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unpad add the format valid #1

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e92b264
unpad add the format valid
edieruby Oct 22, 2020
bbeee06
pad lenth valid
edieruby Oct 23, 2020
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19 changes: 17 additions & 2 deletions pkcs7.go
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Original file line number Diff line number Diff line change
Expand Up @@ -14,11 +14,26 @@ func Pad(buf []byte, size int) ([]byte, error) {
}

func Unpad(padded []byte, size int) ([]byte, error) {
if len(padded)%size != 0 {
paddedLen := len(padded)

if paddedLen%size != 0 {
return nil, errors.New("pkcs7: Padded value wasn't in correct size.")
}

bufLen := len(padded) - int(padded[len(padded)-1])
lastPad := padded[paddedLen-1]
padLen := int(lastPad)

if padLen > size {
return nil, errors.New("pkcs7: Padded value larger than size.")
}

for i := paddedLen - padLen; i < paddedLen; i++ {
if padded[i] != lastPad {
return nil, errors.New("pkcs7: Padded value wasn't in correct format.")
}
}

bufLen := paddedLen - padLen
buf := make([]byte, bufLen)
copy(buf, padded[:bufLen])
return buf, nil
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16 changes: 16 additions & 0 deletions pkcs7_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,22 @@ func TestPkcs7(t *testing.T) {
}
})

t.Run("Unpads error length", func(t *testing.T) {
_, err := Unpad([]byte("123456789012345678901234567890123456789012345678901234567890\x11\x11\x11\x11"), BLOCK_SIZE)
if err == nil {
panic(fmt.Sprint("process error"))
}

})

t.Run("Unpads error format", func(t *testing.T) {
_, err := Unpad([]byte("12345678901\x06\x06\x06\x06\x06"), BLOCK_SIZE)
if err == nil {
panic(fmt.Sprint("process error"))
}

})

t.Run("Handles long", func(t *testing.T) {
longStr := []byte("123456789012345678901234567890123456789012345678901234567890")
padded, _ := Pad(longStr, BLOCK_SIZE)
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