safety checks in group parsing

src/DB.zig

@@ -368,21 +368,25 @@ pub fn packCGroup(self: *const DB, group: *const PackedGroup, buf: []u8) error{
     };
 }
 
-pub fn getGroupByName(self: *const DB, name: []const u8) ?PackedGroup {
+pub fn getGroupByName(self: *const DB, name: []const u8) error{Overflow}!?PackedGroup {
     const idx = bdz.search(self.bdz_groupname, name);
-    if (idx >= self.header.num_groups) return null;
+    if (idx >= self.header.num_groups)
+        return null;
     const offset = self.idx_groupname2group[idx];
-    const group = PackedGroup.fromBytes(@alignCast(8, self.groups[offset << 3 ..])).group;
-    if (!mem.eql(u8, name, group.name())) return null;
+    const group = (try PackedGroup.fromBytes(@alignCast(8, self.groups[offset << 3 ..]))).group;
+    if (!mem.eql(u8, name, group.name()))
+        return null;
     return group;
 }
 
-pub fn getGroupByGid(self: *const DB, gid: u32) ?PackedGroup {
+pub fn getGroupByGid(self: *const DB, gid: u32) error{Overflow}!?PackedGroup {
     const idx = bdz.search_u32(self.bdz_gid, gid);
-    if (idx >= self.header.num_groups) return null;
+    if (idx >= self.header.num_groups)
+        return null;
     const offset = self.idx_gid2group[idx];
-    const group = PackedGroup.fromBytes(@alignCast(8, self.groups[offset << 3 ..])).group;
-    if (gid != group.gid()) return null;
+    const group = (try PackedGroup.fromBytes(@alignCast(8, self.groups[offset << 3 ..]))).group;
+    if (gid != group.gid())
+        return null;
     return group;
 }
 
@@ -393,7 +397,7 @@ pub fn getgrnam(
     buf: []u8,
     omit_members: bool,
 ) error{ Overflow, BufferTooSmall }!?CGroup {
-    const group = self.getGroupByName(name) orelse return null;
+    const group = try self.getGroupByName(name) orelse return null;
     if (omit_members)
         return try packCGroupNoMembers(&group, buf)
     else
@@ -407,7 +411,7 @@ pub fn getgrgid(
     buf: []u8,
     omit_members: bool,
 ) error{ Overflow, BufferTooSmall }!?CGroup {
-    const group = self.getGroupByGid(gid) orelse return null;
+    const group = try self.getGroupByGid(gid) orelse return null;
     if (omit_members)
         return try packCGroupNoMembers(&group, buf)
     else

src/PackedGroup.zig

@@ -39,13 +39,11 @@ pub const Entry = struct {
     end: usize,
 };
 
-pub fn fromBytes(bytes: []align(8) const u8) Entry {
+pub fn fromBytes(bytes: []align(8) const u8) error{Overflow}!Entry {
     const inner = mem.bytesAsValue(Inner, bytes[0..@sizeOf(Inner)]);
     const start_blob = @sizeOf(Inner);
     const end_strings = @sizeOf(Inner) + inner.groupnameLen();
-    const members_offset = compress.uvarint(bytes[end_strings..]) catch |err| switch (err) {
-        error.Overflow => unreachable,
-    };
+    const members_offset = try compress.uvarint(bytes[end_strings..]);
     const end_blob = end_strings + members_offset.bytes_read;
 
     return Entry{
@@ -70,9 +68,9 @@ pub const Iterator = struct {
     total: u32,
     advanced_by: usize = 0,
 
-    pub fn next(it: *Iterator) ?PackedGroup {
+    pub fn next(it: *Iterator) error{Overflow}!?PackedGroup {
         if (it.idx == it.total) return null;
-        const entry = fromBytes(@alignCast(8, it.section[it.next_start..]));
+        const entry = try fromBytes(@alignCast(8, it.section[it.next_start..]));
         it.idx += 1;
         it.next_start += entry.end;
         it.advanced_by = entry.end;
@@ -149,7 +147,7 @@ test "PackedGroup construct" {
 
     var i: u29 = 0;
     var it = PackedGroup.iterator(buf.items, groups.len);
-    while (it.next()) |group| : (i += 1) {
+    while (try it.next()) |group| : (i += 1) {
         try testing.expectEqual(groups[i].gid, group.gid());
         try testing.expectEqualStrings(groups[i].name, group.name());
         try testing.expectEqual(groups[i].members_offset, group.membersOffset());

src/libnss.zig

@@ -369,7 +369,9 @@ fn getgrent_r(
         return c.NSS_STATUS_UNAVAIL;
     });
 
-    const group = it.next() orelse {
+    const group = it.next() catch |err| switch (err) {
+        error.Overflow => return badFile(errnop),
+    } orelse {
         errnop.* = 0;
         return c.NSS_STATUS_NOTFOUND;
     };

src/turbonss-getent.zig

@@ -159,7 +159,7 @@ fn group(stdout: anytype, db: *const DB, keys: []const [*:0]const u8) error{Over
 
     for (keys) |key| {
         const keyZ = mem.span(key);
-        const maybe_packed_group = if (fmt.parseUnsigned(u32, keyZ, 10)) |gid|
+        const maybe_packed_group = try if (fmt.parseUnsigned(u32, keyZ, 10)) |gid|
             db.getGroupByGid(gid)
         else |_|
             db.getGroupByName(keyZ);
@@ -178,7 +178,7 @@ fn group(stdout: anytype, db: *const DB, keys: []const [*:0]const u8) error{Over
 
 fn groupAll(stdout: anytype, db: *const DB) error{Overflow}!u8 {
     var it = PackedGroup.iterator(db.groups, db.header.num_groups);
-    while (it.next()) |g|
+    while (try it.next()) |g|
         if (try printGroup(stdout, db, &g)) |exit_code|
             return exit_code;