Ok, fair warning - this is a little long-winded, but I'd rather give too much detail than not enough. Also, all examples are in slapd.conf format, since there is no documentation for cn=config, and I'm using slapd with -f and -F to make the conversion.
Anyways, I'm working on implementing some rewrite rules with slapo-rwm, using back-relay (or possibly back-meta if that doesn't work out) as the backend on top of which slapo-rwm will sit, to make available some features that would be otherwise not be present with back-ldap, or in the absence of a proxy backend altogether.
In its most basic form, the slapo-rwm overlay can be used without a proxy or relay backend, but the feature I'm after appears to require either the slapd-meta backend or the slapd-relay backend. For now, I've chosen to try with slapd-relay, as my research has indicated it supports the feature I'm after. For reference, this feature I desire is the 'searchResult' rewriteContext, as I'm interested in rewriting dynamic group membership DN's (i.e., the 'member' attribute, as defined in rfc2307bis) as plain uid's, so clients that only know about rfc2307 (and thus, look only for entries of the same format as memberUid and fail to perform any mappings to translate membership DN's to UID's) can make use of the dynamic groups I've created in my directory.
Since my slapd-hdb database's rootDSE is dc=example,dc=com, I really couldn't find any way to get around using a virtual naming context; creating a back-meta database on the same host with the same suffix as the back-hdb database seemed ambiguous at best (in terms of how to ensure that clients would always speak to the back-meta db first), and using the suffix "dc=com" seemed inappropriate, as did creating several relay databases, one for each of the entries below the slapd-hdb database's rootDSE (e.g., ou=Users,dc=example,dc=com, ou=Groups,dc=example,dc=com, etc.). Creating several relay databases in that fashion presents other problems as well, and wouldn't do me any good for clients which query for entries using dc=example,dc=com as their search base.
Given that, and the fact that I'm only looking to remap/rewrite data going to and from a single local database with a single naming context, I decided it was a better idea to create a single back-relay database with a bogus "proxy" naming context and use a suffixmassage to rewrite it, e.g.:
database relay suffix "dc=example-proxy,dc=com" relay "dc=example,dc=com"
overlay rwm rwm-rewriteEngine on rwm-suffixmassage "dc=example-proxy,dc=com" "dc=example,dc=com" rwm-rewriteContext searchResult rwm-rewriteRule "^uid=([^,]+?),ou=Users,dc=example,dc=com$" "$1"
For reference, here is the back-meta database configuration I was going to use before I discovered that back-relay supported the searchResult rewriteContext:
database meta suffix "dc=example-proxy,dc=com"
overlay rwm rwm-rewriteEngine on uri "ldap://localhost/dc=example-proxy,dc=com" rwm-suffixmassage "dc=example-proxy,dc=com" "dc=example,dc=com" rwm-rewriteContext searchResult rwm-rewriteRule "^uid=([^,]+?),ou=Users,dc=example,dc=com$" "$1"
In either case, I have a few questions going forward from this point:
1. Is it legal to rewrite the search result DN's as described in the example above? I'm hoping that since the data being manipulated is going from server -> client and is not being stored in the directory, the attributes I'm rewriting would not be subjected to the syntax requirements of the entry that holds them.
2. Are there any benefits or drawbacks to using a rewriteMap to accomplish this task? In my mind, it just seems like another means to the same end, at least based on the following configuration I came up with:
rwm-rewriteMap ldap dn2uid "ldap://localhost/ou=Users,dc=example,dc=com?uid?sub" rwm-rewriteContext searchResult rwm-rewriteRule "^uid=([^,]+?),ou=Users,dc=example,dc=com$" "${dn2uid($1)}"
3. Is there a better way to go about doing this that I've failed to see or consider?
4. Considering the slapd-meta man page, which mentions that some of its features could potentially result in excessive overhead for some installations, are the features used in the aforementioned configuration(s) efficient enough to scale well in a very busy environment? I'm aware that's a pretty vague and loaded question with lots of variables, so I'm just looking for an educated opinion from a 10,000 foot view, assuming excellent hardware, high network capacity, and heavy - say, 5k, 10k, 15k queries per second - traffic. Performance will obviously be tested before implementing this, but it'd still be nice to have a rough idea of what to expect going in.
