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Add ssh certificate support (#12281)

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* Add ssh certificate support

* Add ssh certificate support to builtin ssh

* Write trusted-user-ca-keys.pem based on configuration

* Update app.example.ini

* Update templates/user/settings/keys_principal.tmpl

Co-authored-by: silverwind <me@silverwind.io>

* Remove unused locale string

* Update options/locale/locale_en-US.ini

Co-authored-by: silverwind <me@silverwind.io>

* Update options/locale/locale_en-US.ini

Co-authored-by: silverwind <me@silverwind.io>

* Update models/ssh_key.go

Co-authored-by: silverwind <me@silverwind.io>

* Add missing creation of SSH.Rootpath

* Update cheatsheet, example and locale strings

* Update models/ssh_key.go

Co-authored-by: zeripath <art27@cantab.net>

* Update models/ssh_key.go

Co-authored-by: zeripath <art27@cantab.net>

* Update models/ssh_key.go

Co-authored-by: zeripath <art27@cantab.net>

* Update models/ssh_key.go

Co-authored-by: zeripath <art27@cantab.net>

* Update models/ssh_key.go

* Optimizations based on feedback

* Validate CA keys for external sshd

* Add filename option and change default filename

Add a SSH_TRUSTED_USER_CA_KEYS_FILENAME option which default is
RUN_USER/.ssh/gitea-trusted-user-ca-keys.pem

Do not write a file when SSH_TRUSTED_USER_CA_KEYS is empty.

Add some more documentation.

* Remove unneeded principalkey functions

* Add blank line

* Apply suggestions from code review

Co-authored-by: zeripath <art27@cantab.net>

* Add SSH_AUTHORIZED_PRINCIPALS_ALLOW option

This adds a SSH_AUTHORIZED_PRINCIPALS_ALLOW which is default
email,username this means that users only can add the principals
that match their email or username.

To allow anything the admin need to set the option anything.

This allows for a safe default in gitea which protects against malicious
users using other user's prinicipals. (before that user could set it).

This commit also has some small other fixes from the last code review.

* Rewrite principal keys file on user deletion

* Use correct rewrite method

* Set correct AuthorizedPrincipalsBackup default setting

* Rewrite principalsfile when adding principals

* Add update authorized_principals option to admin dashboard

* Handle non-primary emails

Signed-off-by: Andrew Thornton <art27@cantab.net>

* Add the command actually to the dashboard template

* Update models/ssh_key.go

Co-authored-by: silverwind <me@silverwind.io>

* By default do not show principal options unless there are CA keys set or they are explicitly set

Signed-off-by: Andrew Thornton <art27@cantab.net>

* allow settings when enabled

* Fix typos in TrustedUserCAKeys path

* Allow every CASignatureAlgorithms algorithm

As this depends on the content of TrustedUserCAKeys we should allow all
signature algorithms as admins can choose the specific algorithm on their
signing CA

* Update models/ssh_key.go

Co-authored-by: Lauris BH <lauris@nix.lv>

* Fix linting issue

Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: zeripath <art27@cantab.net>
Co-authored-by: Lauris BH <lauris@nix.lv>
Co-authored-by: techknowlogick <matti@mdranta.net>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>
This commit is contained in:
Wim 2020-10-11 02:38:09 +02:00 • committed by GitHub
parent 7eb8460132
commit 9066d09c57
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GPG key ID: 4AEE18F83AFDEB23
15 changed files with 557 additions and 28 deletions
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11
modules/cron/tasks_extended.go
View file

@ -67,6 +67,16 @@ func registerRewriteAllPublicKeys() {
})
}
func registerRewriteAllPrincipalKeys() {
RegisterTaskFatal("resync_all_sshprincipals", &BaseConfig{
Enabled: false,
RunAtStart: false,
Schedule: "@every 72h",
}, func(_ context.Context, _ *models.User, _ Config) error {
return models.RewriteAllPrincipalKeys()
})
}
func registerRepositoryUpdateHook() {
RegisterTaskFatal("resync_all_hooks", &BaseConfig{
Enabled: false,
@ -112,6 +122,7 @@ func initExtendedTasks() {
registerDeleteRepositoryArchives()
registerGarbageCollectRepositories()
registerRewriteAllPublicKeys()
registerRewriteAllPrincipalKeys()
registerRepositoryUpdateHook()
registerReinitMissingRepositories()
registerDeleteMissingRepositories()

