A new configuration file called secret.conf is introduced to
let the user configure the path to the secrets encryption key.
This key will be used to encrypt/decrypt the secrets in libvirt.

By default the path is set to the runtime directory
/run/libvirt/secrets, and it is commented in the config file.
After parsing the file, the virtsecretd driver checks if an
encryption key is present in the path and is valid.

If no encryption key is present in the path, then
the service will by default use the encryption key stored in the
CREDENTIALS_DIRECTORY.

Add logic to parse the encryption key file and store the key.
It also checks for the encrypt_data attribute in the config file.
The encryption and decryption logic will be added in the subsequent patches.

Signed-off-by: Arun Menon <armenon@redhat.com>
---
 include/libvirt/virterror.h            |   1 +
 libvirt.spec.in                        |   3 +
 po/POTFILES                            |   1 +
 src/secret/libvirt_secrets.aug         |  40 ++++++
 src/secret/meson.build                 |  19 +++
 src/secret/secret.conf.in              |  14 ++
 src/secret/secret_config.c             | 179 +++++++++++++++++++++++++
 src/secret/secret_config.h             |  40 ++++++
 src/secret/secret_driver.c             |  11 ++
 src/secret/test_libvirt_secrets.aug.in |   6 +
 src/util/virerror.c                    |   3 +
 11 files changed, 317 insertions(+)
 create mode 100644 src/secret/libvirt_secrets.aug
 create mode 100644 src/secret/secret.conf.in
 create mode 100644 src/secret/secret_config.c
 create mode 100644 src/secret/secret_config.h
 create mode 100644 src/secret/test_libvirt_secrets.aug.in

diff --git a/include/libvirt/virterror.h b/include/libvirt/virterror.h
index f02da046a3..fa07c36ceb 100644
--- a/include/libvirt/virterror.h
+++ b/include/libvirt/virterror.h
@@ -353,6 +353,7 @@ typedef enum {
                                            command within timeout (Since: 11.2.0) */
     VIR_ERR_AGENT_COMMAND_FAILED = 113, /* guest agent responded with failure
                                            to a command (Since: 11.2.0) */
+    VIR_ERR_INVALID_ENCR_KEY_SECRET = 114, /* encryption key is invalid (Since: 12.0.0) */
 
 # ifdef VIR_ENUM_SENTINELS
     VIR_ERR_NUMBER_LAST /* (Since: 5.0.0) */
diff --git a/libvirt.spec.in b/libvirt.spec.in
index 8505a220c7..bb1dcc367f 100644
--- a/libvirt.spec.in
+++ b/libvirt.spec.in
@@ -2250,6 +2250,9 @@ exit 0
 %config(noreplace) %{_sysconfdir}/libvirt/virtsecretd.conf
 %{_datadir}/augeas/lenses/virtsecretd.aug
 %{_datadir}/augeas/lenses/tests/test_virtsecretd.aug
+%{_datadir}/augeas/lenses/libvirt_secrets.aug
+%{_datadir}/augeas/lenses/tests/test_libvirt_secrets.aug
+%config(noreplace) %{_sysconfdir}/libvirt/secret.conf
 %{_unitdir}/virtsecretd.service
 %{_unitdir}/virt-secret-init-encryption.service
 %{_unitdir}/virtsecretd.socket
diff --git a/po/POTFILES b/po/POTFILES
index f0aad35c8c..ede667cfaf 100644
--- a/po/POTFILES
+++ b/po/POTFILES
@@ -232,6 +232,7 @@ src/rpc/virnetsshsession.c
 src/rpc/virnettlscert.c
 src/rpc/virnettlsconfig.c
 src/rpc/virnettlscontext.c
+src/secret/secret_config.c
 src/secret/secret_driver.c
 src/security/security_apparmor.c
 src/security/security_dac.c
diff --git a/src/secret/libvirt_secrets.aug b/src/secret/libvirt_secrets.aug
new file mode 100644
index 0000000000..8dda373e62
--- /dev/null
+++ b/src/secret/libvirt_secrets.aug
@@ -0,0 +1,40 @@
+(* /etc/libvirt/secret.conf *)
+
+module Libvirt_secrets =
+   autoload xfm
+
+   let eol   = del /[ \t]*\n/ "\n"
+   let value_sep   = del /[ \t]*=[ \t]*/  " = "
+   let indent = del /[ \t]*/ ""
+
+   let array_sep  = del /,[ \t\n]*/ ", "
+   let array_start = del /\[[ \t\n]*/ "[ "
+   let array_end = del /\]/ "]"
+
+   let str_val = del /\"/ "\"" . store /[^\"]*/ . del /\"/ "\""
+   let bool_val = store /0|1/
+   let int_val = store /[0-9]+/
+   let str_array_element = [ seq "el" . str_val ] . del /[ \t\n]*/ ""
+   let str_array_val = counter "el" . array_start . ( str_array_element . ( array_sep . str_array_element ) * ) ? . array_end
+
+   let str_entry       (kw:string) = [ key kw . value_sep . str_val ]
+   let bool_entry      (kw:string) = [ key kw . value_sep . bool_val ]
+   let int_entry      (kw:string) = [ key kw . value_sep . int_val ]
+   let str_array_entry (kw:string) = [ key kw . value_sep . str_array_val ]
+
+   let secrets_entry = str_entry "secrets_encryption_key"
+                     | bool_entry "encrypt_data"
+
+   (* Each entry in the config is one of the following three ... *)
+   let entry = secrets_entry
+   let comment = [ label "#comment" . del /#[ \t]*/ "# " .  store /([^ \t\n][^\n]*)?/ . del /\n/ "\n" ]
+   let empty = [ label "#empty" . eol ]
+
+   let record = indent . entry . eol
+
+   let lns = ( record | comment | empty ) *
+
+   let filter = incl "/etc/libvirt/secret.conf"
+              . Util.stdexcl
+
+   let xfm = transform lns filter
diff --git a/src/secret/meson.build b/src/secret/meson.build
index 6d47569a4a..e5f026a9db 100644
--- a/src/secret/meson.build
+++ b/src/secret/meson.build
@@ -1,5 +1,6 @@
 secret_driver_sources = [
   'secret_driver.c',
+  'secret_config.c',
 ]
 
