crypto: Escape JSON text (#10794)

Escape the JSON keys+values from the context.

We do not add the HTML escapes, since that is an extra escape level not mandatory for JSON.

cmd/crypto/json.go

@@ -0,0 +1,200 @@
+// MinIO Cloud Storage, (C) 2020 MinIO, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package crypto
+
+import (
+	"bytes"
+	"unicode/utf8"
+)
+
+// Adapted from Go stdlib.
+
+var hexTable = "0123456789abcdef"
+
+// EscapeStringJSON will escape a string for JSON and write it to dst.
+func EscapeStringJSON(dst *bytes.Buffer, s string) {
+	start := 0
+	for i := 0; i < len(s); {
+		if b := s[i]; b < utf8.RuneSelf {
+			if htmlSafeSet[b] {
+				i++
+				continue
+			}
+			if start < i {
+				dst.WriteString(s[start:i])
+			}
+			dst.WriteByte('\\')
+			switch b {
+			case '\\', '"':
+				dst.WriteByte(b)
+			case '\n':
+				dst.WriteByte('n')
+			case '\r':
+				dst.WriteByte('r')
+			case '\t':
+				dst.WriteByte('t')
+			default:
+				// This encodes bytes < 0x20 except for \t, \n and \r.
+				// If escapeHTML is set, it also escapes <, >, and &
+				// because they can lead to security holes when
+				// user-controlled strings are rendered into JSON
+				// and served to some browsers.
+				dst.WriteString(`u00`)
+				dst.WriteByte(hexTable[b>>4])
+				dst.WriteByte(hexTable[b&0xF])
+			}
+			i++
+			start = i
+			continue
+		}
+		c, size := utf8.DecodeRuneInString(s[i:])
+		if c == utf8.RuneError && size == 1 {
+			if start < i {
+				dst.WriteString(s[start:i])
+			}
+			dst.WriteString(`\ufffd`)
+			i += size
+			start = i
+			continue
+		}
+		// U+2028 is LINE SEPARATOR.
+		// U+2029 is PARAGRAPH SEPARATOR.
+		// They are both technically valid characters in JSON strings,
+		// but don't work in JSONP, which has to be evaluated as JavaScript,
+		// and can lead to security holes there. It is valid JSON to
+		// escape them, so we do so unconditionally.
+		// See http://timelessrepo.com/json-isnt-a-javascript-subset for discussion.
+		if c == '\u2028' || c == '\u2029' {
+			if start < i {
+				dst.WriteString(s[start:i])
+			}
+			dst.WriteString(`\u202`)
+			dst.WriteByte(hexTable[c&0xF])
+			i += size
+			start = i
+			continue
+		}
+		i += size
+	}
+	if start < len(s) {
+		dst.WriteString(s[start:])
+	}
+}
+
+// htmlSafeSet holds the value true if the ASCII character with the given
+// array position can be safely represented inside a JSON string, embedded
+// inside of HTML <script> tags, without any additional escaping.
+//
+// All values are true except for the ASCII control characters (0-31), the
+// double quote ("), the backslash character ("\"), HTML opening and closing
+// tags ("<" and ">"), and the ampersand ("&").
+var htmlSafeSet = [utf8.RuneSelf]bool{
+	' ':      true,
+	'!':      true,
+	'"':      false,
+	'#':      true,
+	'$':      true,
+	'%':      true,
+	'&':      false,
+	'\'':     true,
+	'(':      true,
+	')':      true,
+	'*':      true,
+	'+':      true,
+	',':      true,
+	'-':      true,
+	'.':      true,
+	'/':      true,
+	'0':      true,
+	'1':      true,
+	'2':      true,
+	'3':      true,
+	'4':      true,
+	'5':      true,
+	'6':      true,
+	'7':      true,
+	'8':      true,
+	'9':      true,
+	':':      true,
+	';':      true,
+	'<':      false,
+	'=':      true,
+	'>':      false,
+	'?':      true,
+	'@':      true,
+	'A':      true,
+	'B':      true,
+	'C':      true,
+	'D':      true,
+	'E':      true,
+	'F':      true,
+	'G':      true,
+	'H':      true,
+	'I':      true,
+	'J':      true,
+	'K':      true,
+	'L':      true,
+	'M':      true,
+	'N':      true,
+	'O':      true,
+	'P':      true,
+	'Q':      true,
+	'R':      true,
+	'S':      true,
+	'T':      true,
+	'U':      true,
+	'V':      true,
+	'W':      true,
+	'X':      true,
+	'Y':      true,
+	'Z':      true,
+	'[':      true,
+	'\\':     false,
+	']':      true,
+	'^':      true,
+	'_':      true,
+	'`':      true,
+	'a':      true,
+	'b':      true,
+	'c':      true,
+	'd':      true,
+	'e':      true,
+	'f':      true,
+	'g':      true,
+	'h':      true,
+	'i':      true,
+	'j':      true,
+	'k':      true,
+	'l':      true,
+	'm':      true,
+	'n':      true,
+	'o':      true,
+	'p':      true,
+	'q':      true,
+	'r':      true,
+	's':      true,
+	't':      true,
+	'u':      true,
+	'v':      true,
+	'w':      true,
+	'x':      true,
+	'y':      true,
+	'z':      true,
+	'{':      true,
+	'|':      true,
+	'}':      true,
+	'~':      true,
+	'\u007f': true,
+}

cmd/crypto/kms.go

@@ -39,6 +39,7 @@ type Context map[string]string
 //
 // WriteTo sorts the context keys and writes the sorted
 // key-value pairs as canonical JSON object to w.
+// Sort order is based on the un-escaped keys.
 //
 // Note that neither keys nor values are escaped for JSON.
 func (c Context) WriteTo(w io.Writer) (n int64, err error) {
@@ -48,13 +49,19 @@ func (c Context) WriteTo(w io.Writer) (n int64, err error) {
 	}
 	sort.Sort(sortedKeys)
 
