Add patch export to the management interface

1 files changed, 101 insertions, 0 deletions

diff --git a/mullvad-cli/src/cmds/patch.rs b/mullvad-cli/src/cmds/patch.rs
new file mode 100644
index 0000000000..d5a79aaef9
--- /dev/null
+++ b/mullvad-cli/src/cmds/patch.rs
@@ -0,0 +1,101 @@
+use anyhow::{anyhow, Context, Result};
+use mullvad_management_interface::MullvadProxyClient;
+use std::{
+    fs::File,
+    io::{stdin, BufRead, BufReader},
+    path::Path,
+};
+
+/// Maximum size of a settings patch. Bigger files/streams cause the read to fail.
+const MAX_PATCH_BYTES: usize = 10 * 1024;
+
+/// If source is specified, read from the provided file and send it as a settings patch to the daemon.
+/// Otherwise, read the patch from standard input.
+pub async fn import(source: String) -> Result<()> {
+    let json_blob = tokio::task::spawn_blocking(|| get_blob(source))
+        .await
+        .unwrap()?;
+
+    let mut rpc = MullvadProxyClient::new().await?;
+    rpc.apply_json_settings(json_blob)
+        .await
+        .context("Error applying patch")?;
+
+    println!("Settings applied");
+
+    Ok(())
+}
+
+fn get_blob(source: String) -> Result<String> {
+    match source.as_str() {
+        "-" => read_settings_from_stdin().context("Failed to read from stdin"),
+        _ => read_settings_from_file(source).context("Failed to read from path: {source}"),
+    }
+}
+
+/// Read settings from standard input
+fn read_settings_from_stdin() -> Result<String> {
+    read_settings_from_reader(BufReader::new(stdin()))
+}
+
+/// Read settings from a path
+fn read_settings_from_file(path: impl AsRef<Path>) -> Result<String> {
+    read_settings_from_reader(BufReader::new(File::open(path)?))
+}
+
+/// Read until EOF or until newline when the last pair of braces has been closed
+fn read_settings_from_reader(mut reader: impl BufRead) -> Result<String> {
+    let mut buf = [0u8; MAX_PATCH_BYTES];
+
+    let mut was_open = false;
+    let mut close_after_newline = false;
+    let mut brace_count: usize = 0;
+    let mut cursor_pos = 0;
+
+    loop {
+        let Some(cursor) = buf.get_mut(cursor_pos..) else {
+            return Err(anyhow!(
+                "Patch too long: maximum length is {MAX_PATCH_BYTES} bytes"
+            ));
+        };
+
+        let prev_cursor_pos = cursor_pos;
+        let read_n = reader.read(cursor)?;
+        if read_n == 0 {
+            // EOF
+            break;
+        }
+        cursor_pos += read_n;
+
+        let additional_bytes = &buf[prev_cursor_pos..cursor_pos];
+
+        if !close_after_newline {
+            for next in additional_bytes {
+                match next {
+                    b'{' => brace_count += 1,
+                    b'}' => {
+                        brace_count = brace_count.checked_sub(1).with_context(|| {
+                            // exit: too many closing braces
+                            "syntax error: unexpected '}'"
+                        })?
+                    }
+                    _ => (),
+                }
+                was_open |= brace_count > 0;
+            }
+            if brace_count == 0 && was_open {
+                // complete settings
+                close_after_newline = true;
+            }
+        }
+
+        if close_after_newline && additional_bytes.contains(&b'\n') {
+            // done
+            break;
+        }
+    }
+
+    Ok(std::str::from_utf8(&buf[0..cursor_pos])
+        .context("settings must be utf8 encoded")?
+        .to_owned())
+}