1 /*
2 *
3 * Copyright 2020 gRPC authors.
4 *
5 * Licensed under the Apache License, Version 2.0 (the "License");
6 * you may not use this file except in compliance with the License.
7 * You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 *
17 */
18 19 // Package metadata contains functions to set and get metadata from addresses.
20 //
21 // This package is experimental.
22 package metadata
23 24 import (
25 "fmt"
26 "strings"
27 28 "google.golang.org/grpc/metadata"
29 "google.golang.org/grpc/resolver"
30 )
31 32 type mdKeyType string
33 34 const mdKey = mdKeyType("grpc.internal.address.metadata")
35 36 type mdValue metadata.MD
37 38 func (m mdValue) Equal(o any) bool {
39 om, ok := o.(mdValue)
40 if !ok {
41 return false
42 }
43 if len(m) != len(om) {
44 return false
45 }
46 for k, v := range m {
47 ov := om[k]
48 if len(ov) != len(v) {
49 return false
50 }
51 for i, ve := range v {
52 if ov[i] != ve {
53 return false
54 }
55 }
56 }
57 return true
58 }
59 60 // Get returns the metadata of addr.
61 func Get(addr resolver.Address) metadata.MD {
62 attrs := addr.Attributes
63 if attrs == nil {
64 return nil
65 }
66 md, _ := attrs.Value(mdKey).(mdValue)
67 return metadata.MD(md)
68 }
69 70 // Set sets (overrides) the metadata in addr.
71 //
72 // When a SubConn is created with this address, the RPCs sent on it will all
73 // have this metadata.
74 func Set(addr resolver.Address, md metadata.MD) resolver.Address {
75 addr.Attributes = addr.Attributes.WithValue(mdKey, mdValue(md))
76 return addr
77 }
78 79 // Validate validates every pair in md with ValidatePair.
80 func Validate(md metadata.MD) error {
81 for k, vals := range md {
82 if err := ValidatePair(k, vals...); err != nil {
83 return err
84 }
85 }
86 return nil
87 }
88 89 // hasNotPrintable return true if msg contains any characters which are not in %x20-%x7E
90 func hasNotPrintable(msg string) bool {
91 // for i that saving a conversion if not using for range
92 for i := 0; i < len(msg); i++ {
93 if msg[i] < 0x20 || msg[i] > 0x7E {
94 return true
95 }
96 }
97 return false
98 }
99 100 // ValidateKey validates a key with the following rules (pseudo-headers are
101 // skipped):
102 // - the key must contain one or more characters.
103 // - the characters in the key must be in [0-9 a-z _ - .].
104 func ValidateKey(key string) error {
105 // key should not be empty
106 if key == "" {
107 return fmt.Errorf("there is an empty key in the header")
108 }
109 // pseudo-header will be ignored
110 if key[0] == ':' {
111 return nil
112 }
113 // check key, for i that saving a conversion if not using for range
114 for i := 0; i < len(key); i++ {
115 r := key[i]
116 if !(r >= 'a' && r <= 'z') && !(r >= '0' && r <= '9') && r != '.' && r != '-' && r != '_' {
117 return fmt.Errorf("header key %q contains illegal characters not in [0-9a-z-_.]", key)
118 }
119 }
120 return nil
121 }
122 123 // ValidatePair validates a key-value pair with the following rules
124 // (pseudo-header are skipped):
125 // - the key must contain one or more characters.
126 // - the characters in the key must be in [0-9 a-z _ - .].
127 // - if the key ends with a "-bin" suffix, no validation of the corresponding
128 // value is performed.
129 // - the characters in every value must be printable (in [%x20-%x7E]).
130 func ValidatePair(key string, vals ...string) error {
131 if err := ValidateKey(key); err != nil {
132 return err
133 }
134 if strings.HasSuffix(key, "-bin") {
135 return nil
136 }
137 // check value
138 for _, val := range vals {
139 if hasNotPrintable(val) {
140 return fmt.Errorf("header key %q contains value with non-printable ASCII characters", key)
141 }
142 }
143 return nil
144 }
145