[release-branch.go1.14-security] math/big: fix shift for recursive division

The previous s value could cause a crash
for certain inputs.

Will check in tests and documentation improvements later.

Thanks to the Go Ethereum team and the OSS-Fuzz project for reporting this.
Thanks to Rémy Oudompheng and Robert Griesemer for their help
developing and validating the fix.

Fixes CVE-2020-28362

Change-Id: Ibbf455c4436bcdb07c84a34fa6551fb3422356d3
Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/899974
Reviewed-by: Roland Shoemaker <bracewell@google.com>
Reviewed-by: Filippo Valsorda <valsorda@google.com>
(cherry picked from commit 28015462c2a83239543dc2bef651e9a5f234b633)
Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/901064
1 file changed
tree: ab212f6ca16a70cec8dd44d7985f1e9e658fe668
  1. .github/
  2. api/
  3. doc/
  4. lib/
  5. misc/
  6. src/
  7. test/
  8. .gitattributes
  9. .gitignore
  13. favicon.ico
  16. README.md
  17. robots.txt
  18. SECURITY.md

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