x-pack/filebeat/input/{cel,httpjson}: fix PEM key validation (#38405)

Previously the validation was attempting to parse the PEM text as a key
and was also attempting to parse the data as the wrong kind of key.

(cherry picked from commit c29075e)

CHANGELOG.next.asciidoc

@@ -99,6 +99,9 @@ fields added to events containing the Beats version. {pull}37553[37553]
 - Fix a race condition that could crash Filebeat with a "negative WaitGroup counter" error {pull}38094[38094]
 - Fix "failed processing S3 event for object key" error on aws-s3 input when key contains the "+" character {issue}38012[38012] {pull}38125[38125]
 - Fix duplicated addition of regexp extension in CEL input. {pull}38181[38181]
+- Fix the incorrect values generated by the uri_parts processor. {pull}38216[38216]
+- Fix HTTPJSON handling of empty object bodies in POST requests. {issue}33961[33961] {pull}38290[38290]
+- Fix PEM key validation for CEL and HTTPJSON inputs. {pull}38405[38405]
 
 *Heartbeat*
 

x-pack/filebeat/input/cel/config_auth.go

@@ -6,7 +6,6 @@ package cel
 
 import (
 	"context"
-	"crypto/x509"
 	"encoding/json"
 	"errors"
 	"fmt"
@@ -341,7 +340,10 @@ func (o *oAuth2Config) validateOktaProvider() error {
 	}
 	// jwk_pem
 	if o.OktaJWKPEM != "" {
-		_, err := x509.ParsePKCS1PrivateKey([]byte(o.OktaJWKPEM))
+		_, err := pemPKCS8PrivateKey([]byte(o.OktaJWKPEM))
+		if err != nil {
+			return fmt.Errorf("okta validation error: %w", err)
+		}
 		return err
 	}
 	// jwk_file

x-pack/filebeat/input/cel/config_okta_auth.go

@@ -12,6 +12,7 @@ import (
 	"encoding/base64"
 	"encoding/json"
 	"encoding/pem"
+	"errors"
 	"fmt"
 	"math/big"
 	"net/http"
@@ -160,17 +161,24 @@ func (i *base64int) UnmarshalJSON(b []byte) error {
 }
 
 func generateOktaJWTPEM(pemdata string, cnf *oauth2.Config) (string, error) {
-	blk, rest := pem.Decode([]byte(pemdata))
-	if rest := bytes.TrimSpace(rest); len(rest) != 0 {
-		return "", fmt.Errorf("PEM text has trailing data: %s", rest)
-	}
-	key, err := x509.ParsePKCS8PrivateKey(blk.Bytes)
+	key, err := pemPKCS8PrivateKey([]byte(pemdata))
 	if err != nil {
 		return "", err
 	}
 	return signJWT(cnf, key)
 }
 
+func pemPKCS8PrivateKey(pemdata []byte) (any, error) {
+	blk, rest := pem.Decode(pemdata)
+	if rest := bytes.TrimSpace(rest); len(rest) != 0 {
+		return nil, fmt.Errorf("PEM text has trailing data: %d bytes", len(rest))
+	}
+	if blk == nil {
+		return nil, errors.New("no PEM data")
+	}
+	return x509.ParsePKCS8PrivateKey(blk.Bytes)
+}
+
 // signJWT creates a JWT token using required claims and sign it with the
 // private key.
 func signJWT(cnf *oauth2.Config, key any) (string, error) {
@@ -182,7 +190,7 @@ func signJWT(cnf *oauth2.Config, key any) (string, error) {
 		Expiration(now.Add(time.Hour)).
 		Build()
 	if err != nil {
-		return "", err
+		return "", fmt.Errorf("failed to create token: %w", err)
 	}
 	signedToken, err := jwt.Sign(tok, jwt.WithKey(jwa.RS256, key))
 	if err != nil {

x-pack/filebeat/input/cel/config_test.go

@@ -539,6 +539,47 @@ var oAuth2ValidationTests = []struct {
 			},
 		},
 	},
+	{
+		name: "okta_successful_pem_oauth2_validation",
+		input: map[string]interface{}{
+			"auth.oauth2": map[string]interface{}{
+				"provider":  "okta",
+				"client.id": "a_client_id",
+				"token_url": "localhost",
+				"scopes":    []string{"foo"},
+				"okta.jwk_pem": `
+-----BEGIN PRIVATE KEY-----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+MiWqUUInGGBuamqm5g6jI5sM28gQWeTsvC4IRXyes1Eq+uCHSQax15J/Y+3SSgNT
+9kjUYYkvWMwoRcPobRYWSZze7XkP2L8hFJ7EGvAaZGqAWxzgliS9HtnhAoGAONZ/
+UqMw7Zoac/Ga5mhSwrj7ZvXxP6Gqzjofj+eKqrOlB5yMhIX6LJATfH6iq7cAMxxm
+Fu/G4Ll4oB3o5wACtI3wldV/MDtYfJBtoCTjBqPsfNOsZ9hMvBATlsc2qwzKjsAb
+tFhzTevoOYpSD75EcSS/G8Ec2iN9bagatBnpl00CgYBVqAOFZelNfP7dj//lpk8y
+EUAw7ABOq0S9wkpFWTXIVPoBQUipm3iAUqGNPmvr/9ShdZC9xeu5AwKram4caMWJ
+ExRhcDP1hFM6CdmSkIYEgBKvN9N0O4Lx1ba34gk74Hm65KXxokjJHOC0plO7c7ok
+LNV/bIgMHOMoxiGrwyjAhg==
+-----END PRIVATE KEY-----
+`,
+			},
+		},
+	},
 }
 
