[8.12][Fleet] fix API not allowing to upgrade to a newer version when version differs only in patch (#175765)

Fixes https://github.com/elastic/kibana/issues/175766

[8.12][Fleet] Partial backport of
https://github.com/elastic/kibana/pull/175198

To verify:
- add a fleet-server version 8.12.0
- enroll an agent version 8.12.0-SNAPSHOT
- take the agent id and in console run this API request
```
POST kbn:/api/fleet/agents/6a56f865-a611-4921-9f24-87757259223e/upgrade
  {
    "version": "8.12.1-SNAPSHOT"
  }
```
- verify that the API returns 200 

Relates https://github.com/elastic/kibana/issues/168502

x-pack/plugins/fleet/common/services/is_agent_upgradeable.ts

@@ -85,3 +85,16 @@ export function isAgentUpgrading(agent: Agent) {
   }
   return agent.upgrade_started_at && !agent.upgraded_at;
 }
+
+export const differsOnlyInPatch = (
+  versionA: string,
+  versionB: string,
+  allowEqualPatch: boolean = true
+): boolean => {
+  const [majorA, minorA, patchA] = versionA.split('.');
+  const [majorB, minorB, patchB] = versionB.split('.');
+
+  return (
+    majorA === majorB && minorA === minorB && (allowEqualPatch ? patchA >= patchB : patchA > patchB)
+  );
+};

x-pack/plugins/fleet/public/applications/fleet/sections/agents/components/agent_upgrade_modal/index.tsx

@@ -27,7 +27,10 @@ import type { EuiComboBoxOptionOption } from '@elastic/eui';
 import semverGt from 'semver/functions/gt';
 import semverLt from 'semver/functions/lt';
 
-import { AGENT_UPGRADE_COOLDOWN_IN_MIN } from '../../../../../../../common/services';
+import {
+  AGENT_UPGRADE_COOLDOWN_IN_MIN,
+  differsOnlyInPatch,
+} from '../../../../../../../common/services';
 
 import { getMinVersion } from '../../../../../../../common/services/get_min_max_version';
 import {
@@ -44,7 +47,6 @@ import {
   useConfig,
   sendGetAgentStatus,
   useAgentVersion,
-  differsOnlyInPatch,
 } from '../../../../hooks';
 
 import { sendGetAgentsAvailableVersions } from '../../../../hooks';

x-pack/plugins/fleet/public/hooks/use_agent_version.ts

@@ -8,6 +8,8 @@ import { useEffect, useState } from 'react';
 import semverRcompare from 'semver/functions/rcompare';
 import semverLt from 'semver/functions/lt';
 
+import { differsOnlyInPatch } from '../../common/services';
+
 import { useKibanaVersion } from './use_kibana_version';
 import { sendGetAgentsAvailableVersions } from './use_request';
 
@@ -50,16 +52,3 @@ export const useAgentVersion = (): string | undefined => {
 
   return agentVersion;
 };
-
-export const differsOnlyInPatch = (
-  versionA: string,
-  versionB: string,
-  allowEqualPatch: boolean = true
-): boolean => {
-  const [majorA, minorA, patchA] = versionA.split('.');
-  const [majorB, minorB, patchB] = versionB.split('.');
-
-  return (
-    majorA === majorB && minorA === minorB && (allowEqualPatch ? patchA >= patchB : patchA > patchB)
-  );
-};

x-pack/plugins/fleet/server/routes/agent/upgrade_handler.test.ts

@@ -5,7 +5,7 @@
  * 2.0.
  */
 
-import { checkKibanaVersion } from './upgrade_handler';
+import { checkFleetServerVersion, checkKibanaVersion } from './upgrade_handler';
 
 describe('upgrade handler', () => {
   describe('checkKibanaVersion', () => {
@@ -15,7 +15,7 @@ describe('upgrade handler', () => {
 
     it('should throw if upgrade version is higher than kibana version', () => {
       expect(() => checkKibanaVersion('8.5.0', '8.4.0')).toThrowError(
-        'cannot upgrade agent to 8.5.0 because it is higher than the installed kibana version 8.4.0'
+        'Cannot upgrade agent to 8.5.0 because it is higher than the installed kibana version 8.4.0'
       );
     });
 
