Vault-17911: add support for hex values in oid extension (#21830)

* add support for hex values in oid extension

* add changelog

* add length check on split and error handling on unmarshal

builtin/credential/cert/backend_test.go

@@ -14,6 +14,7 @@ import (
 	"crypto/x509/pkix"
 	"encoding/pem"
 	"fmt"
+	"github.com/hashicorp/go-sockaddr"
 	"io"
 	"io/ioutil"
 	"math/big"
@@ -28,8 +29,6 @@ import (
 	"time"
 
 	"github.com/go-test/deep"
-	"github.com/hashicorp/go-sockaddr"
-
 	"golang.org/x/net/http2"
 
 	cleanhttp "github.com/hashicorp/go-cleanhttp"
@@ -1306,6 +1305,12 @@ func TestBackend_ext_singleCert(t *testing.T) {
 			testAccStepLoginInvalid(t, connState),
 			testAccStepCert(t, "web", ca, "foo", allowed{names: "invalid", ext: "2.1.1.1:*,2.1.1.2:The Wrong Value"}, false),
 			testAccStepLoginInvalid(t, connState),
+			testAccStepCert(t, "web", ca, "foo", allowed{names: "example.com", ext: "hex:2.5.29.17:*87047F000002*"}, false),
+			testAccStepLoginInvalid(t, connState),
+			testAccStepCert(t, "web", ca, "foo", allowed{names: "example.com", ext: "hex:2.5.29.17:*87047F000001*"}, false),
+			testAccStepLogin(t, connState),
+			testAccStepCert(t, "web", ca, "foo", allowed{names: "example.com", ext: "2.5.29.17:"}, false),
+			testAccStepLogin(t, connState),
 			testAccStepReadConfig(t, config{EnableIdentityAliasMetadata: false}, connState),
 			testAccStepCert(t, "web", ca, "foo", allowed{metadata_ext: "2.1.1.1,1.2.3.45"}, false),
 			testAccStepLoginWithMetadata(t, connState, "web", map[string]string{"2-1-1-1": "A UTF8String Extension"}, false),

builtin/credential/cert/path_login.go

@@ -10,6 +10,7 @@ import (
 	"crypto/x509"
 	"encoding/asn1"
 	"encoding/base64"
+	"encoding/hex"
 	"encoding/pem"
 	"errors"
 	"fmt"
@@ -507,19 +508,44 @@ func (b *backend) matchesCertificateExtensions(clientCert *x509.Certificate, con
 	// including its ASN.1 type tag bytes. For the sake of simplicity, assume string type
 	// and drop the tag bytes. And get the number of bytes from the tag.
 	clientExtMap := make(map[string]string, len(clientCert.Extensions))
+	hexExtMap := make(map[string]string, len(clientCert.Extensions))
+
 	for _, ext := range clientCert.Extensions {
 		var parsedValue string
-		asn1.Unmarshal(ext.Value, &parsedValue)
+		_, err := asn1.Unmarshal(ext.Value, &parsedValue)
+		if err != nil {
+			clientExtMap[ext.Id.String()] = ""
+		} else {
 			clientExtMap[ext.Id.String()] = parsedValue
 		}
-	// If any of the required extensions don'log match the constraint fails
+
+		hexExtMap[ext.Id.String()] = hex.EncodeToString(ext.Value)
+	}
+
+	// If any of the required extensions don't match the constraint fails
 	for _, requiredExt := range config.Entry.RequiredExtensions {
 		reqExt := strings.SplitN(requiredExt, ":", 2)
+		if len(reqExt) != 2 {
+			return false
+		}
+
+		if reqExt[0] == "hex" {
+			reqHexExt := strings.SplitN(reqExt[1], ":", 2)
+			if len(reqHexExt) != 2 {
+				return false
+			}
+
+			clientExtValue, clientExtValueOk := hexExtMap[reqHexExt[0]]
+			if !clientExtValueOk || !glob.Glob(strings.ToLower(reqHexExt[1]), clientExtValue) {
+				return false
+			}
+		} else {
 			clientExtValue, clientExtValueOk := clientExtMap[reqExt[0]]
 			if !clientExtValueOk || !glob.Glob(reqExt[1], clientExtValue) {
 				return false
 			}
 		}
+	}
 	return true
 }
 

changelog/21830.txt

@@ -0,0 +1,3 @@
+```release-note:improvement
+auth/cert: Adds support for requiring hexadecimal-encoded non-string certificate extension values
+```

website/content/api-docs/auth/cert.mdx

@@ -59,8 +59,9 @@ Sets a CA cert and associated parameters in a role name.
 - `required_extensions` `(string: "" or array: [])` - Require specific Custom
   Extension OIDs to exist and match the pattern. Value is a comma separated
   string or array of `oid:value`. Expects the extension value to be some type
-  of ASN1 encoded string. All conditions _must_ be met. Supports globbing on
-  `value`.
+  of ASN1 encoded string. All conditions _must_ be met. To match on the hex-encoded
+  value of the extension, including non-string extensions, use the format
+  `hex:<oid>:<value>`.Supports globbing on `value`.
 - `allowed_metadata_extensions` `(array:[])` - A comma separated string or
   array of oid extensions. Upon successful authentication, these extensions
   will be added as metadata if they are present in the certificate. The