1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
|
// Copyright 2015 Matthew Holt and The Caddy Authors
//
// 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 caddyhttp
import (
"encoding/json"
"fmt"
"net/http"
"reflect"
"regexp"
"strings"
"github.com/caddyserver/caddy/v2"
"github.com/caddyserver/caddy/v2/caddyconfig/caddyfile"
"github.com/google/cel-go/cel"
"github.com/google/cel-go/checker/decls"
"github.com/google/cel-go/common/types"
"github.com/google/cel-go/common/types/ref"
"github.com/google/cel-go/common/types/traits"
"github.com/google/cel-go/ext"
"github.com/google/cel-go/interpreter/functions"
exprpb "google.golang.org/genproto/googleapis/api/expr/v1alpha1"
)
func init() {
caddy.RegisterModule(MatchExpression{})
}
// MatchExpression matches requests by evaluating a
// [CEL](https://github.com/google/cel-spec) expression.
// This enables complex logic to be expressed using a comfortable,
// familiar syntax.
//
// COMPATIBILITY NOTE: This module is still experimental and is not
// subject to Caddy's compatibility guarantee.
type MatchExpression struct {
// The CEL expression to evaluate. Any Caddy placeholders
// will be expanded and situated into proper CEL function
// calls before evaluating.
Expr string
expandedExpr string
prg cel.Program
}
// CaddyModule returns the Caddy module information.
func (MatchExpression) CaddyModule() caddy.ModuleInfo {
return caddy.ModuleInfo{
ID: "http.matchers.expression",
New: func() caddy.Module { return new(MatchExpression) },
}
}
// MarshalJSON marshals m's expression.
func (m MatchExpression) MarshalJSON() ([]byte, error) {
return json.Marshal(m.Expr)
}
// UnmarshalJSON unmarshals m's expression.
func (m *MatchExpression) UnmarshalJSON(data []byte) error {
return json.Unmarshal(data, &m.Expr)
}
// Provision sets ups m.
func (m *MatchExpression) Provision(_ caddy.Context) error {
// replace placeholders with a function call - this is just some
// light (and possibly naïve) syntactic sugar
m.expandedExpr = placeholderRegexp.ReplaceAllString(m.Expr, placeholderExpansion)
// create the CEL environment
env, err := cel.NewEnv(
cel.Declarations(
decls.NewIdent("request", httpRequestObjectType, nil),
decls.NewFunction(placeholderFuncName,
decls.NewOverload(placeholderFuncName+"_httpRequest_string",
[]*exprpb.Type{httpRequestObjectType, decls.String},
decls.String)),
),
cel.CustomTypeAdapter(celHTTPRequestTypeAdapter{}),
ext.Strings(),
)
if err != nil {
return fmt.Errorf("setting up CEL environment: %v", err)
}
// parse the expression
parsed, issues := env.Parse(m.expandedExpr)
if issues != nil && issues.Err() != nil {
return fmt.Errorf("parsing CEL program: %s", issues.Err())
}
// type-check it
checked, issues := env.Check(parsed)
if issues != nil && issues.Err() != nil {
return fmt.Errorf("type-checking CEL program: %s", issues.Err())
}
// compile the "program"
m.prg, err = env.Program(checked,
cel.Functions(
&functions.Overload{
Operator: placeholderFuncName,
Binary: caddyPlaceholderFunc,
},
),
)
if err != nil {
return fmt.Errorf("compiling CEL program: %s", err)
}
return nil
}
// Match returns true if r matches m.
func (m MatchExpression) Match(r *http.Request) bool {
out, _, _ := m.prg.Eval(map[string]interface{}{
"request": celHTTPRequest{r},
})
if outBool, ok := out.Value().(bool); ok {
return outBool
}
return false
}
// UnmarshalCaddyfile implements caddyfile.Unmarshaler.
func (m *MatchExpression) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
for d.Next() {
m.Expr = strings.Join(d.RemainingArgs(), " ")
}
return nil
}
// httpRequestCELType is the type representation of a native HTTP request.
var httpRequestCELType = types.NewTypeValue("http.Request", traits.ReceiverType)
// cellHTTPRequest wraps an http.Request with
// methods to satisfy the ref.Val interface.
type celHTTPRequest struct {
*http.Request
}
func (cr celHTTPRequest) ConvertToNative(typeDesc reflect.Type) (interface{}, error) {
return cr.Request, nil
}
func (celHTTPRequest) ConvertToType(typeVal ref.Type) ref.Val {
panic("not implemented")
}
func (cr celHTTPRequest) Equal(other ref.Val) ref.Val {
if o, ok := other.Value().(celHTTPRequest); ok {
return types.Bool(o.Request == cr.Request)
}
return types.ValOrErr(other, "%v is not comparable type", other)
}
func (celHTTPRequest) Type() ref.Type { return httpRequestCELType }
func (cr celHTTPRequest) Value() interface{} { return cr }
// celHTTPRequestTypeAdapter can adapt a
// celHTTPRequest to a CEL value.
type celHTTPRequestTypeAdapter struct{}
func (celHTTPRequestTypeAdapter) NativeToValue(value interface{}) ref.Val {
if celReq, ok := value.(celHTTPRequest); ok {
return celReq
}
return types.DefaultTypeAdapter.NativeToValue(value)
}
// Variables used for replacing Caddy placeholders in CEL
// expressions with a proper CEL function call; this is
// just for syntactic sugar.
var (
placeholderRegexp = regexp.MustCompile(`{([\w.-]+)}`)
placeholderExpansion = `caddyPlaceholder(request, "${1}")`
)
var httpRequestObjectType = decls.NewObjectType("http.Request")
// The name of the CEL function which accesses Replacer values.
const placeholderFuncName = "caddyPlaceholder"
// caddyPlaceholderFunc implements the custom CEL function that
// accesses the Replacer on a request and gets values from it.
func caddyPlaceholderFunc(lhs, rhs ref.Val) ref.Val {
celReq, ok := lhs.(celHTTPRequest)
if !ok {
return types.NewErr(
"invalid request of type '%v' to "+placeholderFuncName+"(request, placeholderVarName)",
lhs.Type())
}
phStr, ok := rhs.(types.String)
if !ok {
return types.NewErr(
"invalid placeholder variable name of type '%v' to "+placeholderFuncName+"(request, placeholderVarName)",
rhs.Type())
}
repl := celReq.Context().Value(caddy.ReplacerCtxKey).(*caddy.Replacer)
val, _ := repl.Get(string(phStr))
return types.String(val)
}
// Interface guards
var (
_ caddy.Provisioner = (*MatchExpression)(nil)
_ RequestMatcher = (*MatchExpression)(nil)
_ caddyfile.Unmarshaler = (*MatchExpression)(nil)
_ json.Marshaler = (*MatchExpression)(nil)
_ json.Unmarshaler = (*MatchExpression)(nil)
)
|
