Mirrors/juanfont.headscale
1
0
Fork 0
mirror of https://github.com/juanfont/headscale.git synced 2025-10-28 10:51:44 +01:00
Code Issues Projects Releases Wiki Activity

Merge branch 'main' into feature-random-suffix-on-collision

Browse Source
This commit is contained in:
Kristoffer Dalby 2022-10-11 08:24:21 +02:00 committed by GitHub
commit 03194e2d66
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
12 changed files with 243 additions and 62 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
CHANGELOG.md
View File

@ -15,6 +15,7 @@
- Give a warning when running Headscale with reverse proxy improperly configured for WebSockets [#788](https://github.com/juanfont/headscale/pull/788)
- Fix subnet routers with Primary Routes [#811](https://github.com/juanfont/headscale/pull/811)
- Added support for JSON logs [#653](https://github.com/juanfont/headscale/issues/653)
- Sanitise the node key passed to registration url [#823](https://github.com/juanfont/headscale/pull/823)
- Add support for generating pre-auth keys with tags [#767](https://github.com/juanfont/headscale/pull/767)
- Add support for evaluating `autoApprovers` ACL entries when a machine is registered [#763](https://github.com/juanfont/headscale/pull/763)
- Add config flag to allow Headscale to start if OIDC provider is down [#829](https://github.com/juanfont/headscale/pull/829)

32
Makefile
View File

@ -27,16 +27,40 @@ test:
test_integration: test_integration_cli test_integration_derp test_integration_oidc test_integration_general
test_integration_cli:
go test -failfast -tags integration_cli,integration -timeout 30m -count=1 ./...
docker network rm $$(docker network ls --filter name=headscale --quiet) || true
docker network create headscale-test || true
docker run -t --rm \
--network headscale-test \
-v $$PWD:$$PWD -w $$PWD \
-v /var/run/docker.sock:/var/run/docker.sock golang:1 \
go test -failfast -tags integration_cli,integration -timeout 30m -count=1 ./...
test_integration_derp:
go test -failfast -tags integration_derp,integration -timeout 30m -count=1 ./...
docker network rm $$(docker network ls --filter name=headscale --quiet) || true
docker network create headscale-test || true
docker run -t --rm \
--network headscale-test \
-v $$PWD:$$PWD -w $$PWD \
-v /var/run/docker.sock:/var/run/docker.sock golang:1 \
go test -failfast -tags integration_derp,integration -timeout 30m -count=1 ./...
test_integration_general:
go test -failfast -tags integration_general,integration -timeout 30m -count=1 ./...
docker network rm $$(docker network ls --filter name=headscale --quiet) || true
docker network create headscale-test || true
docker run -t --rm \
--network headscale-test \
-v $$PWD:$$PWD -w $$PWD \
-v /var/run/docker.sock:/var/run/docker.sock golang:1 \
go test -failfast -tags integration_general,integration -timeout 30m -count=1 ./...
test_integration_oidc:
go test -failfast -tags integration_oidc,integration -timeout 30m -count=1 ./...
docker network rm $$(docker network ls --filter name=headscale --quiet) || true
docker network create headscale-test || true
docker run -t --rm \
--network headscale-test \
-v $$PWD:$$PWD -w $$PWD \
-v /var/run/docker.sock:/var/run/docker.sock golang:1 \
go test -failfast -tags integration_oidc,integration -timeout 30m -count=1 ./...
coverprofile_func:
go tool cover -func=coverage.out