@@ -28,6 +28,11 @@ describe('upgrade handler', () => {
       expect(() => checkKibanaVersion('8.4.1-SNAPSHOT', '8.4.0', true)).not.toThrowError();
     });
 
+    it('should not throw if not force is specified and patch is newer', () => {
+      expect(() => checkKibanaVersion('8.4.1', '8.4.0', false)).not.toThrowError();
+      expect(() => checkKibanaVersion('8.4.1-SNAPSHOT', '8.4.0', false)).not.toThrowError();
+    });
+
     it('should throw if force is specified and minor is newer', () => {
       expect(() => checkKibanaVersion('8.5.0', '8.4.0', true)).toThrowError();
     });
@@ -37,4 +42,17 @@ describe('upgrade handler', () => {
       expect(() => checkKibanaVersion('8.4.0', '8.4.0', true)).not.toThrowError();
     });
   });
+
+  describe('checkFleetServerVersion', () => {
+    it('should not throw if no force is specified and patch is newer', () => {
+      const fleetServers = [
+        { local_metadata: { elastic: { agent: { version: '8.3.0' } } } },
+        { local_metadata: { elastic: { agent: { version: '8.4.0' } } } },
+      ] as any;
+      expect(() => checkFleetServerVersion('8.4.1', fleetServers, false)).not.toThrowError();
+      expect(() =>
+        checkFleetServerVersion('8.4.1-SNAPSHOT', fleetServers, false)
+      ).not.toThrowError();
+    });
+  });
 });

x-pack/plugins/fleet/server/routes/agent/upgrade_handler.ts

@@ -25,6 +25,7 @@ import {
   isAgentUpgradeable,
   AGENT_UPGRADE_COOLDOWN_IN_MIN,
   isAgentUpgrading,
+  differsOnlyInPatch,
 } from '../../../common/services';
 import { getMaxVersion } from '../../../common/services/get_min_max_version';
 import { getAgentById } from '../../services/agents';
@@ -192,9 +193,13 @@ export const checkKibanaVersion = (version: string, kibanaVersion: string, force
   if (!versionToUpgradeNumber)
     throw new Error(`version to upgrade ${versionToUpgradeNumber} is not valid`);
 
-  if (!force && semverGt(versionToUpgradeNumber, kibanaVersionNumber)) {
+  if (
+    !force &&
+    semverGt(versionToUpgradeNumber, kibanaVersionNumber) &&
+    !differsOnlyInPatch(versionToUpgradeNumber, kibanaVersionNumber)
+  ) {
     throw new Error(
-      `cannot upgrade agent to ${versionToUpgradeNumber} because it is higher than the installed kibana version ${kibanaVersionNumber}`
+      `Cannot upgrade agent to ${versionToUpgradeNumber} because it is higher than the installed kibana version ${kibanaVersionNumber}`
     );
   }
 
@@ -212,7 +217,7 @@ export const checkKibanaVersion = (version: string, kibanaVersion: string, force
 };
 
 // Check the installed fleet server version
-const checkFleetServerVersion = (
+export const checkFleetServerVersion = (
   versionToUpgradeNumber: string,
   fleetServerAgents: Agent[],
   force = false
@@ -227,7 +232,11 @@ const checkFleetServerVersion = (
     return;
   }
 
-  if (!force && semverGt(versionToUpgradeNumber, maxFleetServerVersion)) {
+  if (
+    !force &&
+    semverGt(versionToUpgradeNumber, maxFleetServerVersion) &&
+    !differsOnlyInPatch(versionToUpgradeNumber, maxFleetServerVersion)
+  ) {
     throw new Error(
       `cannot upgrade agent to ${versionToUpgradeNumber} because it is higher than the latest fleet server version ${maxFleetServerVersion}`
     );

x-pack/test/fleet_api_integration/apis/agents/upgrade.ts

@@ -1226,7 +1226,7 @@ export default function (providerContext: FtrProviderContext) {
       });
 
       it('should respond 400 if trying to bulk upgrade to a version that is higher than the latest fleet server version', async () => {
-        const higherVersion = semver.inc(fleetServerVersion, 'patch');
+        const higherVersion = '7.17.0';
         await es.update({
           id: 'agent1',
           refresh: 'wait_for',