x/crypto/cryptobyte: slice bounds out of range with Unwrite

[catenacyber]

What version of Go are you using (go version)?

$ go version
go version go1.19 linux/amd64

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

go env Output

$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/root/.cache/go-build"
GOENV="/root/.config/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/root/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/root/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/root/.go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/root/.go/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.19"
GCCGO="gccgo"
GOAMD64="v1"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/src/ngolo-fuzzing/go.mod"
GOWORK=""
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -Wl,--no-gc-sections -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build2481516251=/tmp/go-build -gno-record-gcc-switches"

What did you do?

Run https://go.dev/play/p/FlmHh9L0Ef1

What did you expect to see?

The program finishing and printing Hello

What did you see instead?

panic: runtime error: slice bounds out of range [:5404319552844595201] with capacity 1

goroutine 1 [running]:
golang.org/x/crypto/cryptobyte.(*Builder).Unwrite(...)
	/tmp/gopath2977946317/pkg/mod/golang.org/x/crypto@v0.3.0/cryptobyte/builder.go:323
main.main()
	/tmp/sandbox3386522376/prog.go:13 +0x9f

Program exited.

Found by https://github.com/catenacyber/ngolo-fuzzing with oss-fuzz :
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=53734

I guess the fix is to explicitly panic with a string if n < 0

[bcmills]

(attn @FiloSottile @rolandshoemaker @golang/security)

[gopherbot]

Change https://go.dev/cl/464338 mentions this issue: cryptobyte: reject negative Unwrite argument