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Decode path-encoded URL components
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This change causes pct-encoded characters passed via path parameters to
be correctly decoded as described in google.api.http (see: path template
syntax) and as implemented in grpc-http-json-transcoding.

A new configuration option is introduced, `WithDecodeMode()`, which
understands several modes. Backwards compatibility is maintained, with
the hope of UnescapingModeAllExceptReserved becoming the default mode in
V3.
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@v3n
v3n committed Sep 9, 2021
1 parent f60dfa5 commit 4ba1115
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Showing 2 changed files with 192 additions and 7 deletions.
54 changes: 52 additions & 2 deletions runtime/mux.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,31 @@ import (
"google.golang.org/protobuf/proto"
)

// UnescapingMode defines the behavior of grpc-gateway for URL escaping.
type UnescapingMode int

const (
// UnescapingModeLegacy is the default V2 behavior, which escapes the entire
// path string before doing any routing.
UnescapingModeLegacy UnescapingMode = iota

// EscapingTypeExceptReserved unescapes all path parameters except RFC 6570
// reserved characters.
UnescapingModeAllExceptReserved

// EscapingTypeExceptSlash unescapes URL path parameters except path
// seperators, which will be left as "%2F".
UnescapingModeAllExceptSlash

// URL path parameters will be fully decoded.
UnescapingModeAllCharacters

// UnescapingModeDefault is the default escaping type.
// TODO(v3): default this to UnescapingModeAllExceptReserved per grpc-httpjson-transcoding's
// reference implementation
UnescapingModeDefault = UnescapingModeLegacy
)

// A HandlerFunc handles a specific pair of path pattern and HTTP method.
type HandlerFunc func(w http.ResponseWriter, r *http.Request, pathParams map[string]string)

Expand All @@ -31,6 +56,7 @@ type ServeMux struct {
streamErrorHandler StreamErrorHandlerFunc
routingErrorHandler RoutingErrorHandlerFunc
disablePathLengthFallback bool
unescapingMode UnescapingMode
}

// ServeMuxOption is an option that can be given to a ServeMux on construction.
Expand All @@ -48,6 +74,14 @@ func WithForwardResponseOption(forwardResponseOption func(context.Context, http.
}
}

// WithEscapingType sets the escaping type. See the definitions of UnescapingMode
// for more information.
func WithUnescapingMode(mode UnescapingMode) ServeMuxOption {
return func(serveMux *ServeMux) {
serveMux.unescapingMode = mode
}
}

// SetQueryParameterParser sets the query parameter parser, used to populate message from query parameters.
// Configuring this will mean the generated OpenAPI output is no longer correct, and it should be
// done with careful consideration.
Expand Down Expand Up @@ -153,6 +187,7 @@ func NewServeMux(opts ...ServeMuxOption) *ServeMux {
errorHandler: DefaultHTTPErrorHandler,
streamErrorHandler: DefaultStreamErrorHandler,
routingErrorHandler: DefaultRoutingErrorHandler,
unescapingMode: UnescapingModeDefault,
}

for _, opt := range opts {
Expand Down Expand Up @@ -204,6 +239,11 @@ func (s *ServeMux) ServeHTTP(w http.ResponseWriter, r *http.Request) {
return
}

// TODO(v3): remove UnescapingModeLegacy
if s.unescapingMode != UnescapingModeLegacy && r.URL.RawPath != "" {
path = r.URL.RawPath
}

components := strings.Split(path[1:], "/")

if override := r.Header.Get("X-HTTP-Method-Override"); override != "" && s.isPathLengthFallback(r) {
Expand Down Expand Up @@ -244,8 +284,13 @@ func (s *ServeMux) ServeHTTP(w http.ResponseWriter, r *http.Request) {
components[l-1], verb = lastComponent[:idx], lastComponent[idx+1:]
}

pathParams, err := h.pat.Match(components, verb)
pathParams, err := h.pat.MatchAndEscape(components, verb, s.unescapingMode)
if err != nil {
// malformed escape sequence
if err == ErrMalformedSequence {
_, outboundMarshaler := MarshalerForRequest(s, r)
s.routingErrorHandler(ctx, s, outboundMarshaler, w, r, http.StatusBadRequest)
}
continue
}
h.h(w, r, pathParams)
Expand All @@ -259,8 +304,13 @@ func (s *ServeMux) ServeHTTP(w http.ResponseWriter, r *http.Request) {
continue
}
for _, h := range handlers {
pathParams, err := h.pat.Match(components, verb)
pathParams, err := h.pat.MatchAndEscape(components, verb, s.unescapingMode)
if err != nil {
// malformed escape sequence
if err == ErrMalformedSequence {
_, outboundMarshaler := MarshalerForRequest(s, r)
s.routingErrorHandler(ctx, s, outboundMarshaler, w, r, http.StatusBadRequest)
}
continue
}
// X-HTTP-Method-Override is optional. Always allow fallback to POST.
Expand Down
145 changes: 140 additions & 5 deletions runtime/pattern.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,8 @@ var (
ErrNotMatch = errors.New("not match to the path pattern")
// ErrInvalidPattern indicates that the given definition of Pattern is not valid.
ErrInvalidPattern = errors.New("invalid pattern")
// ErrMalformedSequence indicates that an escape sequence was malformed.
ErrMalformedSequence = errors.New("malformed escape sequence")
)

type op struct {
Expand Down Expand Up @@ -140,10 +142,11 @@ func MustPattern(p Pattern, err error) Pattern {
return p
}

