[PATCH] Lookup users and groups in root directory instead of on host

[Daan De Meyer <daan.j.demeyer@gmail.com>]

If a root directory is configured by the user, lookup users and groups
in the /etc/passwd and /etc/group of that root directory instead of the
host's /etc/passwd and /etc/group.

This is especially important when building Debian chroots on distros
that are not Debian based and where the host's /etc/passwd and /etc/group
is using passwd and group entries that differ wildly from those shipped
by Debian or its derivatives, causing dpkg stat-overrides to fail because
a group or user cannot be found in the host's passwd or group entries.
---
 lib/dpkg/db-fsys-override.c | 64 +++++++++++++++++++++++++++++++------
 1 file changed, 54 insertions(+), 10 deletions(-)

diff --git a/lib/dpkg/db-fsys-override.c b/lib/dpkg/db-fsys-override.c
index e079c5ffb..29adaf134 100644
--- a/lib/dpkg/db-fsys-override.c
+++ b/lib/dpkg/db-fsys-override.c
@@ -58,12 +58,34 @@ statdb_parse_uid(const char *str)
 			ohshit(_("invalid statoverride uid %s"), str);
 		uid = (uid_t)value;
 	} else {
-		struct passwd *pw = getpwnam(str);
+		char *passwd;
+		FILE *file;
+
+		uid = (uid_t)-1;
+		passwd = dpkg_fsys_get_path("etc/passwd");
+
+		file = fopen(passwd, "r");
+		free(passwd);
+		if (!file) {
+			if (errno != ENOENT)
+				ohshite(_("failed to open etc/passwd file"));
+		} else {
+			struct passwd *pw;
+
+			errno = 0;
+			while ((pw = fgetpwent(file))) {
+				if (strcmp(pw->pw_name, str) == 0)
+					break;
+			}
 
-		if (pw == NULL)
-			uid = (uid_t)-1;
-		else
-			uid = pw->pw_uid;
+			fclose(file);
+
+			if (errno > 0)
+				ohshite(_("failed to read passwd entry"));
+
+			if (pw)
+				uid = pw->pw_uid;
+		}
 	}
 
 	return uid;
@@ -84,12 +106,34 @@ statdb_parse_gid(const char *str)
 			ohshit(_("invalid statoverride gid %s"), str);
 		gid = (gid_t)value;
 	} else {
-		struct group *gr = getgrnam(str);
+		char *group;
+		FILE *file;
+
+		gid = (gid_t)-1;
+		group = dpkg_fsys_get_path("etc/group");
+
+		file = fopen(group, "r");
+		free(group);
+		if (!file) {
+			if (errno != ENOENT)
+				ohshite(_("failed to open etc/group file"));
+		} else {
+			struct group *gr;
+
+			errno = 0;
+			while ((gr = fgetgrent(file))) {
+				if (strcmp(gr->gr_name, str) == 0)
+					break;
+			}
 
-		if (gr == NULL)
-			gid = (gid_t)-1;
-		else
-			gid = gr->gr_gid;
+			fclose(file);
+
+			if (errno > 0)
+				ohshite(_("failed to read group entry"));
+
+			if (gr)
+				gid = gr->gr_gid;
+		}
 	}
 
 	return gid;
-- 
2.39.2