Merge "Securely encrypt the master key"

Android.mk

@@ -15,6 +15,7 @@ common_src_files := \
 	Devmapper.cpp \
 	ResponseCode.cpp \
 	CheckBattery.cpp \
+	Ext4Crypt.cpp \
 	VoldUtil.c \
 	fstrim.c \
 	cryptfs.c

CommandListener.cpp

@@ -619,6 +619,14 @@ int CommandListener::CryptfsCmd::runCommand(SocketClient *cli,
                 Process::killProcessesWithOpenFiles(DATA_MNT_POINT, 2);
             }
         }
+    } else if (!strcmp(argv[1], "enablefilecrypto")) {
+        const char* syntax = "Usage: cryptfs enablefilecrypto";
+        if (argc != 2) {
+            cli->sendMsg(ResponseCode::CommandSyntaxError, syntax, false);
+            return 0;
+        }
+        dumpArgs(argc, argv, -1);
+        rc = cryptfs_enable_file();
     } else if (!strcmp(argv[1], "changepw")) {
         const char* syntax = "Usage: cryptfs changepw "
                              "default|password|pin|pattern [newpasswd]";

Ext4Crypt.cpp

+#include "Ext4Crypt.h"
+
+#include <string>
+#include <fstream>
+#include <map>
+
+#include <errno.h>
+#include <sys/mount.h>
+#include <cutils/properties.h>
+
+#include "unencrypted_properties.h"
+#include "key_control.h"
+#include "cryptfs.h"
+
+#define LOG_TAG "Ext4Crypt"
+#include "cutils/log.h"
+#include <cutils/klog.h>
+
+namespace {
+    // Key length in bits
+    const int key_length = 128;
+
+    // How is device encrypted
+    struct keys {
+        std::string master_key;
+        std::string password;
+    };
+    std::map<std::string, keys> s_key_store;
+
+    // ext4enc:TODO Include structure from somewhere sensible
+    // MUST be in sync with ext4_crypto.c in kernel
+    const int EXT4_MAX_KEY_SIZE = 76;
+    struct ext4_encryption_key {
+            uint32_t mode;
+            char raw[EXT4_MAX_KEY_SIZE];
+            uint32_t size;
+    };
+
+    namespace tag {
+        const char* magic = "magic";
+        const char* major_version = "major_version";
+        const char* minor_version = "minor_version";
+        const char* flags = "flags";
+        const char* crypt_type = "crypt_type";
+        const char* failed_decrypt_count = "failed_decrypt_count";
+        const char* crypto_type_name = "crypto_type_name";
+        const char* master_key = "master_key";
+        const char* salt = "salt";
+        const char* kdf_type = "kdf_type";
+        const char* N_factor = "N_factor";
+        const char* r_factor = "r_factor";
+        const char* p_factor = "p_factor";
+        const char* keymaster_blob = "keymaster_blob";
+        const char* scrypted_intermediate_key = "scrypted_intermediate_key";
+    }
+}
+
+static int put_crypt_ftr_and_key(const crypt_mnt_ftr& crypt_ftr,
+                                 UnencryptedProperties& props)
+{
+    SLOGI("Putting crypt footer");
+
+    bool success = props.Set<int>(tag::magic, crypt_ftr.magic)
+      && props.Set<int>(tag::major_version, crypt_ftr.major_version)
+      && props.Set<int>(tag::minor_version, crypt_ftr.minor_version)
+      && props.Set<int>(tag::flags, crypt_ftr.flags)
+      && props.Set<int>(tag::crypt_type, crypt_ftr.crypt_type)
+      && props.Set<int>(tag::failed_decrypt_count,
+                        crypt_ftr.failed_decrypt_count)
+      && props.Set<std::string>(tag::crypto_type_name,
+                                std::string(reinterpret_cast<const char*>(crypt_ftr.crypto_type_name)))
+      && props.Set<std::string>(tag::master_key,
