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Add asciisanitizer package and sanitization to http clients (#125)
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,252 @@ | ||
| // Package asciisanitizer implements an ASCII control character sanitizer for UTF-8 strings. | ||
| // It will transform ASCII control codes into equivalent inert characters that are safe for display in the terminal. | ||
| // Without sanitization these ASCII control characters will be interpreted by the terminal. | ||
| // This behaviour can be used maliciously as an attack vector, especially the ASCII control characters \x1B and \x9B. | ||
| package asciisanitizer | ||
|
|
||
| import ( | ||
| "bytes" | ||
| "errors" | ||
| "strings" | ||
| "unicode" | ||
| "unicode/utf8" | ||
|
|
||
| "golang.org/x/text/transform" | ||
| ) | ||
|
|
||
| // Sanitizer implements transform.Transformer interface. | ||
| type Sanitizer struct { | ||
| // JSON tells the Sanitizer to replace strings that will be transformed | ||
| // into control characters when the string is marshaled to JSON. Set to | ||
| // true if the string being sanitized represents JSON formatted data. | ||
| JSON bool | ||
| addEscape bool | ||
| } | ||
|
|
||
| // Transform uses a sliding window algorithm to detect C0 and C1 control characters as they are read and replaces | ||
| // them with equivalent inert characters. Bytes that are not part of a control character are not modified. | ||
| func (t *Sanitizer) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) { | ||
| transfer := func(write, read []byte) error { | ||
| readLength := len(read) | ||
| writeLength := len(write) | ||
| if writeLength > len(dst) { | ||
| return transform.ErrShortDst | ||
| } | ||
| copy(dst, write) | ||
| nDst += writeLength | ||
| dst = dst[writeLength:] | ||
| nSrc += readLength | ||
| src = src[readLength:] | ||
| return nil | ||
| } | ||
|
|
||
| for len(src) > 0 { | ||
| // When sanitizing JSON strings make sure that we have 6 bytes if available. | ||
| if t.JSON && len(src) < 6 && !atEOF { | ||
| err = transform.ErrShortSrc | ||
| return | ||
| } | ||
| r, size := utf8.DecodeRune(src) | ||
| if r == utf8.RuneError { | ||
| if !atEOF { | ||
| err = transform.ErrShortSrc | ||
| return | ||
| } else { | ||
| err = errors.New("invalid UTF-8 string") | ||
| return | ||
| } | ||
| } | ||
| // Replace C0 and C1 control characters. | ||
| if unicode.IsControl(r) { | ||
| if repl, found := mapControlToCaret(r); found { | ||
| err = transfer(repl, src[:size]) | ||
| if err != nil { | ||
| return | ||
| } | ||
| continue | ||
| } | ||
| } | ||
| // Replace JSON C0 and C1 control characters. | ||
| if t.JSON && len(src) >= 6 { | ||
| if repl, found := mapJSONControlToCaret(src[:6]); found { | ||
| if t.addEscape { | ||
| // Add an escape character when necessary to prevent creating | ||
| // invalid JSON with our replacements. | ||
| repl = append([]byte{'\\'}, repl...) | ||
| } | ||
| err = transfer(repl, src[:6]) | ||
| if err != nil { | ||
| return | ||
| } | ||
| continue | ||
| } | ||
| } | ||
| err = transfer(src[:size], src[:size]) | ||
| if err != nil { | ||
| return | ||
| } | ||
| if t.JSON { | ||
| if r == '\\' { | ||
| t.addEscape = !t.addEscape | ||
| } else { | ||
| t.addEscape = false | ||
| } | ||
| } | ||
| } | ||
| return | ||
| } | ||
|
|
||
| // Reset resets the state and allows the Sanitizer to be reused. | ||
| func (t *Sanitizer) Reset() { | ||
| t.addEscape = false | ||
| } | ||
|
|
||
| // mapControlToCaret maps C0 and C1 control characters to their caret notation. | ||
