Sunday, February 24, 2008

Fix Central: A central place to get your Informix fixes

In this article I'll cover one of the sites that IBM uses to improve it's interaction with customers. As many Informix customers know, traditionally we would only have access to the normal releases.
Theese would be like IDS 10.00.FC8, or CSDK 3.00.TC1 etc.
I won't go into details explaining the meaning of all the release code fields, but you probably know that any two letters and one numeric digit following major and minor versions (FC8 and TC1 in the examples) mean that this is a standard, generally available release level (internally called Interim Release). It includes mainly code fixes, but can also include some new features and they are cumulative (FC8 should include all the corrections and features that went into FC7).

But, if you ever hit a bug and contacted support, then you probably ended up with a patch level like 10.00.FC7X5 or 11.10.FC2W1. These have special meanings... The "X" letter, followed by a numeric digit means this is a special build, generated from a customer request, and it includes one or more bug fixes. It is not cumulative, meaning X2 may have a completely disjunct set of fixes from X1 and also X1 on one platform may have nothing in common with X1 on another platform.
"W" means it's a Post Interim Drop (PID). These were introduced a few years ago, and they are build for the major platforms. These release levels include a set of fixes (no new features) and are made from time to time. They are cumulative, meaning all W1 fixes will be included in W2 (unless the fix itself has problems and has to be removed).
The idea behind all this is that the customer should not have to wait for the next commercial interim release to get a product fix, if he hits a bug.

Until June 2007, you would have to open a support case before you could have access to one of this special builds. Then your support engineer would give you specific instructions on how to download the fix from a temporary location (or you could receive the fix by mail if you prefer).
Since that date, IBM made available many of these fixes in a new system or web site, called the Fix Central.
You will need a valid account, associated to a valid Passport Advantage customer account. Then, assuming your PA account entitles you to use the specific version you will have access to some of these fix releases.
This makes the interaction between customers and IBM technical support easier, and it also gives the ability for a customer to access and test the most recent releases by himself. If you fill you're hitting a bug, and after searching the support site you find an APAR (Authorized Program Analysis Report) that matches it, you may search for a fix that solves it in the Fix Central site.
The searches can be made by product family, APAR, release level and platform. So this means you have a lot of flexibility and ease of use.

I'll end this post with some references where you can get more details about all these:

Thursday, February 21, 2008

Cheetah 2: The cat is out for it's second open beta...

As the title suggests, IBM has just made available the IBM Informix Dynamic Server (IDS) 11.50 (codenamed Cheetah 2) for anyone wanting to test it. It's the second open beta of an IDS version (the first happened last year with 11.10 - Cheetah).

The process is a little bit more complex than the previous beta. This time you have to send and email requesting access. The system will provide you with an access code and you'll receive a copy of Carlton Doe's book on IDS 11.

Again IBM proves it's commitment to Informix technology and to it's customers, by providing a new release available in about 1 year.

This beta program includes a non-disclosure agreement and we cannot talk about it... But I'm sure as soon as the new features are announced we'll see a lot of articles about them, and I plan to cover some of them here in detail. For now, please check the release notes :)

So, in order to get hold of your copy, just go to and click on IDS 11.50 beta. As I mentioned above, the process will take longer than last time, but you'll receive your copy of Carlton's book.

Once again R&D has made a wonderful job in providing excellent new features. I'm curious to know for how long the competition will play the 'FUD' song to customers...

Sunday, February 17, 2008

Informix user authentication: PAM for the rescue (part 2)

I hope you had the chance to read and eventually follow part one of these series of articles related to IDS authentication using PAM. If you did, you already know the basics of PAM and how to setup IDS to authenticate against an LDAP or Active Directory server.
But there are still several topics we need to cover to fully understand IDS PAM authentication:

  • Challenge/response and implicit (no password) connections
  • How to setup distributed query environments using PAM
  • Can we develop customized PAM modules?
  • What are the current IDS PAM limitations?

Challenge/response and implicit connections:

Most of us, people working with Informix, know that besides the usual user/password connection we can establish what we usually call implicit connections. These connections are based on trust relations between the client and the server or between a specific user on the client and a user (the same or other) in the server.

