lockdown: Refactor pair record generation/loading logic a bit for efficiency

The current code always requests the public key and set's the SystemBUID, even
if a pair record already exists which has these values ready. The change moves
logic to only do that during generation of new certificates.

1 files changed, 47 insertions, 42 deletions

diff --git a/src/lockdown.c b/src/lockdown.c
index 71bb198..3e9164c 100644
--- a/src/lockdown.c
+++ b/src/lockdown.c
@@ -873,32 +873,64 @@ static plist_t lockdownd_pair_record_to_plist(lockdownd_pair_record_t pair_recor
 }
 
 /**
- * Generates a new pairing record plist and required certificates for the 
- * supplied public key of the device and the host_id of the caller's host
- * computer.
+ * Generates a pair record plist with required certificates for a specific
+ * device. If a pairing exists, it is loaded from the computer instead of being
+ * generated.
  *
- * @param public_key The public key of the device.
- * @param host_id The HostID to use for the pair record plist.
- * @param pair_record_plist Holds the generated pair record.
+ * @param pair_record_plist Holds the pair record.
  *
  * @return LOCKDOWN_E_SUCCESS on success
  */
-static lockdownd_error_t generate_pair_record_plist(const char *udid, char* system_buid, char *host_id, key_data_t public_key, plist_t *pair_record_plist)
+static lockdownd_error_t generate_pair_record_plist(lockdownd_client_t client, plist_t *pair_record_plist)
 {
         lockdownd_error_t ret = LOCKDOWN_E_UNKNOWN_ERROR;
 
+        char* host_id = NULL;
+        char* system_buid = NULL;
+        key_data_t public_key = { NULL, 0 };
+
         key_data_t device_cert = { NULL, 0 };
         key_data_t host_cert = { NULL, 0 };
         key_data_t root_cert = { NULL, 0 };
 
-        userpref_error_t uret = userpref_device_record_get_certs_as_pem(udid, &root_cert, &host_cert, &device_cert);
+        /* load certificates if a pairing exists */
+        userpref_error_t uret = userpref_device_record_get_certs_as_pem(client->udid, &root_cert, &host_cert, &device_cert);
         if ((uret == USERPREF_E_SUCCESS) && (root_cert.size > 0) && (host_cert.size > 0) && (device_cert.size > 0)) {
                 ret = LOCKDOWN_E_SUCCESS;
         }
 
-        if (ret != LOCKDOWN_E_SUCCESS)
-                ret = lockdownd_gen_pair_cert_for_udid(udid, public_key, &device_cert, &host_cert, &root_cert);
+        /* get systembuid and host id */
+        userpref_get_system_buid(&system_buid);
+        userpref_device_record_get_host_id(client->udid, &host_id);
+
+        /* generate new certificates if needed */
         if (ret != LOCKDOWN_E_SUCCESS) {
+                ret = lockdownd_get_device_public_key(client, &public_key);
+                if (ret != LOCKDOWN_E_SUCCESS) {
+                        if (public_key.data)
+                                free(public_key.data);
+                        if (host_id)
+                                free(host_id);
+                        if (system_buid)
+                                free(system_buid);
+                        debug_info("device refused to send public key.");
+                        return ret;
+                }
+                debug_info("device public key follows:\n%.*s", public_key.size, public_key.data);
+
+                userpref_device_record_set_value(client->udid, USERPREF_SYSTEM_BUID_KEY, plist_new_string(system_buid));
+
+                ret = lockdownd_gen_pair_cert_for_udid(client->udid, public_key, &device_cert, &host_cert, &root_cert);
+
+                if (public_key.data)
+                        free(public_key.data);
+        }
+
+        if (ret != LOCKDOWN_E_SUCCESS) {
+                if (host_id)
+                        free(host_id);
+                if (system_buid)
+                        free(system_buid);
                 return ret;
         }
 
@@ -910,6 +942,10 @@ static lockdownd_error_t generate_pair_record_plist(const char *udid, char* syst
         plist_dict_insert_item(*pair_record_plist, "RootCertificate", plist_new_data((const char*)root_cert.data, root_cert.size));
         plist_dict_insert_item(*pair_record_plist, "SystemBUID", plist_new_string(system_buid));
 
+        if (host_id)
+                free(host_id);
+        if (system_buid)
+                free(system_buid);
         if (device_cert.data)
                 free(device_cert.data);
         if (host_cert.data)
@@ -943,10 +979,7 @@ static lockdownd_error_t lockdownd_do_pair(lockdownd_client_t client, lockdownd_
         lockdownd_error_t ret = LOCKDOWN_E_UNKNOWN_ERROR;
         plist_t dict = NULL;
         plist_t dict_record = NULL;
-        key_data_t public_key = { NULL, 0 };
         int pairing_mode = 0; /* 0 = libimobiledevice, 1 = external */
-        char* host_id = NULL;
-        char* system_buid = NULL;
 
         if (pair_record && pair_record->system_buid && pair_record->host_id) {
                 /* valid pair_record passed? */
@@ -959,30 +992,9 @@ static lockdownd_error_t lockdownd_do_pair(lockdownd_client_t client, lockdownd_
 
                 pairing_mode = 1;
         } else {
-                ret = lockdownd_get_device_public_key(client, &public_key);
-                if (ret != LOCKDOWN_E_SUCCESS) {
-                        if (public_key.data)
-                                free(public_key.data);
-                        debug_info("device refused to send public key.");
-                        return ret;
-                }
-                debug_info("device public key follows:\n%.*s", public_key.size, public_key.data);
-
-                /* get libimobiledevice pair_record */
-                userpref_get_system_buid(&system_buid);
-                userpref_device_record_get_host_id(client->udid, &host_id);
-                userpref_device_record_set_value(client->udid, USERPREF_SYSTEM_BUID_KEY, plist_new_string(system_buid));
-
-                ret = generate_pair_record_plist(client->udid, system_buid, host_id, public_key, &dict_record);
-
-                if (host_id)
-                        free(host_id);
-                if (system_buid)
-                        free(system_buid);
+                ret = generate_pair_record_plist(client, &dict_record);
 
                 if (ret != LOCKDOWN_E_SUCCESS) {
-                        if (public_key.data)
-                                free(public_key.data);
                         if (dict_record)
                                 plist_free(dict_record);
                         return ret;
@@ -1019,8 +1031,6 @@ static lockdownd_error_t lockdownd_do_pair(lockdownd_client_t client, lockdownd_
         dict = NULL;
 
         if (ret != LOCKDOWN_E_SUCCESS) {
-                if (public_key.data)
-                        free(public_key.data);
                 plist_free(dict_record);
                 return ret;
         }
@@ -1029,8 +1039,6 @@ static lockdownd_error_t lockdownd_do_pair(lockdownd_client_t client, lockdownd_
         ret = lockdownd_receive(client, &dict);
 
         if (ret != LOCKDOWN_E_SUCCESS) {
-                if (public_key.data)
-                        free(public_key.data);
                 plist_free(dict_record);
                 return ret;
         }
@@ -1112,9 +1120,6 @@ static lockdownd_error_t lockdownd_do_pair(lockdownd_client_t client, lockdownd_
         plist_free(dict);
         dict = NULL;
 
-        if (public_key.data)
-                free(public_key.data);
-
         return ret;
 }