I'm new in hadoop and Flume NG and I need some help.
I don't understand how hdfs security implemented.
Here are lines from configuration from Flume User Guide:
# properties of hdfs-Cluster1-sink
agent_foo.sinks.hdfs-Cluster1-sink.type = hdfs
agent_foo.sinks.hdfs-Cluster1-sink.hdfs.path = hdfs://namenode/flume/webdata
Does it mean that anyone who knows my hdfs path can write any data to my hdfs?
The question is from some time ago, but I'll try to answer it for any other developer dealing with Flume and HDFS security.
Flume's HDFS sink just need the endpoint where the data is going to be persisted. It such an endpoint is secured or not, it depends entirely on Hadoop, not in Flume.
Hadoop ecosystem has several tools and system for implementing security, but focusing on those native elements, we talk about the authentication and authorization methods.
The authentication is based on Kerberos, and as any other auth mechanism, it is the process of determining whether someone or something is, in fact, who or what it is declared to be. So, by using auth it is not enough by knowing a HDFS user name, but you have to demostrate you own such a user by previously authenticating against Kerberos and obtaining a ticket. Authentication may be pasword-based or keytab-based; you can see the keytabs as "certificate files" containing the authentication keys.
The authorization can be implemented at file system, by deciding which permissions has any folder or file within HDFS. Thus, is a certaing file has only 600 permissions, then only its owner will be able to read or write it. Other authorization mechanisms like Hadoop ACLs can be used.
Being said that, if you have a look to the Flume sink, you'll see that there is a couple of parameters about Kerberos:
hdfs.kerberosPrincipal – Kerberos user principal for accessing secure HDFS
hdfs.kerberosKeytab – Kerberos keytab for accessing secure HDFS
In Kerberos terminology, a principal is a unique identity to which Kerberos can assign tickets. Thus, for each enabled user at HDFS you will need a principal registered in Kerberos. The keytab, as previously said, is a container for the authentication keys a certain principal owns.
Thus, if you want to secure your HDFS then install Kerberos, create principals and keytabs for each enabled user and configure the HDFS sink properly. In addition, change the permissions appropriately in your HDFS.
Related
Here https://www.cloudera.com/documentation/enterprise/5-9-x/topics/sentry_intro.html
we can read that
Apache Sentry Overview Apache Sentry is a granular, role-based
authorization module for Hadoop. Sentry provides the ability to
control and enforce precise levels of privileges on data for
authenticated users and applications on a Hadoop cluster. Sentry
currently works out of the box with Apache Hive, Hive
Metastore/HCatalog, Apache Solr, Impala, and HDFS (limited to Hive
table data).
What does it mean exactly that HDFS is limited to Hive table data?
Does it mean that I can't set privileges access for users to particular paths on HDFS?
For example,
I would like to set read access for user_A to path /my_test1
and write/read access for user_B to path /my_test1 and path /my_test2.
Is it possible with Apache Sentry?
Sentry controls do not replace HDFS ACLs. The synchronization between Sentry permissions and HDFS ACLs is one-way; that is, the Sentry plugin on the NameNode will apply Sentry permissions along with HDFS ACLs, so that HDFS enforces access to Hive table data according to Sentry's configuration, even when being accessed with other tools. Thus, HDFS access control is a means to enforcement of policies defined in Sentry in such a case.
Enforcement of arbitrary file access in HDFS should still be done via HDFS ACLs.
I am trying to understand how impersonation works in hadoop environment.
I found a few resources like:
About doAs and proxy users- hadoop-kerberos-guide
and about tokens- delegation-tokens.
But I was not able to connect all the dots wrt the full flow of operations.
My current understanding is :
user does a kinit and executes a end user facing program like
beeline, spark-submit etc.
The program is app specific and gets service tickets for HDFS
It then gets tokens for all the services it may need during the job
exeution and saves the tokens in an HDFS directory.
The program then connects a job executer(using a service ticket for
the job executer??) e.g. yarn with the job info and the token path.
The job executor get the tocken and initializes UGI and all
communication with HDFS is done using the token and kerberos ticket
are not used.