These trusts are configured exactly as the trust relations for the "r" commands (rsh, rcp, rexec etc.).Specifically you must use the /etc/hosts.equiv or the ~user/.rhosts files. Just as a side note, I've found many customers that assume they need these services in order to Informix trusted relations work. This is not correct. You can work with the files even if the services (rshd, rexecd etc.) are down. And it's probably much better to leave the services down since they raise a lot of security issues.
These connections are normally used in environments using 4GL and ESQL/C applications. More modern applications (Java, J2EE, .NET, PHP, Ruby, Python, Perl etc.) use the more usual user/password mechanism. 4GL and ESQL/C can also use user/password, but typically they use the implicit connections for simplicity and because they normally run in more controlled environments.
dbaccess, the ASCII tool that every Informix DBA uses can use both types of connections. If you specify the database in non interactive mode it will try implicit connection, but using the menus or specific instructions will allow you to make user/password connections. So, how does all this relate to IDS PAM authentication? Read on...

PAM is based on a challenge/response mechanism. The modules will throw challenges to applications, and these should respond with the correct answers to these challenges. A correct answer will fulfill the modules requirements and a wrong answer will cause module failure.

So in a sense, you can consider the user/password has a challenge/response case. If the module you're using requires a password and you use a user/password connection everything will be handled transparently for you, assuming the module has been configured in password mode (pamauth=(password) in $INFORMIXSQLHOSTS)

But we can configure the modules in another mode (pamauth=(challenge)). This has to be done if we want to use implicit connections with PAM.
In these cases you have to prepare your application to answer the challenges issued by modules. This is done only in recent versions of Client Software Development Kit (CSDK) and JDBC driver, and the way it works is by allowing you (the developer) to code a callback function to answer challenges. Whenever the authentication modules raise a challenge, the CSDK or JDBC interface code will forward this challenge to your function. Obviously you need to register it as a callback function for PAM authentication. In ESQL/C the API function to do this is called ifx_pam_callback(). You should declare your callback function like this:

int callback(char *challenge, char *response, int msg_style);

and then register it:


The callback function must be declared with three arguments:
  1. char *challenge
    The challenge issued by the authentication module
  2. char *response
    The answer provided by the callback function
  3. int msg_style
    The kind of message the module sent
Depending on the module you're using you may choose to give automatic responses or else forward the challenge to the user and allow him to introduce the answer. The msg_style parameter can be used for this, and is the module choice.
If you choose to ask the user, the same callback function may work with very different modules, as long as the user understands the challenges and can provide a correct answer. This approach implies that you'll have to bother the user, which is a different behavior from the traditional implicit mechanism of authentication.
On the other hand you may choose to code the answers in the callback function, or allow it to find the correct answer automatically. This approach forces you to adapt your callback function if you choose to change the authentication modules. As an example you could arrange the callback functions and a PAM module to authenticate through key exchange, or through a set of questions and answers that only an algorithm could understand. Connections would be allowed only to clients using the correct callback function.

In JDBC the callback mechanism is provided by the IfxPAM() method in IfmxPAM interface.
If you have CSDK installed, you can find an example of a callback function being use in an application. Check $INFORMIXDIR/demo/esqlc/

But the real beauty comes when you also see the other side. That side is the PAM module itself.
To show you this I will borrow an example published in DeveloperWorks, more exactly here.

The authors are three IBMers who have created an example of a PAM module that I will reproduce here with very small changes:

example from
with slight changes and a few comments

#include <link.h>
#include <string.h>
#include <security/pam_appl.h>
#include <security/pam_modules.h>

#ifndef PAM_EXTERN
#define PAM_EXTERN

This implements the main PAM API function. This will be called when we create a
PAM service like:

auth pam_demo_mod required

The function signature is defined in the PAM include modules

pam_sm_authenticate(pam_handle_t *pamh, int flags, int argc, const char *argv[])
struct pam_conv *conv;
struct pam_message msg[3], *msgp;
struct pam_response *resp;
const char *user;
char *answer, *prompt[2], *vanswer[2];
int pam_err, retry;
void *handle = NULL;

Define three prompts. We will raise three challenges. Two questions and an info string.
The answers are shown in parenthesis.
The user will see the questions and the answers. Only for demonstration purposes of course!

prompt[0] = (char *) strdup("Your school name (MIT):");
prompt[1] = (char *) strdup("Your maiden name (SUZE):");

vanswer[0] = (char *) strdup("MIT");
vanswer[1] = (char *) strdup("SUZE");

pam_err = pam_get_item(pamh, PAM_CONV, (void **)&conv);
if (pam_err != PAM_SUCCESS)
return (PAM_SYSTEM_ERR);

msg[0].msg_style = PAM_PROMPT_ECHO_OFF;
msg[0].msg = prompt[0];
msg[1].msg_style = PAM_PROMPT_ECHO_ON;
msg[1].msg = prompt[1];


