1 files changed, 415 insertions, 0 deletions
diff --git a/src/pkg/crypto/openpgp/read.go b/src/pkg/crypto/openpgp/read.go
new file mode 100644
index 000000000..d95f613c6
--- /dev/null
+++ b/src/pkg/crypto/openpgp/read.go
@@ -0,0 +1,415 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package openpgp implements high level operations on OpenPGP messages.
+package openpgp
+
+import (
+	"crypto"
+	"crypto/openpgp/armor"
+	"crypto/openpgp/error"
+	"crypto/openpgp/packet"
+	_ "crypto/sha256"
+	"hash"
+	"io"
+	"os"
+	"strconv"
+)
+
+// SignatureType is the armor type for a PGP signature.
+var SignatureType = "PGP SIGNATURE"
+
+// readArmored reads an armored block with the given type.
+func readArmored(r io.Reader, expectedType string) (body io.Reader, err os.Error) {
+	block, err := armor.Decode(r)
+	if err != nil {
+		return
+	}
+
+	if block.Type != expectedType {
+		return nil, error.InvalidArgumentError("expected '" + expectedType + "', got: " + block.Type)
+	}
+
+	return block.Body, nil
+}
+
+// MessageDetails contains the result of parsing an OpenPGP encrypted and/or
+// signed message.
+type MessageDetails struct {
+	IsEncrypted              bool                // true if the message was encrypted.
+	EncryptedToKeyIds        []uint64            // the list of recipient key ids.
+	IsSymmetricallyEncrypted bool                // true if a passphrase could have decrypted the message.
+	DecryptedWith            Key                 // the private key used to decrypt the message, if any.
+	IsSigned                 bool                // true if the message is signed.
+	SignedByKeyId            uint64              // the key id of the signer, if any.
+	SignedBy                 *Key                // the key of the signer, if available.
+	LiteralData              *packet.LiteralData // the metadata of the contents
+	UnverifiedBody           io.Reader           // the contents of the message.
+
+	// If IsSigned is true and SignedBy is non-zero then the signature will
+	// be verified as UnverifiedBody is read. The signature cannot be
+	// checked until the whole of UnverifiedBody is read so UnverifiedBody
+	// must be consumed until EOF before the data can trusted. Even if a
+	// message isn't signed (or the signer is unknown) the data may contain
+	// an authentication code that is only checked once UnverifiedBody has
+	// been consumed. Once EOF has been seen, the following fields are
+	// valid. (An authentication code failure is reported as a
+	// SignatureError error when reading from UnverifiedBody.)
+	SignatureError os.Error          // nil if the signature is good.
+	Signature      *packet.Signature // the signature packet itself.
+
+	decrypted io.ReadCloser
+}
+
+// A PromptFunction is used as a callback by functions that may need to decrypt
+// a private key, or prompt for a passphrase. It is called with a list of
+// acceptable, encrypted private keys and a boolean that indicates whether a
+// passphrase is usable. It should either decrypt a private key or return a
+// passphrase to try. If the decrypted private key or given passphrase isn't
+// correct, the function will be called again, forever. Any error returned will
+// be passed up.
+type PromptFunction func(keys []Key, symmetric bool) ([]byte, os.Error)
+
+// A keyEnvelopePair is used to store a private key with the envelope that
+// contains a symmetric key, encrypted with that key.
+type keyEnvelopePair struct {
+	key          Key
+	encryptedKey *packet.EncryptedKey
+}
+
+// ReadMessage parses an OpenPGP message that may be signed and/or encrypted.
+// The given KeyRing should contain both public keys (for signature
+// verification) and, possibly encrypted, private keys for decrypting.
+func ReadMessage(r io.Reader, keyring KeyRing, prompt PromptFunction) (md *MessageDetails, err os.Error) {
+	var p packet.Packet
+
+	var symKeys []*packet.SymmetricKeyEncrypted
+	var pubKeys []keyEnvelopePair
+	var se *packet.SymmetricallyEncrypted
+
+	packets := packet.NewReader(r)
+	md = new(MessageDetails)
+	md.IsEncrypted = true
+
+	// The message, if encrypted, starts with a number of packets
+	// containing an encrypted decryption key. The decryption key is either
+	// encrypted to a public key, or with a passphrase. This loop
+	// collects these packets.
+ParsePackets:
+	for {
+		p, err = packets.Next()
+		if err != nil {
+			return nil, err
+		}
+		switch p := p.(type) {
+		case *packet.SymmetricKeyEncrypted:
+			// This packet contains the decryption key encrypted with a passphrase.
+			md.IsSymmetricallyEncrypted = true
+			symKeys = append(symKeys, p)
+		case *packet.EncryptedKey:
+			// This packet contains the decryption key encrypted to a public key.
