lib/{promauth,promscrape}: automatically refresh root CA certificates after changes on disk (#5725)

* lib/{promauth,promscrape}: automatically refresh root CA certificates after changes on disk

Added a custom `http.RoundTripper` implementation which checks for root CA content changes and updates `tls.Config` used by `http.RoundTripper` after detecting CA change.

Client certificate changes are not tracked by this implementation since `tls.Config` already supports passing certificate dynamically by overriding `tls.Config.GetClientCertificate`.

This change implements dynamic reload of root CA only for streaming client used for scraping. Blocking client (`fasthttp.HostClient`) does not support using custom transport so can't use this implementation.

See: https://github.com/VictoriaMetrics/VictoriaMetrics/issues/5526

Signed-off-by: Zakhar Bessarab <z.bessarab@victoriametrics.com>

* lib/promauth/config: update NewRoundTripper API

Update API to allow user to update only parameters required for transport.

Add warning log when reloading Root CA failed.

Signed-off-by: Zakhar Bessarab <z.bessarab@victoriametrics.com>

* lib/promauth/config: fix mutex acquire logic

Signed-off-by: Zakhar Bessarab <z.bessarab@victoriametrics.com>

* lib/promauth/config: replace RWMutex with regular mutex to simplify the code

- remove additional mutex used for getRootCABytes - require callee to use mutex
- replace RWMutex with regular mutex

Signed-off-by: Zakhar Bessarab <z.bessarab@victoriametrics.com>

* lib/promauth/config: refactor

- hold the mutex lock to avoid round tripper being re-created twice
- move recreation logic into separate func to simplify the code

Signed-off-by: Zakhar Bessarab <z.bessarab@victoriametrics.com>

---------

Signed-off-by: Zakhar Bessarab <z.bessarab@victoriametrics.com>
Co-authored-by: Nikolay <nik@victoriametrics.com>

docs/CHANGELOG.md

@@ -64,6 +64,7 @@ See also [LTS releases](https://docs.victoriametrics.com/lts-releases/).
 * FEATURE: [OpenTelemetry](https://docs.victoriametrics.com/#sending-data-via-opentelemetry): add `-opentelemetry.usePrometheusNaming` command-line flag, which can be used for enabling automatic conversion of the ingested metric names and labels into Prometheus-compatible format. See [these docs](https://docs.victoriametrics.com/#sending-data-via-opentelemetry) and [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/6037).
 
 * BUGFIX: prevent from automatic deletion of newly registered time series when it is queried immediately after the addition. The probability of this bug has been increased significantly after [v1.99.0](https://github.com/VictoriaMetrics/VictoriaMetrics/releases/tag/v1.99.0) because of optimizations related to registering new time series. See [this](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/5948) and [this](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/5959) issue.
+* BUGFIX: properly reload root CA certificates from files for [service discovery](https://docs.victoriametrics.com/sd_configs/) and [scraping requests in stream parsing mode](https://docs.victoriametrics.com/vmagent/?highlight=stream&highlight=parse#stream-parsing-mode). See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/5526).
 * BUGFIX: [vmagent](https://docs.victoriametrics.com/vmagent.html): properly set `Host` header in requests to scrape targets if it is specified via [`headers` option](https://docs.victoriametrics.com/sd_configs/#http-api-client-options). Thanks to @fholzer for [the bugreport](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/5969) and [the fix](https://github.com/VictoriaMetrics/VictoriaMetrics/pull/5970).
 * BUGFIX: [vmagent](https://docs.victoriametrics.com/vmagent.html): properly set `Host` header in requests to scrape targets when [`server_name` option at `tls_config`](https://prometheus.io/docs/prometheus/latest/configuration/configuration/#tls_config) is set. Previously the `Host` header was set incorrectly to the target hostname in this case.
 * BUGFIX: do not drop `match[]` filter at [`/api/v1/series`](https://docs.victoriametrics.com/url-examples/#apiv1series) if `-search.ignoreExtraFiltersAtLabelsAPI` command-line flag is set, since missing `match[]` filter breaks `/api/v1/series` requests.

