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Extract padding utility
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Emman
parent
cfe9842cc0
commit
d389da6bcb
15
padding/pads.go
Normal file
15
padding/pads.go
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@ -0,0 +1,15 @@
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package padding
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// Padding interface represents a padding scheme
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type Padding interface {
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BlockSize() int
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Pad(src []byte) []byte
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Unpad(src []byte) ([]byte, error)
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}
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func NewPKCS7Padding(blockSize uint) Padding {
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if blockSize == 0 || blockSize > 255 {
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panic("padding: invalid block size")
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}
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return pkcs7Padding(blockSize)
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}
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44
padding/pkcs7.go
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44
padding/pkcs7.go
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@ -0,0 +1,44 @@
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// https://datatracker.ietf.org/doc/html/rfc5652#section-6.3
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package padding
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import (
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goSubtle "crypto/subtle"
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"errors"
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"github.com/emmansun/gmsm/internal/subtle"
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)
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type pkcs7Padding uint
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func (pad pkcs7Padding) BlockSize() int {
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return int(pad)
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}
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func (pad pkcs7Padding) Pad(src []byte) []byte {
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overhead := pad.BlockSize() - len(src)%pad.BlockSize()
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ret, out := subtle.SliceForAppend(src, overhead)
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for i := 0; i < overhead; i++ {
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out[i] = byte(overhead)
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}
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return ret
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}
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func (pad pkcs7Padding) Unpad(src []byte) ([]byte, error) {
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if len(src)%pad.BlockSize() != 0 {
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return nil, errors.New("pkcs7: invalid src size")
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}
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overhead := src[len(src)-1]
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if overhead == 0 || int(overhead) > pad.BlockSize() {
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return nil, errors.New("pkcs7: invalid padding byte/length")
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}
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tag := make([]byte, pad.BlockSize())
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copy(tag, src[len(src)-pad.BlockSize():])
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for i := pad.BlockSize() - int(overhead); i < pad.BlockSize(); i++ {
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tag[i] = byte(overhead)
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}
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if goSubtle.ConstantTimeCompare(tag, src[len(src)-pad.BlockSize():]) != 1 {
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return nil, errors.New("pkcs7: inconsistent padding bytes")
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}
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return src[:len(src)-int(overhead)], nil
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}
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89
padding/pkcs7_test.go
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89
padding/pkcs7_test.go
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@ -0,0 +1,89 @@
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// https://datatracker.ietf.org/doc/html/rfc5652#section-6.3
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package padding
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import (
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"reflect"
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"testing"
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)
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func Test_pkcs7Padding_Pad(t *testing.T) {
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pad := NewPKCS7Padding(16)
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tests := []struct {
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name string
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src []byte
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want []byte
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}{
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// TODO: Add test cases.
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{"16 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16}},
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{"15 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 1}},
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{"14 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 2, 2}},
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{"13 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 3, 3, 3}},
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{"12 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 4, 4, 4, 4}},
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{"11 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 5, 5, 5, 5, 5}},
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{"10 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 6, 6, 6, 6, 6, 6}},
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{"9 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7, 8}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 7, 7, 7, 7, 7, 7, 7}},
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{"8 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 8, 8, 8, 8, 8, 8, 8}},
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{"7 bytes", []byte{0, 1, 2, 3, 4, 5, 6}, []byte{0, 1, 2, 3, 4, 5, 6, 9, 9, 9, 9, 9, 9, 9, 9, 9}},
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{"6 bytes", []byte{0, 1, 2, 3, 4, 5}, []byte{0, 1, 2, 3, 4, 5, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10}},
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{"5 bytes", []byte{0, 1, 2, 3, 4}, []byte{0, 1, 2, 3, 4, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11}},
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{"4 bytes", []byte{0, 1, 2, 3}, []byte{0, 1, 2, 3, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12}},
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{"3 bytes", []byte{0, 1, 2}, []byte{0, 1, 2, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13}},
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{"2 bytes", []byte{0, 1}, []byte{0, 1, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14}},
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{"1 bytes", []byte{0}, []byte{0, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15}},
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}
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for _, tt := range tests {
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t.Run(tt.name, func(t *testing.T) {
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if got := pad.Pad(tt.src); !reflect.DeepEqual(got, tt.want) {
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t.Errorf("pkcs7Padding.Pad() = %v, want %v", got, tt.want)
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}
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})
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}
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}
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func Test_pkcs7Padding_Unpad(t *testing.T) {
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pad := NewPKCS7Padding(16)
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type args struct {
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src []byte
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}
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tests := []struct {
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name string
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want []byte
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src []byte
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wantErr bool
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}{
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// TODO: Add test cases.
