63 lines
1.6 KiB
Go
63 lines
1.6 KiB
Go
package v4
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import (
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"encoding/hex"
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"strings"
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"time"
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"github.com/aws/aws-sdk-go/aws/credentials"
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)
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type credentialValueProvider interface {
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Get() (credentials.Value, error)
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}
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// StreamSigner implements signing of event stream encoded payloads.
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type StreamSigner struct {
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region string
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service string
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credentials credentialValueProvider
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prevSig []byte
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}
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// NewStreamSigner creates a SigV4 signer used to sign Event Stream encoded messages.
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func NewStreamSigner(region, service string, seedSignature []byte, credentials *credentials.Credentials) *StreamSigner {
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return &StreamSigner{
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region: region,
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service: service,
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credentials: credentials,
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prevSig: seedSignature,
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}
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}
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// GetSignature takes an event stream encoded headers and payload and returns a signature.
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func (s *StreamSigner) GetSignature(headers, payload []byte, date time.Time) ([]byte, error) {
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credValue, err := s.credentials.Get()
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if err != nil {
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return nil, err
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}
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sigKey := deriveSigningKey(s.region, s.service, credValue.SecretAccessKey, date)
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keyPath := buildSigningScope(s.region, s.service, date)
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stringToSign := buildEventStreamStringToSign(headers, payload, s.prevSig, keyPath, date)
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signature := hmacSHA256(sigKey, []byte(stringToSign))
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s.prevSig = signature
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return signature, nil
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}
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func buildEventStreamStringToSign(headers, payload, prevSig []byte, scope string, date time.Time) string {
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return strings.Join([]string{
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"AWS4-HMAC-SHA256-PAYLOAD",
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formatTime(date),
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scope,
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hex.EncodeToString(prevSig),
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hex.EncodeToString(hashSHA256(headers)),
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hex.EncodeToString(hashSHA256(payload)),
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}, "\n")
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}
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