lib/promauth/config.go

@@ -1,6 +1,7 @@
 package promauth
 
 import (
+	"bytes"
 	"context"
 	"crypto/tls"
 	"crypto/x509"
@@ -11,12 +12,14 @@ import (
 	"strings"
 	"sync"
 
-	"github.com/VictoriaMetrics/VictoriaMetrics/lib/fasttime"
-	"github.com/VictoriaMetrics/VictoriaMetrics/lib/fs/fscore"
-	"github.com/VictoriaMetrics/VictoriaMetrics/lib/netutil"
 	"github.com/cespare/xxhash/v2"
 	"golang.org/x/oauth2"
 	"golang.org/x/oauth2/clientcredentials"
+
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/fasttime"
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/fs/fscore"
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/logger"
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/netutil"
 )
 
 // Secret represents a string secret such as password or auth token.
@@ -289,6 +292,8 @@ type Config struct {
 
 	headers       []keyValue
 	headersDigest string
+
+	tctx *tlsContext
 }
 
 type keyValue struct {
@@ -371,6 +376,8 @@ func (ac *Config) String() string {
 		ac.authHeaderDigest, ac.headersDigest, ac.tlsRootCADigest, ac.tlsCertDigest, ac.tlsServerName, ac.tlsInsecureSkipVerify, ac.tlsMinVersion)
 }
 
+const tlsCertsCacheSeconds = 1
+
 // getAuthHeaderFunc must return <value> for 'Authorization: <value>' http request header
 type getAuthHeaderFunc func() (string, error)
 
@@ -390,7 +397,7 @@ func newGetAuthHeaderCached(getAuthHeader getAuthHeaderFunc) getAuthHeaderFunc {
 		defer mu.Unlock()
 		if fasttime.UnixTimestamp() > deadline {
 			ah, err = getAuthHeader()
-			deadline = fasttime.UnixTimestamp() + 1
+			deadline = fasttime.UnixTimestamp() + tlsCertsCacheSeconds
 		}
 		return ah, err
 	}
@@ -413,7 +420,7 @@ func newGetTLSRootCACached(getTLSRootCA getTLSRootCAFunc) getTLSRootCAFunc {
 		defer mu.Unlock()
 		if fasttime.UnixTimestamp() > deadline {
 			rootCA, err = getTLSRootCA()
-			deadline = fasttime.UnixTimestamp() + 1
+			deadline = fasttime.UnixTimestamp() + tlsCertsCacheSeconds
 		}
 		return rootCA, err
 	}
@@ -436,7 +443,7 @@ func newGetTLSCertCached(getTLSCert getTLSCertFunc) getTLSCertFunc {
 		defer mu.Unlock()
 		if fasttime.UnixTimestamp() > deadline {
 			cert, err = getTLSCert(cri)
-			deadline = fasttime.UnixTimestamp() + 1
+			deadline = fasttime.UnixTimestamp() + tlsCertsCacheSeconds
 		}
 		return cert, err
 	}
@@ -466,6 +473,24 @@ func (ac *Config) NewTLSConfig() (*tls.Config, error) {
 	return tlsCfg, nil
 }
 
+// NewRoundTripper returns new http.RoundTripper for the given ac.
+func (ac *Config) NewRoundTripper(builder func(*http.Transport)) (http.RoundTripper, error) {
+	cfg, err := ac.NewTLSConfig()
+	if err != nil {
+		return nil, fmt.Errorf("failed to initialize TLS config: %w", err)
+	}
+
+	if ac == nil {
+		tr := &http.Transport{
+			TLSClientConfig: cfg,
+		}
+		builder(tr)
+		return tr, nil
+	}
+
+	return ac.tctx.NewTLSRoundTripper(cfg, builder)
+}
+
 // NewConfig creates auth config for the given hcc.
 func (hcc *HTTPClientConfig) NewConfig(baseDir string) (*Config, error) {
 	opts := &Options{
@@ -613,6 +638,8 @@ func (opts *Options) NewConfig() (*Config, error) {
 
 		headers:       headers,
 		headersDigest: headersDigest,
+
+		tctx: &tctx,
 	}
 	return ac, nil
 }
@@ -751,6 +778,7 @@ type tlsContext struct {
 	tlsCertDigest string
 