32
api.go
View File

@ -9,6 +9,7 @@ import (
"github.com/gorilla/mux"
"github.com/rs/zerolog/log"
"tailscale.com/types/key"
)
const (
@ -93,7 +94,34 @@ func (h *Headscale) RegisterWebAPI(
) {
vars := mux.Vars(req)
nodeKeyStr, ok := vars["nkey"]
if !ok || nodeKeyStr == "" {
if !NodePublicKeyRegex.Match([]byte(nodeKeyStr)) {
log.Warn().Str("node_key", nodeKeyStr).Msg("Invalid node key passed to registration url")
writer.Header().Set("Content-Type", "text/plain; charset=utf-8")
writer.WriteHeader(http.StatusUnauthorized)
_, err := writer.Write([]byte("Unauthorized"))
if err != nil {
log.Error().
Caller().
Err(err).
Msg("Failed to write response")
}
return
}
// We need to make sure we dont open for XSS style injections, if the parameter that
// is passed as a key is not parsable/validated as a NodePublic key, then fail to render
// the template and log an error.
var nodeKey key.NodePublic
err := nodeKey.UnmarshalText(
[]byte(NodePublicKeyEnsurePrefix(nodeKeyStr)),
)
if !ok || nodeKeyStr == "" || err != nil {
log.Warn().Err(err).Msg("Failed to parse incoming nodekey")
writer.Header().Set("Content-Type", "text/plain; charset=utf-8")
writer.WriteHeader(http.StatusBadRequest)
_, err := writer.Write([]byte("Wrong params"))
@ -130,7 +158,7 @@ func (h *Headscale) RegisterWebAPI(
writer.Header().Set("Content-Type", "text/html; charset=utf-8")
writer.WriteHeader(http.StatusOK)
_, err := writer.Write(content.Bytes())
_, err = writer.Write(content.Bytes())
if err != nil {
log.Error().
Caller().

6
cmd/headscale/cli/mockoidc.go
View File

@ -46,6 +46,10 @@ func mockOIDC() error {
if clientSecret == "" {
return errMockOidcClientSecretNotDefined
}
addrStr := os.Getenv("MOCKOIDC_ADDR")
if addrStr == "" {
return errMockOidcPortNotDefined
}
portStr := os.Getenv("MOCKOIDC_PORT")
if portStr == "" {
return errMockOidcPortNotDefined
@ -61,7 +65,7 @@ func mockOIDC() error {
return err
}
listener, err := net.Listen("tcp", fmt.Sprintf("mockoidc:%d", port))
listener, err := net.Listen("tcp", fmt.Sprintf("%s:%d", addrStr, port))
if err != nil {
return err
}

8
flake.nix
View File

@ -128,7 +128,13 @@
};
in rec {
# `nix develop`
devShell = pkgs.mkShell {buildInputs = devDeps;};
devShell = pkgs.mkShell {
buildInputs = devDeps;
shellHook = ''
export GOFLAGS=-tags="integration,integration_general,integration_oidc,integration_cli,integration_derp"
'';
};
# `nix build`
packages = with pkgs; {

21
integration_cli_test.go
View File

@ -13,6 +13,7 @@ import (
v1 "github.com/juanfont/headscale/gen/go/headscale/v1"
"github.com/ory/dockertest/v3"
"github.com/ory/dockertest/v3/docker"
"github.com/stretchr/testify/assert"
"github.com/stretchr/testify/suite"
)
@ -42,11 +43,11 @@ func (s *IntegrationCLITestSuite) SetupTest() {
s.FailNow(fmt.Sprintf("Could not connect to docker: %s", err), "")
}
if pnetwork, err := s.pool.CreateNetwork("headscale-test"); err == nil {
s.network = *pnetwork
} else {
s.FailNow(fmt.Sprintf("Could not create network: %s", err), "")
network, err := GetFirstOrCreateNetwork(&s.pool, headscaleNetwork)
if err != nil {
s.FailNow(fmt.Sprintf("Failed to create or get network: %s", err), "")
}
s.network = network
headscaleBuildOptions := &dockertest.BuildOptions{
Dockerfile: "Dockerfile",
@ -63,8 +64,12 @@ func (s *IntegrationCLITestSuite) SetupTest() {
Mounts: []string{
fmt.Sprintf("%s/integration_test/etc:/etc/headscale", currentPath),
},
Networks: []*dockertest.Network{&s.network},
Cmd: []string{"headscale", "serve"},
Cmd: []string{"headscale", "serve"},
Networks: []*dockertest.Network{&s.network},
ExposedPorts: []string{"8080/tcp"},
PortBindings: map[docker.Port][]docker.PortBinding{
"8080/tcp": {{HostPort: "8080"}},
},
}
err = s.pool.RemoveContainerByName(headscaleHostname)
@ -87,7 +92,9 @@ func (s *IntegrationCLITestSuite) SetupTest() {
fmt.Println("Created headscale container for CLI tests")
fmt.Println("Waiting for headscale to be ready for CLI tests")
hostEndpoint := fmt.Sprintf("localhost:%s", s.headscale.GetPort("8080/tcp"))
hostEndpoint := fmt.Sprintf("%s:%s",
s.headscale.GetIPInNetwork(&s.network),
s.headscale.GetPort("8080/tcp"))
if err := s.pool.Retry(func() error {
url := fmt.Sprintf("http://%s/health", hostEndpoint)