 driver_source_files += files(secret_driver_sources)
@@ -27,6 +28,24 @@ if conf.has('WITH_SECRETS')
     ],
   }
 
+  secret_conf = configure_file(
+    input: 'secret.conf.in',
+    output: 'secret.conf',
+    copy: true
+  )
+  virt_conf_files += secret_conf
+
+  virt_aug_files += files('libvirt_secrets.aug')
+
+  virt_test_aug_files += {
+    'name': 'test_libvirt_secrets.aug',
+    'aug': files('test_libvirt_secrets.aug.in'),
+    'conf': files('secret.conf.in'),
+    'test_name': 'libvirt_secrets',
+    'test_srcdir': meson.current_source_dir(),
+    'test_builddir': meson.current_build_dir(),
+  }
+
   virt_daemon_confs += {
     'name': 'virtsecretd',
   }
diff --git a/src/secret/secret.conf.in b/src/secret/secret.conf.in
new file mode 100644
index 0000000000..a231c48f8d
--- /dev/null
+++ b/src/secret/secret.conf.in
@@ -0,0 +1,14 @@
+#
+# Configuration file for the secrets driver.
+#
+# The secret encryption key is used to override default encryption
+# key path. The user can create an encryption key and set the secret_encryption_key
+# to the path on which it resides.
+# The key must be 32-bytes long.
+#secrets_encryption_key = "/run/libvirt/secrets/secret-encryption-key"
+
+# The encrypt_data setting is used to indicate if the encryption is on or off.
+# 0 indicates off and 1 indicates on. By default it is on
+# if secrets_encryption_key is set to a non-NULL
+# path, or if a systemd credential named "secrets-encryption-key" exists.
+#encrypt_data = 1
diff --git a/src/secret/secret_config.c b/src/secret/secret_config.c
new file mode 100644
index 0000000000..4e11bca1b6
--- /dev/null
+++ b/src/secret/secret_config.c
@@ -0,0 +1,179 @@
+/*
+ * secret_config.c: secret.conf config file handling
+ *
+ * SPDX-License-Identifier: LGPL-2.1-or-later
+ */
+
+#include <config.h>
+#include <fcntl.h>
+#include "configmake.h"
+#include "datatypes.h"
+#include "virlog.h"
+#include "virerror.h"
+#include "virfile.h"
+#include "virutil.h"
+#include "virsecureerase.h"
+#include "secret_config.h"
+
+
+#define VIR_FROM_THIS VIR_FROM_SECRET
+
+VIR_LOG_INIT("secret.secret_config");
+
+static virClass *virSecretDaemonConfigClass;
+static void virSecretDaemonConfigDispose(void *obj);
+
+static int
+virSecretConfigOnceInit(void)
+{
+    if (!VIR_CLASS_NEW(virSecretDaemonConfig, virClassForObject()))
+        return -1;
+
+    return 0;
+}
+
+
+VIR_ONCE_GLOBAL_INIT(virSecretConfig);
+
+
+int
+virSecretDaemonConfigFilePath(bool privileged, char **configfile)
+{
+    if (privileged) {
+        *configfile = g_strdup(SYSCONFDIR "/libvirt/secret.conf");
+    } else {
+        g_autofree char *configdir = NULL;
+
+        configdir = virGetUserConfigDirectory();
+
+        *configfile = g_strdup_printf("%s/secret.conf", configdir);
+    }
+
+    return 0;
+}
+
+
+static int
+virSecretLoadDaemonConfig(virSecretDaemonConfig *cfg,
+                          const char *filename)
+{
+    g_autoptr(virConf) conf = NULL;
+    int res;
+
+    if (virFileExists(filename)) {
+        conf = virConfReadFile(filename, 0);
+        if (!conf)
+            return -1;
+        res = virConfGetValueBool(conf, "encrypt_data", &cfg->encryptData);
+        if (res < 0) {
+            return -1;
+        } else if (res == 1) {
+            cfg->encryptDataWasSet = true;
+        } else {
+            cfg->encryptDataWasSet = false;
+        }
+
+        if (virConfGetValueString(conf, "secrets_encryption_key",
+                                  &cfg->secretsEncryptionKeyPath) < 0) {
+            return -1;
+        }
+    }
+    return 0;
+}
+
+
+static int
+virGetSecretsEncryptionKey(virSecretDaemonConfig *cfg,
+                           uint8_t **secretsEncryptionKey,
+                           size_t *secretsKeyLen)
+{
+    VIR_AUTOCLOSE fd = -1;
+    int encryptionKeyLength;
+
+    if ((encryptionKeyLength = virFileReadAll(cfg->secretsEncryptionKeyPath,
+                                              VIR_SECRETS_ENCRYPTION_KEY_LEN,
+                                              (char**)secretsEncryptionKey)) < 0) {
+        return -1;
+    }
+    if (encryptionKeyLength != VIR_SECRETS_ENCRYPTION_KEY_LEN) {
+        virReportError(VIR_ERR_INVALID_ENCR_KEY_SECRET,
+                       _("Encryption key length must be '%1$d' '%2$s'"),