Send the two challenges to the client


for (retry=0;retry<2;retry++) msgp =" &msg[retry];" resp =" NULL;" pam_err =" (*conv-">conv)(1, &msgp, &resp, conv->appdata_ptr);
if (pam_err == PAM_SUCCESS){

/* No response needed for text info and error msg */
if ((msg[retry].msg_style == PAM_TEXT_INFO) ||
(msg[retry].msg_style == PAM_ERROR_MSG))
answer = resp->resp;
if (!answer){
pam_err = PAM_AUTH_ERR;
if (strcmp(answer, vanswer[retry])){
pam_err = PAM_AUTH_ERR;
if (resp){
if (resp->resp){
free (resp);
return (pam_err);

The functions below are required, but not used in this module
They are called for account/session etc.
So, we'll just return success

pam_sm_setcred(pam_handle_t *pamh, int flags,
int argc, const char *argv[])
return (PAM_SUCCESS);

pam_sm_acct_mgmt(pam_handle_t *pamh, int flags,
int argc, const char *argv[])
return (PAM_SUCCESS);

pam_sm_open_session(pam_handle_t *pamh, int flags,
int argc, const char *argv[])
return (PAM_SUCCESS);
pam_sm_close_session(pam_handle_t *pamh, int flags,
int argc, const char *argv[])
return (PAM_SUCCESS);

pam_sm_chauthtok(pam_handle_t *pamh, int flags,
int argc, const char *argv[])

Create a file called pam_demo_mod.c with the above code and then compile/link it with:

cc -g -c pam_demo_mod.c
ld -G -o pam_demo_mod.o -lpam

If it works, you should have a module in your current directory. This is your newly created module. As I mentioned in part 1 of this series, it can be really simple to implement a PAM module.

Now, to show you how this works, we'll have to create another PAM service in our IDS instance.
This is similar to what we've done for LDAP authentication. Follow this steps:
  1. Edit $INFORMIXDIR/etc/$ONCONFIG and add another DBSERVERALIAS (let's call it cheetah_chg):

    DBSERVERALIASES cheetah_pam,cheetah_chg,cheetah_drda                # List of alternate dbservernames

  2. Edit your $INFORMIXSQLHOSTS and configure this new service:

    cheetah_chg onsoctcp 1532 s=4,pam_serv=(ids_pam_challenge),pamauth=(challenge)

    Please note:
    1. We must choose a different PAM service name (ids_pam_challenge)
    2. The pamauth option is set to "challenge"
  3. Create a file called /etc/pam.d/ids_pam_challenge with the following line:
    auth required
  4. Copy your newly created to /lib/security (or any other place where your distribution keeps the PAM modules)
  5. Restart your IDS instance

After configuring the server side, it's time to show you the client side. You must use a second machine for this. Follow the following steps:

  1. Make sure you have a stores demo called stores_demo
  2. cd to $INFORMIXDIR/demo/esqlc (in your CSDK installation)
  3. Edit the file called Check the SELECT statement in that file and change it's WHERE clause to "customer_num=104"
  4. compile

    esql -o pamdemo.exe

  5. Setup the $INFORMIXSQLHOST file to have the new port we just created in the other host
  6. set the correct INFORMIXSERVER:

  7. Run pamdemo.exe:
Answer what you see in parenthesis. You will see something like this:

cheetah_chg@manicminer:fnunes-> ./pamdemo.exe
Starting PAM demo
Callback function registered.
Your school name (MIT):: 1:MIT
Your maiden name (SUZE):: 2:SUZE
John Doe

PAM DEMO run completed successfully

You can follow the code, but in brief what happened was that the PAM module we used raised two challenges which were handled and forward to the user by the call back function.
The first challenge expects an answer "MIT" an the second expects "MIT". If any of those are wrong the authentication will fail. The message showed to the user is defined by the callback function, but it can use parameters passed by the module. As I wrote above, this can have the user intervention or not. It's up to the programmer to decide and to implement it in the callback function.
This ends the topic of challenge response and implicit connections using PAM.

How to setup distributed query environments using PAM:

One of the greatest advantage of using PAM comes in fact from a limitation... When you are connected to instance "A" and want to access a database/table in instance "B" you do a distributed query. Something like:

SELECT field1, field2
FROM remote_db@remote_instance:remote_table

In a typical Informix installation, this would require a trusted relation between the host running the instance to which the application is connected and the host running the remote instance.
Once you setup this trust it would be active for any instance... so you would have to be very careful with the database privileges.
Since PAM works by raising challenges between host and client, and because a distributed query can happen at any time, it would be impossible to establish connection between instances/clients when a distributed query was sent. The solution to this problem introduced a great functionality (IMHO it should have been like this since ever)... You may have noticed that since 9.4+ you have another system database called sysuser.
In this database you'll see a table called sysauth with the following structure:

username char(32)
groupname char(32)
servers char(128)
hosts char(128)

This is the place where you define the "trust" relations between your instance and remote hosts and Informix servers.

