Tianyin Xu created HADOOP-12676:
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Summary: Consider the default keytab file of Kerberos
Key: HADOOP-12676
URL: https://issues.apache.org/jira/browse/HADOOP-12676
Project: Hadoop Common
Issue Type: Improvement
Components: security
Affects Versions: 2.6.2, 2.7.1
Reporter: Tianyin Xu
Priority: Minor
In the current implementation of {{SecurityUtil}}, we do not consider the
default keytab file of Kerberos (which is {{/etc/krb5.keytab}} in [MIT Kerberos
defaults|http://web.mit.edu/kerberos/krb5-1.13/doc/mitK5defaults.html#paths]).
If the user does not set the keytab file, an {{IOException}} will be thrown.
{code:title=SecurityUtil.java|borderStyle=solid}
230 public static void login(final Configuration conf,
231 final String keytabFileKey, final String userNameKey, String hostname)
232 throws IOException {
...
237 String keytabFilename = conf.get(keytabFileKey);
238 if (keytabFilename == null || keytabFilename.length() == 0) {
239 throw new IOException("Running in secure mode, but config doesn't
have a keytab");
240 }
{code}
However, the default keytab location is assumed by some of the callers. For
example, in
[{{yarn-default.xml}}|https://hadoop.apache.org/docs/r2.7.1/hadoop-yarn/hadoop-yarn-common/yarn-default.xml],
the defaults of {{yarn.resourcemanager.keytab}}, {{yarn.nodemanager.keytab}},
and {{yarn.timeline-service.keytab}} all point to {{/etc/krb5.keytab}}.
On the other hand, these callers directly call the {{SecurityUtil.login}}
method; therefore, the docs are incorrect that the defaults are actually
{{null}} (as we do not have a default)...
{code:title=NodeManager.java|borderStyle=solid}
protected void doSecureLogin() throws IOException {
SecurityUtil.login(getConfig(), YarnConfiguration.NM_KEYTAB,
YarnConfiguration.NM_PRINCIPAL);
}
{code}
I don't know if we should make {{/etc/krb5.keytab}} as the default in
{{SecurityUtil}}, or ask the callers to correct their assumptions. I post here
as a potential improvement.
Thanks!
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