111
modules/setting/setting.go
View file

@ -28,6 +28,7 @@ import (
shellquote "github.com/kballard/go-shellquote"
"github.com/unknwon/com"
gossh "golang.org/x/crypto/ssh"
ini "gopkg.in/ini.v1"
"strk.kbt.io/projects/go/libravatar"
)
@ -103,24 +104,31 @@ var (
StaticURLPrefix string
SSH = struct {
Disabled bool `ini:"DISABLE_SSH"`
StartBuiltinServer bool `ini:"START_SSH_SERVER"`
BuiltinServerUser string `ini:"BUILTIN_SSH_SERVER_USER"`
Domain string `ini:"SSH_DOMAIN"`
Port int `ini:"SSH_PORT"`
ListenHost string `ini:"SSH_LISTEN_HOST"`
ListenPort int `ini:"SSH_LISTEN_PORT"`
RootPath string `ini:"SSH_ROOT_PATH"`
ServerCiphers []string `ini:"SSH_SERVER_CIPHERS"`
ServerKeyExchanges []string `ini:"SSH_SERVER_KEY_EXCHANGES"`
ServerMACs []string `ini:"SSH_SERVER_MACS"`
KeyTestPath string `ini:"SSH_KEY_TEST_PATH"`
KeygenPath string `ini:"SSH_KEYGEN_PATH"`
AuthorizedKeysBackup bool `ini:"SSH_AUTHORIZED_KEYS_BACKUP"`
MinimumKeySizeCheck bool `ini:"-"`
MinimumKeySizes map[string]int `ini:"-"`
CreateAuthorizedKeysFile bool `ini:"SSH_CREATE_AUTHORIZED_KEYS_FILE"`
ExposeAnonymous bool `ini:"SSH_EXPOSE_ANONYMOUS"`
Disabled bool `ini:"DISABLE_SSH"`
StartBuiltinServer bool `ini:"START_SSH_SERVER"`
BuiltinServerUser string `ini:"BUILTIN_SSH_SERVER_USER"`
Domain string `ini:"SSH_DOMAIN"`
Port int `ini:"SSH_PORT"`
ListenHost string `ini:"SSH_LISTEN_HOST"`
ListenPort int `ini:"SSH_LISTEN_PORT"`
RootPath string `ini:"SSH_ROOT_PATH"`
ServerCiphers []string `ini:"SSH_SERVER_CIPHERS"`
ServerKeyExchanges []string `ini:"SSH_SERVER_KEY_EXCHANGES"`
ServerMACs []string `ini:"SSH_SERVER_MACS"`
KeyTestPath string `ini:"SSH_KEY_TEST_PATH"`
KeygenPath string `ini:"SSH_KEYGEN_PATH"`
AuthorizedKeysBackup bool `ini:"SSH_AUTHORIZED_KEYS_BACKUP"`
AuthorizedPrincipalsBackup bool `ini:"SSH_AUTHORIZED_PRINCIPALS_BACKUP"`
MinimumKeySizeCheck bool `ini:"-"`
MinimumKeySizes map[string]int `ini:"-"`
CreateAuthorizedKeysFile bool `ini:"SSH_CREATE_AUTHORIZED_KEYS_FILE"`
CreateAuthorizedPrincipalsFile bool `ini:"SSH_CREATE_AUTHORIZED_PRINCIPALS_FILE"`
ExposeAnonymous bool `ini:"SSH_EXPOSE_ANONYMOUS"`
AuthorizedPrincipalsAllow []string `ini:"SSH_AUTHORIZED_PRINCIPALS_ALLOW"`
AuthorizedPrincipalsEnabled bool `ini:"-"`
TrustedUserCAKeys []string `ini:"SSH_TRUSTED_USER_CA_KEYS"`
TrustedUserCAKeysFile string `ini:"SSH_TRUSTED_USER_CA_KEYS_FILENAME"`
TrustedUserCAKeysParsed []gossh.PublicKey `ini:"-"`
}{
Disabled: false,
StartBuiltinServer: false,
@ -672,12 +680,38 @@ func NewContext() {
SSH.StartBuiltinServer = false
}
trustedUserCaKeys := sec.Key("SSH_TRUSTED_USER_CA_KEYS").Strings(",")
for _, caKey := range trustedUserCaKeys {
pubKey, _, _, _, err := gossh.ParseAuthorizedKey([]byte(caKey))
if err != nil {
log.Fatal("Failed to parse TrustedUserCaKeys: %s %v", caKey, err)
}
SSH.TrustedUserCAKeysParsed = append(SSH.TrustedUserCAKeysParsed, pubKey)
}
if len(trustedUserCaKeys) > 0 {
// Set the default as email,username otherwise we can leave it empty
sec.Key("SSH_AUTHORIZED_PRINCIPALS_ALLOW").MustString("username,email")
} else {
sec.Key("SSH_AUTHORIZED_PRINCIPALS_ALLOW").MustString("off")
}
SSH.AuthorizedPrincipalsAllow, SSH.AuthorizedPrincipalsEnabled = parseAuthorizedPrincipalsAllow(sec.Key("SSH_AUTHORIZED_PRINCIPALS_ALLOW").Strings(","))
if !SSH.Disabled && !SSH.StartBuiltinServer {
if err := os.MkdirAll(SSH.RootPath, 0700); err != nil {
log.Fatal("Failed to create '%s': %v", SSH.RootPath, err)
} else if err = os.MkdirAll(SSH.KeyTestPath, 0644); err != nil {
log.Fatal("Failed to create '%s': %v", SSH.KeyTestPath, err)
}
if len(trustedUserCaKeys) > 0 && SSH.AuthorizedPrincipalsEnabled {
fname := sec.Key("SSH_TRUSTED_USER_CA_KEYS_FILENAME").MustString(filepath.Join(SSH.RootPath, "gitea-trusted-user-ca-keys.pem"))
if err := ioutil.WriteFile(fname,
[]byte(strings.Join(trustedUserCaKeys, "\n")), 0600); err != nil {
log.Fatal("Failed to create '%s': %v", fname, err)
}
}
}
SSH.MinimumKeySizeCheck = sec.Key("MINIMUM_KEY_SIZE_CHECK").MustBool(SSH.MinimumKeySizeCheck)
@ -689,8 +723,17 @@ func NewContext() {
delete(SSH.MinimumKeySizes, strings.ToLower(key.Name()))
}
}
SSH.AuthorizedKeysBackup = sec.Key("SSH_AUTHORIZED_KEYS_BACKUP").MustBool(true)
SSH.CreateAuthorizedKeysFile = sec.Key("SSH_CREATE_AUTHORIZED_KEYS_FILE").MustBool(true)
SSH.AuthorizedPrincipalsBackup = false
SSH.CreateAuthorizedPrincipalsFile = false
if SSH.AuthorizedPrincipalsEnabled {
SSH.AuthorizedPrincipalsBackup = sec.Key("SSH_AUTHORIZED_PRINCIPALS_BACKUP").MustBool(true)
SSH.CreateAuthorizedPrincipalsFile = sec.Key("SSH_CREATE_AUTHORIZED_PRINCIPALS_FILE").MustBool(true)
}
SSH.ExposeAnonymous = sec.Key("SSH_EXPOSE_ANONYMOUS").MustBool(false)
if err = Cfg.Section("oauth2").MapTo(&OAuth2); err != nil {
@ -944,6 +987,38 @@ func NewContext() {
}
}
func parseAuthorizedPrincipalsAllow(values []string) ([]string, bool) {
anything := false
email := false
username := false
for _, value := range values {
v := strings.ToLower(strings.TrimSpace(value))
switch v {
case "off":
return []string{"off"}, false
case "email":
email = true
case "username":
username = true
case "anything":
anything = true
}
}
if anything {
return []string{"anything"}, true
}
authorizedPrincipalsAllow := []string{}
if username {
authorizedPrincipalsAllow = append(authorizedPrincipalsAllow, "username")
}
if email {
authorizedPrincipalsAllow = append(authorizedPrincipalsAllow, "email")
}
return authorizedPrincipalsAllow, true
}
func loadInternalToken(sec *ini.Section) string {
uri := sec.Key("INTERNAL_TOKEN_URI").String()
if len(uri) == 0 {

