crypto/x509: normalize and expand docs of Parse and Marshal functions

Change-Id: I8f0e109053bbbd8bde4fa64059fd070d8f4acef2
Reviewed-on: https://go-review.googlesource.com/c/go/+/183117Reviewed-by: Adam Langley <agl@golang.org>

src/crypto/x509/pkcs1.go

@@ -41,7 +41,9 @@ type pkcs1PublicKey struct {
 	E int
 }
 
-// ParsePKCS1PrivateKey returns an RSA private key from its ASN.1 PKCS#1 DER encoded form.
+// ParsePKCS1PrivateKey parses an RSA private key in PKCS#1, ASN.1 DER form.
+//
+// This kind of key is commonly encoded in PEM blocks of type "RSA PRIVATE KEY".
 func ParsePKCS1PrivateKey(der []byte) (*rsa.PrivateKey, error) {
 	var priv pkcs1PrivateKey
 	rest, err := asn1.Unmarshal(der, &priv)
@@ -94,7 +96,11 @@ func ParsePKCS1PrivateKey(der []byte) (*rsa.PrivateKey, error) {
 	return key, nil
 }
 
-// MarshalPKCS1PrivateKey converts a private key to ASN.1 DER encoded form.
+// MarshalPKCS1PrivateKey converts an RSA private key to PKCS#1, ASN.1 DER form.
+//
+// This kind of key is commonly encoded in PEM blocks of type "RSA PRIVATE KEY".
+// For a more flexible key format which is not RSA specific, use
+// MarshalPKCS8PrivateKey.
 func MarshalPKCS1PrivateKey(key *rsa.PrivateKey) []byte {
 	key.Precompute()
 
@@ -126,7 +132,9 @@ func MarshalPKCS1PrivateKey(key *rsa.PrivateKey) []byte {
 	return b
 }
 
-// ParsePKCS1PublicKey parses a PKCS#1 public key in ASN.1 DER form.
+// ParsePKCS1PublicKey parses an RSA public key in PKCS#1, ASN.1 DER form.
+//
+// This kind of key is commonly encoded in PEM blocks of type "RSA PUBLIC KEY".
 func ParsePKCS1PublicKey(der []byte) (*rsa.PublicKey, error) {
 	var pub pkcs1PublicKey
 	rest, err := asn1.Unmarshal(der, &pub)
@@ -154,6 +162,8 @@ func ParsePKCS1PublicKey(der []byte) (*rsa.PublicKey, error) {
 }
 
 // MarshalPKCS1PublicKey converts an RSA public key to PKCS#1, ASN.1 DER form.
+//
+// This kind of key is commonly encoded in PEM blocks of type "RSA PUBLIC KEY".
 func MarshalPKCS1PublicKey(key *rsa.PublicKey) []byte {
 	derBytes, _ := asn1.Marshal(pkcs1PublicKey{
 		N: key.N,

src/crypto/x509/pkcs8.go

@@ -24,9 +24,12 @@ type pkcs8 struct {
 	// optional attributes omitted.
 }
 
-// ParsePKCS8PrivateKey parses an unencrypted, PKCS#8 private key. It returns a
-// *rsa.PrivateKey, a *ecdsa.PrivateKey, or a ed25519.PrivateKey. More types
-// might be supported in future versions. See RFC 5208 and RFC 8410.
+// ParsePKCS8PrivateKey parses an unencrypted private key in PKCS#8, ASN.1 DER form.
+//
+// It returns a *rsa.PrivateKey, a *ecdsa.PrivateKey, or a ed25519.PrivateKey.
+// More types might be supported in the future.
+//
+// This kind of key is commonly encoded in PEM blocks of type "PRIVATE KEY".
 func ParsePKCS8PrivateKey(der []byte) (key interface{}, err error) {
 	var privKey pkcs8
 	if _, err := asn1.Unmarshal(der, &privKey); err != nil {
@@ -76,10 +79,12 @@ func ParsePKCS8PrivateKey(der []byte) (key interface{}, err error) {
 	}
 }
 
