The docs for ResponseWriter.Write say
// If the Header
// does not contain a Content-Type line, Write adds a Content-Type set
// to the result of passing the initial 512 bytes of written data to
// DetectContentType.

The header X-Content-Type-Options:nosniff is an explicit directive that
content-type should not be sniffed.

This changes the behavior of Response.WriteHeader so that, when
there is an X-Content-Type-Options:nosniff header, but there is
no Content-type header, the following happens:
1.  A Content-type:application/octet-stream is added
2.  A warning is logged via the server's logging mechanism.

Previously, a content-type would have been silently added based on
heuristic analysis of the first 512B which might allow a hosted
GIF like http://www.thinkfu.com/blog/gifjavascript-polyglots to be
categorized as JavaScript which might allow a CSP bypass, loading
as a script despite `Content-Security-Policy: script-src 'self' `.

----

https://fetch.spec.whatwg.org/#x-content-type-options-header
defines the X-Content-Type-Options header.

["Polyglots: Crossing Origins by Crossing Formats"](http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.905.2946&rep=rep1&type=pdf)
explains Polyglot attacks in more detail.

Change-Id: I2c8800d2e4b4d10d9e08a0e3e5b20334a75f03c0
Reviewed-on: https://go-review.googlesource.com/89275Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

To enable the exec wrapper go_darwin_arm_exec.go to run binaries
on iOS devices, the GOIOS_DEV_ID variable needs to be set to a code
signing identity. The program detect.go attempts to detect suitable
values for GOIOS_DEV_ID (along with GOIOS_APP_ID and GOIOS_TEAM_ID).

Before this change, detect.go would use "security find-identity
-p codesigning -v" to list all available identities for code signing
and pick the first one with "iPhone Developer" in its name. However,
that pick might be invalid since if it was replaced by an identity
issued later.

For example, on the mobile builder:

$ security find-identity -p codesigning -v
  1) 0E251DE41FE4490574E475AC320B47F58D6D3635 "lldb_codesign"
  2) 0358588D07AA6A19478981BA405F40A97F95F187 "iPhone Developer: xxx@xxx (2754T98W8E)"
  3) FC6D96F24A3223C98BF7A2C2C5194D82E04CD23E "iPhone Developer: xxx@xxx (2754T98W8E)"
     3 valid identities found

In this case, the identity 0358588D07AA6A19478981BA405F40A97F95F187
is picked by detect.go even though it has been invalidated by
FC6D96F24A3223C98BF7A2C2C5194D82E04CD23E.

Instead of attempting to find an identity from the "security
find-identity" list, use the identity from the CommonName in the
embedded certificate in the provisioning file. The CommonName only
lists the identity name (iPhone Developer: xxx@xxx (2754T98W8E)),
not the fingerprint (FC6D96F24A3223C98BF7A2C2C5194D82E04CD23E), but
fortunately the codesign tool accepts both.

Identity names may not be unique, as demonstrated by the example,
but that will result in an ambiguity error at codesigning instead of
a more obscure error about an invalid identity when
go_darwin_arm_exec.go runs a binary.
The fix is then to delete the invalid identity from the system
keychain.

While here, find all connected devices instead of the first connected
and only consider provision files that covers them all. This matters
for the mobile builder where two devices are connected.

Change-Id: I6beb59ace3fc5e071ba76222a20a607765943989
Reviewed-on: https://go-review.googlesource.com/105436
Run-TryBot: Elias Naur <elias.naur@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>

After CL 104636 the feature flags in internal/cpu are initialized before
alginit and can now be used for aeshash feature detection. Also remove
now unused runtime variables:
x86:
	support_ssse3
	support_sse42
	support_aes
arm64:
	support_aes

Change-Id: I2f64198d91750eaf3c6cf2aac6e9e17615811ec8
Reviewed-on: https://go-review.googlesource.com/106015
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Once upon a time, the iOS exec wrapper needed to change the current
working directory for the binary being tested. To allow that, the
runtime raised a SIGINT signal that the wrapper caught, changed the
working directory and resumed the process.

These days, the current working directory is passed from the wrapper
to the runtime through a special entry in the app metadata and the
SIGINT handshake is not necessary anymore.

Remove the signaling from the runtime and the exec harness.

Change-Id: Ia53bcc9e4724d2ca00207e22b91ce80a05271b55
Reviewed-on: https://go-review.googlesource.com/106096
Run-TryBot: Elias Naur <elias.naur@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>

Use constant masks and align the definition of isSet with
arm64 and ppc64x.

