X-Git-Url: https://ruderich.org/simon/gitweb/?p=nsscash%2Fnsscash.git;a=blobdiff_plain;f=group.go;h=018a0c32716c665c690c78903b6eccdb5435ac54;hp=b7f7d1b8e8b9c4ce71252570c5d9cc6182b972d9;hb=HEAD;hpb=a015eb7a350cb5e15ac74a14611417641c7d1292

diff --git a/group.go b/group.go
index b7f7d1b..018a0c3 100644
--- a/group.go
+++ b/group.go
@@ -1,6 +1,6 @@
 // Parse /etc/group files and serialize them
 
-// Copyright (C) 2019  Simon Ruderich
+// Copyright (C) 2019-2021  Simon Ruderich
 //
 // This program is free software: you can redistribute it and/or modify
 // it under the terms of the GNU Affero General Public License as published by
@@ -23,6 +23,7 @@ import (
 	"encoding/binary"
 	"fmt"
 	"io"
+	"math"
 	"sort"
 	"strconv"
 	"strings"
@@ -45,7 +46,7 @@ type GroupKey struct {
 	Name    string
 	Passwd  string
 	Gid     uint64
-	Members string
+	Members string // "," separated
 }
 
 func toKey(g Group) GroupKey {
@@ -58,13 +59,24 @@ func toKey(g Group) GroupKey {
 }
 
 // ParseGroups parses a file in the format of /etc/group and returns all
-// entries as Group structs.
+// entries as slice of Group structs.
 func ParseGroups(r io.Reader) ([]Group, error) {
 	var res []Group
 
-	s := bufio.NewScanner(r)
-	for s.Scan() {
-		t := s.Text()
+	s := bufio.NewReader(r)
+	for {
+		t, err := s.ReadString('\n')
+		if err != nil {
+			if err == io.EOF {
+				if t != "" {
+					return nil, fmt.Errorf(
+						"no newline in last line: %q",
+						t)
+				}
+				break
+			}
+			return nil, err
+		}
 
 		x := strings.Split(t, ":")
 		if len(x) != 4 {
@@ -76,6 +88,9 @@ func ParseGroups(r io.Reader) ([]Group, error) {
 			return nil, errors.Wrapf(err, "invalid gid in line %q", t)
 		}
 
+		// ReadString() contains the delimiter
+		x[3] = strings.TrimSuffix(x[3], "\n")
+
 		var members []string
 		// No members must result in empty slice, not slice with the
 		// empty string
@@ -89,15 +104,11 @@ func ParseGroups(r io.Reader) ([]Group, error) {
 			Members: members,
 		})
 	}
-	err := s.Err()
-	if err != nil {
-		return nil, err
-	}
 
 	return res, nil
 }
 
-func SerializeGroup(g Group) []byte {
+func SerializeGroup(g Group) ([]byte, error) {
 	le := binary.LittleEndian
 
 	// Concatenate all (NUL-terminated) strings and store the offsets
@@ -114,10 +125,7 @@ func SerializeGroup(g Group) []byte {
 	offPasswd := uint16(data.Len())
 	data.Write([]byte(g.Passwd))
 	data.WriteByte(0)
-	// Padding to align the following uint16
-	if data.Len()%2 != 0 {
-		data.WriteByte(0)
-	}
+	alignBufferTo(&data, 2) // align the following uint16
 	offMemOff := uint16(data.Len())
 	// Offsets for group members
 	offMem := offMemOff + 2*uint16(len(mems_off))
@@ -128,6 +136,11 @@ func SerializeGroup(g Group) []byte {
 	}
 	// And the group members concatenated as above
 	data.Write(mems.Bytes())
+	// Ensure the offsets can fit the length of this entry
+	if data.Len() > math.MaxUint16 {
+		return nil, fmt.Errorf("group too large to serialize: %v, %v",
+			data.Len(), g)
+	}
 	size := uint16(data.Len())
 
 	var res bytes.Buffer // serialized result
@@ -154,14 +167,9 @@ func SerializeGroup(g Group) []byte {
 	res.Write(data.Bytes())
 	// We must pad each entry so that all uint64 at the beginning of the
 	// struct are 8 byte aligned
-	l := res.Len()
-	if l%8 != 0 {
-		for i := 0; i < 8-l%8; i++ {
-			res.WriteByte(0)
-		}
-	}
+	alignBufferTo(&res, 8)
 
-	return res.Bytes()
+	return res.Bytes(), nil
 }
 
 func SerializeGroups(w io.Writer, grs []Group) error {
@@ -171,7 +179,11 @@ func SerializeGroups(w io.Writer, grs []Group) error {
 	for _, g := range grs {
 		// TODO: warn about duplicate entries
 		offsets[toKey(g)] = uint64(data.Len())
-		data.Write(SerializeGroup(g))
+		x, err := SerializeGroup(g)
+		if err != nil {
+			return err
+		}
+		data.Write(x)
 	}
 
 	// Copy to prevent sorting from modifying the argument
@@ -182,7 +194,7 @@ func SerializeGroups(w io.Writer, grs []Group) error {
 	tmp := make([]byte, 8)
 
 	// Create index "sorted" in input order, used when iterating over all
-	// passwd entries (getgrent_r); keeping the original order makes
+	// group entries (getgrent_r); keeping the original order makes
 	// debugging easier
 	var indexOrig bytes.Buffer
 	for _, g := range grs {