package/pkg-download: lookup hash files in global-patch-dir

Currently, we expect and only use hash files that lie within the package
directory, alongside the .mk file. Those hash files are thus bundled
with Buildroot.

This implies that only what's known to Buildroot can ever get into those
hash files. For packages where the version is fixed (or a static
choice), then we can carry hashes for those known versions.

However, we do have a few packages for which the version is a free-form
entry, where the user can provide a custom location and/or version.  like
a custom VCS tree and revision, or a custom tarball URL. This means that
Buildroot has no way to be able to cary hashes for such custom versions.

This means that there is no integrity check that what was downloaded is
what was expected. For a sha1 in a git tree, this is a minor issue,
because the sha1 by itself is already a hash of the expected content.
But for custom tarballs URLs, or for a tag in a VCS, there is indeed no
integrity check.

Buildroot can't provide such hashes, but interested users may want to
provide those, and currently there is no (easy) way to do so.

We leverage the existing global-patch-dir mechanism to look for extra
hash files. We use the same heuristic that is used for bundled hash
files, and for each global patch directory <dir>, we use the first file
to exist among:
 1. look into <dir>/<package>/<version>/<package>.hash
 2. look into <dir>/<package>/<package>.hash

Reported-by: "Martin Zeiser (mzeiser)" <mzeiser@cisco.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

Config.in

@@ -674,12 +674,12 @@ config BR2_PACKAGE_OVERRIDE_FILE
 	  documentation for more details on this feature.
 
 config BR2_GLOBAL_PATCH_DIR
-	string "global patch directories"
+	string "global patch and hash directories"
 	help
 	  You may specify a space separated list of one or more
-	  directories containing global package patches. For a specific
-	  version <packageversion> of a specific package <packagename>,
-	  patches are applied as follows:
+	  directories containing global package patches and/or hashes.
+	  For a specific version <packageversion> of a specific package
+	  <packagename>, patches are looked up as follows:
 
 	  First, the default Buildroot patch set for the package is
 	  applied from the package's directory in Buildroot.
@@ -693,6 +693,8 @@ config BR2_GLOBAL_PATCH_DIR
 	  exists, then all *.patch files in the directory will be
 	  applied.
 
+	  The hash files are looked up similarly to the patches.
+
 menu "Advanced"
 
 config BR2_FORCE_HOST_BUILD

docs/manual/adding-packages-directory.adoc

@@ -540,6 +540,12 @@ mercurial) because Buildroot currently does not generate reproducible
 tarballs when source code is fetched from such version control
 systems.
 
+Additionally, for packages for which it is possible to specify a custom
+version (e.g. a custom version string, a remote tarball URL, or a VCS
+repository location and changeset), Buildroot can't carry hashes for
+those. It is however possible to xref:customize-hashes[provide a list of
+extra hashes] that can cover such cases.
+
 Hashes should only be added in +.hash+ files for files that are
 guaranteed to be stable. For example, patches auto-generated by Github
 are not guaranteed to be stable, and therefore their hashes can change

docs/manual/customize-patches.adoc

@@ -1,8 +1,10 @@
 // -*- mode:doc -*- ;
 // vim: set syntax=asciidoc:
 
+=== Adding project-specific patches and hashes
+
 [[customize-patches]]
-=== Adding project-specific patches
+==== Providing extra patches
 
 It is sometimes useful to apply 'extra' patches to packages - on top of
 those provided in Buildroot. This might be used to support custom
@@ -57,3 +59,23 @@ are available at a URL. *Note:* +BR2_LINUX_KERNEL_PATCH+ specifies kernel
 patches that are applied after patches available in +BR2_GLOBAL_PATCH_DIR+,
 as it is done from a post-patch hook of the Linux package.
 
