48 lines
1.4 KiB
Go
48 lines
1.4 KiB
Go
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package slack
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import (
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"crypto/hmac"
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"crypto/sha256"
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"encoding/hex"
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"errors"
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"fmt"
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"hash"
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"net/http"
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)
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// SecretsVerifier contains the information needed to verify that the request comes from Slack
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type SecretsVerifier struct {
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slackSig string
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timeStamp string
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hmac hash.Hash
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}
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// NewSecretsVerifier returns a SecretsVerifier object in exchange for an http.Header object and signing secret
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func NewSecretsVerifier(header http.Header, signingSecret string) (SecretsVerifier, error) {
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if header["X-Slack-Signature"][0] == "" || header["X-Slack-Request-Timestamp"][0] == "" {
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return SecretsVerifier{}, errors.New("Headers are empty, cannot create SecretsVerifier")
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}
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hash := hmac.New(sha256.New, []byte(signingSecret))
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hash.Write([]byte(fmt.Sprintf("v0:%s:", header["X-Slack-Request-Timestamp"][0])))
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return SecretsVerifier{
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slackSig: header["X-Slack-Signature"][0],
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timeStamp: header["X-Slack-Request-Timestamp"][0],
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hmac: hash,
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}, nil
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}
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func (v *SecretsVerifier) Write(body []byte) (n int, err error) {
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return v.hmac.Write(body)
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}
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// Ensure compares the signature sent from Slack with the actual computed hash to judge validity
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func (v SecretsVerifier) Ensure() error {
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computed := "v0=" + string(hex.EncodeToString(v.hmac.Sum(nil)))
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if computed == v.slackSig {
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return nil
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}
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return fmt.Errorf("Expected signing signature: %s, but computed: %s", v.slackSig, computed)
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}
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