From 0b9ce0c5e42e7818febddb7bd8c6b0cb7c07b012 Mon Sep 17 00:00:00 2001
From: Rasmus Dahlberg <rasmus.dahlberg@kau.se>
Date: Thu, 5 Nov 2020 12:31:34 +0100
Subject: moved publlic x509 helpers into a separate package

---
 x509util/x509util.go | 134 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 134 insertions(+)
 create mode 100644 x509util/x509util.go

(limited to 'x509util/x509util.go')

diff --git a/x509util/x509util.go b/x509util/x509util.go
new file mode 100644
index 0000000..b33b4e9
--- /dev/null
+++ b/x509util/x509util.go
@@ -0,0 +1,134 @@
+package x509util
+
+import (
+	"fmt"
+
+	"crypto/ed25519"
+	"crypto/x509"
+	"encoding/pem"
+	"io/ioutil"
+)
+
+// LoadTrustAnchors loads a list of PEM-encoded certificates from file
+func LoadTrustAnchors(path string) ([]*x509.Certificate, *x509.CertPool, error) {
+	rest, err := ioutil.ReadFile(path)
+	if err != nil {
+		return nil, nil, fmt.Errorf("failed reading trust anchors: %v", err)
+	}
+
+	pool := x509.NewCertPool()
+	var anchors []*x509.Certificate
+	for len(rest) > 0 {
+		var block *pem.Block
+		block, rest = pem.Decode(rest)
+		if block == nil {
+			break
+		}
+		if block.Type != "CERTIFICATE" {
+			return nil, nil, fmt.Errorf("unexpected PEM block type: %s", block.Type)
+		}
+
+		certificate, err := x509.ParseCertificate(block.Bytes)
+		if err != nil {
+			return nil, nil, fmt.Errorf("invalid trust anchor before rest(%s): %v", rest, err)
+		}
+
+		anchors = append(anchors, certificate)
+		pool.AddCert(certificate)
+	}
+
+	if len(anchors) == 0 {
+		return nil, nil, fmt.Errorf("found no valid trust anchor in: %s", path)
+	}
+	return anchors, pool, nil
+}
+
+// LoadEd25519SigningKey loads an Ed25519 private key from a given path
+func LoadEd25519SigningKey(path string) (ed25519.PrivateKey, error) {
+	data, err := ioutil.ReadFile(path)
+	if err != nil {
+		return nil, fmt.Errorf("failed reading private key: %v", err)
+	}
+	return ParseEd25519PrivateKey(data)
+}
+
+// ParseEd25519PrivateKey parses a PEM-encoded private key block
+func ParseEd25519PrivateKey(data []byte) (ed25519.PrivateKey, error) {
+	block, rest := pem.Decode(data)
+	if block == nil {
+		return nil, fmt.Errorf("pem block: is empty")
+	}
+	if block.Type != "PRIVATE KEY" {
+		return nil, fmt.Errorf("bad pem block type: %v", block.Type)
+	}
+	if len(rest) != 0 {
+		return nil, fmt.Errorf("pem block: trailing data")
+	}
+
+	key, err := x509.ParsePKCS8PrivateKey(block.Bytes)
+	if err != nil {
+		fmt.Errorf("x509 parser failed: %v", err)
+	}
+	switch t := key.(type) {
+	case ed25519.PrivateKey:
+		return key.(ed25519.PrivateKey), nil
+	default:
+		return nil, fmt.Errorf("unexpected signing key type: %v", t)
+	}
+}
+
+// LoadChain loads a PEM-encoded certificate chain from a given path
+func LoadChain(path string) ([]*x509.Certificate, error) {
+	blob, err := ioutil.ReadFile(path)
+	if err != nil {
+		return nil, fmt.Errorf("failed reading certificate chain: %v", err)
+	}
+	return ParseChain(blob)
+}
+
+// ParseChain parses a PEM-encoded certificate chain
+func ParseChain(rest []byte) ([]*x509.Certificate, error) {
+	var chain []*x509.Certificate
+	for len(rest) > 0 {
+		var block *pem.Block
+		block, rest = pem.Decode(rest)
+		if block == nil {
+			break
+		}
+		if block.Type != "CERTIFICATE" {
+			return nil, fmt.Errorf("unexpected pem block type: %v", block.Type)
+		}
+
+		certificate, err := x509.ParseCertificate(block.Bytes)
+		if err != nil {
+			return nil, fmt.Errorf("failed parsing x509 certificate: %v", err)
+		}
+		chain = append(chain, certificate)
+	}
+	return chain, nil
+}
+
+// ParseDerChain parses a list of base64 DER-encoded X.509 certificates, such
+// that the first (zero-index) string is interpretted as an end-entity
+// certificate and the remaining ones as the an intermediate CertPool.
+func ParseDerChain(chain [][]byte) (*x509.Certificate, *x509.CertPool, error) {
+	var certificate *x509.Certificate
+	intermediatePool := x509.NewCertPool()
+	for index, der := range chain {
+		c, err := x509.ParseCertificate(der)
+		if err != nil {
+			return nil, nil, fmt.Errorf("certificate decoding failed: %v", err)
+		}
+
+		if index == 0 {
+			certificate = c
+		} else {
+			intermediatePool.AddCert(c)
+		}
+	}
+	if certificate == nil {
+		return nil, nil, fmt.Errorf("certificate chain is empty")
+	}
+	return certificate, intermediatePool, nil
+}
+
-- 
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