 	getTLSRootCA    getTLSRootCAFunc
+	getRootCAPEM    func() ([]byte, error)
 	tlsRootCADigest string
 
 	serverName         string
@@ -774,16 +802,26 @@ func (tctx *tlsContext) initFromTLSConfig(baseDir string, tc *TLSConfig) error {
 	} else if tc.CertFile != "" || tc.KeyFile != "" {
 		certPath := fscore.GetFilepath(baseDir, tc.CertFile)
 		keyPath := fscore.GetFilepath(baseDir, tc.KeyFile)
-		tctx.getTLSCert = func(*tls.CertificateRequestInfo) (*tls.Certificate, error) {
+		getCertsPEM := func() ([]byte, []byte, error) {
 			// Re-read TLS certificate from disk. This is needed for https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1420
 			certData, err := fscore.ReadFileOrHTTP(certPath)
 			if err != nil {
-				return nil, fmt.Errorf("cannot read TLS certificate from %q: %w", certPath, err)
+				return nil, nil, fmt.Errorf("cannot read TLS certificate from %q: %w", certPath, err)
 			}
 			keyData, err := fscore.ReadFileOrHTTP(keyPath)
 			if err != nil {
-				return nil, fmt.Errorf("cannot read TLS key from %q: %w", keyPath, err)
+				return nil, nil, fmt.Errorf("cannot read TLS key from %q: %w", keyPath, err)
 			}
+
+			return certData, keyData, nil
+		}
+
+		tctx.getTLSCert = func(*tls.CertificateRequestInfo) (*tls.Certificate, error) {
+			certData, keyData, err := getCertsPEM()
+			if err != nil {
+				return nil, err
+			}
+
 			cert, err := tls.X509KeyPair(certData, keyData)
 			if err != nil {
 				return nil, fmt.Errorf("cannot load TLS certificate from `cert_file`=%q, `key_file`=%q: %w", tc.CertFile, tc.KeyFile, err)
@@ -797,35 +835,49 @@ func (tctx *tlsContext) initFromTLSConfig(baseDir string, tc *TLSConfig) error {
 		if !rootCA.AppendCertsFromPEM([]byte(tc.CA)) {
 			return fmt.Errorf("cannot parse data from `ca` value")
 		}
+
 		tctx.getTLSRootCA = func() (*x509.CertPool, error) {
 			return rootCA, nil
 		}
+
+		tctx.getRootCAPEM = func() ([]byte, error) {
+			return []byte(tc.CA), nil
+		}
+
 		h := xxhash.Sum64([]byte(tc.CA))
 		tctx.tlsRootCADigest = fmt.Sprintf("digest(CA)=%d", h)
 	} else if tc.CAFile != "" {
 		path := fscore.GetFilepath(baseDir, tc.CAFile)
-		tctx.getTLSRootCA = func() (*x509.CertPool, error) {
+
+		getRootCAPEM := func() ([]byte, error) {
 			data, err := fscore.ReadFileOrHTTP(path)
 			if err != nil {
 				return nil, fmt.Errorf("cannot read `ca_file`: %w", err)
 			}
+			return data, nil
+		}
+
+		tctx.getTLSRootCA = func() (*x509.CertPool, error) {
+			data, err := getRootCAPEM()
+			if err != nil {
+				return nil, err
+			}
 			rootCA := x509.NewCertPool()
 			if !rootCA.AppendCertsFromPEM(data) {
 				return nil, fmt.Errorf("cannot parse data read from `ca_file` %q", tc.CAFile)
 			}
 			return rootCA, nil
 		}
-		// The Config.NewTLSConfig() is called only once per each scrape target initialization.
-		// So, the tlsRootCADigest must contain the hash of CAFile contents additionally to CAFile itself,
-		// in order to properly reload scrape target configs when CAFile contents changes.
-		data, err := fscore.ReadFileOrHTTP(path)
-		if err != nil {
-			// Do not return the error to the caller, since this may result in fatal error.
-			// The CAFile contents can become available on the next check of scrape configs.
-			data = []byte("read error")
+		tctx.getRootCAPEM = func() ([]byte, error) {
+			data, err := getRootCAPEM()
+			if err != nil {
+				return nil, err
+			}
+			return data, nil
 		}
-		h := xxhash.Sum64(data)
-		tctx.tlsRootCADigest = fmt.Sprintf("caFile=%q, digest(caFile)=%d", tc.CAFile, h)
