uid<-->username question
All,
I was thinking about a scheme to retrieve usernames from UIDs on different machines. I was going to push the passwd file from a participating audit client up to the server. Then I'll store it uniquely according to its IP address (e.g. /var/etc/passwd.192.168.10.10).
Then, I'd change the parse code which looks up the username from getpwuid().
In the case where the host was localhost, I'd still use the getpwuid() call. In the case where it is another host, I'd use fgetpwent() on the particular host's passwd file.
I see that the name-value cache will have to be modified or maybe a UID/hostname/username triplet cache will need to be used instead for UIDs.
On the sender, I was thinking that I already have an excellent audit-based file watch in place. Ideally, on a /etc/passwd addition, I'd like to fire a rule to automatically send the modified hosts file up to the collector machine.
Any thoughts on this? I realize in most systems an LDAP server is adequate for federated logins and no code changes or schemes are necessary. I do not have this and likely never will given my environment. I also have to ensure that the participating systems do not reuse old UIDs or remove expired ones from their password file.
I also realize this code change may be of little use to the general community, but if I do this and others have similar restrictions I'd be happy to share what I do.
Thx in advance,
LCB.
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LC (Lenny) Bruzenak [email protected]
Quoted 6 lines · LC Bruzenak
All,
I was thinking about a scheme to retrieve usernames from UIDs on different machines. I was going to push the passwd file from a participating audit client up to the server. Then I'll store it uniquely according to its IP address (e.g.
/var/etc/passwd.192.168.10.10).
...
Forgot to add - one alternative is to replace the UIDs in the events with the usernames, but I thought that one might be a bigger impact to the code base.
LCB.
Signature · 2 lines
LC (Lenny) Bruzenak [email protected]
Quoted 28 lines · LC Bruzenak
All,
I was thinking about a scheme to retrieve usernames from UIDs on different machines. I was going to push the passwd file from a participating audit client up to the server. Then I'll store it uniquely according to its IP address (e.g.
/var/etc/passwd.192.168.10.10).Then, I'd change the parse code which looks up the username from
getpwuid().In the case where the host was localhost, I'd still use the
getpwuid()call. In the case where it is another host, I'd usefgetpwent()on the particular host's passwd file.
I see that the name-value cache will have to be modified or maybe a UID/hostname/username triplet cache will need to be used instead for UIDs.On the sender, I was thinking that I already have an excellent audit-based file watch in place. Ideally, on a
/etc/passwdaddition, I'd like to fire a rule to automatically send the modified hosts file up to the collector machine.Any thoughts on this? I realize in most systems an LDAP server is adequate for federated logins and no code changes or schemes are necessary. I do not have this and likely never will given my environment. I also have to ensure that the participating systems do not reuse old UIDs or remove expired ones from their password file.
Quoted 8 lines
I also realize this code change may be of little use to the general community, but if I do this and others have similar restrictions I'd be happy to share what I do.
Thx in advance,
LCB.
I think this approach is problematic. First of all the set of uid's from a given machine is ephemeral. The contents of the passwd file needs to be matched to a time interval matching the log data. Secondly, the passwd file is sensitive data, you probably do not want to be shipping that over the network and storing it without a lot of safeguards. Thirdly, it's not just uid's that are have local context (machine local and time local), gid's, ip-addr -> hostname mapping, kernel version dependent data encodings, etc. are just some of the data you won't be able to interpret correctly at some point in the future on some disassociated remote machine.
Because there are many problems with taking the audit log in it's current form and storing it remotely for later analysis in IPA we are not going to collect the audit log in it's default form. Instead we're going to resolve (e.g. interpret using auparse terminology) all the data on the local machine *before* we collect and store it. We plan on doing this by writing a audispd plugin which resolves all the ambiguous local data as it's generated (and hence before it's ever collected). This solves both the locality of time and locality of host issues and tremendously simplifies post-mortum analysis because the log data will have been stripped of ambiguities and replaced with data that can simply be read and used with no extra processing.
Signature · 4 lines
John Dennis <[email protected]> Looking to carve out IT costs? www.redhat.com/carveoutcosts/
Quoted 1 line · John Dennis
LC Bruzenak wrote:
...
Quoted 4 lines
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environment. I also have to ensure that the participating systems do not reuse old UIDs or remove expired ones from their password file.
Quoted 10 lines
I think this approach is problematic. First of all the set of uid's from a given machine is ephemeral. The contents of the passwd file needs to be matched to a time interval matching the log data. Secondly, the passwd file is sensitive data, you probably do not want to be shipping that over the network and storing it without a lot of safeguards. Thirdly, it's not just uid's that are have local context (machine local and time local), gid's, ip-addr -> hostname mapping, kernel version dependent data encodings, etc. are just some of the data you won't be able to interpret correctly at some point in the future on some disassociated remote machine.
Good points John; thanks. Most of the things which apply to "normal" use-cases illustrated by what you describe don't apply to me, and so for the most people I realize what I need is silly.
My UIDs are by fiat not ephemeral. GIDs are not either. If a user's role changes they get a new username with the associated GID. IP<-->hostname mapping isn't via DHCP and won't be in the foreseeable future. Not sure about "kernel version dependent data encodings" but I guess you mean future kernel audit event structure. That one is larger then me anyway I think.
As I said, good points and I also agree that it is problematic. However, given the timeline I'm working on I might have to assume some inadequacy in order to meet schedule.
Quoted 14 lines
Because there are many problems with taking the audit log in it's current form and storing it remotely for later analysis in IPA we are not going to collect the audit log in it's default form. Instead we're going to resolve (e.g. interpret using auparse terminology) all the data on the local machine *before* we collect and store it. We plan on doing this by writing a audispd plugin which resolves all the ambiguous local data as it's generated (and hence before it's ever collected). This solves both the locality of time and locality of host issues and tremendously simplifies post-mortum analysis because the log data will have been stripped of ambiguities and replaced with data that can simply be read and used with no extra processing.
I think this is an excellent approach and when ready for action I'll look to incorporate. So you are normalizing at the source. This is essentially what I figured was a bigger effort than my suggested kludge.
Thanks for the info; I really appreciate it!
LCB.
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LC (Lenny) Bruzenak [email protected]