crypto/x509: reject SHA-1 signatures in Verify [1.18 backport]

[gopherbot]

@FiloSottile requested issue #41682 to be considered for backport to the next 1.18 minor release.

If crypto/x509 aims to be compatible with the WebPKI, then I'm afraid this change has to be rolled back or limited to just certificate signatures.

You are, as always, correct :) we'll limit it to just certificates in Go 1.18.1.

Change https://go.dev/cl/394294 mentions this issue: crypto/x509: only disable SHA-1 verification for certificates

@gopherbot please open a backport issue for Go 1.18, we need to fix what's effectively a regression in WebPKI compatibility.

[toothrot]

Approved. This is a serious issue without a good workaround.

[cherrymui]

This is approved and targeting Go 1.18.1, but doesn't have a CL attached to it. @FiloSottile would you like to make a CL, or do we want to delay it? Thanks.

[gopherbot]

Change https://go.dev/cl/398074 mentions this issue: [release-branch.go1.18] crypto/x509: only disable SHA-1 verification for certificates

[gopherbot]

Closed by merging abb3f05 to release-branch.go1.18.