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src/api/ssh_keys_get.c

 /**
- * Callback function that lists the current ssh keys authorised for access
- * to the initrd.
- * @param[in]   request   incoming HTTP request
- * @param[out]  response  HTTP response to the request
- * @param[in]   user_data extra data to pass between main thread and callbacks
- * @return                internal status code
+ * Read the authorized_keys file of the initrd, and put its lines in a json
+ * array.
+ * @return json array of authorized_keys
  */
-int callback_ssh_keys_get(const struct _u_request * request,
-    struct _u_response * response, void * user_data)
+json_t * readAuthorizedKeysJSON()
 {
-    FILE * authorized_keys;
-    char * line = NULL;
-    size_t line_length = 0;
-    ssize_t read;
-
     json_t * keys = json_object();
 
     // Open file.
-    authorized_keys = fopen("/root/.ssh/authorized_keys", "r");
+    FILE * authorized_keys = fopen(AUTHORIZED_KEYS_PATH, "r");
     // Check if that succeeded.
     if (authorized_keys == NULL)
     {
-        printf("Could not open authorized_keys file\n");
-        return send_simple_response(response, 500, "error",
-            "error reading authorized_keys");
+        return NULL;
     }
 
     // Read file line by line.
-    int index = 0;
+    int index = 1;
     char * field;
+    char * line = NULL;
+    size_t line_length = 0;
+    ssize_t read;
     while ((read = getline(&line, &line_length, authorized_keys)) != -1)
     {
-        // Remove trailing newline.
         asprintf(&field, "%d", index);
+        // Remove trailing newline.
         line[strcspn(line, "\n")] = 0;
         json_object_set(keys, field, json_string(line));
         ++index;
@@ -45,6 +37,39 @@ int callback_ssh_keys_get(const struct _u_request * request,
         free(line);
     }
 
+    return keys;
+}
+
+/**
+ * Callback function that lists the current ssh keys authorised for access
+ * to the initrd.
+ *
+ * Example output:
+ * {"ssh-keys":{"1":"ssh-rsa AAAAB3... example@example.com",
+ * "2":"ssh-rsa AAAAB3...","5":"command=\"/usr/bin/cryptops-client\" ssh-rsa
+ *  AAAAB3... cryptops-test@greenhost"}}
+ *
+ * The indices correspond to line numbers of the authorized_keys file.
+ * Missing indices (like 3 and 4 in the example) arise from empty lines in the
+ * file; those are creted when keys are deleted.
+ *
+ * @param[in]   request   incoming HTTP request
+ * @param[out]  response  HTTP response to the request
+ * @param[in]   user_data extra data to pass between main thread and callbacks
+ * @return                internal status code
+ */
+int callback_ssh_keys_get(const struct _u_request * request,
+    struct _u_response * response, void * user_data)
+{
+    // Read lines of authorized_keys file into json array.
+    json_t * keys = readAuthorizedKeysJSON();
+    if (keys == NULL)
+    {
+        printf("Could not open authorized_keys file\n");
+        return send_simple_response(response, 500, "error",
+            "error reading authorized_keys");
+    }
+
     // Create json response.
     json_t * json_body = NULL;
     json_body = json_object();

src/includes/settings.h

@@ -8,3 +8,5 @@
 #define UNENCRYPTED_MOUNTPOINT "/tmp/mnt-plain"
 #define ENCRYPTED_MOUNTPOINT "/tmp/mnt-encrypted"
 #define TMP_LOCATION "/tmp/" MAPPED_DEVICE_NAME
+#define AUTHORIZED_KEYS_DIR "/root/.ssh"
+#define AUTHORIZED_KEYS_PATH AUTHORIZED_KEYS_DIR "/authorized_keys"