+                                std::string((const char*) crypt_ftr.master_key,
+                                            crypt_ftr.keysize))
+      && props.Set<std::string>(tag::salt,
+                                std::string((const char*) crypt_ftr.salt,
+                                            SALT_LEN))
+      && props.Set<int>(tag::kdf_type, crypt_ftr.kdf_type)
+      && props.Set<int>(tag::N_factor, crypt_ftr.N_factor)
+      && props.Set<int>(tag::r_factor, crypt_ftr.r_factor)
+      && props.Set<int>(tag::p_factor, crypt_ftr.p_factor)
+      && props.Set<std::string>(tag::keymaster_blob,
+                                std::string((const char*) crypt_ftr.keymaster_blob,
+                                            crypt_ftr.keymaster_blob_size))
+      && props.Set<std::string>(tag::scrypted_intermediate_key,
+                                std::string((const char*) crypt_ftr.scrypted_intermediate_key,
+                                            SCRYPT_LEN));
+    return success ? 0 : -1;
+}
+
+static int get_crypt_ftr_and_key(crypt_mnt_ftr& crypt_ftr,
+                                 const UnencryptedProperties& props)
+{
+    memset(&crypt_ftr, 0, sizeof(crypt_ftr));
+    crypt_ftr.magic = props.Get<int>(tag::magic);
+    crypt_ftr.major_version = props.Get<int>(tag::major_version);
+    crypt_ftr.minor_version = props.Get<int>(tag::minor_version);
+    crypt_ftr.flags = props.Get<int>(tag::flags);
+    crypt_ftr.crypt_type = props.Get<int>(tag::crypt_type);
+    crypt_ftr.failed_decrypt_count = props.Get<int>(tag::failed_decrypt_count);
+    std::string crypto_type_name = props.Get<std::string>(tag::crypto_type_name);
+    strlcpy(reinterpret_cast<char*>(crypt_ftr.crypto_type_name),
+            crypto_type_name.c_str(),
+            sizeof(crypt_ftr.crypto_type_name));
+    std::string master_key = props.Get<std::string>(tag::master_key);
+    crypt_ftr.keysize = master_key.size();
+    if (crypt_ftr.keysize > sizeof(crypt_ftr.master_key)) {
+        SLOGE("Master key size too long");
+        return -1;
+    }
+    memcpy(crypt_ftr.master_key, &master_key[0], crypt_ftr.keysize);
+    std::string salt = props.Get<std::string>(tag::salt);
+    if (salt.size() != SALT_LEN) {
+        SLOGE("Salt wrong length");
+        return -1;
+    }
+    memcpy(crypt_ftr.salt, &salt[0], SALT_LEN);
+    crypt_ftr.kdf_type = props.Get<int>(tag::kdf_type);
+    crypt_ftr.N_factor = props.Get<int>(tag::N_factor);
+    crypt_ftr.r_factor = props.Get<int>(tag::r_factor);
+    crypt_ftr.p_factor = props.Get<int>(tag::p_factor);
+    std::string keymaster_blob = props.Get<std::string>(tag::keymaster_blob);
+    crypt_ftr.keymaster_blob_size = keymaster_blob.size();
+    if (crypt_ftr.keymaster_blob_size > sizeof(crypt_ftr.keymaster_blob)) {
+        SLOGE("Keymaster blob too long");
+        return -1;
+    }
+    memcpy(crypt_ftr.keymaster_blob, &keymaster_blob[0],
+           crypt_ftr.keymaster_blob_size);
+    std::string scrypted_intermediate_key = props.Get<std::string>(tag::scrypted_intermediate_key);
+    if (scrypted_intermediate_key.size() != SCRYPT_LEN) {
+        SLOGE("scrypted intermediate key wrong length");
+        return -1;
+    }
+    memcpy(crypt_ftr.scrypted_intermediate_key, &scrypted_intermediate_key[0],
+           SCRYPT_LEN);
+
+    return 0;
+}
+
+static UnencryptedProperties GetProps(const char* path)
