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Diffstat (limited to 'vendor/golang.org/x/crypto/ssh/common.go')
| -rw-r--r-- | vendor/golang.org/x/crypto/ssh/common.go | 404 |
1 files changed, 404 insertions, 0 deletions
diff --git a/vendor/golang.org/x/crypto/ssh/common.go b/vendor/golang.org/x/crypto/ssh/common.go new file mode 100644 index 000000000..290382d05 --- /dev/null +++ b/vendor/golang.org/x/crypto/ssh/common.go @@ -0,0 +1,404 @@ +// 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 ssh + +import ( + "crypto" + "crypto/rand" + "fmt" + "io" + "math" + "sync" + + _ "crypto/sha1" + _ "crypto/sha256" + _ "crypto/sha512" +) + +// These are string constants in the SSH protocol. +const ( + compressionNone = "none" + serviceUserAuth = "ssh-userauth" + serviceSSH = "ssh-connection" +) + +// supportedCiphers lists ciphers we support but might not recommend. +var supportedCiphers = []string{ + "aes128-ctr", "aes192-ctr", "aes256-ctr", + "aes128-gcm@openssh.com", + chacha20Poly1305ID, + "arcfour256", "arcfour128", "arcfour", + aes128cbcID, + tripledescbcID, +} + +// preferredCiphers specifies the default preference for ciphers. +var preferredCiphers = []string{ + "aes128-gcm@openssh.com", + chacha20Poly1305ID, + "aes128-ctr", "aes192-ctr", "aes256-ctr", +} + +// supportedKexAlgos specifies the supported key-exchange algorithms in +// preference order. +var supportedKexAlgos = []string{ + kexAlgoCurve25519SHA256, + // P384 and P521 are not constant-time yet, but since we don't + // reuse ephemeral keys, using them for ECDH should be OK. + kexAlgoECDH256, kexAlgoECDH384, kexAlgoECDH521, + kexAlgoDH14SHA1, kexAlgoDH1SHA1, +} + +// serverForbiddenKexAlgos contains key exchange algorithms, that are forbidden +// for the server half. +var serverForbiddenKexAlgos = map[string]struct{}{ + kexAlgoDHGEXSHA1: {}, // server half implementation is only minimal to satisfy the automated tests + kexAlgoDHGEXSHA256: {}, // server half implementation is only minimal to satisfy the automated tests +} + +// preferredKexAlgos specifies the default preference for key-exchange algorithms +// in preference order. +var preferredKexAlgos = []string{ + kexAlgoCurve25519SHA256, + kexAlgoECDH256, kexAlgoECDH384, kexAlgoECDH521, + kexAlgoDH14SHA1, +} + +// supportedHostKeyAlgos specifies the supported host-key algorithms (i.e. methods +// of authenticating servers) in preference order. +var supportedHostKeyAlgos = []string{ + CertAlgoRSAv01, CertAlgoDSAv01, CertAlgoECDSA256v01, + CertAlgoECDSA384v01, CertAlgoECDSA521v01, CertAlgoED25519v01, + + KeyAlgoECDSA256, KeyAlgoECDSA384, KeyAlgoECDSA521, + KeyAlgoRSA, KeyAlgoDSA, + + KeyAlgoED25519, +} + +// supportedMACs specifies a default set of MAC algorithms in preference order. +// This is based on RFC 4253, section 6.4, but with hmac-md5 variants removed +// because they have reached the end of their useful life. +var supportedMACs = []string{ + "hmac-sha2-256-etm@openssh.com", "hmac-sha2-256", "hmac-sha1", "hmac-sha1-96", +} + +var supportedCompressions = []string{compressionNone} + +// hashFuncs keeps the mapping of supported algorithms to their respective +// hashes needed for signature verification. +var hashFuncs = map[string]crypto.Hash{ + KeyAlgoRSA: crypto.SHA1, + KeyAlgoDSA: crypto.SHA1, + KeyAlgoECDSA256: crypto.SHA256, + KeyAlgoECDSA384: crypto.SHA384, + KeyAlgoECDSA521: crypto.SHA512, + CertAlgoRSAv01: crypto.SHA1, + CertAlgoDSAv01: crypto.SHA1, + CertAlgoECDSA256v01: crypto.SHA256, + CertAlgoECDSA384v01: crypto.SHA384, + CertAlgoECDSA521v01: crypto.SHA512, +} + +// unexpectedMessageError results when the SSH message that we received didn't +// match what we wanted. +func unexpectedMessageError(expected, got uint8) error { + return fmt.Errorf("ssh: unexpected message type %d (expected %d)", got, expected) +} + +// parseError results