-// MarshalPKCS8PrivateKey converts a private key to PKCS#8 encoded form.
-// The following key types are currently supported: *rsa.PrivateKey,
-// *ecdsa.PrivateKey and ed25519.PrivateKey. Unsupported key types result in an
-// error. See RFC 5208 and RFC 8410.
+// MarshalPKCS8PrivateKey converts an RSA private key to PKCS#8, ASN.1 DER form.
+//
+// The following key types are currently supported: *rsa.PrivateKey, *ecdsa.PrivateKey
+// and ed25519.PrivateKey. Unsupported key types result in an error.
+//
+// This kind of key is commonly encoded in PEM blocks of type "PRIVATE KEY".
 func MarshalPKCS8PrivateKey(key interface{}) ([]byte, error) {
 	var privKey pkcs8
 

src/crypto/x509/sec1.go

@@ -28,12 +28,18 @@ type ecPrivateKey struct {
 	PublicKey     asn1.BitString        `asn1:"optional,explicit,tag:1"`
 }
 
-// ParseECPrivateKey parses an ASN.1 Elliptic Curve Private Key Structure.
+// ParseECPrivateKey parses an EC public key in SEC 1, ASN.1 DER form.
+//
+// This kind of key is commonly encoded in PEM blocks of type "EC PUBLIC KEY".
 func ParseECPrivateKey(der []byte) (*ecdsa.PrivateKey, error) {
 	return parseECPrivateKey(nil, der)
 }
 
-// MarshalECPrivateKey marshals an EC private key into ASN.1, DER format.
+// MarshalECPrivateKey converts an EC private key to SEC 1, ASN.1 DER form.
+//
+// This kind of key is commonly encoded in PEM blocks of type "EC PRIVATE KEY".
+// For a more flexible key format which is not EC specific, use
+// MarshalPKCS8PrivateKey.
 func MarshalECPrivateKey(key *ecdsa.PrivateKey) ([]byte, error) {
 	oid, ok := oidFromNamedCurve(key.Curve)
 	if !ok {

src/crypto/x509/x509.go

@@ -44,14 +44,12 @@ type pkixPublicKey struct {
 	BitString asn1.BitString
 }
 
-// ParsePKIXPublicKey parses a DER encoded public key. These values are
-// typically found in PEM blocks with "BEGIN PUBLIC KEY".
+// ParsePKIXPublicKey parses a public key in PKIX, ASN.1 DER form.
 //
-// Supported key types include RSA, DSA, and ECDSA. Unknown key
-// types result in an error.
+// It returns a *rsa.PublicKey, *dsa.PublicKey, *ecdsa.PublicKey, or
+// ed25519.PublicKey. More types might be supported in the future.
 //
-// On success, pub will be of type *rsa.PublicKey, *dsa.PublicKey,
-// *ecdsa.PublicKey, or ed25519.PublicKey.
+// This kind of key is commonly encoded in PEM blocks of type "PUBLIC KEY".
 func ParsePKIXPublicKey(derBytes []byte) (pub interface{}, err error) {
 	var pki publicKeyInfo
 	if rest, err := asn1.Unmarshal(derBytes, &pki); err != nil {
@@ -106,7 +104,12 @@ func marshalPublicKey(pub interface{}) (publicKeyBytes []byte, publicKeyAlgorith
 	return publicKeyBytes, publicKeyAlgorithm, nil
 }
 
-// MarshalPKIXPublicKey serialises a public key to DER-encoded PKIX format.
+// MarshalPKIXPublicKey converts a public key to PKIX, ASN.1 DER form.
+//
+// The following key types are currently supported: *rsa.PublicKey, *ecdsa.PublicKey
+// and ed25519.PublicKey. Unsupported key types result in an error.
+//
+// This kind of key is commonly encoded in PEM blocks of type "PUBLIC KEY".
 func MarshalPKIXPublicKey(pub interface{}) ([]byte, error) {
 	var publicKeyBytes []byte
 	var publicKeyAlgorithm pkix.AlgorithmIdentifier