Is the above high level understanding correct? (I have more follow up queries.)
Can the token mecahnism be skipped and use only kerberos at each
layer, if so, any resources will help.
My final aim is to write a spark connector with impersonation support
for a data storage system which does not use hadoop(tokens) but
supports kerberos.
Thanks & regards
-Sri
I'm totally new in Hadoop. One of SAS users has problem to save a file from SAS Enterprise Guide to Hadoop and I've been asked to check permissions in HDFS that if they have been granted properly. Somehow to make sure users are allowed to move from one side and to add it to the other side.
Where should I check for it on SAS servers? If it is a file or how can I check it?
Your answer with details would be more appreciated.
Thanks.
This question is to vague, but I can offer a few suggestions. First off, the SAS Enterprise Guide user should have a resulting SAS log from his job with any errors.
The Hadoop cluster distribution, version, services being used (For example Knox, Sentry, or Ranger security products must be setup), and authentication (kerberos) all make a difference. I will assume you are not having kerberos issues nor are running Knox, Sentry, Ranger ect, and you are using core hadoop with no Kerberos. If you need help with those you must be more specific.
1. You have to check permissions on the hadoop side for this. You have to know where they are putting the data into hadoop. These are paths in HDFS, not the servers file system.
If connecting to hive, and not specifying any options it is likely /user/hive/warehouse, or /user/username folder.
2 - Hadoop Stickybit enabled by default prevents users from writing to /tmp in HDFS. Some SAS Programs write to /tmp folder in hdfs to save metadata, along with other information.
Run the following command on a Hadoop node to check basic permissions in HDFS.
hadoop fs -ls /
You should see the /tmp folder along with permissions, if the /tmp folder has a "t" at the end the sticky bit is set such as drwxrwxrwt. If the permissions are drwxrwxrwx then sticky bit isn't set, which is good to eliminate permissions issues.
If you have a sticky bit set on /tmp, which is usually by default then you must either remote it, or set an HDFS TEMP directory in the SAS Programs libname for Hadoop cluster.
Please see the following SAS/Access to Hadoop Guide about the libname options at SAS/ACCESS® 9.4 for Relational Databases: Reference, Ninth Edition | LIBNAME Statement Specifics for Hadoop
To remove/change the Hadoop sticky bit see the following article, or from your Hadoop vendor. Configuring Hadoop Security in CDH 5 Step 14: Set the Sticky Bit on HDFS Directories . You will want to do the opposite of this article to remove the stickybit though.
2 - SAS + Authentication + Users -
If your Hadoop cluster is secured using Kerberos then each SAS user much have a valid kerberos ticket to talk to any Hadoop service. There are a number of guides on the SAS Hadoop Support page about Kerberos along with other resources. With kerberos they need a kerberos ticket, not a username or password.
SAS 9.4 Support For Hadoop Reference
If you are not using kerberos then you can either have either the Hadoop default of no authentication, or possibly some services such as Hive could have LDAP enabled.
If you don't have LDAP enabled then you can use any Hadoop username in the libname statement to connect such as hive, hdfs, or yarn. You do not need to enter any password, and this user doesn't have to be the SAS User Account. This is because they default Hadoop configuration does not require authentication. You can use another account such as one you might create for the SAS User in your Hadoop cluster. If you do this you must create a /user/username folder in HDFS by running something like the following as the HDFS superuser, or one with permissions in Hadoop then set the ownership to the user.
hadoop fs -mkdir /user/sasdemo
hadoop fs -chown sasdemo:sasusers /user/sasdemo
Then you can check to make sure it exists with
hadoop fs -ls /user/
Basically whichever user they have in their libname statement in their SAS program must have a users home folder in hadoop. The Hadoop users will have one created by default on install but you will need to create them for any additional users.
If you are using LDAP with Hadoop (not to common from what I've seen) then you will have to have the LDAP username along with a password for the user account in the libname statement. I believe you can encode the password if you like.