34
integration_common_test.go
View File

@ -19,7 +19,8 @@ import (
)
const (
headscaleHostname = "headscale-derp"
headscaleNetwork = "headscale-test"
headscaleHostname = "headscale"
DOCKER_EXECUTE_TIMEOUT = 10 * time.Second
)
@ -32,7 +33,7 @@ var (
tailscaleVersions = []string{
// "head",
// "unstable",
"1.30.0",
"1.30.2",
"1.28.0",
"1.26.2",
"1.24.2",
@ -115,13 +116,19 @@ func ExecuteCommand(
fmt.Println("stdout: ", stdout.String())
fmt.Println("stderr: ", stderr.String())
return stdout.String(), stderr.String(), fmt.Errorf("command failed with: %s", stderr.String())
return stdout.String(), stderr.String(), fmt.Errorf(
"command failed with: %s",
stderr.String(),
)
}
return stdout.String(), stderr.String(), nil
case <-time.After(execConfig.timeout):
return stdout.String(), stderr.String(), fmt.Errorf("command timed out after %s", execConfig.timeout)
return stdout.String(), stderr.String(), fmt.Errorf(
"command timed out after %s",
execConfig.timeout,
)
}
}
@ -316,3 +323,22 @@ func GetEnvBool(key string) (bool, error) {
return v, nil
}
func GetFirstOrCreateNetwork(pool *dockertest.Pool, name string) (dockertest.Network, error) {
networks, err := pool.NetworksByName(name)
if err != nil || len(networks) == 0 {
if _, err := pool.CreateNetwork(name); err == nil {
// Create does not give us an updated version of the resource, so we need to
// get it again.
networks, err := pool.NetworksByName(name)
if err != nil {
return dockertest.Network{}, err
}
return networks[0], nil
}
}
return networks[0], nil
}

