Finish preliminary support for external key source for ssh cas

backend/src/ee/services/ssh/ssh-certificate-authority-fns.ts

@@ -322,6 +322,91 @@ const validateSshPublicKey = async (publicKey: string) => {
   }
 };
 
+export const getKeyAlgorithmFromFingerprintOutput = (output: string): CertKeyAlgorithm | undefined => {
+  const parts = output.trim().split(" ");
+  const bitsInt = parseInt(parts[0], 10);
+  const keyTypeRaw = parts.at(-1)?.replace(/[()]/g, ""); // remove surrounding parentheses
+
+  if (keyTypeRaw === "RSA") {
+    return bitsInt === 2048 ? CertKeyAlgorithm.RSA_2048 : CertKeyAlgorithm.RSA_4096;
+  }
+
+  if (keyTypeRaw === "ECDSA") {
+    return bitsInt === 256 ? CertKeyAlgorithm.ECDSA_P256 : CertKeyAlgorithm.ECDSA_P384;
+  }
+
+  return undefined;
+};
+
+export const normalizeSshPrivateKey = (raw: string): string => {
+  return `${raw
+    .replace(/\r\n/g, "\n") // Windows CRLF → LF
+    .replace(/\r/g, "\n") // Old Mac CR → LF
+    .replace(/\\n/g, "\n") // Double-escaped \n
+    .trim()}\n`;
+};
+
+/**
+ * Validate the format of the SSH private key
+ *
+ * Returns the SSH public key corresponding to the private key
+ * and the key algorithm categorization.
+ */
+export const validateSshPrivateKey = async (privateKey: string) => {
+  const tempDir = await fs.mkdtemp(path.join(os.tmpdir(), "ssh-privkey-"));
+  const privateKeyFile = path.join(tempDir, "id_key");
+
+  try {
+    await fs.writeFile(privateKeyFile, privateKey, {
+      encoding: "utf8",
+      mode: 0o600
+    });
+
+    // This will fail if the private key is malformed or unreadable
+    const { stdout: publicKey } = await execFileAsync("ssh-keygen", ["-y", "-f", privateKeyFile], {
+      timeout: EXEC_TIMEOUT_MS
+    });
+
+    const { stdout: fingerprint } = await execFileAsync("ssh-keygen", ["-lf", privateKeyFile]);
+    const keyAlgorithm = getKeyAlgorithmFromFingerprintOutput(fingerprint);
+
+    if (!keyAlgorithm) {
+      throw new BadRequestError({
+        message: "Failed to validate SSH private key format: The key algorithm is not supported."
+      });
+    }
+
+    return {
+      publicKey,
+      keyAlgorithm
+    };
+  } catch (err) {
+    throw new BadRequestError({
+      message: "Failed to validate SSH private key format: could not be parsed."
+    });
+  } finally {
+    await fs.rm(tempDir, { recursive: true, force: true }).catch(() => {});
+  }
+};
+
+/**
+ * Validate that the provided public and private keys are valid and constitute
+ * a matching SSH key pair.
+ */
+export const validateExternalSshCaKeyPair = async (publicKey: string, privateKey: string) => {
+  await validateSshPublicKey(publicKey);
+
+  const { publicKey: derivedPublicKey, keyAlgorithm } = await validateSshPrivateKey(privateKey);
+
+  if (publicKey.trim() !== derivedPublicKey.trim()) {
+    throw new BadRequestError({
+      message: "Failed to validate matching SSH key pair."
+    });
+  }
+
+  return keyAlgorithm;
+};
+
 /**
  * Create an SSH certificate for a user or host.
  */

backend/src/ee/services/ssh/ssh-certificate-authority-schema.ts

@@ -5,5 +5,6 @@ export const sanitizedSshCa = SshCertificateAuthoritiesSchema.pick({
   projectId: true,
   friendlyName: true,
   status: true,
-  keyAlgorithm: true
+  keyAlgorithm: true,
+  keySource: true
 });

