From c1836d01a4abf4e469896507b36eca50c8ffae8a Mon Sep 17 00:00:00 2001
From: Andrew Gunnerson <accounts+github@chiller3.com>
Date: Wed, 25 Mar 2026 18:37:24 -0400
Subject: [PATCH] cli/payload: Allow unpacking only metadata from delta
 payloads

The images are the only parts that can't be extracted. Having the
unpacked metadata is useful because it allows for manually building a
full payload using the metadata from the delta payload.

Discussion: #582

Signed-off-by: Andrew Gunnerson <accounts+github@chiller3.com>
---
 avbroot/src/cli/payload.rs | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/avbroot/src/cli/payload.rs b/avbroot/src/cli/payload.rs
index 15b84dd..7ef8d58 100644
--- a/avbroot/src/cli/payload.rs
+++ b/avbroot/src/cli/payload.rs
@@ -22,15 +22,12 @@ use crate::{
     util,
 };
 
-fn open_reader(path: &Path, allow_delta: bool) -> Result<(BufReader<File>, PayloadHeader)> {
+fn open_reader(path: &Path) -> Result<(BufReader<File>, PayloadHeader)> {
     let mut reader = File::open(path)
         .map(BufReader::new)
         .with_context(|| format!("Failed to open payload for reading: {path:?}"))?;
     let header = PayloadHeader::from_reader(&mut reader)
         .with_context(|| format!("Failed to read payload header: {path:?}"))?;
-    if !allow_delta && !header.is_full_ota() {
-        bail!("Payload is a delta OTA, not a full OTA");
-    }
 
     Ok((reader, header))
 }
@@ -104,7 +101,7 @@ fn unpack_subcommand(
     cli: &UnpackCli,
     cancel_signal: &AtomicBool,
 ) -> Result<()> {
-    let (mut reader, header) = open_reader(&cli.input, false)?;
+    let (mut reader, header) = open_reader(&cli.input)?;
     let payload_size = reader
         .seek(SeekFrom::End(0))
         .with_context(|| format!("Failed to get file size: {:?}", cli.input))?;
@@ -114,6 +111,10 @@ fn unpack_subcommand(
     write_info(&cli.output_info, &header)?;
 
     if !cli.no_output_images {
+        if !header.is_full_ota() {
+            bail!("Cannot extract images from a delta payload");
+        }
+
         fs::create_dir_all(&cli.output_images)
             .with_context(|| format!("Failed to create directory: {:?}", cli.output_images))?;
 
@@ -260,7 +261,7 @@ fn repack_subcommand(
 ) -> Result<()> {
     let signing_key = load_key(&cli.key)?;
 
-    let (mut reader, header) = open_reader(&cli.input, true)?;
+    let (mut reader, header) = open_reader(&cli.input)?;
 
     info!("Generating new OTA payload");
 
@@ -316,7 +317,7 @@ fn repack_subcommand(
 }
 
 fn info_subcommand(payload_cli: &PayloadCli, cli: &InfoCli) -> Result<()> {
-    let (_, header) = open_reader(&cli.input, true)?;
+    let (_, header) = open_reader(&cli.input)?;
 
     display_header(payload_cli, &header);