44
integration_embedded_derp_test.go
View File

@ -27,18 +27,20 @@ import (
)
const (
namespaceName = "derpnamespace"
totalContainers = 3
headscaleDerpHostname = "headscale-derp"
namespaceName = "derpnamespace"
totalContainers = 3
)
type IntegrationDERPTestSuite struct {
suite.Suite
stats *suite.SuiteInformation
pool dockertest.Pool
networks map[int]dockertest.Network // so we keep the containers isolated
headscale dockertest.Resource
saveLogs bool
pool dockertest.Pool
network dockertest.Network
containerNetworks map[int]dockertest.Network // so we keep the containers isolated
headscale dockertest.Resource
saveLogs bool
tailscales map[string]dockertest.Resource
joinWaitGroup sync.WaitGroup
@ -53,7 +55,7 @@ func TestDERPIntegrationTestSuite(t *testing.T) {
s := new(IntegrationDERPTestSuite)
s.tailscales = make(map[string]dockertest.Resource)
s.networks = make(map[int]dockertest.Network)
s.containerNetworks = make(map[int]dockertest.Network)
s.saveLogs = saveLogs
suite.Run(t, s)
@ -78,7 +80,7 @@ func TestDERPIntegrationTestSuite(t *testing.T) {
log.Printf("Could not purge resource: %s\n", err)
}
for _, network := range s.networks {
for _, network := range s.containerNetworks {
if err := network.Close(); err != nil {
log.Printf("Could not close network: %s\n", err)
}
@ -93,9 +95,15 @@ func (s *IntegrationDERPTestSuite) SetupSuite() {
s.FailNow(fmt.Sprintf("Could not connect to docker: %s", err), "")
}
network, err := GetFirstOrCreateNetwork(&s.pool, headscaleNetwork)
if err != nil {
s.FailNow(fmt.Sprintf("Failed to create or get network: %s", err), "")
}
s.network = network
for i := 0; i < totalContainers; i++ {
if pnetwork, err := s.pool.CreateNetwork(fmt.Sprintf("headscale-derp-%d", i)); err == nil {
s.networks[i] = *pnetwork
s.containerNetworks[i] = *pnetwork
} else {
s.FailNow(fmt.Sprintf("Could not create network: %s", err), "")
}
@ -112,7 +120,8 @@ func (s *IntegrationDERPTestSuite) SetupSuite() {
}
headscaleOptions := &dockertest.RunOptions{
Name: headscaleHostname,
Name: headscaleDerpHostname,
Mounts: []string{
fmt.Sprintf(
"%s/integration_test/etc_embedded_derp:/etc/headscale",
@ -120,6 +129,7 @@ func (s *IntegrationDERPTestSuite) SetupSuite() {
),
},
Cmd: []string{"headscale", "serve"},
Networks: []*dockertest.Network{&s.network},
ExposedPorts: []string{"8443/tcp", "3478/udp"},
PortBindings: map[docker.Port][]docker.PortBinding{
"8443/tcp": {{HostPort: "8443"}},
@ -127,7 +137,7 @@ func (s *IntegrationDERPTestSuite) SetupSuite() {
},
}
err = s.pool.RemoveContainerByName(headscaleHostname)
err = s.pool.RemoveContainerByName(headscaleDerpHostname)
if err != nil {
s.FailNow(
fmt.Sprintf(
@ -153,13 +163,15 @@ func (s *IntegrationDERPTestSuite) SetupSuite() {
hostname, container := s.tailscaleContainer(
fmt.Sprint(i),
version,
s.networks[i],
s.containerNetworks[i],
)
s.tailscales[hostname] = *container
}
log.Println("Waiting for headscale to be ready for embedded DERP tests")
hostEndpoint := fmt.Sprintf("localhost:%s", s.headscale.GetPort("8443/tcp"))
hostEndpoint := fmt.Sprintf("%s:%s",
s.headscale.GetIPInNetwork(&s.network),
s.headscale.GetPort("8443/tcp"))
if err := s.pool.Retry(func() error {
url := fmt.Sprintf("https://%s/health", hostEndpoint)
@ -320,7 +332,7 @@ func (s *IntegrationDERPTestSuite) TearDownSuite() {
log.Printf("Could not purge resource: %s\n", err)
}
for _, network := range s.networks {
for _, network := range s.containerNetworks {
if err := network.Close(); err != nil {
log.Printf("Could not close network: %s\n", err)
}
@ -428,7 +440,9 @@ func (s *IntegrationDERPTestSuite) TestPingAllPeersByHostname() {
}
func (s *IntegrationDERPTestSuite) TestDERPSTUN() {
headscaleSTUNAddr := fmt.Sprintf("localhost:%s", s.headscale.GetPort("3478/udp"))
headscaleSTUNAddr := fmt.Sprintf("%s:%s",
s.headscale.GetIPInNetwork(&s.network),
s.headscale.GetPort("3478/udp"))
client := stun.NewClient()
client.SetVerbose(true)
client.SetVVerbose(true)

29
integration_general_test.go
View File

@ -191,6 +191,17 @@ func (s *IntegrationTestSuite) tailscaleContainer(
},
}
err := s.pool.RemoveContainerByName(hostname)
if err != nil {
s.FailNow(
fmt.Sprintf(
"Could not remove existing container before building test: %s",
err,
),
"",
)
}
pts, err := s.pool.BuildAndRunWithBuildOptions(
tailscaleBuildOptions,
tailscaleOptions,
@ -219,11 +230,11 @@ func (s *IntegrationTestSuite) SetupSuite() {
s.FailNow(fmt.Sprintf("Could not connect to docker: %s", err), "")
}
if pnetwork, err := s.pool.CreateNetwork("headscale-test"); err == nil {
s.network = *pnetwork
} else {
s.FailNow(fmt.Sprintf("Could not create network: %s", err), "")
network, err := GetFirstOrCreateNetwork(&s.pool, headscaleNetwork)
if err != nil {
s.FailNow(fmt.Sprintf("Failed to create or get network: %s", err), "")
}
s.network = network
headscaleBuildOptions := &dockertest.BuildOptions{
Dockerfile: "Dockerfile",
@ -236,10 +247,14 @@ func (s *IntegrationTestSuite) SetupSuite() {
}
headscaleOptions := &dockertest.RunOptions{
Name: "headscale",
Name: headscaleHostname,
Mounts: []string{
fmt.Sprintf("%s/integration_test/etc:/etc/headscale", currentPath),
},
ExposedPorts: []string{"8080/tcp"},
PortBindings: map[docker.Port][]docker.PortBinding{
"8080/tcp": {{HostPort: "8080"}},
},
Networks: []*dockertest.Network{&s.network},
Cmd: []string{"headscale", "serve"},
}
@ -278,7 +293,9 @@ func (s *IntegrationTestSuite) SetupSuite() {
}
log.Println("Waiting for headscale to be ready for core integration tests")
hostEndpoint := fmt.Sprintf("localhost:%s", s.headscale.GetPort("8080/tcp"))
hostEndpoint := fmt.Sprintf("%s:%s",
s.headscale.GetIPInNetwork(&s.network),
s.headscale.GetPort("8080/tcp"))
if err := s.pool.Retry(func() error {
url := fmt.Sprintf("http://%s/health", hostEndpoint)