Change-Id: I0c6eae30da5e3ce797cde0dab4a39855d4d245d9
Reviewed-on: https://go-review.googlesource.com/94759Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

runtime.alginit needs runtime/support_{aes,ssse3,sse41} feature flag
to init aeshash function but internal/cpu.init not be called yet.
This CL will call internal/cpu.initialize before runtime.alginit, so
that we can move all cpu features related code to internal/cpu.

Change-Id: I00b8e403ace3553f8c707563d95f27dade0bc853
Reviewed-on: https://go-review.googlesource.com/104636Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

When I added the Node.copy method, I converted most of the occurrences
but missed a few.

One of them, used only for gdata, was an unnecessary copy given that
gdata does not modify the node it is passed.

No allocation changes in compilebench.

Passes toolstash -cmp on std cmd.

Change-Id: I7fba5212377b75c6d6b3785e594a30568ff0732e
Reviewed-on: https://go-review.googlesource.com/104937
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

EM_AARCH64 is defined as a constant, but the corresponding entry in
machineStrings is missing. Add it.

Change-Id: I6506404386efe608877095e635a290bbc0686215
Reviewed-on: https://go-review.googlesource.com/106035
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

The code reading these variables was removed in CL 41476. They are only
set but never read now, so remove them.

Change-Id: I6b0b8d813e9a3ec2a13586ff92746e00ad1b5bf0
Reviewed-on: https://go-review.googlesource.com/106095
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

Fixes #23617

Note that this CL does not affect darwin/arm and darwin/arm64,
still TBD what, if anything, needs to be done for those.

Change-Id: Ie1ee02a9f4d4d1fb9cd5dc432d900f926cc157db
Reviewed-on: https://go-review.googlesource.com/105975Reviewed-by: Ian Lance Taylor <iant@golang.org>

Fixes #24791

Change-Id: I62ac17313e6e09796586911d88191a36d67f9aa1
Reviewed-on: https://go-review.googlesource.com/106115
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Packages imported by the runtime should follow the same memory
allocation rules as the runtime package.

Change-Id: Id3fadb05605acbd6ac61d7fe6068a2add8bb2308
Reviewed-on: https://go-review.googlesource.com/105995
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

And delete them from asm_test.

Change-Id: I24f421b87e8cb4770c887a6dfd58eacd0088947d
Reviewed-on: https://go-review.googlesource.com/106056Reviewed-by: Keith Randall <khr@golang.org>

And delete them from asm_test.

Change-Id: I9a75efe9858ef9d7ac86065f860c2ae3f25b0941
Reviewed-on: https://go-review.googlesource.com/105597Reviewed-by: Daniel Martí <mvdan@mvdan.cc>

Also, when statically building itabs, compare *types.Sym instead of
name alone so that method sets with duplicate non-exported methods are
handled correctly.

Fixes #24693.

Change-Id: I2db8a3d6e80991a71fef5586a15134b6de116269
Reviewed-on: https://go-review.googlesource.com/105039
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

A package's height is defined as the length of the longest import path
between itself and a leaf package (i.e., package with no imports).

We can't rely on knowing the path of the package being compiled, so
package height is useful for defining a package ordering.

Updates #24693.

Change-Id: I965162c440b6c5397db91b621ea0be7fa63881f1
Reviewed-on: https://go-review.googlesource.com/105038
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

Previously, constant pointer-typed expressions could use either Mpint
or NilVal as their Val depending on their construction, but const.go
expects each type to have a single corresponding Val kind.

This CL changes pointer-typed expressions to exclusively use Mpint.

Fixes #21221.

Change-Id: I6ba36c9b11eb19a68306f0b296acb11a8c254c41
Reviewed-on: https://go-review.googlesource.com/105315
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

This used to be duplicated in methcmp and siglt, because Sig used its
own representation for Syms. Instead, just use Syms, and add a
(*Sym).Less method that both methcmp and siglt can use.

Also, prune some impossible cases purportedly related to blank
methods: the Go spec disallows blank methods in interface method sets,
and addmethod drops blank methods without actually recording them in
the type's method set.

Passes toolstash-check.

Updates #24693.

Change-Id: I24e981659b68504d71518160486989a82505f513
Reviewed-on: https://go-review.googlesource.com/105936Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

gofmt -r 'exportname(s) -> types.IsExported(s)'

Passes toolstash-check.

