252 lines
7.6 KiB
Go
252 lines
7.6 KiB
Go
package sign
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import (
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"bytes"
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"encoding/asn1"
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"encoding/hex"
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"errors"
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"fmt"
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"io"
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"io/ioutil"
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"net/http"
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"strconv"
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"strings"
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"github.com/digitorus/pkcs7"
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"github.com/digitorus/timestamp"
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"crypto/x509"
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)
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type pkiStatusInfo struct {
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Status int
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StatusString string `asn1:"optional"`
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FailInfo int `asn1:"optional"`
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}
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// 2.4.2. Response Format
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type TSAResponse struct {
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Status pkiStatusInfo
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TimeStampToken asn1.RawValue
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}
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var signatureMaxLength = uint32(1000000)
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var signatureByteRangePlaceholder = "/ByteRange[0 ********** ********** **********]"
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func (context *SignContext) createSignaturePlaceholder() (signature string, byte_range_start_byte int64, signature_contents_start_byte int64) {
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signature = strconv.Itoa(int(context.SignData.ObjectId)) + " 0 obj\n"
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signature += "<< /Type /Sig"
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signature += " /Filter /Adobe.PPKLite"
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signature += " /SubFilter /adbe.pkcs7.detached"
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byte_range_start_byte = int64(len(signature)) + 1
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// Create a placeholder for the byte range string, we will replace it later.
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signature += " " + signatureByteRangePlaceholder
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signature_contents_start_byte = int64(len(signature)) + 11
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// Create a placeholder for the actual signature content, we wil replace it later.
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signature += " /Contents<" + strings.Repeat("0", int(signatureMaxLength)) + ">"
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if !context.SignData.Signature.Approval {
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signature += " /Reference [" // array of signature reference dictionaries
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signature += " << /Type /SigRef"
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if context.SignData.Signature.CertType > 0 {
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signature += " /TransformMethod /DocMDP"
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signature += " /TransformParams <<"
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signature += " /Type /TransformParams"
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signature += " /P " + strconv.Itoa(int(context.SignData.Signature.CertType))
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signature += " /V /1.2"
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} else {
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signature += " /TransformMethod /UR3"
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signature += " /TransformParams <<"
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signature += " /Type /TransformParams"
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signature += " /V /2.2"
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}
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signature += " >>" // close TransformParams
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signature += " >>"
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signature += " ]" // end of reference
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}
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if context.SignData.Signature.Info.Name != "" {
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signature += " /Name " + pdfString(context.SignData.Signature.Info.Name)
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}
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if context.SignData.Signature.Info.Location != "" {
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signature += " /Location " + pdfString(context.SignData.Signature.Info.Location)
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}
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if context.SignData.Signature.Info.Reason != "" {
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signature += " /Reason " + pdfString(context.SignData.Signature.Info.Reason)
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}
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if context.SignData.Signature.Info.ContactInfo != "" {
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signature += " /ContactInfo " + pdfString(context.SignData.Signature.Info.ContactInfo)
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}
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signature += " /M " + pdfDateTime(context.SignData.Signature.Info.Date)
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signature += " >>"
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signature += "\nendobj\n"
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return signature, byte_range_start_byte, signature_contents_start_byte
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}
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func (context *SignContext) createSignature() ([]byte, error) {
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// Sadly we can't efficiently sign a file, we need to read all the bytes we want to sign.
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context.OutputFile.Seek(0, 0)
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sign_buf := bytes.NewBuffer(nil)
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io.Copy(sign_buf, context.OutputFile)
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file_content := sign_buf.Bytes()
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// Collect the parts to sign.
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sign_content := make([]byte, 0)
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sign_content = append(sign_content, file_content[context.ByteRangeValues[0]:(context.ByteRangeValues[0]+context.ByteRangeValues[1])]...)
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sign_content = append(sign_content, file_content[context.ByteRangeValues[2]:(context.ByteRangeValues[2]+context.ByteRangeValues[3])]...)
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// Initialize pkcs7 signer.