+		// Does not hash file contents, since they may change at any time.
+		// TLSRoundTripper must be used to automatically update the root CA.
+		tctx.tlsRootCADigest = fmt.Sprintf("caFile=%q", tc.CAFile)
 	}
 	v, err := netutil.ParseTLSVersion(tc.MinVersion)
 	if err != nil {
@@ -834,3 +886,118 @@ func (tctx *tlsContext) initFromTLSConfig(baseDir string, tc *TLSConfig) error {
 	tctx.minVersion = v
 	return nil
 }
+
+// NewTLSRoundTripper returns new http.RoundTripper which automatically updates
+// RootCA in tls.Config whenever it changes.
+func (tctx *tlsContext) NewTLSRoundTripper(cfg *tls.Config, builder func(transport *http.Transport)) (http.RoundTripper, error) {
+	// TLS context is not initialized so use the provided RoundTripper without wrapper
+	if tctx == nil || tctx.getRootCAPEM == nil {
+		tr := &http.Transport{
+			TLSClientConfig: cfg,
+		}
+		builder(tr)
+		return tr, nil
+	}
+
+	var deadline uint64
+	var rootCA []byte
+	var err error
+	getTLSDigestsLocked := func() []byte {
+		if fasttime.UnixTimestamp() > deadline {
+			rootCA, err = tctx.getRootCAPEM()
+			if err != nil {
+				logger.Warnf("cannot load root CA: %s", err)
+			}
+			deadline = fasttime.UnixTimestamp() + tlsCertsCacheSeconds
+		}
+
+		return rootCA
+	}
+	tr := &http.Transport{
+		TLSClientConfig: cfg,
+	}
+	builder(tr)
+
+	return &TLSRoundTripper{
+		builder:              builder,
+		getRootCABytesLocked: getTLSDigestsLocked,
+		getTLSRootCA:         newGetTLSRootCACached(tctx.getTLSRootCA),
+		config:               cfg,
+		tr:                   tr,
+	}, nil
+}
+
+var _ http.RoundTripper = &TLSRoundTripper{}
+
+// TLSRoundTripper is an implementation of http.RoundTripper which automatically
+// updates RootCA in tls.Config whenever it changes.
+type TLSRoundTripper struct {
+	builder              func(*http.Transport)
+	getRootCABytesLocked func() []byte
+	getTLSRootCA         func() (*x509.CertPool, error)
+
+	config *tls.Config
+
+	tr http.RoundTripper
+
+	m           sync.Mutex
+	rootCABytes []byte
+}
+
+// RoundTrip implements http.RoundTripper.RoundTrip.
+// It automatically updates RootCA in tls.Config whenever it changes.
+func (t *TLSRoundTripper) RoundTrip(request *http.Request) (*http.Response, error) {
+	t.m.Lock()
+	rootCABytes := t.getRootCABytesLocked()
+	equal := bytes.Equal(rootCABytes, t.rootCABytes)
+
+	if equal {
+		t.m.Unlock()
+		return t.tr.RoundTrip(request)
+	}
+
+	err := t.recreateRoundTripperLocked(rootCABytes)
+	t.m.Unlock()
+
+	if err != nil {
+		return nil, fmt.Errorf("cannot recreate RoundTripper: %w", err)
+	}
+
+	return t.tr.RoundTrip(request)
+}
+
+func (t *TLSRoundTripper) recreateRoundTripperLocked(rootCABytes []byte) error {
+	newRootCaPool, err := t.getTLSRootCA()
+	if err != nil {
+		return fmt.Errorf("cannot load root CAs: %w", err)
+	}
+	newTLSConfig := t.config.Clone()
+	newTLSConfig.RootCAs = newRootCaPool
+	// Reset ClientSessionCache, since it may contain sessions for the old root CA.
+	newTLSConfig.ClientSessionCache = tls.NewLRUClientSessionCache(0)
+
+	tr := &http.Transport{
+		TLSClientConfig: newTLSConfig,
+	}
+	t.builder(tr)
+
+	oldRt := t.tr
+	t.tr = tr
+	t.rootCABytes = rootCABytes
+	t.config = newTLSConfig
+
+	if oldRt != nil {
+		closeIdleConnections(oldRt)
+	}
+	return nil
+}
+
+type closeIdler interface {
+	CloseIdleConnections()
+}
+
+func closeIdleConnections(t http.RoundTripper) {
+	if ci, ok := t.(closeIdler); ok {
+		ci.CloseIdleConnections()
+	}
+}

