runtime, syscall: only search for Windows DLLs in the System32 directory

Make sure that for any DLL that Go uses itself, we only look for the
DLL in the Windows System32 directory, guarding against DLL preloading
attacks.

(Unless the Windows version is ancient and LoadLibraryEx is
unavailable, in which case the user probably has bigger security
problems anyway.)

This does not change the behavior of syscall.LoadLibrary or NewLazyDLL
if the DLL name is something unused by Go itself.

This change also intentionally does not add any new API surface. Instead,
x/sys is updated with a LoadLibraryEx function and LazyDLL.Flags in:
    https://golang.org/cl/21388

Updates #14959

Change-Id: I8d29200559cc19edf8dcf41dbdd39a389cd6aeb9
Reviewed-on: https://go-review.googlesource.com/21140
Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-on: https://go-review.googlesource.com/21639
Run-TryBot: Andrew Gerrand <adg@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
15 files changed
tree: b6e37305c452a5afb4fb2275bf4ce2813229dc87
  1. api/
  2. doc/
  3. lib/
  4. misc/
  5. src/
  6. test/
  7. .gitattributes
  8. .gitignore
  9. AUTHORS
  10. CONTRIBUTING.md
  11. CONTRIBUTORS
  12. favicon.ico
  13. LICENSE
  14. PATENTS
  15. README.md
  16. robots.txt
  17. VERSION
README.md

The Go Programming Language

Go is an open source programming language that makes it easy to build simple, reliable, and efficient software.

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Please report issues here: https://golang.org/issue/new

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To contribute, please read the contribution guidelines: https://golang.org/doc/contribute.html

Please note that we do not use pull requests.

Unless otherwise noted, the Go source files are distributed under the BSD-style license found in the LICENSE file.


Binary Distribution Notes

If you have just untarred a binary Go distribution, you need to set the environment variable $GOROOT to the full path of the go directory (the one containing this file). You can omit the variable if you unpack it into /usr/local/go, or if you rebuild from sources by running all.bash (see doc/install-source.html). You should also add the Go binary directory $GOROOT/bin to your shell's path.

For example, if you extracted the tar file into $HOME/go, you might put the following in your .profile:

export GOROOT=$HOME/go
export PATH=$PATH:$GOROOT/bin

See https://golang.org/doc/install or doc/install.html for more details.