Lastly, on a somewhat tangential note, given that there's no documentation with respect to cn=config for setting up slapo-rwm (or doing it in conjunction with a proxy backend), is there any way to discover the cn=config attributes and objectclasses for those backend and overlays that's better or more efficient than creating a standard slapd.conf configuration and converting it with slapd using -f and -F? Perhaps an official or unofficial bit of documentation floating around out there other than a few miscellaneous postings on the mailing lists and some ITS contents? On a similar note in the same vein, as far as I can tell, none of the man pages, admin guide sections, or FAQ-O-Matic entries on slapd-relay mention which rewrite contexts are available with it, and I didn't realize that slapd-relay accepted the searchResult rewrite context until I read the servers/slapd/back-relay/README file (while searching for code that might reveal slapo-rwm's cn=config attribute equivalents). Would it be objectionable to update these reference points with said information? I'd be happy to file an ITS and submit patches and/or content for updating the documentation, if Gavin is too busy, unavailable, or would like some help.
Thanks for any and all advice, musings, criticisms, and opinions!
-Ryan
Ok, fair warning - this is a little long-winded, but I'd rather give too much detail than not enough. Also, all examples are in slapd.conf format, since there is no documentation for cn=config, and I'm using slapd with -f and -F to make the conversion.
Anyways, I'm working on implementing some rewrite rules with slapo-rwm, using back-relay (or possibly back-meta if that doesn't work out) as the backend on top of which slapo-rwm will sit, to make available some features that would be otherwise not be present with back-ldap, or in the absence of a proxy backend altogether.
In its most basic form, the slapo-rwm overlay can be used without a proxy or relay backend, but the feature I'm after appears to require either the slapd-meta backend or the slapd-relay backend. For now, I've chosen to try with slapd-relay, as my research has indicated it supports the feature I'm after. For reference, this feature I desire is the 'searchResult' rewriteContext, as I'm interested in rewriting dynamic group membership DN's (i.e., the 'member' attribute, as defined in rfc2307bis) as plain uid's, so clients that only know about rfc2307 (and thus, look only for entries of the same format as memberUid and fail to perform any mappings to translate membership DN's to UID's) can make use of the dynamic groups I've created in my directory.
Since my slapd-hdb database's rootDSE is dc=example,dc=com, I really couldn't find any way to get around using a virtual naming context; creating a back-meta database on the same host with the same suffix as the back-hdb database seemed ambiguous at best (in terms of how to ensure that clients would always speak to the back-meta db first), and using the suffix "dc=com" seemed inappropriate, as did creating several relay databases, one for each of the entries below the slapd-hdb database's rootDSE (e.g., ou=Users,dc=example,dc=com, ou=Groups,dc=example,dc=com, etc.). Creating several relay databases in that fashion presents other problems as well, and wouldn't do me any good for clients which query for entries using dc=example,dc=com as their search base.
Given that, and the fact that I'm only looking to remap/rewrite data going to and from a single local database with a single naming context, I decided it was a better idea to create a single back-relay database with a bogus "proxy" naming context and use a suffixmassage to rewrite it, e.g.:
database relay suffix "dc=example-proxy,dc=com" relay "dc=example,dc=com"
overlay rwm rwm-rewriteEngine on rwm-suffixmassage "dc=example-proxy,dc=com" "dc=example,dc=com" rwm-rewriteContext searchResult rwm-rewriteRule "^uid=([^,]+?),ou=Users,dc=example,dc=com$" "$1"
The result of this mapping does not yield a valid DN; as such, this rewriting is incorrect. Also, I don't see how it could be useful, as LDAP clients usually expect DNs to be DN-valued.
For reference, here is the back-meta database configuration I was going to use before I discovered that back-relay supported the searchResult rewriteContext:
database meta suffix "dc=example-proxy,dc=com"
overlay rwm rwm-rewriteEngine on uri "ldap://localhost/dc=example-proxy,dc=com" rwm-suffixmassage "dc=example-proxy,dc=com" "dc=example,dc=com" rwm-rewriteContext searchResult rwm-rewriteRule "^uid=([^,]+?),ou=Users,dc=example,dc=com$" "$1"
In either case, I have a few questions going forward from this point:
- Is it legal to rewrite the search result DN's as described in the
example above? I'm hoping that since the data being manipulated is going from server -> client and is not being stored in the directory, the attributes I'm rewriting would not be subjected to the syntax requirements of the entry that holds them.
