The problem is basically how the centralized validation is supposed to work. For e.g. the Linux kernel, it's doable because all code in the kernel must (almost by definition) interact with some other part of the kernel. Thus someone else than the code owner, being responsible for those other parts of the kernel, can be tasked with signing off on the new code being good and non-malicious.
But for NPM or PyPI, where anyone can upload anything, how's that supposed to work? It's perfectly fine for someone to put a package called "removeallfiles" on PyPI which executes "sudo rm -rf /". This isn't (by itself) malicious code. The same code, but obfuscated and put in the package name "isarray", is perhaps obviously malicious. But what about something in the middle, e.g. some form of practical joke package? What central authority decides what is allowed and what is not on PyPI?
Signing is a tangential issue. As long as you're trusting the dev who uploaded the code, what difference does it make whether they used password or public key auth (effectively)?
But for NPM or PyPI, where anyone can upload anything, how's that supposed to work? It's perfectly fine for someone to put a package called "removeallfiles" on PyPI which executes "sudo rm -rf /". This isn't (by itself) malicious code. The same code, but obfuscated and put in the package name "isarray", is perhaps obviously malicious. But what about something in the middle, e.g. some form of practical joke package? What central authority decides what is allowed and what is not on PyPI?
Signing is a tangential issue. As long as you're trusting the dev who uploaded the code, what difference does it make whether they used password or public key auth (effectively)?