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pkg-infra: add possiblity to check downloaded files against known hashes

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Some of the packages that Buildroot might build are sensitive packages,
related to security: openssl, dropbear, ca-certificates...

Some of those packages are downloaded over plain http, because there is
no way to get them over a secure channel, such as https.

In these dark times of pervasive surveillance, the potential for harm that
a tampered-with package could generate, we may want to check the integrity
of those sensitive packages.

So, each package may now provide a list of hashes for all files that needs
to be downloaded, and Buildroot will just fail if any downloaded file does
not match its known hash, in which case it is removed.

Hashes can be any of the md5, sha1 or sha2 variants, and will be checked
even if the file was pre-downloaded.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Baruch Siach <baruch@tkos.co.il>
Cc: Arnout Vandecappelle <arnout@mind.be>
Cc: Gustavo Zacarias <gustavo@zacarias.com.ar>
Reviewed-by: Samuel Martin <s.martin49@gmail.com>
Cc: Thomas De Schampheleire <patrickdepinguin@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
This commit is contained in:
Yann E. MORIN 2014-07-03 21:36:21 +02:00 committed by Peter Korsgaard
parent 19afad50f5
commit 9bd8b59526
2 changed files with 93 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
package/pkg-download.mk
View File

@ -58,6 +58,17 @@ domainseparator=$(if $(1),$(1),/)
# github(user,package,version): returns site of GitHub repository
github = https://github.com/$(1)/$(2)/archive/$(3)
# Helper for checking a tarball's checksum
# If the hash does not match, remove the incorrect file
# $(1): the path to the file with the hashes
# $(2): the full path to the file to check
define VERIFY_HASH
if ! support/download/check-hash $(1) $(2); then \
rm -f $(2); \
exit 1; \
fi
endef
################################################################################
# The DOWNLOAD_* helpers are in charge of getting a working copy
# of the source repository for their corresponding SCM,
@ -148,7 +159,8 @@ endef
define DOWNLOAD_SCP
test -e $(DL_DIR)/$(2) || \
$(EXTRA_ENV) support/download/scp '$(call stripurischeme,$(call qstrip,$(1)))' \
$(DL_DIR)/$(2)
$(DL_DIR)/$(2) && \
$(call VERIFY_HASH,$(PKGDIR)/$($(PKG)_NAME).hash,$(DL_DIR)/$(2))
endef
define SOURCE_CHECK_SCP
@ -179,7 +191,8 @@ endef
define DOWNLOAD_WGET
test -e $(DL_DIR)/$(2) || \
$(EXTRA_ENV) support/download/wget '$(call qstrip,$(1))' $(DL_DIR)/$(2)
$(EXTRA_ENV) support/download/wget '$(call qstrip,$(1))' $(DL_DIR)/$(2) && \
$(call VERIFY_HASH,$(PKGDIR)/$($(PKG)_NAME).hash,$(DL_DIR)/$(2))
endef
define SOURCE_CHECK_WGET
@ -193,7 +206,8 @@ endef
define DOWNLOAD_LOCALFILES
test -e $(DL_DIR)/$(2) || \
$(EXTRA_ENV) support/download/cp $(call stripurischeme,$(call qstrip,$(1))) \
$(DL_DIR)
$(DL_DIR) && \
$(call VERIFY_HASH,$(PKGDIR)/$($(PKG)_NAME).hash,$(DL_DIR)/$(2))
endef
define SOURCE_CHECK_LOCALFILES

76
support/download/check-hash Executable file
View File

@ -0,0 +1,76 @@
#!/bin/bash
set -e
# Helper to check a file matches its known hash
# Call it with:
# $1: the full path to the file to check
# $2: the path of the file containing all the the expected hashes
h_file="${1}"
file="${2}"
# Does the hash-file exist?
if [ ! -f "${h_file}" ]; then
exit 0
fi
# Check one hash for a file
# $1: known hash
# $2: file (full path)
check_one_hash() {
_h="${1}"
_known="${2}"
_file="${3}"
# Note: sha3 is not supported, since there is currently no implementation
# (the NIST has yet to publish the parameters).
case "${_h}" in
md5|sha1) ;;
sha224|sha256|sha384|sha512) ;;
*) # Unknown hash, exit with error
printf "ERROR: unknown hash '%s' for '%s'\n" \
"${_h}" "${_file##*/}" >&2
exit 1
;;
esac
# Do the hashes match?
_hash=$( ${_h}sum "${_file}" |cut -d ' ' -f 1 )
if [ "${_hash}" = "${_known}" ]; then
printf "%s: OK (%s: %s)\n" "${_file##*/}" "${_h}" "${_hash}"
return 0
fi
printf "ERROR: %s has wrong %s hash:\n" "${_file##*/}" "${_h}" >&2
printf "ERROR: expected: %s\n" "${_known}" >&2
printf "ERROR: got : %s\n" "${_hash}" >&2
printf "ERROR: Incomplete download, or man-in-the-middle (MITM) attack\n" >&2
exit 1
}
# Do we know one or more hashes for that file?
nb_checks=0
while read t h f; do
case "${t}" in
''|'#'*)
# Skip comments and empty lines
continue
;;
*)
if [ "${f}" = "${file##*/}" ]; then
check_one_hash "${t}" "${h}" "${file}"
: $((nb_checks++))
fi
;;
esac
done <"${h_file}"
if [ ${nb_checks} -eq 0 ]; then
if [ -n "${BR2_ENFORCE_CHECK_HASH}" ]; then
printf "ERROR: No hash found for %s\n" "${file}" >&2
exit 1
else
printf "WARNING: No hash found for %s\n" "${file}" >&2
fi
fi