You might sideload an Android app, or manually install its APK package, if you're using a custom version of Android that doesn't include Google's Play Store. Alternately, the app might be experimental, under development, or perhaps no longer maintained and offered by its developer. Until now, the existence of sideload-ready APKs on the web was something that seemed to be tolerated, if warned against, by Google.
This quiet standstill is being shaken up by a new feature in Google's Play Integrity API. As reported by Android Authority, developer tools to push "remediation" dialogs during sideloading debuted at Google's I/O conference in May, have begun showing up on users' phones. Sideloaders of apps from the British shop Tesco, fandom app BeyBlade X, and ChatGPT have reported "Get this app from Play" prompts, which cannot be worked around. An Android gaming handheld user encountered a similarly worded prompt from Diablo Immortal on their device three months ago.
Google's Play Integrity API is how apps have previously blocked access when loaded onto phones that are in some way modified from a stock OS with all Google Play integrations intact. Recently, a popular two-factor authentication app blocked access on rooted phones, including the security-minded GrapheneOS. Apps can call the Play Integrity API and get back an "integrity verdict," relaying if the phone has a "trustworthy" software environment, has Google Play Protect enabled, and passes other software checks.
Graphene has questioned the veracity of Google's Integrity API and SafetyNet Attestation systems, recommending instead standard Android hardware attestation. Rahman notes that apps do not have to take an all-or-nothing approach to integrity checking. Rather than block installation entirely, apps could call on the API only during sensitive actions, issuing a warning there. But not having a Play Store connection can also deprive developers of metrics, allow for installation on incompatible devices (and resulting bad reviews), and, of course, open the door to paid app piracy.
Why do you think apps should verify their integrity in the first place? In the case of banking apps or other online apps, the APIs they use should be secure in the first place so a user can't achieve anything meaningful by modifying API calls. In the case of offline games with monetization, a hacker who makes a pirated APK will also remove the restriction so legitimate players on non standart ROMs will get screwed. In the case of messaging apps with a "delete messages" or "one time view" function ie. Whatsapp, the sender shouldn't take that their actions will be respected by other clients because modded apps exist and Whatsapp doesn't care if you install it on a rooted device.
This!
APK signatures exist and they're enough for making sure the file you got isn't modified. Warning people when they use apks for stuff like banking, I get, but if they wanna take the risk, it's on them.
Blocking root makes no sense because I'd argue that if the person knows enough to root their phone and got past all those bricked phone/thermonuclear war warnings, the onus is on them to not get their keychain compromised by giving root to some random app. Again, a warning is fine.
Aside from that, people need to understand: THE CLIENT IS NEVER SECURE. NO EXCEPTIONS.
Any self respecting secure API is made under the assumption that all the calls are coming from some malicious state actor using
curluntil proven beyond doubt that it's an actual user.API are secure only if you can secure the authentication details. A modified app (be it as something modified and distributed on a unsanctioned channel, or custom injected by another malicious actor/app) can easily siphon out your authentication tokens to a third party unbeknownst to you the user. However, if the app verifies it came from the approved source and have not been tempered with, then it is much easier to lean on ASLR and other OS level security to make it harder to extract the authentication info.
Multiplayer game operators have obligation to curb modified clients so their actual paying clients have a levelled playing field. By ensuring their apps are only distributed via approved channels and unmodified by malicious players, this improves their odds at warding off cheaters creating a bad time for those that actually pay them to play fairly.
These are just simple cases where this kind of security is beneficial. I am glad Android is finally catching up in this regard.
Downloading APKs from reputable sources and signature checking can help with this one. Android will refuse to upgrade an app if APK has a different signature anyways.
If this is possible there are bigger problems.
There isn't much I can say for that.