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{"16 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16}, false},
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{"15 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 1}, false},
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{"14 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 2, 2}, false},
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{"13 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 3, 3, 3}, false},
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{"12 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 4, 4, 4, 4}, false},
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{"11 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 5, 5, 5, 5, 5}, false},
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{"10 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 6, 6, 6, 6, 6, 6}, false},
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{"9 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7, 8}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 7, 7, 7, 7, 7, 7, 7}, false},
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{"8 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 8, 8, 8, 8, 8, 8, 8}, false},
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{"7 bytes", []byte{0, 1, 2, 3, 4, 5, 6}, []byte{0, 1, 2, 3, 4, 5, 6, 9, 9, 9, 9, 9, 9, 9, 9, 9}, false},
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{"6 bytes", []byte{0, 1, 2, 3, 4, 5}, []byte{0, 1, 2, 3, 4, 5, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10}, false},
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{"5 bytes", []byte{0, 1, 2, 3, 4}, []byte{0, 1, 2, 3, 4, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11}, false},
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{"4 bytes", []byte{0, 1, 2, 3}, []byte{0, 1, 2, 3, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12}, false},
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{"3 bytes", []byte{0, 1, 2}, []byte{0, 1, 2, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13}, false},
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{"2 bytes", []byte{0, 1}, []byte{0, 1, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14}, false},
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{"1 bytes", []byte{0}, []byte{0, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15}, false},
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{"invalid src length", nil, []byte{0, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15}, true},
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{"invalid padding byte", nil, []byte{0, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 17}, true},
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{"inconsistent padding bytes", nil, []byte{0, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 14, 15}, true},
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}
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for _, tt := range tests {
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t.Run(tt.name, func(t *testing.T) {
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got, err := pad.Unpad(tt.src)
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if (err != nil) != tt.wantErr {
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t.Errorf("pkcs7Padding.Unpad() error = %v, wantErr %v", err, tt.wantErr)
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return
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}
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if !reflect.DeepEqual(got, tt.want) {
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t.Errorf("pkcs7Padding.Unpad() = %v, want %v", got, tt.want)
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}
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})
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}
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}
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@ -4,38 +4,13 @@ import (
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"bytes"
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"crypto/cipher"
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"encoding/hex"
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"errors"
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"fmt"
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"testing"
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"github.com/emmansun/gmsm/padding"
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"github.com/emmansun/gmsm/sm4"
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)
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func paddingPKCS7(buf []byte, blockSize int) []byte {
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bufLen := len(buf)
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padLen := blockSize - bufLen%blockSize
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padded := make([]byte, bufLen+padLen)
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copy(padded, buf)
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for i := 0; i < padLen; i++ {
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padded[bufLen+i] = byte(padLen)
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}
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return padded
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}
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func unpaddingPKCS7(padded []byte, size int) ([]byte, error) {
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if len(padded)%size != 0 {
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return nil, errors.New("pkcs7: Padded value wasn't in correct size")
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}
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paddedByte := int(padded[len(padded)-1])
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if (paddedByte > size) || (paddedByte < 1) {
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return nil, fmt.Errorf("Invalid decrypted text, no padding")
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}
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bufLen := len(padded) - paddedByte
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buf := make([]byte, bufLen)
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copy(buf, padded[:bufLen])
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return buf, nil
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}
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var cbcSM4Tests = []struct {
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name string
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key []byte
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@ -143,6 +118,7 @@ var cbcSM4Tests = []struct {
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}
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func TestCBCEncrypterSM4(t *testing.T) {
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pad := padding.NewPKCS7Padding(sm4.BlockSize)
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for _, test := range cbcSM4Tests {
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c, err := sm4.NewCipher(test.key)
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if err != nil {
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@ -152,7 +128,7 @@ func TestCBCEncrypterSM4(t *testing.T) {
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encrypter := cipher.NewCBCEncrypter(c, test.iv)
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plainText := paddingPKCS7(test.in, sm4.BlockSize)
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plainText := pad.Pad(test.in)
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data := make([]byte, len(plainText))
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copy(data, plainText)
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@ -170,6 +146,7 @@ func TestCBCEncrypterSM4(t *testing.T) {
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}
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func TestCBCDecrypterSM4(t *testing.T) {
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pad := padding.NewPKCS7Padding(sm4.BlockSize)
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for _, test := range cbcSM4Tests {
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c, err := sm4.NewCipher(test.key)
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if err != nil {
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@ -183,7 +160,7 @@ func TestCBCDecrypterSM4(t *testing.T) {
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copy(data, test.out)
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decrypter.CryptBlocks(data, data)
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data, err = unpaddingPKCS7(data, sm4.BlockSize)
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data, err = pad.Unpad(data)
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if err != nil {
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t.Fatal(err)
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}
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