Testing Connections to Hadoop from SAS Program
You can modify the following SAS code to do a basic test to put one of the sashelp datasets into Hadoop using a serial connection to HiveServer2 using SAS Enterprise Guide. This is only a very basic test but should prove you can write to Hadoop.
libname myhive hadoop server=hiveserver.example.com port=10000 schema=default user=hive;
data myhive.cars;set sashelp.cars;run;
Then if you want you can use the Hadoop client of your choice to find the data in Hadoop in the location you stored it, likely /user/hive/warehouse.
hadoop fs -ls /user/hive/warehouse
And/Or you should be able to run a proc contents in SAS Enterprise Guide to display the contents of the Hadoop Hive table you just put into Hadoop.
PROC CONTENTS DATA=myhive.cars;run;
Hope this helps, good luck!
To find the proper groups who can access files in the HDFS, we need to check the Sentry.
The file ACL's are described in the Sentry, so if you want to give/revoke access to anyone, it can be done through it.
On the left hand side is the file location and right hand side is the ACL's of the groups.
Two different groups of people plan to use our hadoop cluster, but I don't want them to see each other's data.
How can I prevent this functionality on hadoop cluster ?
I understand that if you set a environment variable you can easily impersonate the hadoop superuser and access all data in HDFS. Is there an simpler way to prevent this or kerberos and ldap based security is the only way to go?
Kerberos is the only way to prevent users in Hadoop from impersonating as hdfs superuser and misusing privileges.
Its very simple for users to impersonate as hdfs user (who happens to be the superuser of hadoop in most distributions). Anyone could do that by specifying the env variable HADOOP_USER_NAME to hdfs.
I am trying to learn how Kerberos can be implemented in Hadoop.
I have gone through this doc https://issues.apache.org/jira/browse/HADOOP-4487
I have also gone through Basic Kerberos stuff (https://www.youtube.com/watch?v=KD2Q-2ToloE)
1) The Apache doc uses the word "Token" whereas the general doc over the internet uses the term "Ticket".
Are Token and Ticket same ?
2) The Apache doc also "DataNodes do not enforce any access control on accesses to its data blocks.
This makes it possible for an unauthorized client to read a data block as
long as she can supply its block ID. It’s also possible for anyone to write
arbitrary data blocks to DataNodes."
My thoughts on this:-
I can fetch the block Id from file path using the command:-
hadoop#Studio-1555:/opt/hadoop/hadoop-1.0.2/bin$ ./hadoop fsck /hadoop/mapred/system/jobtracker.info -files -blocks
FSCK started by hadoop from /127.0.0.1 for path /hadoop/mapred/system/jobtracker.info at Mon Jul 09 06:57:14 EDT 2012
/hadoop/mapred/system/jobtracker.info 4 bytes, 1 block(s): OK
0. blk_-9148080207111019586_1001 len=4 repl=1
As I was authorized to access this file jobtracker.info, I was able to find its blockID using the above command.
I think that if I add some offset to this block ID and write to that datanode.
How can I explicitly mention the blockID while writing a file to HDFS.(What is the command ?)
Any other way to write arbitrary data blocks to DataNodes ?
Please tell me if my approach is wrong ?
Are Token and Ticket same ?
No. Tickets are issued by Kerberos and then servers in Hadoop (NameNode or JobTracker) issue tokens to provide authentication within the Hadoop cluster. Hadoop does not rely on Kerberos to authenticate running tasks, for instance, but uses its own tokens that were issued based on the Kerberos tickets.
The Apache doc also "DataNodes do not enforce any access control on accesses to its data blocks.
I'm guessing you're taking that from the JIRA where access control was provided (https://issues.apache.org/jira/browse/HADOOP-4359) via BlockAccessTokens. Assuming this is turned on - which it should be in a secure cluster - one cannot access a block on a datanode without such a token, which is issued by the NameNode after authentication and authorization via Kerberos and HDFS' own file system permissions.
How can I access the Datanode and write data arbitrarily ?
I am not sure what you mean here. Do you mean when the user does not have permission? As Jacob mentioned
you will not get a valid BlockAccessToken unless the user has the permissions to access the Data based on the file system permissions, assuming that you have secure Hadoop cluster.