- Are there any benefits or drawbacks to using a rewriteMap to accomplish
this task? In my mind, it just seems like another means to the same end, at least based on the following configuration I came up with:
rwm-rewriteMap ldap dn2uid "ldap://localhost/ou=Users,dc=example,dc=com?uid?sub" rwm-rewriteContext searchResult rwm-rewriteRule "^uid=([^,]+?),ou=Users,dc=example,dc=com$" "${dn2uid($1)}"
Same as above. You're performing an internal search to obtain information you already have, and cast it in invalid form.
- Is there a better way to go about doing this that I've failed to see or
consider?
Consider why you need it: broken client? Fix the client. Anything else? Perhaps LDAP is not what you need; in any case, move such mangling into the client.
- Considering the slapd-meta man page, which mentions that some of its
features could potentially result in excessive overhead for some installations, are the features used in the aforementioned configuration(s) efficient enough to scale well in a very busy environment? I'm aware that's a pretty vague and loaded question with lots of variables, so I'm just looking for an educated opinion from a 10,000 foot view, assuming excellent hardware, high network capacity, and heavy - say, 5k, 10k, 15k queries per second - traffic. Performance will obviously be tested before implementing this, but it'd still be nice to have a rough idea of what to expect going in.
Pure rewriting may not impact too much; rewriteMaps that rewuire further internal lookups may yield significant overhead. Of course, if you setup things like ACL checking that involves significant internal searches on a database that makes extensive use of rewriting, things can get even worse.
Lastly, on a somewhat tangential note, given that there's no documentation with respect to cn=config for setting up slapo-rwm (or doing it in conjunction with a proxy backend), is there any way to discover the cn=config attributes and objectclasses for those backend and overlays that's better or more efficient than creating a standard slapd.conf configuration and converting it with slapd using -f and -F? Perhaps an official or unofficial bit of documentation floating around out there other than a few miscellaneous postings on the mailing lists and some ITS contents? On a similar note in the same vein, as far as I can tell, none of the man pages, admin guide sections, or FAQ-O-Matic entries on slapd-relay mention which rewrite contexts are available with it, and I didn't realize that slapd-relay accepted the searchResult rewrite context until I read the servers/slapd/back-relay/README file (while searching for code that might reveal slapo-rwm's cn=config attribute equivalents). Would it be objectionable to update these reference points with said information? I'd be happy to file an ITS and submit patches and/or content for updating the documentation, if Gavin is too busy, unavailable, or would like some help.
None that I'm aware of. The FAQ is interactive; if by extensive experimenting, or by looking at the code, you want to contribute, it'd be more than welcome. Please note that 2.4.22 contains some improvements to slapo-rwm cn=config handling; you may want to stick with that release.
p.
masarati@aero.polimi.it wrote:
Ok, fair warning - this is a little long-winded, but I'd rather give too much detail than not enough. Also, all examples are in slapd.conf format, since there is no documentation for cn=config, and I'm using slapd with -f and -F to make the conversion.
Anyways, I'm working on implementing some rewrite rules with slapo-rwm, using back-relay (or possibly back-meta if that doesn't work out) as the backend on top of which slapo-rwm will sit, to make available some features that would be otherwise not be present with back-ldap, or in the absence of a proxy backend altogether.
In its most basic form, the slapo-rwm overlay can be used without a proxy or relay backend, but the feature I'm after appears to require either the slapd-meta backend or the slapd-relay backend. For now, I've chosen to try with slapd-relay, as my research has indicated it supports the feature I'm after. For reference, this feature I desire is the 'searchResult' rewriteContext, as I'm interested in rewriting dynamic group membership DN's (i.e., the 'member' attribute, as defined in rfc2307bis) as plain uid's, so clients that only know about rfc2307 (and thus, look only for entries of the same format as memberUid and fail to perform any mappings to translate membership DN's to UID's) can make use of the dynamic groups I've created in my directory.
Since my slapd-hdb database's rootDSE is dc=example,dc=com, I really couldn't find any way to get around using a virtual naming context; creating a back-meta database on the same host with the same suffix as the back-hdb database seemed ambiguous at best (in terms of how to ensure that clients would always speak to the back-meta db first), and using the suffix "dc=com" seemed inappropriate, as did creating several relay databases, one for each of the entries below the slapd-hdb database's rootDSE (e.g., ou=Users,dc=example,dc=com, ou=Groups,dc=example,dc=com, etc.). Creating several relay databases in that fashion presents other problems as well, and wouldn't do me any good for clients which query for entries using dc=example,dc=com as their search base.