Change-Id: I6b428bd039c135be66d8b81c325d4e08bae69f24
Reviewed-on: https://go-review.googlesource.com/105938Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

When I added the text/template/parse lines, I thought that both removed
and added APIs should be listed here (i.e. both -pkg and +pkg lines).
However that was wrong, as one can see by reading cmd/api/goapi.go, or
seeing how removing the +pkg lines does not break the API test.

Change-Id: I0a8dcd6db44762dadb58728acfb844bf118c9d45
Reviewed-on: https://go-review.googlesource.com/105376
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Multi-byte comparison operations were used on amd64, arm64, i386
and s390x for comparisons with constant arrays, but only amd64 and
i386 for comparisons with string constants. This CL combines the
check for platform capability, since they have the same requirements,
and also enables both on ppc64le which also supports load merging.

Note that these optimizations currently use little endian byte order
which results in byte reversal instructions on s390x. This should
be fixed at some point.

Change-Id: Ie612d13359b50c77f4d7c6e73fea4a59fa11f322
Reviewed-on: https://go-review.googlesource.com/102558
Run-TryBot: Michael Munday <mike.munday@ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

If one is somewhat new to the command line or shell, it might be
surprising that changes applied to a file like $HOME/.profile will
seemingly not take effect, even if new shells are started.

Add a note about how shells usually only load these when the user logs
into a machine, to minimize the amount of people stuck and confused by
this.

Fixes #24756.

Change-Id: Ic68d8c97933f3f080b151a107633ecad76a163a4
Reviewed-on: https://go-review.googlesource.com/105557Reviewed-by: Agniva De Sarker <agniva.quicksilver@gmail.com>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

Fixes golint warning about "if block ends with a return statement, so drop this else and outdent its block".

Change-Id: Id17ad0bf37ba939386b177b709e9e3c067d8ba21
Reviewed-on: https://go-review.googlesource.com/105736
Run-TryBot: Iskander Sharipov <iskander.sharipov@intel.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Special cases described in TODO comments are
fixed in https://golang.org/cl/6901.

One of those blocks was needed until old 6a assembler was removed.
This happened in https://golang.org/cl/12784.

Fixes #24734 (Also contains more details and reasoning)

Change-Id: If1f2f155d36ab236b16ae6f309a0716e00aa6371
Reviewed-on: https://go-review.googlesource.com/105156
Run-TryBot: Iskander Sharipov <iskander.sharipov@intel.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

Change-Id: Ic507cb740395e76d1d011a5a2f395b96c3d172a2
Reviewed-on: https://go-review.googlesource.com/105915Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

A test for CL 102036.

Change-Id: Ief6dcb4f478670813fbe22ea75a06815a4b201a3
Reviewed-on: https://go-review.googlesource.com/105875
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Insert appropriate race/msan calls before each memory operation during
SSA construction.

This is conceptually simple, but subtle because we need to be careful
that inserted instrumentation calls don't clobber arguments that are
currently being prepared for a user function call.

reorder1 already handles introducing temporary variables for arguments
in some cases. This CL changes it to use them for all arguments when
instrumenting.

Also, we can't SSA struct types with more than one field while
instrumenting. Otherwise, concurrent uses of disjoint fields within an
SSA-able struct can introduce false races.

This is both somewhat better and somewhat worse than the old racewalk
instrumentation pass. We're now able to easily recognize cases like
constructing non-escaping closures on the stack or accessing closure
variables don't need instrumentation calls. On the other hand,
spilling escaping parameters to the heap now results in an
instrumentation call.

Overall, this CL results in a small net reduction in the number of
instrumentation calls, but a small net increase in binary size for
instrumented executables. cmd/go ends up with 5.6% fewer calls, but a
2.4% larger binary.

Fixes #19054.

Change-Id: I70d1dd32ad6340e6fdb691e6d5a01452f58e97f3
Reviewed-on: https://go-review.googlesource.com/102817Reviewed-by: Cherry Zhang <cherryyz@google.com>

The patch adds support for LDR(register offset) instruction.
And add the test cases and negative tests.

Change-Id: I5b32c6a5065afc4571116d4896f7ebec3c0416d3
Reviewed-on: https://go-review.googlesource.com/87955Reviewed-by: Cherry Zhang <cherryyz@google.com>

ssa's pos parameter on the Const* funcs is unused, so remove it.

ld's alloc parameter on elfnote is always true, so remove the arguments
and simplify the code.

Finally, arm's addpltreloc never has its return parameter used, so
remove it.

Change-Id: I63387ecf6ab7b5f7c20df36be823322bb98427b8
Reviewed-on: https://go-review.googlesource.com/104456
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

And delete them from asm_test.