+                       VIR_SECRETS_ENCRYPTION_KEY_LEN,
+                       cfg->secretsEncryptionKeyPath);
+        return -1;
+    }
+
+    *secretsKeyLen = (size_t)encryptionKeyLength;
+    return 0;
+}
+
+
+virSecretDaemonConfig *
+virSecretDaemonConfigNew(bool privileged)
+{
+    g_autoptr(virSecretDaemonConfig) cfg = NULL;
+    g_autofree char *configdir = NULL;
+    g_autofree char *configfile = NULL;
+    g_autofree char *rundir = NULL;
+    const char *credentialsDirectory;
+
+    if (virSecretConfigInitialize() < 0)
+        return NULL;
+
+    if (!(cfg = virObjectNew(virSecretDaemonConfigClass)))
+        return NULL;
+
+    if (virSecretDaemonConfigFilePath(privileged, &configfile) < 0)
+        return NULL;
+
+    if (virSecretLoadDaemonConfig(cfg, configfile) < 0)
+        return NULL;
+
+    credentialsDirectory = getenv("CREDENTIALS_DIRECTORY");
+
+    if (!cfg->secretsEncryptionKeyPath && credentialsDirectory) {
+        cfg->secretsEncryptionKeyPath = g_strdup_printf("%s/secrets-encryption-key",
+                                                        credentialsDirectory);
+        if (!virFileExists(cfg->secretsEncryptionKeyPath)) {
+            g_clear_pointer(&cfg->secretsEncryptionKeyPath, g_free);
+        }
+    }
+
+    if (!cfg->encryptDataWasSet) {
+        if (!cfg->secretsEncryptionKeyPath) {
+            /* No path specified by user or environment, disable encryption */
+            cfg->encryptData = false;
+        } else {
+            cfg->encryptData = true;
+        }
+    } else {
+        if (cfg->encryptData) {
+            if (!cfg->secretsEncryptionKeyPath) {
+                /* Built-in default path must be used */
+                rundir = virGetUserRuntimeDirectory();
+                cfg->secretsEncryptionKeyPath = g_strdup_printf("%s/secrets/encryption-key",
+                                                                rundir);
+            }
+        }
+    }
+    VIR_DEBUG("Secrets encryption key path: %s", NULLSTR(cfg->secretsEncryptionKeyPath));
+
+    if (cfg->encryptData) {
+        if (virGetSecretsEncryptionKey(cfg,
+                                       &cfg->secretsEncryptionKey,
+                                       &cfg->secretsKeyLen) < 0) {
+            return NULL;
+        }
+    }
+    return g_steal_pointer(&cfg);
+}
+
+
+static void
+virSecretDaemonConfigDispose(void *obj)
+{
+    virSecretDaemonConfig *cfg = obj;
+
+    virSecureErase(cfg->secretsEncryptionKey, cfg->secretsKeyLen);
+    g_free(cfg->secretsEncryptionKeyPath);
+}
diff --git a/src/secret/secret_config.h b/src/secret/secret_config.h
new file mode 100644
index 0000000000..888acf272b
--- /dev/null
+++ b/src/secret/secret_config.h
@@ -0,0 +1,40 @@
+/*
+ * secret_config.h: secret.conf config file handling
+ *
+ * SPDX-License-Identifier: LGPL-2.1-or-later
+ */
+
+#pragma once
+
+#include "internal.h"
+#include "virinhibitor.h"
+#include "secret_event.h"
+#define VIR_SECRETS_ENCRYPTION_KEY_LEN 32
+
+typedef struct _virSecretDaemonConfig virSecretDaemonConfig;
+struct _virSecretDaemonConfig {
+    virObject parent;
+    /* secrets encryption key path from secret.conf file */
+    char *secretsEncryptionKeyPath;
+
+    /* Store the key to encrypt secrets on the disk */
+    unsigned char *secretsEncryptionKey;
+
+    size_t secretsKeyLen;
+
+    /* Indicates if the newly written secrets are encrypted or not.
+     */
+    bool encryptData;
+
+    /* Indicates if the config file has encrypt_data set or not.
+     */
+    bool encryptDataWasSet;
+};
+
+G_DEFINE_AUTOPTR_CLEANUP_FUNC(virSecretDaemonConfig, virObjectUnref);
+
+int virSecretDaemonConfigFilePath(bool privileged, char **configfile);
+virSecretDaemonConfig *virSecretDaemonConfigNew(bool privileged);
+int virSecretDaemonConfigLoadFile(virSecretDaemonConfig *data,
+                                  const char *filename,
+                                  bool allow_missing);
diff --git a/src/secret/secret_driver.c b/src/secret/secret_driver.c
index 04c3ca49f1..9b13772ad3 100644
--- a/src/secret/secret_driver.c
+++ b/src/secret/secret_driver.c
@@ -42,6 +42,7 @@
 #include "secret_event.h"
 #include "virutil.h"
 #include "virinhibitor.h"
+#include "secret_config.h"
 
