GoToSocial/vendor/github.com/go-fed/httpsig/digest.go

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package httpsig
import (
"bytes"
"crypto"
"encoding/base64"
"fmt"
"hash"
"net/http"
"strings"
)
type DigestAlgorithm string
const (
DigestSha256 DigestAlgorithm = "SHA-256"
DigestSha512 = "SHA-512"
)
var digestToDef = map[DigestAlgorithm]crypto.Hash{
DigestSha256: crypto.SHA256,
DigestSha512: crypto.SHA512,
}
// IsSupportedDigestAlgorithm returns true if hte string is supported by this
// library, is not a hash known to be weak, and is supported by the hardware.
func IsSupportedDigestAlgorithm(algo string) bool {
uc := DigestAlgorithm(strings.ToUpper(algo))
c, ok := digestToDef[uc]
return ok && c.Available()
}
func getHash(alg DigestAlgorithm) (h hash.Hash, toUse DigestAlgorithm, err error) {
upper := DigestAlgorithm(strings.ToUpper(string(alg)))
c, ok := digestToDef[upper]
if !ok {
err = fmt.Errorf("unknown or unsupported Digest algorithm: %s", alg)
} else if !c.Available() {
err = fmt.Errorf("unavailable Digest algorithm: %s", alg)
} else {
h = c.New()
toUse = upper
}
return
}
const (
digestHeader = "Digest"
digestDelim = "="
)
func addDigest(r *http.Request, algo DigestAlgorithm, b []byte) (err error) {
_, ok := r.Header[digestHeader]
if ok {
err = fmt.Errorf("cannot add Digest: Digest is already set")
return
}
var h hash.Hash
var a DigestAlgorithm
h, a, err = getHash(algo)
if err != nil {
return
}
h.Write(b)
sum := h.Sum(nil)
r.Header.Add(digestHeader,
fmt.Sprintf("%s%s%s",
a,
digestDelim,
base64.StdEncoding.EncodeToString(sum[:])))
return
}
func addDigestResponse(r http.ResponseWriter, algo DigestAlgorithm, b []byte) (err error) {
_, ok := r.Header()[digestHeader]
if ok {
err = fmt.Errorf("cannot add Digest: Digest is already set")
return
}
var h hash.Hash
var a DigestAlgorithm
h, a, err = getHash(algo)
if err != nil {
return
}
h.Write(b)
sum := h.Sum(nil)
r.Header().Add(digestHeader,
fmt.Sprintf("%s%s%s",
a,
digestDelim,
base64.StdEncoding.EncodeToString(sum[:])))
return
}
func verifyDigest(r *http.Request, body *bytes.Buffer) (err error) {
d := r.Header.Get(digestHeader)
if len(d) == 0 {
err = fmt.Errorf("cannot verify Digest: request has no Digest header")
return
}
elem := strings.SplitN(d, digestDelim, 2)
if len(elem) != 2 {
err = fmt.Errorf("cannot verify Digest: malformed Digest: %s", d)
return
}
var h hash.Hash
h, _, err = getHash(DigestAlgorithm(elem[0]))
if err != nil {
return
}
h.Write(body.Bytes())
sum := h.Sum(nil)
encSum := base64.StdEncoding.EncodeToString(sum[:])
if encSum != elem[1] {
err = fmt.Errorf("cannot verify Digest: header Digest does not match the digest of the request body")
return
}
return
}