from a malformed SSH message. +func parseError(tag uint8) error { + return fmt.Errorf("ssh: parse error in message type %d", tag) +} + +func findCommon(what string, client []string, server []string) (common string, err error) { + for _, c := range client { + for _, s := range server { + if c == s { + return c, nil + } + } + } + return "", fmt.Errorf("ssh: no common algorithm for %s; client offered: %v, server offered: %v", what, client, server) +} + +// directionAlgorithms records algorithm choices in one direction (either read or write) +type directionAlgorithms struct { + Cipher string + MAC string + Compression string +} + +// rekeyBytes returns a rekeying intervals in bytes. +func (a *directionAlgorithms) rekeyBytes() int64 { + // According to RFC4344 block ciphers should rekey after + // 2^(BLOCKSIZE/4) blocks. For all AES flavors BLOCKSIZE is + // 128. + switch a.Cipher { + case "aes128-ctr", "aes192-ctr", "aes256-ctr", gcmCipherID, aes128cbcID: + return 16 * (1 << 32) + + } + + // For others, stick with RFC4253 recommendation to rekey after 1 Gb of data. + return 1 << 30 +} + +type algorithms struct { + kex string + hostKey string + w directionAlgorithms + r directionAlgorithms +} + +func findAgreedAlgorithms(isClient bool, clientKexInit, serverKexInit *kexInitMsg) (algs *algorithms, err error) { + result := &algorithms{} + + result.kex, err = findCommon("key exchange", clientKexInit.KexAlgos, serverKexInit.KexAlgos) + if err != nil { + return + } + + result.hostKey, err = findCommon("host key", clientKexInit.ServerHostKeyAlgos, serverKexInit.ServerHostKeyAlgos) + if err != nil { + return + } + + stoc, ctos := &result.w, &result.r + if isClient { + ctos, stoc = stoc, ctos + } + + ctos.Cipher, err = findCommon("client to server cipher", clientKexInit.CiphersClientServer, serverKexInit.CiphersClientServer) + if err != nil { + return + } + + stoc.Cipher, err = findCommon("server to client cipher", clientKexInit.CiphersServerClient, serverKexInit.CiphersServerClient) + if err != nil { + return + } + + ctos.MAC, err = findCommon("client to server MAC", clientKexInit.MACsClientServer, serverKexInit.MACsClientServer) + if err != nil { + return + } + + stoc.MAC, err = findCommon("server to client MAC", clientKexInit.MACsServerClient, serverKexInit.MACsServerClient) + if err != nil { + return + } + + ctos.Compression, err = findCommon("client to server compression", clientKexInit.CompressionClientServer, serverKexInit.CompressionClientServer) + if err != nil { + return + } + + stoc.Compression, err = findCommon("server to client compression", clientKexInit.CompressionServerClient, serverKexInit.CompressionServerClient) + if err != nil { + return + } + + return result, nil +} + +// If rekeythreshold is too small, we can't make any progress sending +// stuff. +const minRekeyThreshold uint64 = 256 + +// Config contains configuration data common to both ServerConfig and +// ClientConfig. +type Config struct { + // Rand provides the source of entropy for cryptographic + // primitives. If Rand is nil, the cryptographic random reader + // in package crypto/rand will be used. + Rand io.Reader + + // The maximum number of bytes sent or received after which a + // new key is negotiated. It must be at least 256. If + // unspecified, a size suitable for the chosen cipher is used. + RekeyThreshold uint64 + + // The allowed key exchanges algorithms. If unspecified then a + // default set of algorithms is used. + KeyExchanges []string + + // The allowed cipher algorithms. If unspecified then a sensible + // default is used. + Ciphers []string + + // The allowed MAC algorithms. If unspecified then a sensible default + // is used. + MACs []string +} + +// SetDefaults sets sensible values for unset fields in config. This is +// exported for testing: Configs passed to SSH functions are