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padding: ISO/IEC 9797 method 2

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Sun Yimin 2023-08-08 17:35:16 +08:00 committed by GitHub
parent 33d9dc7db7
commit 6478a408e6
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3 changed files with 138 additions and 0 deletions
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49
padding/iso9797_m2.go Normal file
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@ -0,0 +1,49 @@
package padding
import (
"errors"
"github.com/emmansun/gmsm/internal/alias"
)
// Add a single bit with value 1 to the end of the data.
// Then if necessary add bits with value 0 to the end of the data until the padded data is a multiple of n.
//
// https://en.wikipedia.org/wiki/ISO/IEC_9797-1
// also GB/T 17964-2021 C.2 Padding method 2
type iso9797M2Padding uint
func (pad iso9797M2Padding) BlockSize() int {
return int(pad)
}
func (pad iso9797M2Padding) Pad(src []byte) []byte {
overhead := pad.BlockSize() - len(src)%pad.BlockSize()
ret, out := alias.SliceForAppend(src, overhead)
out[0] = 0x80
for i := 1; i < overhead; i++ {
out[i] = 0
}
return ret
}
// Unpad decrypted plaintext, non-constant-time
func (pad iso9797M2Padding) Unpad(src []byte) ([]byte, error) {
srcLen := len(src)
if srcLen == 0 || srcLen%pad.BlockSize() != 0 {
return nil, errors.New("iso/iec 9797-1 method 2: src length is not multiple of block size")
}
padStart := -1
for i, b := range src[srcLen-pad.BlockSize() : srcLen] {
if b == 0x80 {
padStart = i
} else if b != 0 && padStart >=0 {
padStart = -1
}
}
if padStart >= 0 {
return src[:srcLen-pad.BlockSize()+padStart], nil
}
return src, nil
}

82
padding/iso9797_m2_test.go Normal file
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@ -0,0 +1,82 @@
package padding
import (
"reflect"
"testing"
)
func Test_iso9797M2Padding_Pad(t *testing.T) {
iso9797 := NewISO9797M2Padding(16)
tests := []struct {
name string
src []byte
want []byte
}{
{"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, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}},
{"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, 0x80}},
{"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, 0x80, 0}},
{"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, 0x80, 0, 0}},
{"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, 0x80, 0, 0, 0}},
{"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, 0x80, 0, 0, 0, 0}},
{"10 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0x80, 0, 0, 0, 0, 0}},
{"9 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7, 8}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 0x80, 0, 0, 0, 0, 0, 0}},
{"8 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 0x80, 0, 0, 0, 0, 0, 0, 0}},
{"7 bytes", []byte{0, 1, 2, 3, 4, 5, 6}, []byte{0, 1, 2, 3, 4, 5, 6, 0x80, 0, 0, 0, 0, 0, 0, 0, 0}},
{"6 bytes", []byte{0, 1, 2, 3, 4, 5}, []byte{0, 1, 2, 3, 4, 5, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0}},
{"5 bytes", []byte{0, 1, 2, 3, 4}, []byte{0, 1, 2, 3, 4, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}},
{"4 bytes", []byte{0, 1, 2, 3}, []byte{0, 1, 2, 3, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}},
{"3 bytes", []byte{0, 1, 2}, []byte{0, 1, 2, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}},
{"2 bytes", []byte{0, 1}, []byte{0, 1, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}},
{"1 bytes", []byte{0}, []byte{0, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
if got := iso9797.Pad(tt.src); !reflect.DeepEqual(got, tt.want) {
t.Errorf("iso9797M2Padding.Pad() = %v, want %v", got, tt.want)
}
})
}
}
func Test_iso9797M2Padding_Unpad(t *testing.T) {
iso9797 := NewISO9797M2Padding(16)
tests := []struct {
name string
want []byte
src []byte
wantErr bool
}{
{"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, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, false},
{"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, 0x80}, false},
{"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, 0x80, 0}, false},
{"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, 0x80, 0, 0}, false},
{"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, 0x80, 0, 0, 0}, false},
{"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, 0x80, 0, 0, 0, 0}, false},
{"10 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0x80, 0, 0, 0, 0, 0}, false},
{"9 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7, 8}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 0x80, 0, 0, 0, 0, 0, 0}, false},
{"8 bytes", []byte{0, 1, 2, 3, 4, 5, 6, 7}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 0x80, 0, 0, 0, 0, 0, 0, 0}, false},
{"7 bytes", []byte{0, 1, 2, 3, 4, 5, 6}, []byte{0, 1, 2, 3, 4, 5, 6, 0x80, 0, 0, 0, 0, 0, 0, 0, 0}, false},
{"6 bytes", []byte{0, 1, 2, 3, 4, 5}, []byte{0, 1, 2, 3, 4, 5, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0}, false},
{"5 bytes", []byte{0, 1, 2, 3, 4}, []byte{0, 1, 2, 3, 4, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, false},
{"4 bytes", []byte{0, 1, 2, 3}, []byte{0, 1, 2, 3, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, false},
{"3 bytes", []byte{0, 1, 2}, []byte{0, 1, 2, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, false},
{"2 bytes", []byte{0, 1}, []byte{0, 1, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, false},
{"1 bytes", []byte{0}, []byte{0, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, false},
{"1 bytes with tag", []byte{0x80}, []byte{0x80, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, false},
{"3 bytes with tag", []byte{0x80, 0, 0x80}, []byte{0x80, 0, 0x80, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, false},
{"19 bytes with tag", []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 0x80, 0, 0x80}, []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 0x80, 0, 0x80, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, false},
{"invalid src length", nil, []byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, true},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
got, err := iso9797.Unpad(tt.src)
if (err != nil) != tt.wantErr {
t.Errorf("case %v: iso9797M2Padding.Unpad() error = %v, wantErr %v", tt.name, err, tt.wantErr)
return
}
if !reflect.DeepEqual(got, tt.want) {
t.Errorf("case %v: iso9797M2Padding.Unpad() = %v, want %v", tt.name, got, tt.want)
}
})
}
}

7
padding/schemes.go
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@ -21,3 +21,10 @@ func NewANSIX923Padding(blockSize uint) Padding {
} }
return ansiX923Padding(blockSize) return ansiX923Padding(blockSize)
} }
func NewISO9797M2Padding(blockSize uint) Padding {
if blockSize == 0 || blockSize > 255 {
panic("padding: invalid block size")
}
return iso9797M2Padding(blockSize)
}