Change-Id: I0e33d58274951ab5acb67b0117b60ef617ea887a
Reviewed-on: https://go-review.googlesource.com/105735
Run-TryBot: Alberto Donizetti <alb.donizetti@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>

Change-Id: Ibb793158a190758cebc00b58c12e3b8b106c0548
GitHub-Last-Rev: 6a6d949eb252ec6d3e76920fc2f50ef5ac3cdb5a
GitHub-Pull-Request: golang/go#24702
Reviewed-on: https://go-review.googlesource.com/104896Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Fixes #24753

Change-Id: Ic6049da98b8eee41223df71ffafa71a894915bd7
Reviewed-on: https://go-review.googlesource.com/105455Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

NumComponents is used by racewalk to decide whether reads and writes
might occur to subobjects of an address. For that purpose,
blank fields matter.

It is also used to decide whether to inline == and != for a type.
For that purpose, blank fields may be ignored.

Add a parameter to NumComponents to support this distinction.
While we're here, document NumComponents, as requested in CL 59334.

Change-Id: I8c2021b172edadd6184848a32a74774dde1805c8
Reviewed-on: https://go-review.googlesource.com/103755
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

Found with megacheck (S1007).

Change-Id: Icb15fd5bfefa8e0b39a1bfa9ec3e9af3eff6b390
Reviewed-on: https://go-review.googlesource.com/105415
Run-TryBot: Iskander Sharipov <iskander.sharipov@intel.com>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Finish porting arm64 slice zeroing codegen tests; delete them from
asm_test.

Change-Id: Id2532df8ba1c340fa662a6b5238daa3de30548be
Reviewed-on: https://go-review.googlesource.com/105136
Run-TryBot: Alberto Donizetti <alb.donizetti@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Giovanni Bajo <rasky@develer.com>

This ensures that gdb tests run on Windows by ignoring any line ending.

Works with gdb 7.7, however with gdb 7.9 and 7.12 gets an error
error:

    internal-error: buildsym_init: Assertion `free_pendings == NULL'
    failed.

Updates #21380

Change-Id: I6a6e5b2a1b5efdca4dfce009fcb9c134c87497d6
Reviewed-on: https://go-review.googlesource.com/102419
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>

In particular, to pull a few fixes that were causing some tests to be
flaky on our build dashboard.

Fixes #24405.
Fixes #24508.
Fixes #24611.

Change-Id: I713156ad11c924e4a4b603144d10395523d526ed
Reviewed-on: https://go-review.googlesource.com/105275
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

This change replaces the vendored socks client implementation with the
bundle of golang.org/x/net/internal/socks package which contains fixes
for 19354 and 11682.

golang.org/x/net/internal/socks becomes socks_bundle.go.

At git rev 61147c4. (golang.org/cl/38278)

Updates #11682.
Updates #18508.
Updates #19354.
Fixes #19688.
Updates #21333.

Change-Id: I8cf6c3f5eb87c24685a7592be015729f84fbed77
Reviewed-on: https://go-review.googlesource.com/41031
Run-TryBot: Mikio Hara <mikioh.mikioh@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

This provides a way to enforce pure Go implementation of os/user
lookup functions on UNIX platforms by means of "osusergo" build tag,
in a manner similar to netgo/netcgo tags in the net package.

If "osusergo" build tag is set, Go implementation is selected.

If "osusergo" build tag is NOT set, the old behavior is retained,
that is to use cgo (libc-backed) implementation if both cgo and such
and such implementation are available.

The reason behind this change is to make it possible to build proper
static binaries on Linux. The problem is, glibc implementation of
getpw*, getgrp* and getgrouplist functions relies on presense of
libnss*.so libraries during runtime, making it impossible to build
a self-contained static binary which uses both cgo and os/user.
In such case, linker warnings like this are shown:

> warning: Using 'getgrouplist' in statically linked applications
> requires at runtime the shared libraries from the glibc version
> used for linking

While this can be solved by recompiling glibc with --enable-static-nss
flag or using a different libc implementation (like musl on Alpine Linux),
it is not always practical or even possible.

Fixes #23265

Change-Id: I383a448a2ecf15493ec93dbd5d076b6330cb14cb
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
Reviewed-on: https://go-review.googlesource.com/92456
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Found using go-simple.

Change-Id: I349e80a8c083688539bb4267564f02e3d7913da5
Reviewed-on: https://go-review.googlesource.com/105195Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>