I will extend my example above... As you may have noticed I have a host called "Pacman" running an IDS 11.10 instance with the names cheetah (standard port), cheetah_pam (pam in password mode), cheetah_chg (PAM in challenge mode) and cheetah_drda (the new protocol DRDA). The other host I used to run the pamdemo.exe example is called "ManicMiner". In this host I have created another instance called cheetah2. I then start dbaccess on manicminer against instance cheetah2 by running:

cheetah2@manicminer:informix-> dbaccess stores_demo -

Database selected.

> select * from stores_demo@cheetah:customer;

956: Client host or user informix@manicminer is not trusted by the server.

No such file or directory
Error in line 1
Near character position 42

The error is expected. I tried to connect to the remote instance normal authentication port and have no trust between Pacman and ManicMiner. Let's see what happens with the PAM enabled port:

cheetah2@manicminer:informix-> dbaccess stores_demo -

Database selected.

> select * from stores_demo@cheetah_pam:customer;

950: User informix@manicminer is not known on the database server.
Error in line 1
Near character position 46

Interesting... I can't access it, as expected, but we have a different error (-950, instead of the usual -956). Let's check it with finderr:

User username is not known on the database server.

This statement refers to a database on another computer system, but the other database server does not accept your account name. You must have a valid trusted login identity on any database server you access remotely. See your database administrator about putting your login ID in 'sysuser:sysauth' on the remote server. This message appears on PAM enabled servers.

Well, it explicitly tells us to use the sysauth table of the sysuser database of the remote instance... So let's get back to the Pacman server and run:> dbaccess sysuser -

Database selected.

> insert into sysauth (username, servers, hosts ) values ( 'informix', 'cheetah2', 'manicminer' );

1 row(s) inserted.


And now, again on ManicMiner, the same query:

cheetah2@manicminer:informix-> dbaccess stores_demo -

Database selected.

> select * from stores_demo@cheetah_pam:customer;

customer_num 101
fname Ludwig
lname Pauli
company All Sports Supplies
address1 213 Erstwild Court
city Sunnyvale
state CA
zipcode 94086
phone 408-789-8075


28 row(s) retrieved.

So, in order to authorize distributed queries in PAM enabled engines/ports, you have to setup the authorizations in the sysauth table of the sysuser database.
You need to specify the username, the instance of origin (servers column) and the hosts originating the query (hosts column). Note the following:
  • Although it's possible to specify more than one server or host in the respective columns (separated by spaces and/or commas), you should always indicate only one server/host per row. This will be easier to maintain (if you need to remove for example) using scripting and it's possible this may change, and in the future it may only support one value
  • The host field specifies the machine where the query comes from. This will be the remote instance host and not the client application host. The existence of both servers and hosts columns allows you to have two instances with the same name in your organization and distinguish between them. I wouldn't suggest having two instances with the same name, but you may want to have it. One for production and the other for quality for example.
  • The groupname apparently is not used at this time. Personally I would love to see this field be used for specifying the default role for the user... But this is just my wish...

Can we develop customized PAM modules?

Well, the quick answer is yes. Above is an example of a dummy PAM module. As you can see it's not very complex. You just have to send challenges and receive responses. You may even just check certain properties setup by the PAM framework and decide if they verify certain criteria (things like time of day, number of sessions for that user, machine load etc.). I would say that with PAM, sky is the limit... But as we'll see further ahead there are still some limitations.

One thing that you must have in mind, in case you think about writing your own modules is security. Be aware, that you'll be defining your database authentication mechanism. You have to be careful! Your code cannot compromise authentication security nor database stability and performance. But don't let this scare you. There are plenty of PAM modules using open source licensing schemes... So, there's a good chance that whatever you need was already developed by someone, and if not, you can get examples and PAM modules skeletons to start with.

What are the current IDS PAM limitations?