copied and have +// default values set automatically. +func (c *Config) SetDefaults() { + if c.Rand == nil { + c.Rand = rand.Reader + } + if c.Ciphers == nil { + c.Ciphers = preferredCiphers + } + var ciphers []string + for _, c := range c.Ciphers { + if cipherModes[c] != nil { + // reject the cipher if we have no cipherModes definition + ciphers = append(ciphers, c) + } + } + c.Ciphers = ciphers + + if c.KeyExchanges == nil { + c.KeyExchanges = preferredKexAlgos + } + + if c.MACs == nil { + c.MACs = supportedMACs + } + + if c.RekeyThreshold == 0 { + // cipher specific default + } else if c.RekeyThreshold < minRekeyThreshold { + c.RekeyThreshold = minRekeyThreshold + } else if c.RekeyThreshold >= math.MaxInt64 { + // Avoid weirdness if somebody uses -1 as a threshold. + c.RekeyThreshold = math.MaxInt64 + } +} + +// buildDataSignedForAuth returns the data that is signed in order to prove +// possession of a private key. See RFC 4252, section 7. +func buildDataSignedForAuth(sessionID []byte, req userAuthRequestMsg, algo, pubKey []byte) []byte { + data := struct { + Session []byte + Type byte + User string + Service string + Method string + Sign bool + Algo []byte + PubKey []byte + }{ + sessionID, + msgUserAuthRequest, + req.User, + req.Service, + req.Method, + true, + algo, + pubKey, + } + return Marshal(data) +} + +func appendU16(buf []byte, n uint16) []byte { + return append(buf, byte(n>>8), byte(n)) +} + +func appendU32(buf []byte, n uint32) []byte { + return append(buf, byte(n>>24), byte(n>>16), byte(n>>8), byte(n)) +} + +func appendU64(buf []byte, n uint64) []byte { + return append(buf, + byte(n>>56), byte(n>>48), byte(n>>40), byte(n>>32), + byte(n>>24), byte(n>>16), byte(n>>8), byte(n)) +} + +func appendInt(buf []byte, n int) []byte { + return appendU32(buf, uint32(n)) +} + +func appendString(buf []byte, s string) []byte { + buf = appendU32(buf, uint32(len(s))) + buf = append(buf, s...) + return buf +} + +func appendBool(buf []byte, b bool) []byte { + if b { + return append(buf, 1) + } + return append(buf, 0) +} + +// newCond is a helper to hide the fact that there is no usable zero +// value for sync.Cond. +func newCond() *sync.Cond { return sync.NewCond(new(sync.Mutex)) } + +// window represents the buffer available to clients +// wishing to write to a channel. +type window struct { + *sync.Cond + win uint32 // RFC 4254 5.2 says the window size can grow to 2^32-1 + writeWaiters int + closed bool +} + +// add adds win to the amount of window available +// for consumers. +func (w *window) add(win uint32) bool { + // a zero sized window adjust is a noop. + if win == 0 { + return true + } + w.L.Lock() + if w.win+win < win { + w.L.Unlock() + return false + } + w.win += win + // It is unusual that multiple goroutines would be attempting to reserve + // window space, but not guaranteed. Use broadcast to notify all waiters + // that additional window is available. + w.Broadcast() + w.L.Unlock() + return true +} + +// close sets the window to closed, so all reservations fail +// immediately. +func (w *window) close() { + w.L.Lock() + w.closed = true + w.Broadcast() + w.L.Unlock() +} + +// reserve reserves win from the available window capacity. +// If no capacity remains, reserve will block. reserve may +// return less than requested. +func (w *window) reserve(win uint32) (uint32, error) { + var err error + w.L.Lock() + w.writeWaiters++ + w.Broadcast() + for w.win == 0 && !w.closed { + w.Wait() + } + w.writeWaiters-- + if w.win < win { + win = w.win + } + w.win -= win + if w.closed { + err = io.EOF + } + w.L.Unlock() + return win, err +} + +// waitWriterBlocked waits until some goroutine is blocked for further +// writes. It is used in tests only. +func (w *window) waitWriterBlocked() { + w.Cond.L.Lock() + for w.writeWaiters == 0 { + w.Cond.Wait() + } + w.Cond.L.Unlock() +} |