lib/promauth/config_test.go

@@ -1,9 +1,20 @@
 package promauth
 
 import (
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/tls"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"encoding/pem"
+	"math/big"
+	"net"
 	"net/http"
 	"net/http/httptest"
+	"net/url"
+	"os"
 	"testing"
+	"time"
 
 	"gopkg.in/yaml.v2"
 )
@@ -593,3 +604,143 @@ func TestConfigHeaders(t *testing.T) {
 	f([]string{"foo: bar"}, "Foo: bar\r\n")
 	f([]string{"Foo-Bar: Baz s:sdf", "A:b", "X-Forwarded-For: A-B:c"}, "Foo-Bar: Baz s:sdf\r\nA: b\r\nX-Forwarded-For: A-B:c\r\n")
 }
+
+func TestTLSConfigWithCertificatesFilesUpdate(t *testing.T) {
+	// Generate and save a self-signed CA certificate and a certificate signed by the CA
+	caPEM, certPEM, keyPEM := generateCertificates(t)
+	_ = os.WriteFile("testdata/ca.pem", caPEM, 0644)
+	_ = os.WriteFile("testdata/cert.pem", certPEM, 0644)
+	_ = os.WriteFile("testdata/key.pem", keyPEM, 0644)
+
+	defer func() {
+		for _, p := range []string{
+			"testdata/ca.pem",
+			"testdata/cert.pem",
+			"testdata/key.pem",
+		} {
+			_ = os.Remove(p)
+		}
+	}()
+
+	cert, err := tls.LoadX509KeyPair("testdata/cert.pem", "testdata/key.pem")
+	if err != nil {
+		t.Fatalf("cannot load generated certificate: %s", err)
+	}
+
+	tlsConfig := &tls.Config{}
+	tlsConfig.Certificates = []tls.Certificate{cert}
+
+	s := httptest.NewUnstartedServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+	}))
+	s.TLS = tlsConfig
+	s.StartTLS()
+	serverURL, _ := url.Parse(s.URL)
+
+	opts := Options{
+		TLSConfig: &TLSConfig{
+			CAFile: "testdata/ca.pem",
+		},
+	}
+	ac, err := opts.NewConfig()
+	if err != nil {
+		t.Fatalf("unexpected error when parsing config: %s", err)
+	}
+	tr, err := ac.NewRoundTripper(func(tr *http.Transport) {})
+	if err != nil {
+		t.Fatalf("unexpected error when creating roundtripper: %s", err)
+	}
+
+	client := http.Client{
+		Transport: tr,
+	}
+
+	resp, err := client.Do(&http.Request{
+		Method: http.MethodGet,
+		URL:    serverURL,
+	})
+	if err != nil {
+		t.Fatalf("unexpected error when making request: %s", err)
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		t.Fatalf("expected status code %d; got %d", http.StatusOK, resp.StatusCode)
+	}
+
+	// Update CA file with new CA and get config
+	ca2PEM, _, _ := generateCertificates(t)
+	_ = os.WriteFile("testdata/ca.pem", ca2PEM, 0644)
+
+	// Wait for cert cache expiration
+	time.Sleep(2 * tlsCertsCacheSeconds * time.Second)
+
+	_, err = client.Do(&http.Request{
+		Method: http.MethodGet,
+		URL:    serverURL,
+	})
+	if err == nil {
+		t.Fatal("expected TLS verification error, got nil")
+	}
+}
+
+func generateCertificates(t *testing.T) ([]byte, []byte, []byte) {
+	// Small key size for faster tests
+	const testCertificateBits = 1024
+
+	ca := &x509.Certificate{
+		SerialNumber: big.NewInt(2024),
+		Subject: pkix.Name{
+			Organization: []string{"Test CA"},
+		},
+		NotBefore:             time.Now(),
+		NotAfter:              time.Now().AddDate(10, 0, 0),
+		IsCA:                  true,
+		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth, x509.ExtKeyUsageServerAuth},
+		KeyUsage:              x509.KeyUsageDigitalSignature | x509.KeyUsageCertSign,
+		BasicConstraintsValid: true,
+	}
+	caPrivKey, err := rsa.GenerateKey(rand.Reader, testCertificateBits)
+	if err != nil {
+		t.Fatal(err)
+	}
+	caBytes, err := x509.CreateCertificate(rand.Reader, ca, ca, &caPrivKey.PublicKey, caPrivKey)
+	if err != nil {
+		t.Fatal(err)
+	}
+	caPEM := pem.EncodeToMemory(&pem.Block{
+		Type:  "CERTIFICATE",
+		Bytes: caBytes,
+	})
+
+	cert := &x509.Certificate{
+		SerialNumber: big.NewInt(2020),
+		Subject: pkix.Name{
+			Organization: []string{"Test Cert"},
+		},
+		IPAddresses:           []net.IP{net.ParseIP("127.0.0.1")},
+		NotBefore:             time.Now(),
+		NotAfter:              time.Now().AddDate(10, 0, 0),
+		IsCA:                  false,
+		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth, x509.ExtKeyUsageServerAuth},
+		KeyUsage:              x509.KeyUsageDigitalSignature,
+		BasicConstraintsValid: true,
+	}
+	key, err := rsa.GenerateKey(rand.Reader, testCertificateBits)
+	if err != nil {
+		t.Fatal(err)
+	}
+	certBytes, err := x509.CreateCertificate(rand.Reader, cert, ca, &key.PublicKey, caPrivKey)
+	if err != nil {
+		t.Fatal(err)
+	}
+	certPEM := pem.EncodeToMemory(&pem.Block{
+		Type:  "CERTIFICATE",
+		Bytes: certBytes,
+	})
+	keyPEM := pem.EncodeToMemory(&pem.Block{
+		Type:  "RSA PRIVATE KEY",
+		Bytes: x509.MarshalPKCS1PrivateKey(key),
+	})
+
+	return caPEM, certPEM, keyPEM
+}

