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()) }