more safety checks in user parsing

src/DB.zig

@@ -342,7 +342,7 @@ pub fn packCGroup(self: *const DB, group: *const PackedGroup, buf: []u8) error{
 
     var i: usize = 0;
     while (try it.next()) |member_offset| : (i += 1) {
-        const entry = PackedUser.fromBytes(@alignCast(8, self.users[member_offset << 3 ..]));
+        const entry = try PackedUser.fromBytes(@alignCast(8, self.users[member_offset << 3 ..]));
         const start = buf_offset;
         const name = entry.user.name();
         if (buf_offset + name.len + 1 > buf.len)
@@ -458,34 +458,36 @@ pub fn writeUser(self: *const DB, user: PackedUser, buf: []u8) error{BufferTooSm
     };
 }
 
-pub fn getUserByName(self: *const DB, name: []const u8) ?PackedUser {
+pub fn getUserByName(self: *const DB, name: []const u8) error{Overflow}!?PackedUser {
     const idx = bdz.search(self.bdz_username, name);
     // bdz may return a hash that's bigger than the number of users
-    if (idx >= self.header.num_users) return null;
+    if (idx >= self.header.num_users)
+        return null;
     const offset = self.idx_name2user[idx];
-    const user = PackedUser.fromBytes(@alignCast(8, self.users[offset << 3 ..])).user;
+    const user = (try PackedUser.fromBytes(@alignCast(8, self.users[offset << 3 ..]))).user;
     if (!mem.eql(u8, name, user.name())) return null;
     return user;
 }
 
 // get a CUser entry by name.
-pub fn getpwnam(self: *const DB, name: []const u8, buf: []u8) error{BufferTooSmall}!?CUser {
+pub fn getpwnam(self: *const DB, name: []const u8, buf: []u8) error{ Overflow, BufferTooSmall }!?CUser {
-    const user = self.getUserByName(name) orelse return null;
+    const user = try self.getUserByName(name) orelse return null;
     return try self.writeUser(user, buf);
 }
 
-pub fn getUserByUid(self: *const DB, uid: u32) ?PackedUser {
+pub fn getUserByUid(self: *const DB, uid: u32) error{Overflow}!?PackedUser {
     const idx = bdz.search_u32(self.bdz_uid, uid);
-    if (idx >= self.header.num_users) return null;
+    if (idx >= self.header.num_users)
+        return null;
     const offset = self.idx_uid2user[idx];
-    const user = PackedUser.fromBytes(@alignCast(8, self.users[offset << 3 ..])).user;
+    const user = (try PackedUser.fromBytes(@alignCast(8, self.users[offset << 3 ..]))).user;
     if (uid != user.uid()) return null;
     return user;
 }
 
 // get a CUser entry by uid.
-pub fn getpwuid(self: *const DB, uid: u32, buf: []u8) error{BufferTooSmall}!?CUser {
+pub fn getpwuid(self: *const DB, uid: u32, buf: []u8) error{ Overflow, BufferTooSmall }!?CUser {
-    const user = self.getUserByUid(uid) orelse return null;
+    const user = try self.getUserByUid(uid) orelse return null;
     return try self.writeUser(user, buf);
 }
 

src/PackedUser.zig

@@ -83,13 +83,11 @@ pub const Entry = struct {
     end: usize,
 };
 
-pub fn fromBytes(blob: []align(8) const u8) Entry {
+pub fn fromBytes(blob: []align(8) const u8) error{Overflow}!Entry {
     const start_var_payload = @bitSizeOf(Inner) / 8;
     const inner = @ptrCast(*align(8) const Inner, blob[0..start_var_payload]);
     const end_strings = start_var_payload + inner.stringLength();
-    const gids_offset = compress.uvarint(blob[end_strings..]) catch |err| switch (err) {
+    const gids_offset = try compress.uvarint(blob[end_strings..]);
-        error.Overflow => unreachable,
-    };
     const end_payload = end_strings + gids_offset.bytes_read;
 
     return Entry{
@@ -110,9 +108,9 @@ pub const Iterator = struct {
     total: u32,
     advanced_by: usize = 0,
 
