[PATCH v2] download: handle possibly invalid local tarballs

[Petr Štetiar]

Currently it's assumed, that already downloaded tarballs are always
fine, so no checksum checking is performed and the tarball is used even
if it might be corrupted.

>From now on, we're going to always check the downloaded tarballs before
considering them valid.

Steps to reproduce:

 1. Remove cached tarball

   rm dl/libubox-2020-08-06-9e52171d.tar.xz

 2. Download valid tarball again

   make package/libubox/download

 3. Invalidate the tarball

   sed -i 's/PKG_MIRROR_HASH:=../PKG_MIRROR_HASH:=ff/' package/libs/libubox/Makefile

 4. Now compile with corrupt tarball source

   make package/libubox/{clean,compile}

Signed-off-by: Petr Štetiar <ynezz at true.cz>
---

 Changes since v1:

  * fixed infinite re-downloading of the source tarball when using KERNEL_GIT_LOCAL_REPOSITORY

 include/host-build.mk |  2 ++
 include/package.mk    |  2 ++
 scripts/download.pl   | 18 ++++++++++++++++++
 3 files changed, 22 insertions(+)

diff --git a/include/host-build.mk b/include/host-build.mk
index 7d84ab0f5fc4..4ac140518113 100644
--- a/include/host-build.mk
+++ b/include/host-build.mk
@@ -186,6 +186,8 @@ ifndef DUMP
     clean-build: host-clean-build
   endif
 
+  $(DL_DIR)/$(FILE): FORCE
+
   $(_host_target)host-prepare: $(HOST_STAMP_PREPARED)
   $(_host_target)host-configure: $(HOST_STAMP_CONFIGURED)
   $(_host_target)host-compile: $(HOST_STAMP_BUILT) $(HOST_STAMP_INSTALLED)
diff --git a/include/package.mk b/include/package.mk
index 50bd838180d8..5eb4460db86c 100644
--- a/include/package.mk
+++ b/include/package.mk
@@ -189,6 +189,8 @@ define Build/CoreTargets
   $(call Build/Autoclean)
   $(call DefaultTargets)
 
+  $(DL_DIR)/$(FILE): FORCE
+
   download:
 	$(foreach hook,$(Hooks/Download),
 		$(call $(hook))$(sep)
diff --git a/scripts/download.pl b/scripts/download.pl
index 351b06a08b2f..2d87f47f842b 100755
--- a/scripts/download.pl
+++ b/scripts/download.pl
@@ -262,6 +262,24 @@ foreach my $mirror (@ARGV) {
 push @mirrors, 'https://sources.openwrt.org';
 push @mirrors, 'https://mirror2.openwrt.org/sources';
 
+if (-f "$target/$filename") {
+	$hash_cmd and do {
+		if (system("cat '$target/$filename' | $hash_cmd > '$target/$filename.hash'")) {
+			die "Failed to generate hash for $filename\n";
+		}
+
+		my $sum = `cat "$target/$filename.hash"`;
+		$sum =~ /^(\w+)\s*/ or die "Could not generate file hash\n";
+		$sum = $1;
+
+		exit 0 if $sum eq $file_hash;
+
+		die "Hash of the local file $filename does not match (file: $sum, requested: $file_hash) - deleting download.\n";
+		unlink "$target/$filename";
+		cleanup();
+	};
+}
+
 while (!-f "$target/$filename") {
 	my $mirror = shift @mirrors;
 	$mirror or die "No more mirrors to try - giving up.\n";