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
|
package minio
import (
"encoding/base64"
"fmt"
"strings"
"time"
)
// expirationDateFormat date format for expiration key in json policy.
const expirationDateFormat = "2006-01-02T15:04:05.999Z"
// policyCondition explanation:
// http://docs.aws.amazon.com/AmazonS3/latest/API/sigv4-HTTPPOSTConstructPolicy.html
//
// Example:
//
// policyCondition {
// matchType: "$eq",
// key: "$Content-Type",
// value: "image/png",
// }
//
type policyCondition struct {
matchType string
condition string
value string
}
// PostPolicy - Provides strict static type conversion and validation
// for Amazon S3's POST policy JSON string.
type PostPolicy struct {
// Expiration date and time of the POST policy.
expiration time.Time
// Collection of different policy conditions.
conditions []policyCondition
// ContentLengthRange minimum and maximum allowable size for the
// uploaded content.
contentLengthRange struct {
min int64
max int64
}
// Post form data.
formData map[string]string
}
// NewPostPolicy - Instantiate new post policy.
func NewPostPolicy() *PostPolicy {
p := &PostPolicy{}
p.conditions = make([]policyCondition, 0)
p.formData = make(map[string]string)
return p
}
// SetExpires - Sets expiration time for the new policy.
func (p *PostPolicy) SetExpires(t time.Time) error {
if t.IsZero() {
return ErrInvalidArgument("No expiry time set.")
}
p.expiration = t
return nil
}
// SetKey - Sets an object name for the policy based upload.
func (p *PostPolicy) SetKey(key string) error {
if strings.TrimSpace(key) == "" || key == "" {
return ErrInvalidArgument("Object name is empty.")
}
policyCond := policyCondition{
matchType: "eq",
condition: "$key",
value: key,
}
if err := p.addNewPolicy(policyCond); err != nil {
return err
}
p.formData["key"] = key
return nil
}
// SetKeyStartsWith - Sets an object name that an policy based upload
// can start with.
func (p *PostPolicy) SetKeyStartsWith(keyStartsWith string) error {
if strings.TrimSpace(keyStartsWith) == "" || keyStartsWith == "" {
return ErrInvalidArgument("Object prefix is empty.")
}
policyCond := policyCondition{
matchType: "starts-with",
condition: "$key",
value: keyStartsWith,
}
if err := p.addNewPolicy(policyCond); err != nil {
return err
}
p.formData["key"] = keyStartsWith
return nil
}
// SetBucket - Sets bucket at which objects will be uploaded to.
func (p *PostPolicy) SetBucket(bucketName string) error {
if strings.TrimSpace(bucketName) == "" || bucketName == "" {
return ErrInvalidArgument("Bucket name is empty.")
}
policyCond := policyCondition{
matchType: "eq",
condition: "$bucket",
value: bucketName,
}
if err := p.addNewPolicy(policyCond); err != nil {
return err
}
p.formData["bucket"] = bucketName
return nil
}
// SetContentType - Sets content-type of the object for this policy
// based upload.
func (p *PostPolicy) SetContentType(contentType string) error {
if strings.TrimSpace(contentType) == "" || contentType == "" {
return ErrInvalidArgument("No content type specified.")
}
policyCond := policyCondition{
matchType: "eq",
condition: "$Content-Type",
value: contentType,
}
if err := p.addNewPolicy(policyCond); err != nil {
return err
}
p.formData["Content-Type"] = contentType
return nil
}
// SetContentLengthRange - Set new min and max content length
// condition for all incoming uploads.
func (p *PostPolicy) SetContentLengthRange(min, max int64) error {
if min > max {
return ErrInvalidArgument("Minimum limit is larger than maximum limit.")
}
if min < 0 {
return ErrInvalidArgument("Minimum limit cannot be negative.")
}
if max < 0 {
return ErrInvalidArgument("Maximum limit cannot be negative.")
}
p.contentLengthRange.min = min
p.contentLengthRange.max = max
return nil
}
// addNewPolicy - internal helper to validate adding new policies.
func (p *PostPolicy) addNewPolicy(policyCond policyCondition) error {
if policyCond.matchType == "" || policyCond.condition == "" || policyCond.value == "" {
return ErrInvalidArgument("Policy fields are empty.")
}
p.conditions = append(p.conditions, policyCond)
return nil
}
// Stringer interface for printing policy in json formatted string.
func (p PostPolicy) String() string {
return string(p.marshalJSON())
}
// marshalJSON - Provides Marshalled JSON in bytes.
func (p PostPolicy) marshalJSON() []byte {
expirationStr := `"expiration":"` + p.expiration.Format(expirationDateFormat) + `"`
var conditionsStr string
conditions := []string{}
for _, po := range p.conditions {
conditions = append(conditions, fmt.Sprintf("[\"%s\",\"%s\",\"%s\"]", po.matchType, po.condition, po.value))
}
if p.contentLengthRange.min != 0 || p.contentLengthRange.max != 0 {
conditions = append(conditions, fmt.Sprintf("[\"content-length-range\", %d, %d]",
p.contentLengthRange.min, p.contentLengthRange.max))
}
if len(conditions) > 0 {
conditionsStr = `"conditions":[` + strings.Join(conditions, ",") + "]"
}
retStr := "{"
retStr = retStr + expirationStr + ","
retStr = retStr + conditionsStr
retStr = retStr + "}"
return []byte(retStr)
}
// base64 - Produces base64 of PostPolicy's Marshalled json.
func (p PostPolicy) base64() string {
return base64.StdEncoding.EncodeToString(p.marshalJSON())
}
|