Given that, and the fact that I'm only looking to remap/rewrite data going to and from a single local database with a single naming context, I decided it was a better idea to create a single back-relay database with a bogus "proxy" naming context and use a suffixmassage to rewrite it, e.g.:
database relay suffix "dc=example-proxy,dc=com" relay "dc=example,dc=com"
overlay rwm rwm-rewriteEngine on rwm-suffixmassage "dc=example-proxy,dc=com" "dc=example,dc=com" rwm-rewriteContext searchResult rwm-rewriteRule "^uid=([^,]+?),ou=Users,dc=example,dc=com$" "$1"
The result of this mapping does not yield a valid DN; as such, this rewriting is incorrect. Also, I don't see how it could be useful, as LDAP clients usually expect DNs to be DN-valued.
In this case, dscl (Mac OS X's directory services client) expects a UID, not a DN, as is the POSIX standard for group members, and doesn't know how to parse usernames in groups that use DN's to identify their members. Instead, they expect UID's, and since there appears to be no way to do this client side with dscl (believe me, I did try to find one before resorting to this), I have constructed the above rewriteRule to do this for them. This should not impact my Linux clients either, as nslcd (a daemon created in a fork of nss_ldap by Arthur de Jong) only performs DN-to-UID translations if the group members are represented as DN-valued attribute values. My question wasn't whether or not the result is a valid DN - it's whether or not it would actually work, functionally speaking. Is that the case, regardless of how ugly or undesirable it might be?
For reference, here is the back-meta database configuration I was going to use before I discovered that back-relay supported the searchResult rewriteContext:
database meta suffix "dc=example-proxy,dc=com"
overlay rwm rwm-rewriteEngine on uri "ldap://localhost/dc=example-proxy,dc=com" rwm-suffixmassage "dc=example-proxy,dc=com" "dc=example,dc=com" rwm-rewriteContext searchResult rwm-rewriteRule "^uid=([^,]+?),ou=Users,dc=example,dc=com$" "$1"
In either case, I have a few questions going forward from this point:
- Is it legal to rewrite the search result DN's as described in the
example above? I'm hoping that since the data being manipulated is going from server -> client and is not being stored in the directory, the attributes I'm rewriting would not be subjected to the syntax requirements of the entry that holds them.
- Are there any benefits or drawbacks to using a rewriteMap to accomplish
this task? In my mind, it just seems like another means to the same end, at least based on the following configuration I came up with:
rwm-rewriteMap ldap dn2uid "ldap://localhost/ou=Users,dc=example,dc=com?uid?sub" rwm-rewriteContext searchResult rwm-rewriteRule "^uid=([^,]+?),ou=Users,dc=example,dc=com$" "${dn2uid($1)}"
Same as above. You're performing an internal search to obtain information you already have, and cast it in invalid form.
If there was any other way at all to do this, I would, believe me. But, OS X's LDAPv3 plugin for dscl simply does not know how to utilize DN-valued group members, and provides no way to customize the way search results are parsed. So again, I understand that the information is not a valid DN, but again, if functionally speaking this works, then that's what I'll have to do to leverage my rfc2307bis-style dynamic groups on OS X.
- Is there a better way to go about doing this that I've failed to see or
consider?
Consider why you need it: broken client? Fix the client. Anything else? Perhaps LDAP is not what you need; in any case, move such mangling into the client.
LDAP is what I need, and unfortunately, "fixing the client" (as in hacking and recompiling dscl's LDAPv3 plugin) would potentially invalidate a warranty of service and support.
- Considering the slapd-meta man page, which mentions that some of its
features could potentially result in excessive overhead for some installations, are the features used in the aforementioned configuration(s) efficient enough to scale well in a very busy environment? I'm aware that's a pretty vague and loaded question with lots of variables, so I'm just looking for an educated opinion from a 10,000 foot view, assuming excellent hardware, high network capacity, and heavy - say, 5k, 10k, 15k queries per second - traffic. Performance will obviously be tested before implementing this, but it'd still be nice to have a rough idea of what to expect going in.
