Using java -Djavax.net.debug=… to examine data flows, including TLS

Jan 2021. This page gets many hits. Please can you tell me if the information below is what you were looking for, or if you were looking for more information, such as understanding the trace flow, and finding problems.   Please send me an email or post a comment below with information on what you were looking for, and I’ll see what I can do.

There are different levels you can get from the -Djavax.net.debug option.  You can display its options using -Djavax.net.debug=help .

Ive added a section on -Djava.security.debug=… which looks at keystore access.

Ive also added a examples of what each trace option give you.

I’ve also put up a post which describes the trace, and has an annotated output (from both ends), showing common problems and possible solutions.

With -Djavax.net.debug you get

all turn on all debugging
ssl turn on ssl debugging

The following can be used with ssl:
  record       enable per-record tracing
  handshake    print each handshake message
  keygen       print key generation data
  session      print session activity
  defaultctx   print default SSL initialization
  sslctx       print SSLContext tracing
  sessioncache print session cache tracing
  keymanager   print key manager tracing
  trustmanager print trust manager tracing
  pluggability print pluggability tracing

handshake debugging can be widened with:
  data         hex dump of each handshake message
  verbose      verbose handshake message printing

record debugging can be widened with:
  plaintext    hex dump of record plaintext
  packet       print raw SSL/TLS packets

and your program exits.

To display specific levels of detail you can use

-Djavax.net.debug=ssl:record or -Djavax.net.debug=ssl:handshake

To specify more than one option use

-Djavax.net.debug=ssl:keymanager:record

-Djava.security.debug=

Out of all the options below, I found certpath,provider provided the most useful information for seeing what was happening with certificates and the handshake.  For example

certpath: X509CertSelector.match(SN: 1a
Issuer: CN=TEMP4Certification Authority, OU=TEST, O=TEMP
Subject: CN=SERVER, OU=SSS, O=ZZZZ)
certpath: X509CertSelector.match: subject DNs don’t match
certpath: ForwardBuilder.getMatchingCACerts: found 0 CA certs
certpath: SunCertPathBuilder.depthFirstSearchForward(): certs.size=0
certpath: PKIXCertPathValidator.engineValidate()…
certpath: AdaptableX509CertSelector.match: subject key IDs don’t match. Expected: [] Cert’s: []
certpath: NO – don’t try this trustedCert
certpath: X509CertSelector.match(SN: 0
Issuer: CN=TEMP4Certification Authority, OU=TEST, O=TEMP
Subject: CN=TEMP4Certification Authority, OU=TEST, O=TEMP)
certpath: X509CertSelector.match returning: true
certpath: YES – try this trustedCert
certpath: anchor.getTrustedCert().getSubjectX500Principal() = CN=TEMP4Certification Authority, OU=TEST, O=TEMP
certpath: AlgorithmChecker.contains: SHA256withRSA
Provider: MessageDigest.SHA-256 algorithm from: SUN

I grepped with pkcs12: and got

pkcs12: Loading PKCS#7 encryptedData (PBEWithSHA1AndRC2_40 iterations: 2048)
pkcs12: Loading PKCS#7 data
pkcs12: Checking keystore integrity (HmacPBESHA1 iterations: 2048)
pkcs12: PKCS12KeyStore load: private key count: 1. secret key count: 0. certificate count: 1
pkcs12: Retrieved a protected private key at alias ‘ss’ (PBEWithSHA1AndDESede iterations: 2048)
pkcs12: Retrieved a 1-certificate chain at alias ‘ss’

The options…

all              turn on all debugging - this produces millions of lines of
                 output for one handshake! 
access           print all checkPermission results 
certpath        PKIX CertPathBuilder and CertPathValidator debugging 
combiner         SubjectDomainCombiner debugging 
gssloginconfig   GSS LoginConfigImpl debugging 
configfile       JAAS ConfigFile loading 
configparser     JAAS ConfigFile parsing 
jar              jar verification 
logincontext     login context results 
jca              JCA engine class debugging 
policy           loading and granting 
provider        security provider debugging 
pkcs11           PKCS11 session manager debugging 
pkcs11keystore   PKCS11 KeyStore debugging 
sunpkcs11        SunPKCS11 provider debugging 
scl              permissions SecureClassLoader assigns 
ts               timestamping

The following can be used with access:

stack            include stack trace 
domain           dump all domains in context 
failure          before throwing exception, dump stack and domain that 
                 didn't have permission 
thread           include the thread name 

The following can be used with stack and domain:

permission=<classname> 
                only dump output if specified permission is being checked 
codebase=<URL>  only dump output if specified codebase  is being checked 
permname=<name> only dump output if the specified name matches the 
                permission getName() 
permactions=<actions>  only dump output if the specified actions 
                matches the permission getActions() 

The following can be used with provider: 

engine=<engines> only dump output for the specified list of JCA engines.  
                Supported values: 
                   Cipher, KeyAgreement, KeyGenerator, 
                   KeyPairGenerator, KeyStore, Mac, 
                   MessageDigest, SecureRandom, Signature. 

