crypto/x509: invalid certificate policies

[fancycode]

Go version

go1.22.0 linux/amd64

Output of go env in your module/workspace:

GO111MODULE=''
GOARCH='amd64'
GOBIN=''
GOCACHE='/home/user/.cache/go-build'
GOENV='/home/user/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='amd64'
GOHOSTOS='linux'
GOINSECURE=''
GOMODCACHE='/home/user/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='linux'
GOPATH='/home/user/go'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/home/user/devel/go-1.22'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/home/user/devel/go-1.22/pkg/tool/linux_amd64'
GOVCS=''
GOVERSION='go1.22.0'
GCCGO='gccgo'
GOAMD64='v1'
AR='ar'
CC='gcc'
CXX='g++'
CGO_ENABLED='1'
GOMOD=''
GOWORK=''
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
PKG_CONFIG='pkg-config'
GOGCCFLAGS='-fPIC -m64 -pthread -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build2225582694=/tmp/go-build -gno-record-gcc-switches'

What did you do?

Test program:

package main

import (
	"crypto/x509"
	"log"
	"os"
)

func main() {
	data, err := os.ReadFile("cert.crt")
	if err != nil {
		log.Fatal(err)
	}

	crt, err := x509.ParseCertificate(data)
	if err != nil {
		log.Fatal(err)
	}

	log.Printf("Certificate: %s", crt.Subject)
}

Sample certificate (uncompress with gunzip):
cert.crt.gz

Run:

go run test.go

What did you see happen?

2024/02/28 11:40:48 x509: invalid certificate policies
exit status 1

Decoding with openssl works:

openssl x509 -in cert.crt -inform der -text -noout
Certificate:
    Data:
        Version: 3 (0x2)
        Serial Number:
            7c:6d:cd:78:18:4a:91:c6:05:9b:b7:24:55:38:d5:36
...

What did you expect to see?

2024/02/28 11:40:48 Certificate: <the-subject-of-the-certificate>

[mateusz834]

It looks like a badly encoded certificate, this error is returned from this branch

go/src/crypto/x509/parser.go

Lines 446 to 448 in 33013e8

	if !der.ReadASN1(&cp, cryptobyte_asn1.SEQUENCE) || !cp.ReadASN1(&OIDBytes, cryptobyte_asn1.OBJECT_IDENTIFIER) {
	return nil, errors.New("x509: invalid certificate policies")
	}

[mateusz834]

Yep, it is badly encoded it hits this case:

https://github.com/golang/crypto/blob/0aab8d07aefab378c763e8f36aa007544a862aa9/cryptobyte/asn1.go#L800-L802

The last ObjectIdentifier has the length encoded using two bytes, but it should be encoded with one byte.

30810e060c2b0601040181e82d01010b01