89
integration_oidc_test.go
View File

@ -25,7 +25,8 @@ import (
)
const (
oidcHeadscaleHostname = "headscale"
oidcHeadscaleHostname = "headscale-oidc"
oidcMockHostname = "headscale-mock-oidc"
oidcNamespaceName = "oidcnamespace"
totalOidcContainers = 3
)
@ -95,33 +96,25 @@ func (s *IntegrationOIDCTestSuite) SetupSuite() {
s.FailNow(fmt.Sprintf("Could not connect to docker: %s", err), "")
}
if pnetwork, err := s.pool.CreateNetwork("headscale-test"); err == nil {
s.network = *pnetwork
} else {
s.FailNow(fmt.Sprintf("Could not create network: %s", err), "")
}
// Create does not give us an updated version of the resource, so we need to
// get it again.
networks, err := s.pool.NetworksByName("headscale-test")
network, err := GetFirstOrCreateNetwork(&s.pool, headscaleNetwork)
if err != nil {
s.FailNow(fmt.Sprintf("Could not get network: %s", err), "")
s.FailNow(fmt.Sprintf("Failed to create or get network: %s", err), "")
}
s.network = networks[0]
s.network = network
log.Printf("Network config: %v", s.network.Network.IPAM.Config[0])
s.Suite.T().Log("Setting up mock OIDC")
mockOidcOptions := &dockertest.RunOptions{
Name: "mockoidc",
Hostname: "mockoidc",
Name: oidcMockHostname,
Cmd: []string{"headscale", "mockoidc"},
ExposedPorts: []string{"10000/tcp"},
Networks: []*dockertest.Network{&s.network},
PortBindings: map[docker.Port][]docker.PortBinding{
"10000/tcp": {{HostPort: "10000"}},
},
Networks: []*dockertest.Network{&s.network},
Env: []string{
fmt.Sprintf("MOCKOIDC_ADDR=%s", oidcMockHostname),
"MOCKOIDC_PORT=10000",
"MOCKOIDC_CLIENT_ID=superclient",
"MOCKOIDC_CLIENT_SECRET=supersecret",
@ -133,6 +126,17 @@ func (s *IntegrationOIDCTestSuite) SetupSuite() {
ContextDir: ".",
}
err = s.pool.RemoveContainerByName(oidcMockHostname)
if err != nil {
s.FailNow(
fmt.Sprintf(
"Could not remove existing container before building test: %s",
err,
),
"",
)
}
if pmockoidc, err := s.pool.BuildAndRunWithBuildOptions(
headscaleBuildOptions,
mockOidcOptions,
@ -142,6 +146,35 @@ func (s *IntegrationOIDCTestSuite) SetupSuite() {
s.FailNow(fmt.Sprintf("Could not start mockOIDC container: %s", err), "")
}
s.Suite.T().Logf("Waiting for headscale mock oidc to be ready for tests")
hostEndpoint := fmt.Sprintf(
"%s:%s",
s.mockOidc.GetIPInNetwork(&s.network),
s.mockOidc.GetPort("10000/tcp"),
)
if err := s.pool.Retry(func() error {
url := fmt.Sprintf("http://%s/oidc/.well-known/openid-configuration", hostEndpoint)
resp, err := http.Get(url)
if err != nil {
log.Printf("headscale mock OIDC tests is not ready: %s\n", err)
return err
}
if resp.StatusCode != http.StatusOK {
return fmt.Errorf("status code not OK")
}
return nil
}); err != nil {
// TODO(kradalby): If we cannot access headscale, or any other fatal error during
// test setup, we need to abort and tear down. However, testify does not seem to
// support that at the moment:
// https://github.com/stretchr/testify/issues/849
return // fmt.Errorf("Could not connect to headscale: %s", err)
}
s.Suite.T().Log("headscale-mock-oidc container is ready for embedded OIDC tests")
oidcCfg := fmt.Sprintf(`
oidc:
issuer: http://%s:10000/oidc
@ -216,10 +249,14 @@ oidc:
}
s.Suite.T().Logf("Waiting for headscale to be ready for embedded OIDC tests")
hostEndpoint := fmt.Sprintf("localhost:%s", s.headscale.GetPort("8443/tcp"))
hostMockEndpoint := fmt.Sprintf(
"%s:%s",
s.headscale.GetIPInNetwork(&s.network),
s.headscale.GetPort("8443/tcp"),
)
if err := s.pool.Retry(func() error {
url := fmt.Sprintf("https://%s/health", hostEndpoint)
url := fmt.Sprintf("https://%s/health", hostMockEndpoint)
insecureTransport := http.DefaultTransport.(*http.Transport).Clone()
insecureTransport.TLSClientConfig = &tls.Config{InsecureSkipVerify: true}
client := &http.Client{Transport: insecureTransport}
@ -294,6 +331,8 @@ func (s *IntegrationOIDCTestSuite) AuthenticateOIDC(
resp, err := client.Get(loginURL.String())
assert.Nil(s.T(), err)
log.Printf("auth body, err: %#v, %s", resp, err)
body, err := io.ReadAll(resp.Body)
assert.Nil(s.T(), err)
@ -308,7 +347,6 @@ func (s *IntegrationOIDCTestSuite) joinOIDC(
endpoint, hostname string,
tailscale dockertest.Resource,
) (*url.URL, error) {
command := []string{
"tailscale",
"up",
@ -374,7 +412,13 @@ func (s *IntegrationOIDCTestSuite) tailscaleContainer(
DockerAllowNetworkAdministration,
)
if err != nil {
log.Fatalf("Could not start tailscale container version %s: %s", version, err)
s.FailNow(
fmt.Sprintf(
"Could not start tailscale container version %s: %s",
version,
err,
),
)
}
log.Printf("Created %s container\n", hostname)
@ -497,7 +541,12 @@ func (s *IntegrationOIDCTestSuite) TestPingAllPeersByAddress() {
[]string{},
)
assert.Nil(t, err)
log.Printf("result for %s: stdout: %s, stderr: %s\n", hostname, stdout, stderr)
log.Printf(
"result for %s: stdout: %s, stderr: %s\n",
hostname,
stdout,
stderr,
)
assert.Contains(t, stdout, "pong")
})
}