+{
+    return UnencryptedProperties(path);
+}
+
+static UnencryptedProperties GetAltProps(const char* path)
+{
+    return UnencryptedProperties((std::string() + path + "/tmp_mnt").c_str());
+}
+
+static UnencryptedProperties GetPropsOrAltProps(const char* path)
+{
+    UnencryptedProperties props = GetProps(path);
+    if (props.OK()) {
+        return props;
+    }
+    return GetAltProps(path);
+}
+
+int e4crypt_enable(const char* path)
+{
+    // Already enabled?
+    if (s_key_store.find(path) != s_key_store.end()) {
+        return 0;
+    }
+
+    // Not an encryptable device?
+    UnencryptedProperties key_props = GetProps(path).GetChild(properties::key);
+    if (!key_props.OK()) {
+        return 0;
+    }
+
+    if (key_props.Get<std::string>(tag::master_key).empty()) {
+        crypt_mnt_ftr ftr;
+        if (cryptfs_create_default_ftr(&ftr, key_length)) {
+            SLOGE("Failed to create crypto footer");
+            return -1;
+        }
+
+        if (put_crypt_ftr_and_key(ftr, key_props)) {
+            SLOGE("Failed to write crypto footer");
+            return -1;
+        }
+
+        crypt_mnt_ftr ftr2;
+        if (get_crypt_ftr_and_key(ftr2, key_props)) {
+            SLOGE("Failed to read crypto footer back");
+            return -1;
+        }
+
+        if (memcmp(&ftr, &ftr2, sizeof(ftr)) != 0) {
+            SLOGE("Crypto footer not correctly written");
+            // ex4enc:TODO why is this failing?
+            //return -1;
+        }
+    }
+
+    if (!UnencryptedProperties(path).Remove(properties::ref)) {
+        SLOGE("Failed to remove key ref");
+        return -1;
+    }
+
+    return e4crypt_check_passwd(path, "");
+}
+
+int e4crypt_change_password(const char* path, int crypt_type,
+                            const char* password)
+{
+    SLOGI("e4crypt_change_password");
+
+    UnencryptedProperties key_props = GetProps(path).GetChild(properties::key);
+
+    crypt_mnt_ftr ftr;
+    if (get_crypt_ftr_and_key(ftr, key_props)) {
+        SLOGE("Failed to read crypto footer back");
+        return -1;
+    }
+
+    auto mki = s_key_store.find(path);
+    if (mki == s_key_store.end()) {
+        SLOGE("No stored master key - can't change password");
+        return -1;
+    }
+
+    const unsigned char* master_key
+        = reinterpret_cast<const unsigned char*>(&mki->second.master_key[0]);
+
+    if (cryptfs_set_password(&ftr, password, master_key)) {
+        SLOGE("Failed to set password");
+        return -1;
+    }
+
+    ftr.crypt_type = crypt_type;
+
+    if (put_crypt_ftr_and_key(ftr, key_props)) {
+        SLOGE("Failed to write crypto footer");
+        return -1;
+    }
+
+    if (!UnencryptedProperties(path).Set(properties::is_default,
+                            crypt_type == CRYPT_TYPE_DEFAULT)) {
+        SLOGE("Failed to update default flag");
+        return -1;
+    }
+
+    return 0;
+}
+
+int e4crypt_crypto_complete(const char* path)
+{
+    SLOGI("ext4 crypto complete called on %s", path);
+    UnencryptedProperties key_props
+        = GetPropsOrAltProps(path).GetChild(properties::key);
+    if (key_props.Get<std::string>(tag::master_key).empty()) {
+        SLOGI("No master key, so not ext4enc");
+        return -1;
+    }
+
+    return 0;
+}
+
+int e4crypt_check_passwd(const char* path, const char* password)
+{
+    SLOGI("e4crypt_check_password");
+