backend/src/ee/services/ssh/ssh-certificate-authority-service.ts

@@ -9,12 +9,19 @@ import { TSshCertificateBodyDALFactory } from "@app/ee/services/ssh-certificate/
 import { TSshCertificateDALFactory } from "@app/ee/services/ssh-certificate/ssh-certificate-dal";
 import { TSshCertificateTemplateDALFactory } from "@app/ee/services/ssh-certificate-template/ssh-certificate-template-dal";
 import { BadRequestError, NotFoundError } from "@app/lib/errors";
+import { CertKeyAlgorithm } from "@app/services/certificate/certificate-types";
 import { TKmsServiceFactory } from "@app/services/kms/kms-service";
 import { KmsDataKey } from "@app/services/kms/kms-types";
 
 import { SshCertTemplateStatus } from "../ssh-certificate-template/ssh-certificate-template-types";
-import { createSshCert, createSshKeyPair, getSshPublicKey } from "./ssh-certificate-authority-fns";
 import {
+  createSshCert,
+  createSshKeyPair,
+  getSshPublicKey,
+  validateExternalSshCaKeyPair
+} from "./ssh-certificate-authority-fns";
+import {
+  SshCaKeySource,
   SshCaStatus,
   TCreateSshCaDTO,
   TDeleteSshCaDTO,
@@ -59,7 +66,10 @@ export const sshCertificateAuthorityServiceFactory = ({
   const createSshCa = async ({
     projectId,
     friendlyName,
-    keyAlgorithm,
+    keyAlgorithm: requestedKeyAlgorithm,
+    publicKey: externalPk,
+    privateKey: externalSk,
+    keySource,
     actorId,
     actorAuthMethod,
     actor,
@@ -80,18 +90,37 @@ export const sshCertificateAuthorityServiceFactory = ({
     );
 
     const newCa = await sshCertificateAuthorityDAL.transaction(async (tx) => {
+      let publicKey: string;
+      let privateKey: string;
+      let keyAlgorithm: CertKeyAlgorithm = requestedKeyAlgorithm;
+
+      if (keySource === SshCaKeySource.INTERNAL) {
+        // generate SSH CA key pair internally
+        ({ publicKey, privateKey } = await createSshKeyPair(requestedKeyAlgorithm));
+      } else {
+        // use external SSH CA key pair
+        if (!externalPk || !externalSk) {
+          throw new BadRequestError({
+            message: "Public and private keys are required if generateSigningKey is false"
+          });
+        }
+        publicKey = externalPk;
+        privateKey = externalSk;
+
+        keyAlgorithm = await validateExternalSshCaKeyPair(publicKey, privateKey);
+      }
+
       const ca = await sshCertificateAuthorityDAL.create(
         {
           projectId,
           friendlyName,
           status: SshCaStatus.ACTIVE,
-          keyAlgorithm
+          keyAlgorithm,
+          keySource
         },
         tx
       );
 
-      const { publicKey, privateKey } = await createSshKeyPair(keyAlgorithm);
-
       const { encryptor: secretManagerEncryptor } = await kmsService.createCipherPairWithDataKey({
         type: KmsDataKey.SecretManager,
         projectId

backend/src/ee/services/ssh/ssh-certificate-authority-types.ts

@@ -7,6 +7,11 @@ export enum SshCaStatus {
   DISABLED = "disabled"
 }
 
+export enum SshCaKeySource {
+  INTERNAL = "internal",
+  EXTERNAL = "external"
+}
+
 export enum SshCertType {
   USER = "user",
   HOST = "host"
@@ -15,6 +20,9 @@ export enum SshCertType {
 export type TCreateSshCaDTO = {
   friendlyName: string;
   keyAlgorithm: CertKeyAlgorithm;
+  publicKey?: string;
+  privateKey?: string;
+  keySource: SshCaKeySource;
 } & TProjectPermission;
 
 export type TGetSshCaDTO = {