Generate subject name from x509 certificate in string format

php Editor Strawberry Generating the subject name from the x509 certificate in string format is an important operation, which can help developers extract key information from the certificate. By parsing the x509 certificate in string format, we can obtain the subject name of the certificate, including the issuer, validity period, public key and other information of the certificate. This process is important for building secure network communications, verifying the legitimacy of certificates, and protecting user privacy. In PHP, we can use the functions provided by the OpenSSL extension to implement this function and handle x509 certificates simply and efficiently.

Question content

I am trying to generate the distinguished name from x509.certificate.

The format I expect is:

"cn=<common_name>,ou=<org_unit>,o=,dnqualifier=+7he5grzxim+lkemb5fs98e+fpy="

(I replaced some values ​​with labels)

With my code, I get the expected string without the dnqualifier part, like this:

cn=<common_name>,ou=<org_unit>,o=,2.5.4.46=#131c537771614a5531514c2449444e4846373755547a1f5749653955303d"

it's here, 2.5.4.46 is the asn.1 object id of "dnqualifier" Reference: Link The value looks like a hexadecimal string.

Is there a standard way (or a simple workaround) to get the distinguished name in the expected format? That is, the text "dnqualifier" should appear instead of its objectidentifier, and the actual string value should appear instead of hexadecimal.

My code looks like this:

package main

import (
    "crypto/x509"
    "encoding/pem"
    "fmt"

    "github.com/sirupsen/logrus"
)

func main() {

    cert := "" // certificate string here
    block, rest := pem.decode([]byte(cert))
    if len(rest) != 0 {
        logrus.error("certificate string not fully decoded : ", rest)
    }

    certificate, err := x509.parsecertificate(block.bytes)
    if err != nil {
        logrus.witherror(err).error("error parsing certificate")
    }

    fmt.println(certificate.subject.string())
}

From this code certificate.subject.string() the output given is as follows: cn=<common_name>,ou=<org_unit>,o=<org>,2.5.4.46=#131c537771614a5531514c2449444e4846373755547a1f5749653955303d" </org></org_unit></common_name>

in addition,

fmt.printf("%+v\n", cert.subject.tordnsequence())

and

var sub pkix.RDNSequence
asn1.Unmarshal(certificate.RawSubject, &sub)

Neither helps.

Solution

The standard library only provides a limited list of attributes:

var attributetypenames = map[string]string{
    "2.5.4.6":  "c",
    "2.5.4.10": "o",
    "2.5.4.11": "ou",
    "2.5.4.3":  "cn",
    "2.5.4.5":  "serialnumber",
    "2.5.4.7":  "l",
    "2.5.4.8":  "st",
    "2.5.4.9":  "street",
    "2.5.4.17": "postalcode",
}

For other properties, it just uses the object identifier as the name and encodes the value as a hexadecimal string where possible (see (rdnsequence).string):

oidstring := tv.type.string()
typename, ok := attributetypenames[oidstring]
if !ok {
    derbytes, err := asn1.marshal(tv.value)
    if err == nil {
        s += oidstring + "=#" + hex.encodetostring(derbytes)
        continue // no value escaping necessary.
    }

    typename = oidstring
}

valuestring := fmt.sprint(tv.value)
escaped := make([]rune, 0, len(valuestring))

It does not provide any knobs for us to get customized strings. So we have to do it ourselves.

I suggest listing the properties we want and appending them to the string returned from certificate.subject.tordnsequence().string(). like this:

package main

import (
    "crypto/x509"
    "crypto/x509/pkix"
    "encoding/pem"
    "fmt"
)

func tostring(name pkix.name) string {
    s := name.tordnsequence().string()

    // list the extra attributes that should be added.
    attributetypenames := map[string]string{
        "2.5.4.43": "initials",
        "2.5.4.46": "dnqualifier",
    }

    for typ, typename := range attributetypenames {
        for _, atv := range name.names {
            oidstring := atv.type.string()
            if oidstring == typ {
                // to keep this demo simple, i just call fmt.sprint to get the string.
                // maybe you want to escape some of the characters.
                // see https://github.com/golang/go/blob/1db23771afc7b9b259e926db35602ecf5047ae23/src/crypto/x509/pkix/pkix.go#l67-l86
                s += "," + typename + "=" + fmt.sprint(atv.value)
                break
            }
        }
    }
    return s
}

func main() {
    block, _ := pem.decode([]byte(cert))
    certificate, err := x509.parsecertificate(block.bytes)
    if err != nil {
        panic(err)
    }

    fmt.println(certificate.subject.string())
    fmt.println()
    fmt.println(certificate.subject.tordnsequence().string())
    fmt.println()
    fmt.println(tostring(certificate.subject))
}

