diff options
Diffstat (limited to 'vendor/golang.org/x/crypto/ssh/certs.go')
| -rw-r--r-- | vendor/golang.org/x/crypto/ssh/certs.go | 519 |
1 files changed, 519 insertions, 0 deletions
diff --git a/vendor/golang.org/x/crypto/ssh/certs.go b/vendor/golang.org/x/crypto/ssh/certs.go new file mode 100644 index 00000000..5c9fadce --- /dev/null +++ b/vendor/golang.org/x/crypto/ssh/certs.go @@ -0,0 +1,519 @@ +// Copyright 2012 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 ( + "bytes" + "errors" + "fmt" + "io" + "net" + "sort" + "time" +) + +// These constants from [PROTOCOL.certkeys] represent the algorithm names +// for certificate types supported by this package. +const ( + CertAlgoRSAv01 = "ssh-rsa-cert-v01@openssh.com" + CertAlgoDSAv01 = "ssh-dss-cert-v01@openssh.com" + CertAlgoECDSA256v01 = "ecdsa-sha2-nistp256-cert-v01@openssh.com" + CertAlgoECDSA384v01 = "ecdsa-sha2-nistp384-cert-v01@openssh.com" + CertAlgoECDSA521v01 = "ecdsa-sha2-nistp521-cert-v01@openssh.com" + CertAlgoED25519v01 = "ssh-ed25519-cert-v01@openssh.com" +) + +// Certificate types distinguish between host and user +// certificates. The values can be set in the CertType field of +// Certificate. +const ( + UserCert = 1 + HostCert = 2 +) + +// Signature represents a cryptographic signature. +type Signature struct { + Format string + Blob []byte +} + +// CertTimeInfinity can be used for OpenSSHCertV01.ValidBefore to indicate that +// a certificate does not expire. +const CertTimeInfinity = 1<<64 - 1 + +// An Certificate represents an OpenSSH certificate as defined in +// [PROTOCOL.certkeys]?rev=1.8. +type Certificate struct { + Nonce []byte + Key PublicKey + Serial uint64 + CertType uint32 + KeyId string + ValidPrincipals []string + ValidAfter uint64 + ValidBefore uint64 + Permissions + Reserved []byte + SignatureKey PublicKey + Signature *Signature +} + +// genericCertData holds the key-independent part of the certificate data. +// Overall, certificates contain an nonce, public key fields and +// key-independent fields. +type genericCertData struct { + Serial uint64 + CertType uint32 + KeyId string + ValidPrincipals []byte + ValidAfter uint64 + ValidBefore uint64 + CriticalOptions []byte + Extensions []byte + Reserved []byte + SignatureKey []byte + Signature []byte +} + +func marshalStringList(namelist []string) []byte { + var to []byte + for _, name := range namelist { + s := struct{ N string }{name} + to = append(to, Marshal(&s)...) + } + return to +} + +type optionsTuple struct { + Key string + Value []byte +} + +type optionsTupleValue struct { + Value string +} + +// serialize a map of critical options or extensions +// issue #10569 - per [PROTOCOL.certkeys] and SSH implementation, +// we need two length prefixes for a non-empty string value +func marshalTuples(tups map[string]string) []byte { + keys := make([]string, 0, len(tups)) + for key := range tups { + keys = append(keys, key) + } + sort.Strings(keys) + + var ret []byte + for _, key := range keys { + s := optionsTuple{Key: key} + if value := tups[key]; len(value) > 0 { + s.Value = Marshal(&optionsTupleValue{value}) + } + ret = append(ret, Marshal(&s)...) + } + return ret +} + +// issue #10569 - per [PROTOCOL.certkeys] and SSH implementation, +// we need two length prefixes for a non-empty option value +func parseTuples(in []byte) (map[string]string, error) { + tups := map[string]string{} + var lastKey string + var haveLastKey bool + + for len(in) > 0 { + var key, val, extra []byte + var ok bool + + if key, in, ok = parseString(in); !ok { + return nil, errShortRead + } + keyStr := string(key) + // according to [PROTOCOL.certkeys], the names must be in + // lexical order. + if haveLastKey && keyStr <= lastKey { + return nil, fmt.Errorf("ssh: certificate options are not in lexical order") + } + lastKey, haveLastKey = keyStr, true + // the next field is a data field, which if non-empty has a string embedded + if val, in, ok = parseString(in); !ok { + return nil, errShortRead + } + if len(val) > 0 { + val, extra, ok = parseString(val) + if !ok { + return nil, errShortRead + } + if len(extra) > 0 { + return nil, fmt.Errorf("ssh: unexpected trailing data after certificate option value") + } + tups[keyStr] = string(val) + } else { + tups[keyStr] = "" + } + } + return tups, nil +} + +func parseCert(in []byte, privAlgo string) (*Certificate, error) { + nonce, rest, ok := parseString(in) + if !ok { + return nil, errShortRead + } + + key, rest, err := parsePubKey(rest, privAlgo) + if err != nil { + return nil, err + } + + var g genericCertData + if err := Unmarshal(rest, &g); err != nil { + return nil, err + } + + c := &Certificate{ + Nonce: nonce, + Key: key, + Serial: g.Serial, + CertType: g.CertType, + KeyId: g.KeyId, + ValidAfter: g.ValidAfter, + ValidBefore: g.ValidBefore, + } + + for principals := g.ValidPrincipals; len(principals) > 0; { + principal, rest, ok := parseString(principals) + if !ok { + return nil, errShortRead + } + c.ValidPrincipals = append(c.ValidPrincipals, string(principal)) + principals = rest + } + + c.CriticalOptions, err = parseTuples(g.CriticalOptions) + if err != nil { + return nil, err + } + c.Extensions, err = parseTuples(g.Extensions) + if err != nil { + return nil, err + } + c.Reserved = g.Reserved + k, err := ParsePublicKey(g.SignatureKey) + if err != nil { + return nil, err + } + + c.SignatureKey = k + c.Signature, rest, ok = parseSignatureBody(g.Signature) + if !ok || len(rest) > 0 { + return nil, errors.New("ssh: signature parse error") + } + + return c, nil +} + +type openSSHCertSigner struct { + pub *Certificate + signer Signer +} + +// NewCertSigner returns a Signer that signs with the given Certificate, whose +// private key is held by signer. It returns an error if the public key in cert +// doesn't match the key used by signer. +func NewCertSigner(cert *Certificate, signer Signer) (Signer, error) { + if bytes.Compare(cert.Key.Marshal(), signer.PublicKey().Marshal()) != 0 { + return nil, errors.New("ssh: signer and cert have different public key") + } + + return &openSSHCertSigner{cert, signer}, nil +} + +func (s *openSSHCertSigner) Sign(rand io.Reader, data []byte) (*Signature, error) { + return s.signer.Sign(rand, data) +} + +func (s *openSSHCertSigner) PublicKey() PublicKey { + return s.pub +} + +const sourceAddressCriticalOption = "source-address" + +// CertChecker does the work of verifying a certificate. Its methods +// can be plugged into ClientConfig.HostKeyCallback and +// ServerConfig.PublicKeyCallback. For the CertChecker to work, +// minimally, the IsAuthority callback should be set. +type CertChecker struct { + // SupportedCriticalOptions lists the CriticalOptions that the + // server application layer understands. These are only used + // for user certificates. + SupportedCriticalOptions []string + + // IsUserAuthority should return true if the key is recognized as an + // authority for the given user certificate. This allows for + // certificates to be signed by other certificates. This must be set + // if this CertChecker will be checking user certificates. + IsUserAuthority func(auth PublicKey) bool + + // IsHostAuthority should report whether the key is recognized as + // an authority for this host. This allows for certificates to be + // signed by other keys, and for those other keys to only be valid + // signers for particular hostnames. This must be set if this + // CertChecker will be checking host certificates. + IsHostAuthority