 #define VIR_FROM_THIS VIR_FROM_SECRET
 
@@ -70,6 +71,10 @@ struct _virSecretDriverState {
 
     /* Immutable pointer, self-locking APIs */
     virInhibitor *inhibitor;
+
+    /* Require lock to get reference on 'config',
+     * then lockless thereafter */
+    virSecretDaemonConfig *config;
 };
 
 static virSecretDriverState *driver;
@@ -454,6 +459,7 @@ secretStateCleanupLocked(void)
     VIR_FREE(driver->configDir);
 
     virObjectUnref(driver->secretEventState);
+    virObjectUnref(driver->config);
     virInhibitorFree(driver->inhibitor);
 
     if (driver->lockFD != -1)
@@ -518,6 +524,8 @@ secretStateInitialize(bool privileged,
                              driver->stateDir);
         goto error;
     }
+    if (!(driver->config = virSecretDaemonConfigNew(driver->privileged)))
+        goto error;
 
     driver->inhibitor = virInhibitorNew(
         VIR_INHIBITOR_WHAT_NONE,
@@ -553,6 +561,9 @@ secretStateReload(void)
     if (!driver)
         return -1;
 
+    if (!(driver->config = virSecretDaemonConfigNew(driver->privileged)))
+        return -1;
+
     ignore_value(virSecretLoadAllConfigs(driver->secrets, driver->configDir));
 
     return 0;
diff --git a/src/secret/test_libvirt_secrets.aug.in b/src/secret/test_libvirt_secrets.aug.in
new file mode 100644
index 0000000000..1bb205e0f2
--- /dev/null
+++ b/src/secret/test_libvirt_secrets.aug.in
@@ -0,0 +1,6 @@
+module Test_libvirt_secrets =
+  @CONFIG@
+
+   test Libvirt_secrets.lns get conf =
+{ "secrets_encryption_key" = "/run/libvirt/secrets/secret-encryption-key" }
+{ "encrypt_data" = "1" }
diff --git a/src/util/virerror.c b/src/util/virerror.c
index abb014b522..b7d23f81c7 100644
--- a/src/util/virerror.c
+++ b/src/util/virerror.c
@@ -1296,6 +1296,9 @@ static const virErrorMsgTuple virErrorMsgStrings[] = {
     [VIR_ERR_AGENT_COMMAND_FAILED] = {
         N_("guest agent command failed"),
         N_("guest agent command failed: %1$s") },
+    [VIR_ERR_INVALID_ENCR_KEY_SECRET] = {
+        N_("Invalid encryption key for the secret"),
+        N_("Invalid encryption key for the secret: %1$s") },
 };
 
 G_STATIC_ASSERT(G_N_ELEMENTS(virErrorMsgStrings) == VIR_ERR_NUMBER_LAST);
-- 
2.51.1