+			md.EncryptedToKeyIds = append(md.EncryptedToKeyIds, p.KeyId)
+			switch p.Algo {
+			case packet.PubKeyAlgoRSA, packet.PubKeyAlgoRSAEncryptOnly, packet.PubKeyAlgoElGamal:
+				break
+			default:
+				continue
+			}
+			var keys []Key
+			if p.KeyId == 0 {
+				keys = keyring.DecryptionKeys()
+			} else {
+				keys = keyring.KeysById(p.KeyId)
+			}
+			for _, k := range keys {
+				pubKeys = append(pubKeys, keyEnvelopePair{k, p})
+			}
+		case *packet.SymmetricallyEncrypted:
+			se = p
+			break ParsePackets
+		case *packet.Compressed, *packet.LiteralData, *packet.OnePassSignature:
+			// This message isn't encrypted.
+			if len(symKeys) != 0 || len(pubKeys) != 0 {
+				return nil, error.StructuralError("key material not followed by encrypted message")
+			}
+			packets.Unread(p)
+			return readSignedMessage(packets, nil, keyring)
+		}
+	}
+
+	var candidates []Key
+	var decrypted io.ReadCloser
+
+	// Now that we have the list of encrypted keys we need to decrypt at
+	// least one of them or, if we cannot, we need to call the prompt
+	// function so that it can decrypt a key or give us a passphrase.
+FindKey:
+	for {
+		// See if any of the keys already have a private key available
+		candidates = candidates[:0]
+		candidateFingerprints := make(map[string]bool)
+
+		for _, pk := range pubKeys {
+			if pk.key.PrivateKey == nil {
+				continue
+			}
+			if !pk.key.PrivateKey.Encrypted {
+				if len(pk.encryptedKey.Key) == 0 {
+					pk.encryptedKey.Decrypt(pk.key.PrivateKey)
+				}
+				if len(pk.encryptedKey.Key) == 0 {
+					continue
+				}
+				decrypted, err = se.Decrypt(pk.encryptedKey.CipherFunc, pk.encryptedKey.Key)
+				if err != nil && err != error.KeyIncorrectError {
+					return nil, err
+				}
+				if decrypted != nil {
+					md.DecryptedWith = pk.key
+					break FindKey
+				}
+			} else {
+				fpr := string(pk.key.PublicKey.Fingerprint[:])
+				if v := candidateFingerprints[fpr]; v {
+					continue
+				}
+				candidates = append(candidates, pk.key)
+				candidateFingerprints[fpr] = true
+			}
+		}
+
+		if len(candidates) == 0 && len(symKeys) == 0 {
+			return nil, error.KeyIncorrectError
+		}
+
+		if prompt == nil {
+			return nil, error.KeyIncorrectError
+		}
+
+		passphrase, err := prompt(candidates, len(symKeys) != 0)
+		if err != nil {
+			return nil, err
+		}
+
+		// Try the symmetric passphrase first
+		if len(symKeys) != 0 && passphrase != nil {
+			for _, s := range symKeys {
+				err = s.Decrypt(passphrase)
+				if err == nil && !s.Encrypted {
+					decrypted, err = se.Decrypt(s.CipherFunc, s.Key)
+					if err != nil && err != error.KeyIncorrectError {
+						return nil, err
+					}
+					if decrypted != nil {
+						break FindKey
+					}
+				}
+
+			}
+		}
+	}
+
+	md.decrypted = decrypted
+	packets.Push(decrypted)
+	return readSignedMessage(packets, md, keyring)
+}
+
+// readSignedMessage reads a possibly signed message if mdin is non-zero then
+// that structure is updated and returned. Otherwise a fresh MessageDetails is
+// used.
+func readSignedMessage(packets *packet.Reader, mdin *MessageDetails, keyring KeyRing) (md *MessageDetails, err os.Error) {
+	if mdin == nil {
+		mdin = new(MessageDetails)
+	}
+	md = mdin
+
+	var p packet.Packet
+	var h hash.Hash
+	var wrappedHash hash.Hash
+FindLiteralData:
+	for {
+		p, err = packets.Next()
+		if err != nil {
+			return nil, err
+		}
+		switch p := p.(type) {
+		case *packet.Compressed:
+			packets.Push(p.Body)
+		case *packet.OnePassSignature:
+			if !p.IsLast {
+				return nil, error.UnsupportedError("nested signatures")
+			}
+
+			h, wrappedHash, err = hashForSignature(p.Hash, p.SigType)
+			if err != nil {
+				md = nil
+				return
+			}
+
+			md.IsSigned = true
+			md.SignedByKeyId = p.KeyId
+			keys := keyring.KeysById(p.KeyId)
+			for i, key := range keys {
+				if key.SelfSignature.FlagsValid && !key.SelfSignature.FlagSign {
+					continue
+				}
+				md.SignedBy = &keys[i]
+				break
+			}
+		case *packet.LiteralData:
+			md.LiteralData = p
+			break FindLiteralData
+		}
+	}
+
+	if md.SignedBy != nil {
+		md.UnverifiedBody = &signatureCheckReader{packets, h, wrappedHash, md}
+	} else if md.decrypted != nil {
+		md.UnverifiedBody = checkReader{md}
+	} else {
+		md.UnverifiedBody = md.LiteralData.Body
+	}
+
+	return md, nil
+}
+
+// hashForSignature returns a pair of hashes that can be used to verify a
+// signature. The signature may specify that the contents of the signed message
+// should be preprocessed (i.e. to normalize line endings). Thus this function
+// returns two hashes. The second should be used to hash the message itself and
+// performs any needed preprocessing.