func(auth PublicKey, address string) bool + + // Clock is used for verifying time stamps. If nil, time.Now + // is used. + Clock func() time.Time + + // UserKeyFallback is called when CertChecker.Authenticate encounters a + // public key that is not a certificate. It must implement validation + // of user keys or else, if nil, all such keys are rejected. + UserKeyFallback func(conn ConnMetadata, key PublicKey) (*Permissions, error) + + // HostKeyFallback is called when CertChecker.CheckHostKey encounters a + // public key that is not a certificate. It must implement host key + // validation or else, if nil, all such keys are rejected. + HostKeyFallback HostKeyCallback + + // IsRevoked is called for each certificate so that revocation checking + // can be implemented. It should return true if the given certificate + // is revoked and false otherwise. If nil, no certificates are + // considered to have been revoked. + IsRevoked func(cert *Certificate) bool +} + +// CheckHostKey checks a host key certificate. This method can be +// plugged into ClientConfig.HostKeyCallback. +func (c *CertChecker) CheckHostKey(addr string, remote net.Addr, key PublicKey) error { + cert, ok := key.(*Certificate) + if !ok { + if c.HostKeyFallback != nil { + return c.HostKeyFallback(addr, remote, key) + } + return errors.New("ssh: non-certificate host key") + } + if cert.CertType != HostCert { + return fmt.Errorf("ssh: certificate presented as a host key has type %d", cert.CertType) + } + if !c.IsHostAuthority(cert.SignatureKey, addr) { + return fmt.Errorf("ssh: no authorities for hostname: %v", addr) + } + + hostname, _, err := net.SplitHostPort(addr) + if err != nil { + return err + } + + // Pass hostname only as principal for host certificates (consistent with OpenSSH) + return c.CheckCert(hostname, cert) +} + +// Authenticate checks a user certificate. Authenticate can be used as +// a value for ServerConfig.PublicKeyCallback. +func (c *CertChecker) Authenticate(conn ConnMetadata, pubKey PublicKey) (*Permissions, error) { + cert, ok := pubKey.(*Certificate) + if !ok { + if c.UserKeyFallback != nil { + return c.UserKeyFallback(conn, pubKey) + } + return nil, errors.New("ssh: normal key pairs not accepted") + } + + if cert.CertType != UserCert { + return nil, fmt.Errorf("ssh: cert has type %d", cert.CertType) + } + if !c.IsUserAuthority(cert.SignatureKey) { + return nil, fmt.Errorf("ssh: certificate signed by unrecognized authority") + } + + if err := c.CheckCert(conn.User(), cert); err != nil { + return nil, err + } + + return &cert.Permissions, nil +} + +// CheckCert checks CriticalOptions, ValidPrincipals, revocation, timestamp and +// the signature of the certificate. +func (c *CertChecker) CheckCert(principal string, cert *Certificate) error { + if c.IsRevoked != nil && c.IsRevoked(cert) { + return fmt.Errorf("ssh: certicate serial %d revoked", cert.Serial) + } + + for opt := range cert.CriticalOptions { + // sourceAddressCriticalOption will be enforced by + // serverAuthenticate + if opt == sourceAddressCriticalOption { + continue + } + + found := false + for _, supp := range c.SupportedCriticalOptions { + if supp == opt { + found = true + break + } + } + if !found { + return fmt.Errorf("ssh: unsupported critical option %q in certificate", opt) + } + } + + if len(cert.ValidPrincipals) > 0 { + // By default, certs are valid for all users/hosts. + found := false + for _, p := range cert.ValidPrincipals { + if p == principal { + found = true + break + } + } + if !found { + return fmt.Errorf("ssh: principal %q not in the set of valid principals for given certificate: %q", principal, cert.ValidPrincipals) + } + } + + clock := c.Clock + if clock == nil { + clock = time.Now + } + + unixNow := clock().Unix() + if after := int64(cert.ValidAfter); after < 0 || unixNow < int64(cert.ValidAfter) { + return fmt.Errorf("ssh: cert is not yet valid") + } + if before := int64(cert.ValidBefore); cert.ValidBefore != uint64(CertTimeInfinity) && (unixNow >= before || before < 0) { + return fmt.Errorf("ssh: cert has expired") + } + if err := cert.SignatureKey.Verify(cert.bytesForSigning(), cert.Signature); err != nil { + return fmt.Errorf("ssh: certificate signature does not verify") + } + + return nil +} + +// SignCert sets c.SignatureKey to the authority's public key and stores a +// Signature, by authority, in the certificate. +func (c *Certificate) SignCert(rand io.Reader, authority Signer) error { + c.Nonce = make([]byte, 32) + if _, err := io.ReadFull(rand, c.Nonce); err != nil { + return err + } + c.SignatureKey = authority.PublicKey() + + sig, err := authority.Sign(rand, c.bytesForSigning()) + if err != nil { + return err + } + c.Signature = sig + return nil +} + +var certAlgoNames = map[string]string{ + KeyAlgoRSA: CertAlgoRSAv01, + KeyAlgoDSA: CertAlgoDSAv01, + KeyAlgoECDSA256: CertAlgoECDSA256v01, + KeyAlgoECDSA384: CertAlgoECDSA384v01, + KeyAlgoECDSA521: CertAlgoECDSA521v01, + KeyAlgoED25519: CertAlgoED25519v01, +} + +// certToPrivAlgo returns the underlying algorithm for a certificate algorithm. +// Panics if a non-certificate algorithm is passed. +func certToPrivAlgo(algo string) string { + for privAlgo, pubAlgo := range certAlgoNames { + if pubAlgo == algo { + return privAlgo + } + } + panic("unknown cert algorithm") +} + +func (cert *Certificate) bytesForSigning() []byte { + c2 := *cert + c2.Signature = nil + out := c2.Marshal() + // Drop trailing signature length. + return out[:len(out)-4] +} + +// Marshal serializes c into OpenSSH's wire format. It is part of the +// PublicKey interface. +func (c *Certificate) Marshal() []byte { + generic := genericCertData{ + Serial: c.Serial, + CertType: c.CertType, + KeyId: c.KeyId, + ValidPrincipals: marshalStringList(c.ValidPrincipals), + ValidAfter: uint64(c.ValidAfter), + ValidBefore: uint64(c.ValidBefore), + CriticalOptions: marshalTuples(c.CriticalOptions), + Extensions: marshalTuples(c.Extensions), + Reserved: c.Reserved, + SignatureKey: c.SignatureKey.Marshal(), + } + if c.Signature != nil { + generic.Signature = Marshal(c.Signature) + } + genericBytes := Marshal(&generic) + keyBytes := c.Key.Marshal() + _, keyBytes, _ = parseString(keyBytes) + prefix := Marshal(&struct { + Name string + Nonce []byte + Key []byte `ssh:"rest"` + }{c.Type(), c.Nonce, keyBytes}) + + result := make([]byte, 0, len(prefix)+len(genericBytes)) + result = append(result, prefix...) + result = append(result, genericBytes...) + return result +} + +// Type returns the key name. It is part of the PublicKey interface. +func (c *Certificate) Type() string { + algo, ok := certAlgoNames[c.Key.Type()] + if !ok { + panic("unknown cert key type " + c.Key.Type()) + } + return algo +} + +// Verify verifies a signature against the certificate's public +// key. It is part of the PublicKey interface. +func (c *Certificate) Verify(data []byte, sig *Signature) error { + return c.Key.Verify(data, sig) +} + +func parseSignatureBody(in []byte) (out *Signature, rest []byte, ok bool) { + format, in, ok := parseString(in) + if !ok { + return + } + + out = &Signature{ + Format: string(format), + } + + if out.Blob, in, ok = parseString(in); !ok { + return + } + + return out, in, ok +} + +func parseSignature(in []byte) (out *Signature, rest []byte, ok bool) { + sigBytes, rest, ok := parseString(in) + if !ok { + return + } + + out, trailing, ok := parseSignatureBody(sigBytes) + if !ok || len(trailing) > 0 { + return nil, nil, false + } + return +} |