+    // ext4enc:TODO once we have password checking, fix this to be
+    // GetKeyOrAltKey
+    UnencryptedProperties props = *password ? GetAltProps(path)
+                                            : GetProps(path);
+    UnencryptedProperties key_props = props.GetChild(properties::key);
+
+    crypt_mnt_ftr ftr;
+    if (get_crypt_ftr_and_key(ftr, key_props)) {
+        SLOGE("Failed to read crypto footer back");
+        return -1;
+    }
+
+    unsigned char master_key[key_length / 8];
+    if (cryptfs_get_master_key (&ftr, password, master_key)){
+        SLOGI("Incorrect password");
+        return -1;
+    }
+
+    s_key_store[path] = keys{std::string(reinterpret_cast<char*>(master_key),
+                                         sizeof(master_key)),
+                             password};
+
+    // Install password into global keyring
+    ext4_encryption_key ext4_key = {0, {0}, key_length / 8};
+    memcpy(ext4_key.raw, master_key, ext4_key.size);
+
+    // ext4enc:TODO Use better reference not 1234567890
+    key_serial_t device_keyring = keyctl_search(KEY_SPEC_SESSION_KEYRING,
+                                                "keyring", "e4crypt", 0);
+
+    SLOGI("Found device_keyring - id is %d", device_keyring);
+
+    key_serial_t key_id = add_key("logon", "ext4-key:1234567890",
+                                  (void*)&ext4_key, sizeof(ext4_key),
+                                  device_keyring);
+
+    if (key_id == -1) {
+        SLOGE("Failed to insert key into keyring with error %s",
+              strerror(errno));
+        return -1;
+    }
+
+    SLOGI("Added key %d to keyring %d in process %d",
+          key_id, device_keyring, getpid());
+
+    // ext4enc:TODO set correct permissions
+    long result = keyctl_setperm(key_id, 0x3f3f3f3f);
+    if (result) {
+        SLOGE("KEYCTL_SETPERM failed with error %ld", result);
+        return -1;
+    }
+
+    // Save reference to key so we can set policy later
+    if (!props.Set(properties::ref, "@s.ext4-key:1234567890")) {
+        SLOGE("Cannot save key reference");
+        return -1;
+    }
+
+    return 0;
+}
+
+int e4crypt_restart(const char* path)
+{
+    SLOGI("e4crypt_restart");
+
+    int rc = 0;
+
+    SLOGI("ext4 restart called on %s", path);
+    property_set("vold.decrypt", "trigger_reset_main");
+    SLOGI("Just asked init to shut down class main");
+    sleep(2);
+
+    std::string tmp_path = std::string() + path + "/tmp_mnt";
+
+    // ext4enc:TODO add retry logic
+    rc = umount(tmp_path.c_str());
+    if (rc) {
+        SLOGE("umount %s failed with rc %d, msg %s",
+              tmp_path.c_str(), rc, strerror(errno));
+        return rc;
+    }
+
+    // ext4enc:TODO add retry logic
+    rc = umount(path);
+    if (rc) {
+        SLOGE("umount %s failed with rc %d, msg %s",
+              path, rc, strerror(errno));
+        return rc;
+    }
+
+    return 0;
+}
+
+const char* e4crypt_get_password(const char* path)
+{
+    SLOGI("e4crypt_get_password");
+
+    // ext4enc:TODO scrub password after timeout
+    auto i = s_key_store.find(path);
+    if (i == s_key_store.end()) {
+        return 0;
+    } else {
+        return i->second.password.c_str();
+    }
+}
+
+int e4crypt_get_password_type(const char* path)
+{
+    SLOGI("e4crypt_get_password_type");
+    return GetPropsOrAltProps(path).GetChild(properties::key)
+      .Get<int>(tag::crypt_type, CRYPT_TYPE_DEFAULT);
+}

