crypto/x509: certificate with empty Authority Key Identifier extension considered invalid

[dulanshuangqiao]

Go version

go version go1.18.1 linux/amd64

Output of go env in your module/workspace:

GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/liu/.cache/go-build"
GOENV="/home/liu/.config/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/home/liu/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/liu/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/lib/go-1.18"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/lib/go-1.18/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.18.1"
GCCGO="gccgo"
GOAMD64="v1"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/dev/null"
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 -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build3649475886=/tmp/go-build -gno-record-gcc-switches"

What did you do?

I used crypto/x509 of golang to convert the der certificate to a pem certificate. For my test case, there was an Authority Key Identifier extension with an empty value.

What did you see happen?

Golang considered it an invalid Authority Key Identifier extension, but openssl and gnutls did not.

What did you expect to see?

According to rfc5280, the keyIdentifier, authorityCertIssuer, and authorityCertSerialNumber of the Authority Key Identifier extension are all OPTIONAL

[gabyhelp]

Related Issues

• crypto/x509: ParseCertificate should error on invalid tag for PolicyMappings #70074 (closed)
• repeated extension #70039 (closed)
• crypto/x509: parser should error on Subject Information Access and Policy Constraints being makred as critical #70278
• crypto/x509: wrong value of RevocationList.AuthorityKeyId #67571 (closed)
• crypto does not recognize the extension "authority key identifier" #43868 (closed)
• crypto/x509: AuthorityKeyId on self-signed certificates #15194 (closed)
• crypto/x509: the ParseRevocationList() doesn't seem to populate the AuthorityKeyId correctly #57461 (closed)

Related Code Changes

• crypto/x509: don't fail on optional auth key id fields

Related Discussions

• x509 marshaling extra-extensions

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

[seankhliao]

please show a reproducer. also 1.18 is not a supported version.
Note that the RFC says:

The keyIdentifier field of the authorityKeyIdentifier extension MUST
be included in all certificates generated by conforming CAs to
facilitate certification path construction. There is one exception;
where a CA distributes its public key in the form of a "self-signed"
certificate, the authority key identifier MAY be omitted.

and it should be allowed from #15194