+
+[[customize-hashes]]
+==== Providing extra hashes
+
+Buildroot bundles a xref:adding-packages-hash[list of hashes] against
+which it checks the integrity of the downloaded archives, or of those
+it generates locally from VCS checkouts. However, it can only do so
+for the known versions; for packages where it is possible to specify
+a custom version (e.g. a custom version string, a remote tarball URL,
+or a VCS repository location and changeset), Buildroot can't carry
+hashes for those.
+
+For users concerned with the integrity of such downloads, it is possible
+to provide a list of hashes that Buildroot can use to check arbitrary
+downloaded files. Those extra hashes are looked up similarly to the
+extra patches (above); for each directory in +BR2_GLOBAL_PATCH_DIR+,
+the first file to exist is used to check a package download:
+
+* +<global-patch-dir>/<packagename>/<packageversion>/<packagename>.hash+
+* +<global-patch-dir>/<packagename>/<packagename>.hash+

package/pkg-download.mk

@@ -115,7 +115,7 @@ define DOWNLOAD
 		-d '$($(2)_DL_DIR)' \
 		-D '$(DL_DIR)' \
 		-f '$(notdir $(1))' \
-		-H '$($(2)_HASH_FILE)' \
+		$(foreach f,$($(2)_HASH_FILES),-H '$(f)') \
 		-n '$($(2)_BASENAME_RAW)' \
 		-N '$($(2)_RAWNAME)' \
 		-o '$($(2)_DL_DIR)/$(notdir $(1))' \

package/pkg-generic.mk

@@ -509,11 +509,15 @@ else
 endif
 $(2)_VERSION := $$(call sanitize,$$($(2)_DL_VERSION))
 
-$(2)_HASH_FILE = \
+$(2)_HASH_FILES = \
 	$$(strip \
-		$$(if $$(wildcard $$($(2)_PKGDIR)/$$($(2)_VERSION)/$$($(2)_RAWNAME).hash),\
-			$$($(2)_PKGDIR)/$$($(2)_VERSION)/$$($(2)_RAWNAME).hash,\
-			$$($(2)_PKGDIR)/$$($(2)_RAWNAME).hash))
+		$$(foreach d, $$($(2)_PKGDIR) $$(addsuffix /$$($(2)_RAWNAME), $$(call qstrip,$$(BR2_GLOBAL_PATCH_DIR))),\
+			$$(if $$(wildcard $$(d)/$$($(2)_VERSION)/$$($(2)_RAWNAME).hash),\
+				$$(d)/$$($(2)_VERSION)/$$($(2)_RAWNAME).hash,\
+				$$(d)/$$($(2)_RAWNAME).hash\
+			)\
+		)\
+	)
 
 ifdef $(3)_OVERRIDE_SRCDIR
   $(2)_OVERRIDE_SRCDIR ?= $$($(3)_OVERRIDE_SRCDIR)
@@ -1138,7 +1142,7 @@ ifneq ($$(call qstrip,$$($(2)_SOURCE)),)
 ifeq ($$(call qstrip,$$($(2)_LICENSE_FILES)),)
 	$(Q)$$(call legal-warning-pkg,$$($(2)_BASENAME_RAW),cannot save license ($(2)_LICENSE_FILES not defined))
 else
-	$(Q)$$(foreach F,$$($(2)_LICENSE_FILES),$$(call legal-license-file,$$(call UPPERCASE,$(4)),$$($(2)_RAWNAME),$$($(2)_BASENAME_RAW),$$(F),$$($(2)_DIR)/$$(F),$$($(2)_HASH_FILE))$$(sep))
+	$(Q)$$(foreach F,$$($(2)_LICENSE_FILES),$$(call legal-license-file,$$(call UPPERCASE,$(4)),$$($(2)_RAWNAME),$$($(2)_BASENAME_RAW),$$(F),$$($(2)_DIR)/$$(F),$$($(2)_HASH_FILES))$$(sep))
 endif # license files
 
 ifeq ($$($(2)_REDISTRIBUTE),YES)

package/pkg-utils.mk

@@ -280,7 +280,7 @@ define legal-manifest # {HOST|TARGET}, pkg, version, license, license-files, sou
 	echo '"$(2)","$(3)","$(4)","$(5)","$(6)","$(7)","$(8)"' >>$(LEGAL_MANIFEST_CSV_$(1))
 endef
 
-define legal-license-file # {HOST|TARGET}, pkgname, pkgname-pkgver, filename, file-fullpath, pkg-hashfile
+define legal-license-file # {HOST|TARGET}, pkgname, pkgname-pkgver, filename, file-fullpath, pkg-hashfiles
 	mkdir -p $(LICENSE_FILES_DIR_$(1))/$(3)/$(dir $(4)) && \
 	{ \
 		support/download/check-hash $(5) $(4) $(6); \