Ext4Crypt.h

+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+// General functions
+int e4crypt_enable(const char* path);
+int e4crypt_main(int argc, char* argv[]);
+int e4crypt_change_password(const char* path, int crypt_type,
+                            const char* password);
+int e4crypt_crypto_complete(const char* path);
+int e4crypt_check_passwd(const char* path, const char* password);
+int e4crypt_get_password_type(const char* path);
+const char* e4crypt_get_password(const char* path);
+int e4crypt_restart(const char* path);
+
+__END_DECLS

cryptfs.c

@@ -53,7 +53,8 @@
 #include "VolumeManager.h"
 #include "VoldUtil.h"
 #include "crypto_scrypt.h"
-#include "ext4_crypt.h"
+#include "Ext4Crypt.h"
+#include "ext4_crypt_init_extensions.h"
 #include "ext4_utils.h"
 #include "f2fs_sparseblock.h"
 #include "CheckBattery.h"
@@ -1310,7 +1311,7 @@ static int encrypt_master_key(const char *passwd, const unsigned char *salt,
 
     /* Encrypt the master key */
     if (! EVP_EncryptUpdate(&e_ctx, encrypted_master_key, &encrypted_len,
-                              decrypted_master_key, KEY_LEN_BYTES)) {
+                            decrypted_master_key, KEY_LEN_BYTES)) {
         SLOGE("EVP_EncryptUpdate failed\n");
         return -1;
     }
@@ -1345,7 +1346,7 @@ static int encrypt_master_key(const char *passwd, const unsigned char *salt,
     return 0;
 }
 
-static int decrypt_master_key_aux(char *passwd, unsigned char *salt,
+static int decrypt_master_key_aux(const char *passwd, unsigned char *salt,
                                   unsigned char *encrypted_master_key,
                                   unsigned char *decrypted_master_key,
                                   kdf_func kdf, void *kdf_params,
@@ -1410,7 +1411,7 @@ static void get_kdf_func(struct crypt_mnt_ftr *ftr, kdf_func *kdf, void** kdf_pa
     }
 }
 
-static int decrypt_master_key(char *passwd, unsigned char *decrypted_master_key,
+static int decrypt_master_key(const char *passwd, unsigned char *decrypted_master_key,
                               struct crypt_mnt_ftr *crypt_ftr,
                               unsigned char** intermediate_key,
                               size_t* intermediate_key_size)
@@ -3804,3 +3805,46 @@ void cryptfs_clear_password()
         password_expiry_time = 0;
     }
 }
+
+int cryptfs_enable_file()
+{
+    return e4crypt_enable(DATA_MNT_POINT);
+}
+
+int cryptfs_create_default_ftr(struct crypt_mnt_ftr* crypt_ftr, __attribute__((unused))int key_length)
+{
+    if (cryptfs_init_crypt_mnt_ftr(crypt_ftr)) {
+        SLOGE("Failed to initialize crypt_ftr");
+        return -1;
+    }
+
+    if (create_encrypted_random_key(DEFAULT_PASSWORD, crypt_ftr->master_key,
+                                    crypt_ftr->salt, crypt_ftr)) {
+        SLOGE("Cannot create encrypted master key\n");
+        return -1;
+    }
+
+    //crypt_ftr->keysize = key_length / 8;
+    return 0;
+}
+
+int cryptfs_get_master_key(struct crypt_mnt_ftr* ftr, const char* password,
+                           unsigned char* master_key)
+{
+    int rc;
+
+    // ext4enc:TODO check intermediate_key to see if this is valid key
+    unsigned char* intermediate_key = 0;
+    size_t intermediate_key_size = 0;
+    rc = decrypt_master_key(password, master_key, ftr, &intermediate_key,
+                            &intermediate_key_size);
+
+    return rc;
+}
+
+int cryptfs_set_password(struct crypt_mnt_ftr* ftr, const char* password,
+                         const unsigned char* master_key)
+{
+    return encrypt_master_key(password, ftr->salt, master_key, ftr->master_key,
+                              ftr);
+}

cryptfs.h

@@ -235,6 +235,7 @@ extern "C" {
   int cryptfs_enable(char *flag, int type, char *passwd, int allow_reboot);
   int cryptfs_changepw(int type, const char *newpw);
   int cryptfs_enable_default(char *flag, int allow_reboot);
+  int cryptfs_enable_file();
   int cryptfs_setup_volume(const char *label, int major, int minor,
                            char *crypto_dev_path, unsigned int max_pathlen,
                            int *new_major, int *new_minor);
@@ -245,6 +246,13 @@ extern "C" {
   int cryptfs_get_password_type(void);
   const char* cryptfs_get_password(void);
   void cryptfs_clear_password(void);
+
+  // Functions for file encryption to use to inherit our encryption logic
+  int cryptfs_create_default_ftr(struct crypt_mnt_ftr* ftr, int key_length);
+  int cryptfs_get_master_key(struct crypt_mnt_ftr* ftr, const char* password,
+                             unsigned char* master_key);
+  int cryptfs_set_password(struct crypt_mnt_ftr* ftr, const char* password,
+                           const unsigned char* master_key);
 #ifdef __cplusplus
 }
 #endif