LOG(ERROR) << "Failed to install key in " << key_path;
         return false;
     }

KeyUtil.h

@@ -27,11 +27,14 @@ 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, std::string* raw_ref);
+bool evictKey(const std::string& mountpoint, const std::string& raw_ref);
 bool retrieveAndInstallKey(bool create_if_absent, const KeyAuthentication& key_authentication,
                            const std::string& key_path, const std::string& tmp_path,
-                           std::string* key_ref);
+                           const std::string& volume_uuid, 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);
 

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 */