// Match examines components if it matches to the Pattern.
// If it matches, the function returns a mapping from field paths to their captured values.
// If otherwise, the function returns an error.
func (p Pattern) Match(components []string, verb string) (map[string]string, error) {
// MatchAndEscape examines components if it matches to the Pattern. If it matches,
// the function returns a mapping from field paths to their captured values while
// applying the provided unescaping mode, returning an error if the URL encoding
// is malformed. Otherwise, the function returns an error.
func (p Pattern) MatchAndEscape(components []string, verb string, unescapingMode UnescapingMode) (map[string]string, error) {
if p.verb != verb {
if p.verb != "" {
return nil, ErrNotMatch
Expand All @@ -161,6 +164,8 @@ func (p Pattern) Match(components []string, verb string) (map[string]string, err
captured := make([]string, len(p.vars))
l := len(components)
for _, op := range p.ops {
var err error

switch op.code {
case utilities.OpNop:
continue
Expand All @@ -173,6 +178,10 @@ func (p Pattern) Match(components []string, verb string) (map[string]string, err
if lit := p.pool[op.operand]; c != lit {
return nil, ErrNotMatch
}
} else if op.code == utilities.OpPush {
if c, err = unescape(c, unescapingMode, false); err != nil {
return nil, ErrMalformedSequence
}
}
stack = append(stack, c)
pos++
Expand All @@ -182,7 +191,11 @@ func (p Pattern) Match(components []string, verb string) (map[string]string, err
return nil, ErrNotMatch
}
end -= p.tailLen
stack = append(stack, strings.Join(components[pos:end], "/"))
c := strings.Join(components[pos:end], "/")
if c, err = unescape(c, unescapingMode, true); err != nil {
return nil, ErrMalformedSequence
}
stack = append(stack, c)
pos = end
case utilities.OpConcatN:
n := op.operand
Expand All @@ -204,6 +217,15 @@ func (p Pattern) Match(components []string, verb string) (map[string]string, err
return bindings, nil
}

// Match examines components if it matches to the Pattern.
// If it matches, the function returns a mapping from field paths to their captured values.
// If otherwise, the function returns an error.
//
// Deprecated: Use MatchAndEscape.
func (p Pattern) Match(components []string, verb string) (map[string]string, error) {
return p.MatchAndEscape(components, verb, UnescapingModeDefault)
}

// Verb returns the verb part of the Pattern.
func (p Pattern) Verb() string { return p.verb }

Expand Down Expand Up @@ -234,3 +256,116 @@ func (p Pattern) String() string {
}
return "/" + segs
}

/*
* The following code is adopted and modified from Go's standard library
* and carries the attached license.
*
* Copyright 2009 The Go Authors. All rights reserved.
* Use of this source code is governed by a BSD-style
* license that can be found in the LICENSE file.
*/

// ishex returns whether or not the given byte is a valid hex character
func ishex(c byte) bool {
switch {
case '0' <= c && c <= '9':
return true
case 'a' <= c && c <= 'f':
return true
case 'A' <= c && c <= 'F':
return true
}
return false
}


func isRFC6570Reserved(c byte) bool {
switch c {
case '!', '#', '$', '&', '\'', '(', ')', '*',
'+', ',', '/', ':', ';', '=', '?', '@', '[', ']':
return true
default:
return false
}
}

// unhex converts a hex point to the bit representation
func unhex(c byte) byte {
switch {
case '0' <= c && c <= '9':
return c - '0'
case 'a' <= c && c <= 'f':
return c - 'a' + 10
case 'A' <= c && c <= 'F':
return c - 'A' + 10
}
return 0
}

// shouldUnescapeWithMode returns true if the character is escapable with the
// given mode
func shouldUnescapeWithMode(c byte, mode UnescapingMode) bool {
switch mode {
case UnescapingModeAllExceptReserved:
if isRFC6570Reserved(c) {
return false
}
case UnescapingModeAllExceptSlash:
if c == '/' {
return false
}
case UnescapingModeAllCharacters:
return true
}
return true
}

// unescape unescapes a path string using the provided mode
func unescape(s string, mode UnescapingMode, multisegment bool) (string, error) {
// TODO(v3): remove UnescapingModeLegacy
if mode == UnescapingModeLegacy {
return s, nil
}

if !multisegment {
mode = UnescapingModeAllCharacters
}

// Count %, check that they're well-formed.
n := 0
for i := 0; i < len(s); {
if s[i] == '%' {
n++
if i+2 >= len(s) || !ishex(s[i+1]) || !ishex(s[i+2]) {
s = s[i:]
if len(s) > 3 {
s = s[:3]
}

return "", ErrMalformedSequence
}
}
i += 3
}

var t strings.Builder
t.Grow(len(s))
for i := 0; i < len(s); i++ {
switch s[i] {
case '%':
c := unhex(s[i+1])<<4 | unhex(s[i+2])
if shouldUnescapeWithMode(c, mode) {
t.WriteByte(c)
i += 2
continue
}
fallthrough
default:
t.WriteByte(s[i])
}
}

return t.String(), nil
}

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