47
modules/ssh/ssh.go
View file

@ -5,6 +5,7 @@
package ssh
import (
"bytes"
"crypto/rand"
"crypto/rsa"
"crypto/x509"
@ -136,6 +137,52 @@ func publicKeyHandler(ctx ssh.Context, key ssh.PublicKey) bool {
return false
}
// check if we have a certificate
if cert, ok := key.(*gossh.Certificate); ok {
if len(setting.SSH.TrustedUserCAKeys) == 0 {
return false
}
// look for the exact principal
for _, principal := range cert.ValidPrincipals {
pkey, err := models.SearchPublicKeyByContentExact(principal)
if err != nil {
log.Error("SearchPublicKeyByContentExact: %v", err)
return false
}
if models.IsErrKeyNotExist(err) {
continue
}
c := &gossh.CertChecker{
IsUserAuthority: func(auth gossh.PublicKey) bool {
for _, k := range setting.SSH.TrustedUserCAKeysParsed {
if bytes.Equal(auth.Marshal(), k.Marshal()) {
return true
}
}
return false
},
}
// check the CA of the cert
if !c.IsUserAuthority(cert.SignatureKey) {
return false
}
// validate the cert for this principal
if err := c.CheckCert(principal, cert); err != nil {
return false
}
ctx.SetValue(giteaKeyID, pkey.ID)
return true
}
}
pkey, err := models.SearchPublicKeyByContent(strings.TrimSpace(string(gossh.MarshalAuthorizedKey(key))))
if err != nil {
log.Error("SearchPublicKeyByContent: %v", err)