2
integration_test/etc_oidc/base_config.yaml
View File

@ -11,7 +11,7 @@ private_key_path: private.key
noise:
private_key_path: noise_private.key
listen_addr: 0.0.0.0:8443
server_url: https://localhost:8443
server_url: https://headscale-oidc:8443
tls_cert_path: "/etc/headscale/tls/server.crt"
tls_key_path: "/etc/headscale/tls/server.key"
tls_client_auth_mode: disabled

7
utils.go
View File

@ -17,6 +17,7 @@ import (
"os"
"path/filepath"
"reflect"
"regexp"
"strconv"
"strings"
@ -64,6 +65,8 @@ const (
ZstdCompression = "zstd"
)
var NodePublicKeyRegex = regexp.MustCompile("nodekey:[a-fA-F0-9]+")
func MachinePublicKeyStripPrefix(machineKey key.MachinePublic) string {
return strings.TrimPrefix(machineKey.String(), machinePublicHexPrefix)
}
@ -325,7 +328,9 @@ func GenerateRandomStringDNSSafe(size int) (string, error) {
if err != nil {
return "", err
}
str = strings.ToLower(strings.ReplaceAll(strings.ReplaceAll(str, "_", ""), "-", ""))
str = strings.ToLower(
strings.ReplaceAll(strings.ReplaceAll(str, "_", ""), "-", ""),
)
}
return str[:size], nil