lib/promscrape/client.go

@@ -11,9 +11,10 @@ import (
 	"strings"
 	"time"
 
+	"github.com/VictoriaMetrics/metrics"
+
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/bytesutil"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/flagutil"
-	"github.com/VictoriaMetrics/metrics"
 )
 
 var (
@@ -43,20 +44,13 @@ type client struct {
 
 func newClient(ctx context.Context, sw *ScrapeWork) (*client, error) {
 	isTLS := strings.HasPrefix(sw.ScrapeURL, "https://")
-	var tlsCfg *tls.Config
-	if isTLS {
-		var err error
-		tlsCfg, err = sw.AuthConfig.NewTLSConfig()
-		if err != nil {
-			return nil, fmt.Errorf("cannot initialize tls config: %w", err)
-		}
-	}
 	setHeaders := func(req *http.Request) error {
 		return sw.AuthConfig.SetHeaders(req, true)
 	}
 	setProxyHeaders := func(_ *http.Request) error {
 		return nil
 	}
+	var tlsCfg *tls.Config
 	proxyURL := sw.ProxyURL
 	if !isTLS && proxyURL.IsHTTPOrHTTPS() {
 		pu := proxyURL.GetURL()
@@ -75,20 +69,29 @@ func newClient(ctx context.Context, sw *ScrapeWork) (*client, error) {
 	if pu := sw.ProxyURL.GetURL(); pu != nil {
 		proxyURLFunc = http.ProxyURL(pu)
 	}
-	hc := &http.Client{
-		Transport: &http.Transport{
-			TLSClientConfig:        tlsCfg,
-			Proxy:                  proxyURLFunc,
-			TLSHandshakeTimeout:    10 * time.Second,
-			IdleConnTimeout:        2 * sw.ScrapeInterval,
-			DisableCompression:     *disableCompression || sw.DisableCompression,
-			DisableKeepAlives:      *disableKeepAlive || sw.DisableKeepAlive,
-			DialContext:            statStdDial,
-			MaxIdleConnsPerHost:    100,
-			MaxResponseHeaderBytes: int64(maxResponseHeadersSize.N),
-		},
-		Timeout: sw.ScrapeTimeout,
+
+	rt, err := sw.AuthConfig.NewRoundTripper(func(tr *http.Transport) {
+		if !isTLS && proxyURL.IsHTTPOrHTTPS() {
+			tr.TLSClientConfig = tlsCfg
+		}
+
+		tr.Proxy = proxyURLFunc
+		tr.TLSHandshakeTimeout = 10 * time.Second
+		tr.IdleConnTimeout = 2 * sw.ScrapeInterval
+		tr.DisableCompression = *disableCompression || sw.DisableCompression
+		tr.DisableKeepAlives = *disableKeepAlive || sw.DisableKeepAlive
+		tr.DialContext = statStdDial
+		tr.MaxIdleConnsPerHost = 100
+		tr.MaxResponseHeaderBytes = int64(maxResponseHeadersSize.N)
+	})
+	if err != nil {
+		return nil, fmt.Errorf("cannot initialize tls config: %w", err)
 	}
+
+	hc := &http.Client{
+		Transport: rt,
+	}
+
 	if sw.DenyRedirects {
 		hc.CheckRedirect = func(_ *http.Request, _ []*http.Request) error {
 			return http.ErrUseLastResponse

