87 lines
2.5 KiB
Go
87 lines
2.5 KiB
Go
package v4
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import (
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"context"
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"crypto/sha256"
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"encoding/hex"
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"github.com/aws/aws-sdk-go-v2/aws"
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v4Internal "github.com/aws/aws-sdk-go-v2/aws/signer/internal/v4"
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"strings"
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"time"
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)
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// EventStreamSigner is an AWS EventStream protocol signer.
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type EventStreamSigner interface {
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GetSignature(ctx context.Context, headers, payload []byte, signingTime time.Time, optFns ...func(*StreamSignerOptions)) ([]byte, error)
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}
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// StreamSignerOptions is the configuration options for StreamSigner.
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type StreamSignerOptions struct{}
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// StreamSigner implements Signature Version 4 (SigV4) signing of event stream encoded payloads.
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type StreamSigner struct {
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options StreamSignerOptions
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credentials aws.Credentials
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service string
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region string
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prevSignature []byte
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signingKeyDeriver *v4Internal.SigningKeyDeriver
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}
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// NewStreamSigner returns a new AWS EventStream protocol signer.
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func NewStreamSigner(credentials aws.Credentials, service, region string, seedSignature []byte, optFns ...func(*StreamSignerOptions)) *StreamSigner {
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o := StreamSignerOptions{}
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for _, fn := range optFns {
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fn(&o)
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}
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return &StreamSigner{
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options: o,
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credentials: credentials,
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service: service,
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region: region,
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signingKeyDeriver: v4Internal.NewSigningKeyDeriver(),
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prevSignature: seedSignature,
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}
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}
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// GetSignature signs the provided header and payload bytes.
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func (s *StreamSigner) GetSignature(ctx context.Context, headers, payload []byte, signingTime time.Time, optFns ...func(*StreamSignerOptions)) ([]byte, error) {
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options := s.options
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for _, fn := range optFns {
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fn(&options)
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}
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prevSignature := s.prevSignature
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st := v4Internal.NewSigningTime(signingTime.UTC())
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sigKey := s.signingKeyDeriver.DeriveKey(s.credentials, s.service, s.region, st)
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scope := v4Internal.BuildCredentialScope(st, s.region, s.service)
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stringToSign := s.buildEventStreamStringToSign(headers, payload, prevSignature, scope, &st)
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signature := v4Internal.HMACSHA256(sigKey, []byte(stringToSign))
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s.prevSignature = signature
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return signature, nil
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}
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func (s *StreamSigner) buildEventStreamStringToSign(headers, payload, previousSignature []byte, credentialScope string, signingTime *v4Internal.SigningTime) string {
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hash := sha256.New()
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return strings.Join([]string{
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"AWS4-HMAC-SHA256-PAYLOAD",
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signingTime.TimeFormat(),
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credentialScope,
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hex.EncodeToString(previousSignature),
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hex.EncodeToString(makeHash(hash, headers)),
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hex.EncodeToString(makeHash(hash, payload)),
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}, "\n")
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}
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