【本文转自http://blogs.sun.com/andreas/entry/no_more_unable_to_find】
Some of you may be familiar with the (not very user friendly) exception message javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
when trying to open an SSL connection to a host using JSSE. What this usually means is that the server is using a test certificate (possibly generated using keytool) rather than a certificate from a well known commercial Certification Authority such as Verisign or GoDaddy. Web browsers display warning dialogs in this case, but since JSSE cannot assume an interactive user is present it just throws an exception by default.
Certificate validation is a very important part of SSL security, but I am not writing this entry to explain the details. If you are interested, you can start by reading the Wikipedia blurb. I am writing this entry to show a simple way to talk to that host with the test certificate, if you really want to.
Basically, you want to add the server's certificate to the KeyStore with your trusted certificates. There are any number of ways to achieve that, but a simple solution is to compile and run the attached program as java InstallCert hostname, for example
% java InstallCert ecc.fedora.redhat.comLoading KeyStore /usr/jdk/instances/jdk1.5.0/jre/lib/security/cacerts...Opening connection to ecc.fedora.redhat.com:443...Starting SSL handshake...javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested targetat com.sun.net.ssl.internal.ssl.Alerts.getSSLException(Alerts.java:150)at com.sun.net.ssl.internal.ssl.SSLSocketImpl.fatal(SSLSocketImpl.java:1476)at com.sun.net.ssl.internal.ssl.Handshaker.fatalSE(Handshaker.java:174)at com.sun.net.ssl.internal.ssl.Handshaker.fatalSE(Handshaker.java:168)at com.sun.net.ssl.internal.ssl.ClientHandshaker.serverCertificate(ClientHandshaker.java:846)at com.sun.net.ssl.internal.ssl.ClientHandshaker.processMessage(ClientHandshaker.java:106)at com.sun.net.ssl.internal.ssl.Handshaker.processLoop(Handshaker.java:495)at com.sun.net.ssl.internal.ssl.Handshaker.process_record(Handshaker.java:433)at com.sun.net.ssl.internal.ssl.SSLSocketImpl.readRecord(SSLSocketImpl.java:815)at com.sun.net.ssl.internal.ssl.SSLSocketImpl.performInitialHandshake(SSLSocketImpl.java:1025)at com.sun.net.ssl.internal.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:1038)at InstallCert.main(InstallCert.java:63)Caused by: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested targetat sun.security.validator.PKIXValidator.doBuild(PKIXValidator.java:221)at sun.security.validator.PKIXValidator.engineValidate(PKIXValidator.java:145)at sun.security.validator.Validator.validate(Validator.java:203)at com.sun.net.ssl.internal.ssl.X509TrustManagerImpl.checkServerTrusted(X509TrustManagerImpl.java:172)at InstallCert$SavingTrustManager.checkServerTrusted(InstallCert.java:158)at com.sun.net.ssl.internal.ssl.JsseX509TrustManager.checkServerTrusted(SSLContextImpl.java:320)at com.sun.net.ssl.internal.ssl.ClientHandshaker.serverCertificate(ClientHandshaker.java:839)... 7 moreCaused by: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested targetat sun.security.provider.certpath.SunCertPathBuilder.engineBuild(SunCertPathBuilder.java:236)at java.security.cert.CertPathBuilder.build(CertPathBuilder.java:194)at sun.security.validator.PKIXValidator.doBuild(PKIXValidator.java:216)... 13 moreServer sent 2 certificate(s): 1 Subject CN=ecc.fedora.redhat.com, O=example.com, C=US Issuer CN=Certificate Shack, O=example.com, C=US sha1 2e 7f 76 9b 52 91 09 2e 5d 8f 6b 61 39 2d 5e 06 e4 d8 e9 c7 md5 dd d1 a8 03 d7 6c 4b 11 a7 3d 74 28 89 d0 67 54 2 Subject CN=Certificate Shack, O=example.com, C=US Issuer CN=Certificate Shack, O=example.com, C=US sha1 fb 58 a7 03 c4 4e 3b 0e e3 2c 40 2f 87 64 13 4d df e1 a1 a6 md5 72 a0 95 43 7e 41 88 18 ae 2f 6d 98 01 2c 89 68 Enter certificate to add to trusted keystore or 'q' to quit: [1]
What happened was that the program opened a connection to the specified host and started an SSL handshake. It printed the exception stack trace of the error that occured and shows you the certificates used by the server. Now it prompts you for the certificate you want to add to your trusted KeyStore. You should only do this if you are sure that this is the certificate of the trusted host you want to connect to. You may want to check the MD5 and SHA1 certificate fingerprints against a fingerprint generated on the server (e.g. using keytool) to make sure it is the correct certificate.