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signed_data, err := pkcs7.NewSignedData(sign_content)
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if err != nil {
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return nil, err
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}
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signer_config := pkcs7.SignerInfoConfig{}
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if context.SignData.TSA.URL != "" {
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timestamp_response, err := context.GetTSA(sign_content)
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if err != nil {
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return nil, err
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}
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var rest []byte
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var resp TSAResponse
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if rest, err = asn1.Unmarshal(timestamp_response, &resp); err != nil {
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return nil, err
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}
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if len(rest) > 0 {
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return nil, errors.New("trailing data in Time-Stamp response")
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}
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if resp.Status.Status > 0 {
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return nil, errors.New(fmt.Sprintf("%s: %s", timestamp.FailureInfo(resp.Status.FailInfo).String(), resp.Status.StatusString))
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}
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if len(resp.TimeStampToken.Bytes) == 0 {
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return nil, errors.New("no pkcs7 data in Time-Stamp response")
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}
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timestamp_attribute := pkcs7.Attribute{
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Type: asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 9, 16, 2, 14},
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Value: resp.TimeStampToken,
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}
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signer_config.ExtraUnsignedAttributes = append(signer_config.ExtraUnsignedAttributes, timestamp_attribute)
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}
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if context.SignData.RevocationFunction != nil {
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if (len(context.SignData.CertificateChains) > 0) {
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certificate_chain := context.SignData.CertificateChains[0]
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if (len(certificate_chain) > 0) {
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for i, certificate := range certificate_chain {
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if i < len(certificate_chain)-1 {
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err = context.SignData.RevocationFunction(certificate, certificate_chain[i + 1], &context.SignData.RevocationData)
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if err != nil {
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return nil, err
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}
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} else {
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err = context.SignData.RevocationFunction(certificate, nil, &context.SignData.RevocationData)
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if err != nil {
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return nil, err
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}
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}
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}
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}
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}
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revocation_attribute := pkcs7.Attribute{
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Type: asn1.ObjectIdentifier{1, 2, 840, 113583, 1, 1, 8},
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Value: context.SignData.RevocationData,
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}
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signer_config.ExtraSignedAttributes = append(signer_config.ExtraSignedAttributes, revocation_attribute)
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}
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// Add the first certificate chain without our own certificate.
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var certificate_chain []*x509.Certificate
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if (len(context.SignData.CertificateChains) > 0 && len(context.SignData.CertificateChains[0]) > 1) {
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certificate_chain = context.SignData.CertificateChains[0][1:]
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}
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// Add the signer and sign the data.
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if err := signed_data.AddSignerChain(context.SignData.Certificate, context.SignData.Signer, certificate_chain, signer_config); err != nil {
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return nil, err
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}
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// PDF needs a detached signature, meaning the content isn't included.
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signed_data.Detach()
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return signed_data.Finish()
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}
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func (context *SignContext) GetTSA(sign_content []byte) (timestamp_response []byte, err error) {
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sign_reader := bytes.NewReader(sign_content)
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ts_request, err := timestamp.CreateRequest(sign_reader, nil)
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if err != nil {
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return nil, err
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}
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ts_request_reader := bytes.NewReader(ts_request)
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req, err := http.NewRequest("POST", context.SignData.TSA.URL, ts_request_reader)
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if err != nil {
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return nil, err
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}
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req.Header.Add("Content-Type", "application/timestamp-query")
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req.Header.Add("Content-Transfer-Encoding", "binary")
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if context.SignData.TSA.Username != "" && context.SignData.TSA.Password != "" {
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req.SetBasicAuth(context.SignData.TSA.Username, context.SignData.TSA.Password)
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}
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client := &http.Client{}
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resp, err := client.Do(req)
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code := 0
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if resp != nil {
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code = resp.StatusCode
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}
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if err != nil || (code < 200 || code > 299) {
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if err == nil {
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defer resp.Body.Close()
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body, _ := ioutil.ReadAll(resp.Body)
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err = errors.New("Non success response (" + strconv.Itoa(code) + "): " + string(body))
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} else {
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err = errors.New("Non success response (" + strconv.Itoa(code) + ")")
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}
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return nil, err
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}
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defer resp.Body.Close()
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timestamp_response_body, err := ioutil.ReadAll(resp.Body)
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if err != nil {
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return nil, err
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}
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return timestamp_response_body, nil
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}
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func (context *SignContext) replaceSignature() error {
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signature, err := context.createSignature()
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if err != nil {
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return err
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}
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dst := make([]byte, hex.EncodedLen(len(signature)))
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hex.Encode(dst, signature)
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if uint32(len(dst)) > signatureMaxLength {
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return errors.New("Signature is too big to fit in reserved space.")
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}
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context.OutputFile.WriteAt(dst, context.ByteRangeValues[0]+context.ByteRangeValues[1]+1)
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return nil
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}
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