Custom data in X509

[email protected]

simon@symphony:~/ssl/intermediate$ openssl x509 -text -noout -in ../user/[email protected] 
Certificate:
    Data:
        Version: 3 (0x2)
        Serial Number: 4100 (0x1004)
    Signature Algorithm: sha256WithRSAEncryption
        Issuer: C=GB, ST=England, O=Acme Corp, OU=Acme Corp Certificate Authority, CN=Acme Corp Intermediate CA
        Validity
            Not Before: Jan 30 22:04:22 2016 GMT
            Not After : Jan 29 22:04:22 2017 GMT
        Subject: C=GB, ST=England, L=Manchester, O=Acme Corp, OU=Acme Corp DevOps, [email protected]
        Subject Public Key Info:
            Public Key Algorithm: rsaEncryption
                Public-Key: (2048 bit)
                Modulus:
                    00:e5:93:eb:d4:a4:4b:f9:55:94:17:97:5e:6b:7a:
                    00:88:fd:9b:9f:49:e9:59:b7:3a:61:be:37:62:55:
                    4c:23:d6:0a:17:cd:00:67:ac:8a:70:82:e1:95:95:
                    16:b0:ad:35:4a:82:26:3a:0a:26:37:c6:2e:7a:6e:
                    83:57:41:21:d8:d4:05:58:33:54:76:37:b2:20:69:
                    27:43:9f:6b:06:60:b7:53:9b:72:7a:80:d3:cf:b6:
                    6d:37:f3:c0:8a:fe:26:86:d3:48:1d:43:f0:3a:61:
                    1c:80:0e:70:ab:f9:78:4b:74:16:81:57:bb:04:22:
                    59:18:ee:3c:72:57:2e:17:57:77:0e:8d:36:97:d8:
                    12:ff:ec:f8:32:85:ff:d4:de:7a:78:5b:c7:3c:08:
                    44:63:cf:4e:c5:37:da:9f:1d:0f:f3:26:78:1c:40:
                    1a:9f:43:88:10:e9:27:5c:cf:94:16:e1:c1:2e:c6:
                    d7:49:62:b8:ba:94:d9:e9:30:a8:73:b4:90:00:01:
                    83:c9:b3:ad:8f:98:bf:ff:af:90:d4:0d:0a:7f:0c:
                    ee:16:49:a7:96:c5:20:1e:53:04:40:1c:05:01:66:
                    25:12:fb:06:cf:57:68:02:eb:b9:cd:51:2b:67:9b:
                    20:ff:71:80:55:d0:b2:af:7e:cc:66:93:82:d6:73:
                    77:db
                Exponent: 65537 (0x10001)
        X509v3 extensions:
            X509v3 Basic Constraints: 
                CA:FALSE
            Netscape Cert Type: 
                SSL Client
            X509v3 Subject Key Identifier: 
                68:A5:13:22:7A:E2:0E:DD:8E:EA:B6:D0:43:5E:DD:D9:E6:E9:C8:A1
            X509v3 Authority Key Identifier: 
                keyid:A2:80:CF:D7:CB:2F:CE:B7:70:17:55:DA:C5:AB:C2:30:E9:38:B7:DD

            X509v3 Key Usage: critical
                Digital Signature, Non Repudiation, Key Encipherment
            X509v3 Extended Key Usage: 
                TLS Web Client Authentication
            1.10.96.1: 
                .!{"key1":"value1","key2":"value2"}
    Signature Algorithm: sha256WithRSAEncryption
         a6:c4:89:67:a8:6e:fe:b8:6e:0e:f1:9a:4c:d5:05:a8:58:ef:
         68:35:69:4a:00:00:3a:41:90:66:4c:cd:c8:d7:fc:f3:72:cf:
         e9:27:b3:3d:7e:f5:cd:ad:b4:e4:7f:00:f2:c4:30:0f:ca:57:
         1b:fc:99:cc:bc:bc:92:68:e3:07:94:36:eb:34:c2:14:88:56:
         77:23:ef:ad:52:29:1d:bd:c4:c5:71:61:66:bf:49:d6:7c:a4:
         d2:48:d3:d6:47:c8:25:a7:de:04:2d:70:59:37:56:72:a5:a6:
         f7:58:de:c4:66:f9:6b:88:90:dd:4c:ee:3e:ad:27:26:57:f3:
         00:ac:67:ba:e4:6d:ae:c1:a5:63:6d:1f:63:ad:78:be:d7:cb:
         2f:e8:96:73:0f:90:0f:85:e9:72:18:2a:18:79:e9:ba:53:d6:
         fa:c5:a9:1e:08:e8:73:dc:fa:9d:fc:d3:a7:ea:c2:73:c6:e2:
         4d:51:58:f5:3e:c0:63:95:ba:c7:9c:8f:d8:34:1c:c5:02:33:
         1c:37:15:7e:85:b3:de:a4:19:db:73:06:f4:69:99:da:13:1e:
         1a:b3:de:e0:6f:6d:8f:93:1d:92:cf:74:93:7f:48:69:53:b4:
         98:a0:23:9b:ac:9f:84:19:4c:a1:fd:26:3f:3a:ab:4d:fb:c3:
         91:f3:ca:d8:28:12:c5:25:44:75:5e:ea:0f:28:22:11:d1:a7:
         a1:b2:e1:68:72:f8:06:54:18:0c:8a:f6:2d:6c:5f:7f:b7:c7:
         f7:0d:80:fa:70:75:43:90:d7:1a:3e:3b:d8:ad:6f:07:22:0c:
         6a:95:7a:dc:80:f6:ea:41:21:54:7f:46:15:3f:ad:c8:61:0d:
         0d:f9:77:a2:1e:96:97:62:7d:09:e7:cd:06:06:5c:00:f7:fc:
         66:25:4c:7d:54:63:d2:3a:66:d4:6a:df:ec:87:00:3e:49:29:
         af:18:73:a5:9e:b0:4b:f5:14:f9:bf:e3:5b:a4:1f:76:22:9e:
         9b:19:e2:ac:d7:2d:b7:8f:00:31:3a:65:34:72:c4:17:a5:bc:
         d2:0d:11:d1:66:ae:ca:c6:ed:7f:78:a8:b8:ca:78:25:94:c7:
         77:85:0c:2f:fb:1b:66:ac:72:8b:69:6e:28:d9:6e:60:6e:b2:
         bd:a3:da:95:36:39:bf:83:6a:ac:ec:bf:f4:a1:ef:c1:5f:ae:
         e8:62:ae:54:c3:57:d0:b3:5b:dd:b2:79:3b:4f:d3:c5:31:8c:
         41:e7:8f:ac:6b:e9:40:5d:0a:70:3d:80:ac:45:b3:8e:48:e3:
         26:85:92:88:9e:0d:1a:f8:a0:3e:1d:91:c2:e5:41:b0:0d:87:
         5a:31:c9:e8:71:8f:4e:51