[pacman-dev] [PATCH 3/3] pacman: add file checksum validation against mtree

[Emil Velikov]

With libarchive v3.5.0 we have API to fetch the digest from the mtree.
Use that to validate if the installed files are modified or not.

As always, a modified backup file will trigger a warning but will not
result in an actual failure.

TODO: localization... no idea how that is even done :-)
NOTE: indentation is likely all over the place - first time I see ts=2

Signed-off-by: Emil Velikov <emil.l.velikov at gmail.com>
---
 src/pacman/check.c | 66 +++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 59 insertions(+), 7 deletions(-)

diff --git a/src/pacman/check.c b/src/pacman/check.c
index 02217d0f..083c547d 100644
--- a/src/pacman/check.c
+++ b/src/pacman/check.c
@@ -176,19 +176,70 @@ static int check_file_size(const char *pkgname, const char *filepath,
 	return 0;
 }
 
-/* placeholders - libarchive currently does not read checksums from mtree files
-static int check_file_md5sum(const char *pkgname, const char *filepath,
-		struct stat *st, struct archive_entry *entry, int backup)
+#if ARCHIVE_VERSION_NUMBER >= 3005000
+static int check_file_cksum(const char *pkgname, const char *filepath,
+		int backup, const char *cksum_name, const char *cksum_calc, const char *cksum_mtree)
 {
+	if(!cksum_calc || !cksum_mtree) {
+		if(!config->quiet) {
+			pm_printf(ALPM_LOG_WARNING, _("%s: %s (failed to compute %s checksum)\n"),
+					pkgname, filepath, cksum_name);
+		}
+		return 1;
+	}
+
+	if(strcmp(cksum_calc, cksum_mtree) != 0) {
+		if(backup) {
+			if(!config->quiet) {
+				printf("%s%s%s: ", config->colstr.title, _("backup file"),
+						config->colstr.nocolor);
+				printf(_("%s: %s (%s checksum mismatch)\n"),
+						pkgname, filepath, cksum_name);
+			}
+			return 0;
+		}
+		if(!config->quiet) {
+			pm_printf(ALPM_LOG_WARNING, _("%s: %s (%s checksum mismatch)\n"),
+					pkgname, filepath, cksum_name);
+		}
+		return 1;
+	}
+
 	return 0;
 }
+#endif
+
+static int check_file_md5sum(const char *pkgname, const char *filepath,
+		struct archive_entry *entry, int backup)
+{
+	int errors = 0;
+#if ARCHIVE_VERSION_NUMBER >= 3005000
+	char *cksum_calc = alpm_compute_md5sum(filepath);
+	char *cksum_mtree = hex_representation(archive_entry_digest(entry,
+													ARCHIVE_ENTRY_DIGEST_MD5), 16);
+	errors = check_file_cksum(pkgname, filepath, backup, "MD5", cksum_calc,
+									cksum_mtree);
+	free(cksum_mtree);
+	free(cksum_calc);
+#endif
+	return (errors != 0 ? 1 : 0);
+}
 
 static int check_file_sha256sum(const char *pkgname, const char *filepath,
-		struct stat *st, struct archive_entry *entry, int backup)
+		struct archive_entry *entry, int backup)
 {
-	return 0;
+	int errors = 0;
+#if ARCHIVE_VERSION_NUMBER >= 3005000
+	char *cksum_calc = alpm_compute_sha256sum(filepath);
+	char *cksum_mtree = hex_representation(archive_entry_digest(entry,
+													ARCHIVE_ENTRY_DIGEST_SHA256), 32);
+	errors = check_file_cksum(pkgname, filepath, backup, "SHA256", cksum_calc,
+									cksum_mtree);
+	free(cksum_mtree);
+	free(cksum_calc);
+#endif
+	return (errors != 0 ? 1 : 0);
 }
-*/
 
 /* Loop through the files of the package to check if they exist. */
 int check_pkg_fast(alpm_pkg_t *pkg)
@@ -369,7 +420,8 @@ int check_pkg_full(alpm_pkg_t *pkg)
 
 		if(type == AE_IFREG) {
 			file_errors += check_file_size(pkgname, filepath, &st, entry, backup);
-			/* file_errors += check_file_md5sum(pkgname, filepath, &st, entry, backup); */
+			file_errors += check_file_md5sum(pkgname, filepath, entry, backup);
+			file_errors += check_file_sha256sum(pkgname, filepath, entry, backup);
 		}
 
 		if(config->quiet && file_errors) {
-- 
2.29.2