+	escape := func(s string) string {
+		buf := bytes.NewBuffer(make([]byte, 0, len(s)))
+		EscapeStringJSON(buf, s)
+		return buf.String()
+	}
+
 	nn, err := io.WriteString(w, "{")
 	if err != nil {
 		return n + int64(nn), err
 	}
 	n += int64(nn)
 	for i, k := range sortedKeys {
-		s := fmt.Sprintf("\"%s\":\"%s\",", k, c[k])
+		s := fmt.Sprintf("\"%s\":\"%s\",", escape(k), escape(c[k]))
 		if i == len(sortedKeys)-1 {
 			s = s[:len(s)-1] // remove last ','
 		}
@@ -73,6 +80,7 @@ func (c Context) WriteTo(w io.Writer) (n int64, err error) {
 //
 // AppendTo sorts the context keys and writes the sorted
 // key-value pairs as canonical JSON object to w.
+// Sort order is based on the un-escaped keys.
 //
 // Note that neither keys nor values are escaped for JSON.
 func (c Context) AppendTo(dst []byte) (output []byte) {
@@ -87,9 +95,9 @@ func (c Context) AppendTo(dst []byte) (output []byte) {
 	if len(c) == 1 {
 		for k, v := range c {
 			out.WriteString(`{"`)
-			out.WriteString(k)
+			EscapeStringJSON(out, k)
 			out.WriteString(`":"`)
-			out.WriteString(v)
+			EscapeStringJSON(out, v)
 			out.WriteString(`"}`)
 		}
 		return out.Bytes()
@@ -104,9 +112,9 @@ func (c Context) AppendTo(dst []byte) (output []byte) {
 	out.WriteByte('{')
 	for i, k := range sortedKeys {
 		out.WriteByte('"')
-		out.WriteString(k)
+		EscapeStringJSON(out, k)
 		out.WriteString(`":"`)
-		out.WriteString(c[k])
+		EscapeStringJSON(out, c[k])
 		out.WriteByte('"')
 		if i < len(sortedKeys)-1 {
 			out.WriteByte(',')

cmd/crypto/kms_test.go

@@ -65,11 +65,15 @@ var contextWriteToTests = []struct {
 	Context      Context
 	ExpectedJSON string
 }{
-	{Context: Context{}, ExpectedJSON: "{}"},                                                    // 0
+	0: {Context: Context{}, ExpectedJSON: "{}"},
-	{Context: Context{"a": "b"}, ExpectedJSON: `{"a":"b"}`},                                     // 1
+	1: {Context: Context{"a": "b"}, ExpectedJSON: `{"a":"b"}`},
-	{Context: Context{"a": "b", "c": "d"}, ExpectedJSON: `{"a":"b","c":"d"}`},                   // 2
+	2: {Context: Context{"a": "b", "c": "d"}, ExpectedJSON: `{"a":"b","c":"d"}`},
-	{Context: Context{"c": "d", "a": "b"}, ExpectedJSON: `{"a":"b","c":"d"}`},                   // 3
+	3: {Context: Context{"c": "d", "a": "b"}, ExpectedJSON: `{"a":"b","c":"d"}`},
-	{Context: Context{"0": "1", "-": "2", ".": "#"}, ExpectedJSON: `{"-":"2",".":"#","0":"1"}`}, // 4
+	4: {Context: Context{"0": "1", "-": "2", ".": "#"}, ExpectedJSON: `{"-":"2",".":"#","0":"1"}`},
+	// rfc 8259 escapes
+	5: {Context: Context{"0": "1", "key\\": "val\tue\r\n", "\"": "\""}, ExpectedJSON: `{"\"":"\"","0":"1","key\\":"val\tue\r\n"}`},
+	// html sensitive escapes
+	6: {Context: Context{"a": "<>&"}, ExpectedJSON: `{"a":"\u003c\u003e\u0026"}`},
 }
 
 func TestContextWriteTo(t *testing.T) {
@@ -101,7 +105,7 @@ func TestContextAppendTo(t *testing.T) {
 }
 
 func BenchmarkContext_AppendTo(b *testing.B) {
-	tests := []Context{{}, {"bucket": "warp-benchmark-bucket"}, {"0": "1", "-": "2", ".": "#"}, {"34trg": "dfioutr89", "ikjfdghkjf": "jkedfhgfjkhg", "sdfhsdjkh": "if88889", "asddsirfh804": "kjfdshgdfuhgfg78-45604586#$%"}}
+	tests := []Context{{}, {"bucket": "warp-benchmark-bucket"}, {"0": "1", "-": "2", ".": "#"}, {"34trg": "dfioutr89", "ikjfdghkjf": "jkedfhgfjkhg", "sdfhsdjkh": "if88889", "asddsirfh804": "kjfdshgdfuhgfg78-45604586#$%<>&"}}
 	for _, test := range tests {
 		b.Run(fmt.Sprintf("%d-elems", len(test)), func(b *testing.B) {
 			dst := make([]byte, 0, 1024)