 func TestConfigOauth2Validation(t *testing.T) {

x-pack/filebeat/input/httpjson/config_auth.go

@@ -6,7 +6,6 @@ package httpjson
 
 import (
 	"context"
-	"crypto/x509"
 	"encoding/json"
 	"errors"
 	"fmt"
@@ -309,8 +308,11 @@ func (o *oAuth2Config) validateOktaProvider() error {
 	}
 	// jwk_pem
 	if o.OktaJWKPEM != "" {
-		_, err := x509.ParsePKCS1PrivateKey([]byte(o.OktaJWKPEM))
-		return err
+		_, err := pemPKCS8PrivateKey([]byte(o.OktaJWKPEM))
+		if err != nil {
+			return fmt.Errorf("okta validation error: %w", err)
+		}
+		return nil
 	}
 	// jwk_file
 	if o.OktaJWKFile != "" {

x-pack/filebeat/input/httpjson/config_okta_auth.go

@@ -12,6 +12,7 @@ import (
 	"encoding/base64"
 	"encoding/json"
 	"encoding/pem"
+	"errors"
 	"fmt"
 	"math/big"
 	"net/http"
@@ -158,17 +159,24 @@ func (i *base64int) UnmarshalJSON(b []byte) error {
 }
 
 func generateOktaJWTPEM(pemdata string, cnf *oauth2.Config) (string, error) {
-	blk, rest := pem.Decode([]byte(pemdata))
-	if rest := bytes.TrimSpace(rest); len(rest) != 0 {
-		return "", fmt.Errorf("PEM text has trailing data: %s", rest)
-	}
-	key, err := x509.ParsePKCS8PrivateKey(blk.Bytes)
+	key, err := pemPKCS8PrivateKey([]byte(pemdata))
 	if err != nil {
 		return "", err
 	}
 	return signJWT(cnf, key)
 }
 
+func pemPKCS8PrivateKey(pemdata []byte) (any, error) {
+	blk, rest := pem.Decode(pemdata)
+	if rest := bytes.TrimSpace(rest); len(rest) != 0 {
+		return nil, fmt.Errorf("PEM text has trailing data: %d bytes", len(rest))
+	}
+	if blk == nil {
+		return nil, errors.New("no PEM data")
+	}
+	return x509.ParsePKCS8PrivateKey(blk.Bytes)
+}
+
 // signJWT creates a JWT token using required claims and sign it with the private key.
 func signJWT(cnf *oauth2.Config, key any) (string, error) {
 	now := time.Now()
@@ -179,7 +187,7 @@ func signJWT(cnf *oauth2.Config, key any) (string, error) {
 		Expiration(now.Add(time.Hour)).
 		Build()
 	if err != nil {
-		return "", err
+		return "", fmt.Errorf("failed to create token: %w", err)
 	}
 	signedToken, err := jwt.Sign(tok, jwt.WithKey(jwa.RS256, key))
 	if err != nil {

x-pack/filebeat/input/httpjson/config_test.go

@@ -499,6 +499,47 @@ func TestConfigOauth2Validation(t *testing.T) {
 				},
 			},
 		},
+		{
+			name: "okta successful pem oauth2 validation",
+			input: map[string]interface{}{
+				"auth.oauth2": map[string]interface{}{
+					"provider":  "okta",
+					"client.id": "a_client_id",
+					"token_url": "localhost",
+					"scopes":    []string{"foo"},
+					"okta.jwk_pem": `
+-----BEGIN PRIVATE KEY-----
+MIIEvAIBADANBgkqhkiG9w0BAQEFAASCBKYwggSiAgEAAoIBAQCOuef3HMRhohVT
+5kSoAJgV+atpDjkwTwkOq+ImnbBlv75GaApG90w8VpjXjhqN/1KJmwfyrKiquiMq
+OPu+o/672Dys5rUAaWSbT7wRF1GjLDDZrM0GHRdV4DGxM/LKI8I5yE1Mx3EzV+D5
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+LNV/bIgMHOMoxiGrwyjAhg==
+-----END PRIVATE KEY-----
+`,
+				},
+			},
+		},
 	}
 
 	for _, c := range cases {