Initial QSfera import

Server/vendor/github.com/lestrrat-go/jwx/v3/cert/chain.go

@@ -0,0 +1,80 @@
+package cert
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+
+	"github.com/lestrrat-go/jwx/v3/internal/tokens"
+)
+
+// Chain represents a certificate chain as used in the `x5c` field of
+// various objects within JOSE.
+//
+// It stores the certificates as a list of base64 encoded []byte
+// sequence. By definition these values must PKIX encoded.
+type Chain struct {
+	certificates [][]byte
+}
+
+func (cc Chain) MarshalJSON() ([]byte, error) {
+	var buf bytes.Buffer
+	buf.WriteByte(tokens.OpenSquareBracket)
+	for i, cert := range cc.certificates {
+		if i > 0 {
+			buf.WriteByte(tokens.Comma)
+		}
+		buf.WriteByte('"')
+		buf.Write(cert)
+		buf.WriteByte('"')
+	}
+	buf.WriteByte(tokens.CloseSquareBracket)
+	return buf.Bytes(), nil
+}
+
+func (cc *Chain) UnmarshalJSON(data []byte) error {
+	var tmp []string
+	if err := json.Unmarshal(data, &tmp); err != nil {
+		return fmt.Errorf(`failed to unmarshal certificate chain: %w`, err)
+	}
+
+	certs := make([][]byte, len(tmp))
+	for i, cert := range tmp {
+		certs[i] = []byte(cert)
+	}
+	cc.certificates = certs
+	return nil
+}
+
+// Get returns the n-th ASN.1 DER + base64 encoded certificate
+// stored. `false` will be returned in the second argument if
+// the corresponding index is out of range.
+func (cc *Chain) Get(index int) ([]byte, bool) {
+	if index < 0 || index >= len(cc.certificates) {
+		return nil, false
+	}
+
+	return cc.certificates[index], true
+}
+
+// Len returns the number of certificates stored in this Chain
+func (cc *Chain) Len() int {
+	return len(cc.certificates)
+}
+
+var pemStart = []byte("----- BEGIN CERTIFICATE -----")
+var pemEnd = []byte("----- END CERTIFICATE -----")
+
+func (cc *Chain) AddString(der string) error {
+	return cc.Add([]byte(der))
+}
+
+func (cc *Chain) Add(der []byte) error {
+	// We're going to be nice and remove marker lines if they
+	// give it to us
+	der = bytes.TrimPrefix(der, pemStart)
+	der = bytes.TrimSuffix(der, pemEnd)
+	der = bytes.TrimSpace(der)
+	cc.certificates = append(cc.certificates, der)
+	return nil
+}