-    pub fn next(it: *Iterator) ?PackedUser {
+    pub fn next(it: *Iterator) error{Overflow}!?PackedUser {
         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;
@@ -296,7 +294,7 @@ test "PackedUser construct section" {
 
     var i: u29 = 0;
     var it1 = PackedUser.iterator(buf.items, users.len, test_shell_reader);
-    while (it1.next()) |user| : (i += 1) {
+    while (try it1.next()) |user| : (i += 1) {
         try testing.expectEqual(users[i].uid, user.uid());
         try testing.expectEqual(users[i].gid, user.gid());
         try testing.expectEqual(user.additionalGidsOffset(), additional_gids);

src/libnss.zig

@@ -140,6 +140,7 @@ fn getpwuid_r(
     errnop: *c_int,
 ) c.enum_nss_status {
     var cuser = db.getpwuid(uid, buffer[0..buflen]) catch |err| switch (err) {
+        error.Overflow => return badFile(errnop),
         error.BufferTooSmall => {
             errnop.* = @enumToInt(os.E.RANGE);
             return c.NSS_STATUS_TRYAGAIN;
@@ -178,6 +179,7 @@ fn getpwnam_r(
 
     var buf = buffer[0..buflen];
     const cuser = db.getpwnam(nameSlice, buf) catch |err| switch (err) {
+        error.Overflow => return badFile(errnop),
         error.BufferTooSmall => {
             errnop.* = @enumToInt(os.E.RANGE);
             return c.NSS_STATUS_TRYAGAIN;
@@ -424,7 +426,9 @@ fn getpwent_r(
         return c.NSS_STATUS_UNAVAIL;
     });
 
-    const user = it.next() orelse {
+    const user = it.next() catch |err| switch (err) {
+        error.Overflow => return badFile(errnop),
+    } orelse {
         errnop.* = 0;
         return c.NSS_STATUS_NOTFOUND;
     };
@@ -470,7 +474,9 @@ fn initgroups_dyn(
     errnop: *c_int,
 ) c.enum_nss_status {
     const db = state.file.db;
-    const user = db.getUserByName(mem.sliceTo(user_name, 0)) orelse {
+    const user = db.getUserByName(mem.sliceTo(user_name, 0)) catch |err| switch (err) {
+        error.Overflow => return badFile(errnop),
+    } orelse {
         errnop.* = @enumToInt(os.E.NOENT);
         return c.NSS_STATUS_NOTFOUND;
     };

src/turbonss-analyze.zig

@@ -159,7 +159,12 @@ fn execute(
             db.header.num_users,
             db.shellReader(),
         );
-        while (it.next()) |packed_user| {
+        while (it.next() catch |err| switch (err) {
+            error.Overflow => {
+                stderr.print("ERROR: file '{s}' is corrupted\n", .{db_file}) catch {};
+                return 1;
+            },
+        }) |packed_user| {
             const offset = packed_user.additional_gids_offset;
             const additional_gids = db.additional_gids[offset..];
             const vit = compress.varintSliceIterator(additional_gids) catch |err| {

src/turbonss-getent.zig

@@ -120,12 +120,12 @@ fn execute(
 
 fn passwd(stdout: anytype, db: *const DB, keys: []const [*:0]const u8) error{Overflow}!u8 {
     if (keys.len == 0)
-        return passwdAll(stdout, db);
+        return try passwdAll(stdout, db);
     var some_notfound = false;
     const shell_reader = db.shellReader();
     for (keys) |key| {
         const keyZ = mem.span(key);
-        const maybe_packed_user = if (fmt.parseUnsigned(u32, keyZ, 10)) |uid|
+        const maybe_packed_user = try if (fmt.parseUnsigned(u32, keyZ, 10)) |uid|
             db.getUserByUid(uid)
         else |_|
             db.getUserByName(keyZ);
@@ -142,10 +142,10 @@ fn passwd(stdout: anytype, db: *const DB, keys: []const [*:0]const u8) error{Ove
     return if (some_notfound) 2 else 0;
 }
 
-fn passwdAll(stdout: anytype, db: *const DB) u8 {
+fn passwdAll(stdout: anytype, db: *const DB) error{Overflow}!u8 {
     const shell_reader = db.shellReader();
     var it = PackedUser.iterator(db.users, db.header.num_users, shell_reader);
-    while (it.next()) |packed_user| {
+    while (try it.next()) |packed_user| {
         const line = packed_user.toUser(db.shellReader()).toLine();
         stdout.writeAll(line.constSlice()) catch return 3;
     }
@@ -194,7 +194,7 @@ fn printGroup(stdout: anytype, db: *const DB, g: *const PackedGroup) error{Overf
     var line_writer = io.bufferedWriter(stdout);
     var i: usize = 0;
     while (try it.next()) |member_offset| : (i += 1) {
-        const puser = PackedUser.fromBytes(@alignCast(8, db.users[member_offset << 3 ..]));
+        const puser = try PackedUser.fromBytes(@alignCast(8, db.users[member_offset << 3 ..]));
         const name = puser.user.name();
         if (i != 0)
             _ = line_writer.write(",") catch return 3;