lib/promscrape/discovery/kubernetes/api_watcher.go

@@ -251,19 +251,20 @@ func newGroupWatcher(apiServer string, ac *promauth.Config, namespaces []string,
 	if proxyURL != nil {
 		proxy = http.ProxyURL(proxyURL)
 	}
-	tlsConfig, err := ac.NewTLSConfig()
+	tr, err := ac.NewRoundTripper(func(tr *http.Transport) {
+		tr.Proxy = proxy
+		tr.TLSHandshakeTimeout = 10 * time.Second
+		tr.IdleConnTimeout = *apiServerTimeout
+		tr.MaxIdleConnsPerHost = 100
+	})
+
 	if err != nil {
 		return nil, fmt.Errorf("cannot initialize tls config: %w", err)
 	}
+
 	client := &http.Client{
-		Transport: &http.Transport{
-			TLSClientConfig:     tlsConfig,
-			Proxy:               proxy,
-			TLSHandshakeTimeout: 10 * time.Second,
-			IdleConnTimeout:     *apiServerTimeout,
-			MaxIdleConnsPerHost: 100,
-		},
-		Timeout: *apiServerTimeout,
+		Transport: tr,
+		Timeout:   *apiServerTimeout,
 	}
 	ctx, cancel := context.WithCancel(context.Background())
 	gw := &groupWatcher{

lib/promscrape/discovery/openstack/api.go

@@ -94,15 +94,14 @@ func newAPIConfig(sdc *SDConfig, baseDir string) (*apiConfig, error) {
 			cfg.client.CloseIdleConnections()
 			return nil, fmt.Errorf("cannot parse TLS config: %w", err)
 		}
-		tlsConfig, err := ac.NewTLSConfig()
+		tr, err := ac.NewRoundTripper(func(tr *http.Transport) {
+			tr.MaxIdleConnsPerHost = 100
+		})
 		if err != nil {
 			cfg.client.CloseIdleConnections()
 			return nil, fmt.Errorf("cannot initialize TLS config: %w", err)
 		}
-		cfg.client.Transport = &http.Transport{
-			TLSClientConfig:     tlsConfig,
-			MaxIdleConnsPerHost: 100,
-		}
+		cfg.client.Transport = tr
 	}
 	// use public compute endpoint by default
 	if len(cfg.availability) == 0 {

lib/promscrape/discovery/yandexcloud/api.go

@@ -47,7 +47,7 @@ func getAPIConfig(sdc *SDConfig, baseDir string) (*apiConfig, error) {
 }
 