If you've changed your mind, enter 'q'. If you really want to add the certificate, enter '1'. (You could also add a CA certificate by entering a different certificate, but you usually don't want to do that'). Once you have made your choice, the program will print the following:
[[ Version: V3 Subject: CN=ecc.fedora.redhat.com, O=example.com, C=US Signature Algorithm: MD5withRSA, OID = 1.2.840.113549.1.1.4 Key: SunPKCS11-Solaris RSA public key, 1024 bits (id 5158256, session object) modulus: 140293302288466085274866181686970602165522667589063544116658036494119107498734550077161245433850213169487333723373771289481596631394860935156104797710288057781815681467804130363725535408476281463861118595123047466945591390881582717369665139734007428157801756704486871104982140936574395319969584127568303024757 public exponent: 65537 Validity: [From: Wed Jan 18 13:16:12 PST 2006, To: Wed Apr 18 14:16:12 PDT 2007] Issuer: CN=Certificate Shack, O=example.com, C=US SerialNumber: [ 0f]Certificate Extensions: 2[1]: ObjectId: 2.16.840.1.113730.1.1 Criticality=falseNetscapeCertType [ SSL server][2]: ObjectId: 2.5.29.15 Criticality=falseKeyUsage [ Key_Encipherment]] Algorithm: [MD5withRSA] Signature:0000: 6D F4 2A 63 76 2A 05 70 A2 21 0E 1E 4A 31 BE 6B m.*cv*.p.!..J1.k0010: 15 64 D8 BB 35 36 82 B0 0D 2A 96 FA 7A 9F A1 59 .d..56...*..z..Y0020: CA 90 C3 28 C5 A6 9B 59 05 3B EB B2 8D C9 5E 38 ...(...Y.;....^80030: 62 ED 1A D7 93 DF 2A A5 D6 54 94 23 15 A2 0C E5 b.....*..T.#....0040: 13 40 2C 3E 59 E4 2A EB 51 AC 9E 28 44 23 87 B1 .@,>Y.*.Q..(D#..0050: 34 0B AC F3 E0 39 CA B8 35 B4 78 07 BF 28 4C C4 4....9..5.x..(L.0060: 9A 2B A3 E9 04 26 78 19 F0 62 EA 0A B5 BB DC 0B .+...&x..b......0070: 90 59 E7 77 90 F8 BC 8A 1B 74 4B 4D C1 F8 3B 6C .Y.w.....tKM..;l]Added certificate to keystore 'jssecacerts' using alias 'ecc.fedora.redhat.com-1'
It displayed the complete certificate and then added it to a Java KeyStore 'jssecacerts' in the current directory. To use it in your program, either configure JSSE to use it as its trust store (as explained in the documentation) or copy it into your $JAVA_HOME/jre/lib/security directory. If you want all Java applications to recognize the certificate as trusted and not just JSSE, you could also overwrite the cacerts file in that directory.
After all that, JSSE will be able to complete a handshake with the host, which you can verify by running the program again:
% java InstallCert ecc.fedora.redhat.comLoading KeyStore jssecacerts...Opening connection to ecc.fedora.redhat.com:443...Starting SSL handshake...No errors, certificate is already trustedServer sent 2 certificate(s): 1 Subject CN=ecc.fedora.redhat.com, O=example.com, C=US Issuer CN=Certificate Shack, O=example.com, C=US sha1 2e 7f 76 9b 52 91 09 2e 5d 8f 6b 61 39 2d 5e 06 e4 d8 e9 c7 md5 dd d1 a8 03 d7 6c 4b 11 a7 3d 74 28 89 d0 67 54 2 Subject CN=Certificate Shack, O=example.com, C=US Issuer CN=Certificate Shack, O=example.com, C=US sha1 fb 58 a7 03 c4 4e 3b 0e e3 2c 40 2f 87 64 13 4d df e1 a1 a6 md5 72 a0 95 43 7e 41 88 18 ae 2f 6d 98 01 2c 89 68 Enter certificate to add to trusted keystore or 'q' to quit: [1]qKeyStore not changed
I hope that helps. For more information about the InstallCert program, have a look at the source code. I am sure you can figure out how it works.