| func mapControlToCaret(r rune) ([]byte, bool) { | ||
| //\t (09), \n (10), \v (11), \r (13) are safe C0 characters and are not sanitized. | ||
| m := map[rune]string{ | ||
| 0: `^@`, | ||
| 1: `^A`, | ||
| 2: `^B`, | ||
| 3: `^C`, | ||
| 4: `^D`, | ||
| 5: `^E`, | ||
| 6: `^F`, | ||
| 7: `^G`, | ||
| 8: `^H`, | ||
| 12: `^L`, | ||
| 14: `^N`, | ||
| 15: `^O`, | ||
| 16: `^P`, | ||
| 17: `^Q`, | ||
| 18: `^R`, | ||
| 19: `^S`, | ||
| 20: `^T`, | ||
| 21: `^U`, | ||
| 22: `^V`, | ||
| 23: `^W`, | ||
| 24: `^X`, | ||
| 25: `^Y`, | ||
| 26: `^Z`, | ||
| 27: `^[`, | ||
| 28: `^\\`, | ||
| 29: `^]`, | ||
| 30: `^^`, | ||
| 31: `^_`, | ||
| 128: `^@`, | ||
| 129: `^A`, | ||
| 130: `^B`, | ||
| 131: `^C`, | ||
| 132: `^D`, | ||
| 133: `^E`, | ||
| 134: `^F`, | ||
| 135: `^G`, | ||
| 136: `^H`, | ||
| 137: `^I`, | ||
| 138: `^J`, | ||
| 139: `^K`, | ||
| 140: `^L`, | ||
| 141: `^M`, | ||
| 142: `^N`, | ||
| 143: `^O`, | ||
| 144: `^P`, | ||
| 145: `^Q`, | ||
| 146: `^R`, | ||
| 147: `^S`, | ||
| 148: `^T`, | ||
| 149: `^U`, | ||
| 150: `^V`, | ||
| 151: `^W`, | ||
| 152: `^X`, | ||
| 153: `^Y`, | ||
| 154: `^Z`, | ||
| 155: `^[`, | ||
| 156: `^\\`, | ||
| 157: `^]`, | ||
| 158: `^^`, | ||
| 159: `^_`, | ||
| } | ||
| if c, ok := m[r]; ok { | ||
| return []byte(c), true | ||
| } | ||
| return nil, false | ||
| } | ||
|
|
||
| // mapJSONControlToCaret maps JSON C0 and C1 control characters to their caret notation. | ||
| // JSON control characters are six byte strings, representing a unicode code point, | ||
| // ranging from \u0000 to \u001F and \u0080 to \u009F. | ||
| func mapJSONControlToCaret(b []byte) ([]byte, bool) { | ||
| if len(b) != 6 { | ||
| return nil, false | ||
| } | ||
| if !bytes.HasPrefix(b, []byte(`\u00`)) { | ||
| return nil, false | ||
| } | ||
| //\t (\u0009), \n (\u000a), \v (\u000b), \r (\u000d) are safe C0 characters and are not sanitized. | ||
| m := map[string]string{ | ||
| `\u0000`: `^@`, | ||
| `\u0001`: `^A`, | ||
| `\u0002`: `^B`, | ||
| `\u0003`: `^C`, | ||
| `\u0004`: `^D`, | ||
| `\u0005`: `^E`, | ||
| `\u0006`: `^F`, | ||
| `\u0007`: `^G`, | ||
| `\u0008`: `^H`, | ||
| `\u000c`: `^L`, | ||
| `\u000e`: `^N`, | ||
| `\u000f`: `^O`, | ||
| `\u0010`: `^P`, | ||
| `\u0011`: `^Q`, | ||
| `\u0012`: `^R`, | ||
| `\u0013`: `^S`, | ||
| `\u0014`: `^T`, | ||
| `\u0015`: `^U`, | ||
| `\u0016`: `^V`, | ||
| `\u0017`: `^W`, | ||
| `\u0018`: `^X`, | ||
| `\u0019`: `^Y`, | ||
| `\u001a`: `^Z`, | ||
| `\u001b`: `^[`, | ||
| `\u001c`: `^\\`, | ||
| `\u001d`: `^]`, | ||
| `\u001e`: `^^`, | ||
| `\u001f`: `^_`, | ||
| `\u0080`: `^@`, | ||
| `\u0081`: `^A`, | ||
| `\u0082`: `^B`, | ||
| `\u0083`: `^C`, | ||
| `\u0084`: `^D`, | ||
| `\u0085`: `^E`, | ||
| `\u0086`: `^F`, | ||
| `\u0087`: `^G`, | ||
| `\u0088`: `^H`, | ||
| `\u0089`: `^I`, | ||
| `\u008a`: `^J`, | ||
| `\u008b`: `^K`, | ||
| `\u008c`: `^L`, | ||
| `\u008d`: `^M`, | ||
| `\u008e`: `^N`, | ||
| `\u008f`: `^O`, | ||
| `\u0090`: `^P`, | ||
| `\u0091`: `^Q`, | ||
| `\u0092`: `^R`, | ||
| `\u0093`: `^S`, | ||
| `\u0094`: `^T`, | ||
| `\u0095`: `^U`, | ||
| `\u0096`: `^V`, | ||
| `\u0097`: `^W`, | ||
| `\u0098`: `^X`, | ||
| `\u0099`: `^Y`, | ||
| `\u009a`: `^Z`, | ||
| `\u009b`: `^[`, | ||
| `\u009c`: `^\\`, | ||
| `\u009d`: `^]`, | ||
| `\u009e`: `^^`, | ||
| `\u009f`: `^_`, | ||
| } | ||
| if c, ok := m[strings.ToLower(string(b))]; ok { | ||
| return []byte(c), true | ||
| } | ||
| return nil, false | ||
| } |
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