+func hashForSignature(hashId crypto.Hash, sigType packet.SignatureType) (hash.Hash, hash.Hash, os.Error) {
+	h := hashId.New()
+	if h == nil {
+		return nil, nil, error.UnsupportedError("hash not available: " + strconv.Itoa(int(hashId)))
+	}
+
+	switch sigType {
+	case packet.SigTypeBinary:
+		return h, h, nil
+	case packet.SigTypeText:
+		return h, NewCanonicalTextHash(h), nil
+	}
+
+	return nil, nil, error.UnsupportedError("unsupported signature type: " + strconv.Itoa(int(sigType)))
+}
+
+// checkReader wraps an io.Reader from a LiteralData packet. When it sees EOF
+// it closes the ReadCloser from any SymmetricallyEncrypted packet to trigger
+// MDC checks.
+type checkReader struct {
+	md *MessageDetails
+}
+
+func (cr checkReader) Read(buf []byte) (n int, err os.Error) {
+	n, err = cr.md.LiteralData.Body.Read(buf)
+	if err == os.EOF {
+		mdcErr := cr.md.decrypted.Close()
+		if mdcErr != nil {
+			err = mdcErr
+		}
+	}
+	return
+}
+
+// signatureCheckReader wraps an io.Reader from a LiteralData packet and hashes
+// the data as it is read. When it sees an EOF from the underlying io.Reader
+// it parses and checks a trailing Signature packet and triggers any MDC checks.
+type signatureCheckReader struct {
+	packets        *packet.Reader
+	h, wrappedHash hash.Hash
+	md             *MessageDetails
+}
+
+func (scr *signatureCheckReader) Read(buf []byte) (n int, err os.Error) {
+	n, err = scr.md.LiteralData.Body.Read(buf)
+	scr.wrappedHash.Write(buf[:n])
+	if err == os.EOF {
+		var p packet.Packet
+		p, scr.md.SignatureError = scr.packets.Next()
+		if scr.md.SignatureError != nil {
+			return
+		}
+
+		var ok bool
+		if scr.md.Signature, ok = p.(*packet.Signature); !ok {
+			scr.md.SignatureError = error.StructuralError("LiteralData not followed by Signature")
+			return
+		}
+
+		scr.md.SignatureError = scr.md.SignedBy.PublicKey.VerifySignature(scr.h, scr.md.Signature)
+
+		// The SymmetricallyEncrypted packet, if any, might have an
+		// unsigned hash of its own. In order to check this we need to
+		// close that Reader.
+		if scr.md.decrypted != nil {
+			mdcErr := scr.md.decrypted.Close()
+			if mdcErr != nil {
+				err = mdcErr
+			}
+		}
+	}
+	return
+}
+
+// CheckDetachedSignature takes a signed file and a detached signature and
+// returns the signer if the signature is valid. If the signer isn't know,
+// UnknownIssuerError is returned.
+func CheckDetachedSignature(keyring KeyRing, signed, signature io.Reader) (signer *Entity, err os.Error) {
+	p, err := packet.Read(signature)
+	if err != nil {
+		return
+	}
+
+	sig, ok := p.(*packet.Signature)
+	if !ok {
+		return nil, error.StructuralError("non signature packet found")
+	}
+
+	if sig.IssuerKeyId == nil {
+		return nil, error.StructuralError("signature doesn't have an issuer")
+	}
+
+	keys := keyring.KeysById(*sig.IssuerKeyId)
+	if len(keys) == 0 {
+		return nil, error.UnknownIssuerError
+	}
+
+	h, wrappedHash, err := hashForSignature(sig.Hash, sig.SigType)
+	if err != nil {
+		return
+	}
+
+	_, err = io.Copy(wrappedHash, signed)
+	if err != nil && err != os.EOF {
+		return
+	}
+
+	for _, key := range keys {
+		if key.SelfSignature.FlagsValid && !key.SelfSignature.FlagSign {
+			continue
+		}
+		err = key.PublicKey.VerifySignature(h, sig)
+		if err == nil {
+			return key.Entity, nil
+		}
+	}
+
+	if err != nil {
+		return
+	}
+
+	return nil, error.UnknownIssuerError
+}
+
+// CheckArmoredDetachedSignature performs the same actions as
+// CheckDetachedSignature but expects the signature to be armored.
+func CheckArmoredDetachedSignature(keyring KeyRing, signed, signature io.Reader) (signer *Entity, err os.Error) {
+	body, err := readArmored(signature, SignatureType)
+	if err != nil {
+		return
+	}
+
+	return CheckDetachedSignature(keyring, signed, body)
+}