var cert = `-----begin certificate-----
miigvdccbksgawibagiupminkycv6nqggfhrq1sj/y/4gykwdqyjkozihvcnaqel
bqawgfsxgzazbgnvbammennly3vyzs5legftcgxllmnvbtelmakga1uebhmcwfgx
etapbgnvbacmcez1bibmyw5kmsgwjgydvqqkdb9neunviexmqybmveqgsu5dichk
lmiuys4gt3vyq28pmriweaydvqqldaltu0wgrgvwdc4xczajbgnvbagmallzmsqw
igyjkozihvcnaqkbfhvzc2wtywrtaw5azxhhbxbszs5jb20xetapbgnvbckmcepv
ag4grg9lmqwwcgydvqqedaneb2uxdtalbgnvbcombepvag4xddakbgnvbcsma0py
rdenmasga1uelhmec29tztaefw0ymza2mtixndi2mzhafw0ynda2mtexndi2mzha
mih7mrswgqydvqqddbjzzwn1cmuuzxhhbxbszs5jb20xczajbgnvbaytalhymrew
dwydvqqhdahgdw4gtgfuzdeomcyga1uecgwftxldbybmtemgtfreieloqyaozc5i
lmeuie91cknvktesmbaga1uecwwju1nmierlchqumqswcqydvqqidajzwtekmcig
csqgsib3dqejaryvc3nslwfkbwluqgv4yw1wbguuy29tmrewdwydvqqpdahkb2hu
iervztemmaoga1uebawdrg9lmq0wcwydvqqqdarkb2humqwwcgydvqqrdankweqx
dtalbgnvbc4tbhnvbwuwggiima0gcsqgsib3dqebaquaa4icdwawggikaoicaqdl
i0xuep6r94lf5yn0lqni2qljtf4yiuapwsph1g6jutldcr5f70bkaxagznzkxssb
rgu+zwviphu1kilnx1youhfdzdx0ecmayw22zet4p8f88slnmhquxixjypopo+2b
hz8u1by7ojdccw94jhmhbug07whiu8y54wijgjv3xwnvgaorjtxs3csubmldfki7
s9gfgvqpokqpbbl+v37vbvkzgs3bw4lf7apyqe9q63q2held8/aabatujhgn1bzs
truvda9fkktdlvkn6furaeccdc+eaonpsxwimp/d01wukofojywmbgbm7a/bpby0
uxyqwmkxztquxd8mdaev89oao4ijuo8q50+9xehtb/q4tdhzjjw5k6xxqfxatrqa
/xmn8fmitvddirxqaz4ttvpdeqxnudh3retzbgoqzy4mqcgzv723tdbfzlgiqnif
1atjueotmbl7juj/1qulrpb+/ayzgqrg0xlpjr3h1essebn1ts8elvk5z6ekp5ur
rjlv3z2qq1vsn/ngnqkviyeppwj1wgxkkmaz3d6i3gixqpmklno2wdorwf/m+opu
c5+bl8nhpc0hirodi8vnkbj5mimqazwfnfhq1vveihkzxfeuee8y1r7ju/mo5qd1
z6wato77vcqd2g1xgqdjy7hrzgvmx/m9rrhqe57gyqidaqabozywndatbgnvhsue
ddakbggrbgefbqcdatadbgnvhq4efgqu8wifqbhufesmbdsbjclj4zhcynewdqyj
kozihvcnaqelbqadggibafx4qapmwkzd6juofcdmdxynjzlgyu0vtosjaor5vck8
qk/rhpqmg/j+eoikjy+xyh72wuovp25z2c99gyeyx3ve2ttsqq9uhz5eeonvi4h5
em68s5hwpywwo2u5fsvcofmpbeft/vtuvt+jczpxvrzz3a9zbwkapivoclp5y9ik
slzrkbvosafanfeffk/kyootrnoe/ahpezua8efkrlh4ggp8nzzcjamwwaoqkf3o
hufizyaenja6sm37id3eqwvsrtwkrrdkci6nqcpf0tpvxwazist2+tyimbuhacq7
qc1vhul9oyabhgjkgvhqsxxuybobqaoxdvmjueapdzgzfljlpari7aao1vamft1/
+4ulio1p9egkqdtzuu4grvbwo1pftj/alp2o/b/fnecevlphnlast+frldymrnsz
r3uv47pzpuka1+zivmpkk0kwjcb1xdficpj0t9uc7bmueyrxkf9zytbf9iqzlfnl
1lrxdod7/tf/gjlwbtiei8gwi38fimhy6iawl2epk1gzq3wep0km/lx6ol5dgmrr
2sbczecqhzvb7ya7k28iff2wma9txl/nbdhw57/7bclkbevaniwgvuqroggrmlxg
z1xp51mthl8bl2zn+q4x7xjvfvxbetfwxa8b9vlho1qkdzcdrgzt5jebpm5zgj5k
-----end certificate-----`

Output:

CN=secure.example.com,OU=SSL Dept.,O=MyCo LLC LTD INC (d.b.a. OurCo),L=Fun Land,ST=YY,C=XX,2.5.4.46=#1304736f6d65,2.5.4.43=#13034a5844,2.5.4.42=#13044a6f686e,2.5.4.4=#1303446f65,2.5.4.41=#13084a6f686e20446f65,1.2.840.113549.1.9.1=#0c1573736c2d61646d696e406578616d706c652e636f6d

CN=secure.example.com,OU=SSL Dept.,O=MyCo LLC LTD INC (d.b.a. OurCo),L=Fun Land,ST=YY,C=XX

CN=secure.example.com,OU=SSL Dept.,O=MyCo LLC LTD INC (d.b.a. OurCo),L=Fun Land,ST=YY,C=XX,initials=JXD,dnQualifier=some

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