Unfortunately, by the time this article is being written, there are quite a few limitations. I will try to enumerate them, and at the same time give you some insight on the status of these limitations. Some of them are perfectly known to the R&D teams, and they'll solve it as soon as possible. But given the current release schedule and the list of features they want to put in IDS it's not easy to start working on some of this issues. Let's see the list. Bear in mind this is my personal view. Nothing here represents IBM positions on any of these topics, and this does not represent any assumption on how or when these issues may be addressed:

  1. PAM is not yet supported in .NET clients
    This is a known issue.
  2. PAM authentication still requires that the OS knows about the user
    The reasons for this odd behavior relate to some features that depend on the existence on an OS identity: SET EXPLAIN to file and SYSTEM command in the stored procedures are two examples of this
    R&D is aware of this problem and accordingly to some talks they already have ideas for solving this
  3. PAM layer does not setup all the PAM framework variables. The PAM API defines these internal variables:
      The service name
    • PAM_USER
      The user name
      The user authentication token
      The old user authentication token
    • PAM_TTY
      The tty name
      The remote host name
      The remote user name
    • PAM_CONV
      The pam_conv structure

    At this time, IDS does not establish PAM_RHOST and PAM_RUSER. PAM_RHOST would be good to have... PAM_RUSER is also not set but I have doubts it could be securely establish by IDS. The client libraries can send it, but to assume this is secure would be a mistake since the connection packets can, theoretically be handcrafted.
    I personally believe adding PAM_RHOST would be an easy fix, but I don't know the code...
  4. The groupname field of the sysuser:sysauth table is apparently not used. Accordingly to same sources this would be the OS group of the user. I really don't see great advantage in this. What I would love to see is a way to specify the default role for a remote user (eventually different from his default role, even if this is defined). This would make sense, because we would be able to specify the user default role depending on the connection origin for distributed queries
  5. Documentation!
    PAM is an area where the documentation doesn't live up to its standards (remember that Informix manuals received industry recognition...). All the features should be clearly documented... In fact, this was the main reason to publish these two articles

I think I covered most of the aspects of PAM authentication in IBM Informix Dynamic Server.
With this and the examples on this and the previous article I think anyone should have enough information to test it.

I'd like to end with some references to other material that may be useful, and relates to this:

As always, if you have any comment or doubt don't hesitate in leaving a comment or contact me.
Hope this helps to clarify PAM authentication in IDS. Hopefully more customer feedback and requirements will give R&D more reasons to solve the issues and to improve this functionality.

Friday, February 01, 2008

ILO - Special offer from IIUG

The Informix International Users Group ( IIUG ) has just announced in it's January 2008 Insider publication an offer that will allow you to experiment the new IBM training offer: Instructor Led Online (ILO)

This kind of training adds an instructor "presence" to the traditional self-study eLearning scheme. This kind of training includes the usual material, access to a virtual machine environment and the presentations and help provided by an instructor using technologies like conference calls and webcasts.

The obvious advantage of this kind of training is the cost and the possibility of having students spread across geographic locations. Sometimes it's hard to get the required number of students at a specific time, all available in one location. In this situations, ILO can join people that would never be able to get together in a physical location. On the other hand, given the absence of physical installations, and physical equipment that would otherwise need to be provided by the training supplier, the costs can be considerably lower. The costs will be even lower if you consider traveling and accommodation costs for students. Of course this has it's downsides... The interaction will never be the same, but this greatly depends on the instructor and the students. One should, as a student, be as much participative as we would be in a classic training room, and it's the instructor obligation to facilitate the student's participation.

Another common misconception about this kind of training, is the idea that the students don't have to take full time for these classes. I personally have experienced this type of training as a student, and I can assure you this was a full time task. You have to attend the instructors sessions, and you must reserve time for self-study and exercise resolution. Otherwise you'll lag behind, and it will be harder to recover than in a classic training (I'd risk to say, impossible to catch up...). So if you ever think about ILO and you picture yourself attending it while you pursue your daily tasks... forget it!

Some of us, in particular in countries like Portugal, still look at this kind of training with some doubts. Maybe it's because we tend to be less disciplined, or just because we're more conservative, but I really think this can reach a very interesting cost/benefits ratio and also facilitate training for people living in less populated regions.

So, I suggest that all Informix DBA, programmers etc. take this opportunity to experience it, without costs... I think this offer will not include VM access for exercising, but please take into account that in a real ILO training this will be provided. In fact I have the pleasure and honor to have done several exercise tests for IBM Informix courses that were updated to version 11 in this environment. The purpose of this is to make sure that the exercises done in the physical training room can also be accomplished successfully in the VM environment.

The complete info and also the registration for this ILO demo can be accessed directly here. You must be a member of IIUG, but as you probably already know, this has no costs at all.