Note: Separate multiple options with a comma

-Djavax.net.debug=ssl:record

gave

records doing read and write
...
SSLSocketOutputRecord.java:241|WRITE: TLS12 handshake, length = 294
SSLSocketInputRecord.java:214|READ: TLSv1.2 handshake, length = 2948
...

-Djavax.net.debug=ssl:handshake

gave all of the sections.

-Djavax.net.debug=ssl:handshake:verbose

gave the same as ssl:handshake +

Signature algorithm, ed448, is not supported by the underlying providers
SignatureScheme.java:373|Ignore unsupported signature scheme: ed25519
SignatureScheme.java:373|Ignore unsupported signature scheme: ed448
SignatureScheme.java:393|Ignore disabled signature scheme: rsa_md5

-Djavax.net.debug=ssl:keygen

gave: No records.

-Djavax.net.debug=ssl:session

gave just

Session initialized:  Session(1611922238363|TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384)

Djavax.net.debug=ssl:defaultctx

gave No records.

-Djavax.net.debug=ssl:sslctx

gave

javax.net.ssl|DEBUG|01|main|2021-01-29 12:29:48.847 GMT|X509TrustManagerImpl.java:79|adding as trusted certificates (
  "certificate" : {
      "subject"            : "CN=DANCA1, OU=DAN, O=DAN",
...
  "certificate" : {
    "subject"            : "CN=SS, O=SSS, C=GB",
... 
  "certificate" : {
    "subject"            : "CN=ecec, O=cpwebuser, C=GB",
...
System property jdk.tls.client.cipherSuites is set to 'null'
System property jdk.tls.server.cipherSuites is set to 'null'
jdk.tls.keyLimits:  entry = AES/GCM/NoPadding KeyUpdate 2^37. AES/GCM/NOPADDING:KEYUPDATE = 137438953472
Ignore unsupported cipher suite: TLS_AES_256_GCM_SHA384
found key for : ecec (
  "certificate" : {
       "subject"            : "CN=ecec, O=cpwebuser, C=GB",
 
    "subject"            : "CN=SSCA256, OU=CA, O=SSS, C=GB",
  ...
found key for : mqweb (
  "certificate" : {...   
trigger seeding of SecureRandom
done seeding of SecureRandom
...
Produced ClientHello handshake message (
"ClientHello": {
...
Consuming ECDH ServerKeyExchange handshake message (
"ECDH ServerKeyExchange": {
  "parameters": {
    "named group": "secp256r1"
    "ecdh public": {
      0000: 04 5F 30 8E 64 45 55 C0   
      0010: 55 23 1B 69 CA FF 78 8D  
      0020: B5 59 72 BA B4 95 8A 4C  
      0030: 2B 37 55 3D F2 A5 3D 71  
      0040: 34                                               
    },
  },

-Djavax.net.debug=ssl:sessioncache

gave: No records.

-Djavax.net.debug=ssl:keymanager

gave

found key for : ecec (<br>"certificate" : {
"version": "v3",
...

found key for : mqweb (
"certificate" : {
...

-Djavax.net.debug=ssl:trustmanager

gave

adding as trusted certificates</strong> (
"certificate" : {
...
"subject" : "CN=mqweb8, O=cpwebuser, C=GB",
...
"certificate" : {
...
subject" : "CN=DANCA1, OU=DAN, O=DAN",
...
Found trusted certificate</strong> (
"certificate" : {
...
"issuer" : "CN=DANCA1, OU=DAN, O=DAN",
...
"subject" : "CN=DANCA1, OU=DAN, O=DAN",
...
ss private or public key is not of EC algorithm
<p>Where <em>adding as</em> ...&nbsp; is what the local trust store found, and <em>found trusted </em> is what as sent from the server as part of the certificateRequest.</p>

Where adding as… ; is what the local trust store found, and Found trusted certificate is what as sent from the server as part of the certificateRequest.

-Djavax.net.debug=ssl:pluggability

No records.