- The kube-controller-manager managed signers can now have distinct signing certificates and keys.  See the help about `--cluster-signing-[signer-name]-{cert,key}-file`.  `--cluster-signing-{cert,key}-file` is still the default. ([#90822](https://github.com/kubernetes/kubernetes/pull/90822), [@deads2k](https://github.com/deads2k)) [SIG API Machinery, Apps and Auth]

        final byte[] buffer = this.getContext().getBufferCache().getBuffer();
        try {
            // synchronize around encode and write so that the ordering for SMB1 signing can be maintained
            synchronized (this.outLock) {
                final int n = smb.encode(buffer, 4);
                Encdec.enc_uint32be(n & 0xFFFF, buffer, 0); /* 4 byte session message header */

    * configuration scripts to allow configuration of signing duration of
    * certificates issued via the Certificate Signing Request API.

	c.Assert(err, nil)
	response, err = s.client.Do(request)
	c.Assert(err, nil)
	verifyError(c, response, "SignatureDoesNotMatch", "The request signature we calculated does not match the signature you provided. Check your key and signing method.", http.StatusForbidden)
}

// This tests validate if PUT handler can successfully detect SHA256 mismatch.
func (s *TestSuiteCommon) TestSHA256Mismatch(c *check) {
	// generate a random bucket name.

- Kubeadm: warn but do not error out on missing "ca.key" files for root CA, front-proxy CA and etcd CA, during "kubeadm join --control-plane" if the user has provided all certificates, keys and kubeconfig files which require signing with the given CA keys. ([#94988](https://github.com/kubernetes/kubernetes/pull/94988), [@neolit123](https://github.com/neolit123)) [SIG Cluster Lifecycle]

### Other (Cleanup or Flake)

	},
	ErrSignatureDoesNotMatch: {
		Code:           "SignatureDoesNotMatch",
		Description:    "The request signature we calculated does not match the signature you provided. Check your key and signing method.",
		HTTPStatusCode: http.StatusForbidden,
	},
	ErrMethodNotAllowed: {
		Code:           "MethodNotAllowed",
		Description:    "The specified method is not allowed against this resource.",

### Other notable changes

* The kube-apiserver --service-account-key-file option can be specified multiple times, or can point to a file containing multiple keys, to enable rotation of signing keys. ([#34029](https://github.com/kubernetes/kubernetes/pull/34029), [@liggitt](https://github.com/liggitt))

		uploadTestObject(t, apiRouter, credentials, bucketName, input.objectName, input.partLengths, input.metaData, false)
	}

	// function type for creating signed requests - used to repeat
	// requests with V2 and V4 signing.
	type testSignedReqFn func(method, urlStr string, contentLength int64,
		body io.ReadSeeker, accessKey, secretKey string, metamap map[string]string) (*http.Request,
		error)

kube-controller-manager has dropped support for the `--insecure-experimental-approve-all-kubelet-csrs-for-group` flag. It is accepted in 1.7, but ignored. Instead, the csrapproving controller uses authorization checks to determine whether to approve certificate signing requests: ([#45619](https://github.com/kubernetes/kubernetes/pull/45619), [@mikedanese](https://github.com/mikedanese))

    * Before upgrading, users must ensure their controller manager will enable the csrapproving controller, create...

- Added support to the kube-apiserver for an alpha feature enabling external signing of service account tokens and fetching of public verifying keys, by enabling the Alpha `ExternalServiceAccountTokenSigner` feature gate and specifying `--service-account-signing-endpoint`. The flag value can either be the location of a Unix domain socket on a filesystem, or be prefixed with an @ symbol and name a Unix domain socket in...