 func newAPIConfig(sdc *SDConfig, baseDir string) (*apiConfig, error) {
-	transport := &http.Transport{
+	var transport http.RoundTripper = &http.Transport{
 		MaxIdleConnsPerHost: 100,
 	}
 	if sdc.TLSConfig != nil {
@@ -59,11 +59,12 @@ func newAPIConfig(sdc *SDConfig, baseDir string) (*apiConfig, error) {
 		if err != nil {
 			return nil, fmt.Errorf("cannot parse TLS config: %w", err)
 		}
-		tlsConfig, err := ac.NewTLSConfig()
+		transport, err = ac.NewRoundTripper(func(tr *http.Transport) {
+			tr.MaxIdleConnsPerHost = 100
+		})
 		if err != nil {
 			return nil, fmt.Errorf("cannot initialize TLS config: %w", err)
 		}
-		transport.TLSClientConfig = tlsConfig
 	}
 	cfg := &apiConfig{
 		client: &http.Client{

lib/promscrape/discoveryutils/client.go

@@ -2,7 +2,6 @@ package discoveryutils
 
 import (
 	"context"
-	"crypto/tls"
 	"errors"
 	"flag"
 	"fmt"
@@ -14,10 +13,11 @@ import (
 	"sync"
 	"time"
 
+	"github.com/VictoriaMetrics/metrics"
+
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/promauth"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/proxy"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/timerpool"
-	"github.com/VictoriaMetrics/metrics"
 )
 
 var (
@@ -106,42 +106,40 @@ func NewClient(apiServer string, ac *promauth.Config, proxyURL *proxy.URL, proxy
 		}
 	}
 
-	isTLS := u.Scheme == "https"
-	var tlsCfg *tls.Config
-	if isTLS {
-		var err error
-		tlsCfg, err = ac.NewTLSConfig()
-		if err != nil {
-			return nil, fmt.Errorf("cannot initialize tls config: %w", err)
-		}
-	}
-
 	var proxyURLFunc func(*http.Request) (*url.URL, error)
 	if pu := proxyURL.GetURL(); pu != nil {
 		proxyURLFunc = http.ProxyURL(pu)
 	}
 
+	tr, err := ac.NewRoundTripper(func(tr *http.Transport) {
+		tr.Proxy = proxyURLFunc
+		tr.TLSHandshakeTimeout = 10 * time.Second
+		tr.MaxIdleConnsPerHost = *maxConcurrency
+		tr.ResponseHeaderTimeout = DefaultClientReadTimeout
+		tr.DialContext = dialFunc
+	})
+	if err != nil {
+		return nil, fmt.Errorf("cannot initialize tls config: %w", err)
+	}
+
+	blockingTR, err := ac.NewRoundTripper(func(tr *http.Transport) {
+		tr.Proxy = proxyURLFunc
+		tr.TLSHandshakeTimeout = 10 * time.Second
+		tr.MaxIdleConnsPerHost = 1000
+		tr.ResponseHeaderTimeout = BlockingClientReadTimeout
+		tr.DialContext = dialFunc
+	})
+	if err != nil {
+		return nil, fmt.Errorf("cannot initialize tls config: %w", err)
+	}
+
 	client := &http.Client{
-		Timeout: DefaultClientReadTimeout,
-		Transport: &http.Transport{
-			TLSClientConfig:       tlsCfg,
-			Proxy:                 proxyURLFunc,
-			TLSHandshakeTimeout:   10 * time.Second,
-			MaxIdleConnsPerHost:   *maxConcurrency,
-			ResponseHeaderTimeout: DefaultClientReadTimeout,
-			DialContext:           dialFunc,
-		},
+		Timeout:   DefaultClientReadTimeout,
+		Transport: tr,
 	}
 	blockingClient := &http.Client{
-		Timeout: BlockingClientReadTimeout,
-		Transport: &http.Transport{
-			TLSClientConfig:       tlsCfg,
-			Proxy:                 proxyURLFunc,
-			TLSHandshakeTimeout:   10 * time.Second,
-			MaxIdleConnsPerHost:   1000,
-			ResponseHeaderTimeout: BlockingClientReadTimeout,
-			DialContext:           dialFunc,
-		},
+		Timeout:   BlockingClientReadTimeout,
+		Transport: blockingTR,
 	}
 
 	setHTTPHeaders := func(_ *http.Request) error { return nil }