Pure rewriting may not impact too much; rewriteMaps that rewuire further internal lookups may yield significant overhead. Of course, if you setup things like ACL checking that involves significant internal searches on a database that makes extensive use of rewriting, things can get even worse.
Great, thanks so much for that assessment, Pierangelo.
Lastly, on a somewhat tangential note, given that there's no documentation with respect to cn=config for setting up slapo-rwm (or doing it in conjunction with a proxy backend), is there any way to discover the cn=config attributes and objectclasses for those backend and overlays that's better or more efficient than creating a standard slapd.conf configuration and converting it with slapd using -f and -F? Perhaps an official or unofficial bit of documentation floating around out there other than a few miscellaneous postings on the mailing lists and some ITS contents? On a similar note in the same vein, as far as I can tell, none of the man pages, admin guide sections, or FAQ-O-Matic entries on slapd-relay mention which rewrite contexts are available with it, and I didn't realize that slapd-relay accepted the searchResult rewrite context until I read the servers/slapd/back-relay/README file (while searching for code that might reveal slapo-rwm's cn=config attribute equivalents). Would it be objectionable to update these reference points with said information? I'd be happy to file an ITS and submit patches and/or content for updating the documentation, if Gavin is too busy, unavailable, or would like some help.
None that I'm aware of. The FAQ is interactive; if by extensive experimenting, or by looking at the code, you want to contribute, it'd be more than welcome. Please note that 2.4.22 contains some improvements to slapo-rwm cn=config handling; you may want to stick with that release.
p.
Duly noted, and thanks again for your advice here, and any future advice on this topic.
Respectfully, Ryan
masarati@aero.polimi.it wrote:
Ok, fair warning - this is a little long-winded, but I'd rather give too much detail than not enough. Also, all examples are in slapd.conf format, since there is no documentation for cn=config, and I'm using slapd with -f and -F to make the conversion.
Anyways, I'm working on implementing some rewrite rules with slapo-rwm, using back-relay (or possibly back-meta if that doesn't work out) as the backend on top of which slapo-rwm will sit, to make available some features that would be otherwise not be present with back-ldap, or in the absence of a proxy backend altogether.
In its most basic form, the slapo-rwm overlay can be used without a proxy or relay backend, but the feature I'm after appears to require either the slapd-meta backend or the slapd-relay backend. For now, I've chosen to try with slapd-relay, as my research has indicated it supports the feature I'm after. For reference, this feature I desire is the 'searchResult' rewriteContext, as I'm interested in rewriting dynamic group membership DN's (i.e., the 'member' attribute, as defined in rfc2307bis) as plain uid's, so clients that only know about rfc2307 (and thus, look only for entries of the same format as memberUid and fail to perform any mappings to translate membership DN's to UID's) can make use of the dynamic groups I've created in my directory.
Since my slapd-hdb database's rootDSE is dc=example,dc=com, I really couldn't find any way to get around using a virtual naming context; creating a back-meta database on the same host with the same suffix as the back-hdb database seemed ambiguous at best (in terms of how to ensure that clients would always speak to the back-meta db first), and using the suffix "dc=com" seemed inappropriate, as did creating several relay databases, one for each of the entries below the slapd-hdb database's rootDSE (e.g., ou=Users,dc=example,dc=com, ou=Groups,dc=example,dc=com, etc.). Creating several relay databases in that fashion presents other problems as well, and wouldn't do me any good for clients which query for entries using dc=example,dc=com as their search base.
Given that, and the fact that I'm only looking to remap/rewrite data going to and from a single local database with a single naming context, I decided it was a better idea to create a single back-relay database with a bogus "proxy" naming context and use a suffixmassage to rewrite it, e.g.:
database relay suffix "dc=example-proxy,dc=com" relay "dc=example,dc=com"
overlay rwm rwm-rewriteEngine on rwm-suffixmassage "dc=example-proxy,dc=com" "dc=example,dc=com" rwm-rewriteContext searchResult rwm-rewriteRule "^uid=([^,]+?),ou=Users,dc=example,dc=com$" "$1"
The result of this mapping does not yield a valid DN; as such, this rewriting is incorrect. Also, I don't see how it could be useful, as LDAP clients usually expect DNs to be DN-valued.
In this case, dscl (Mac OS X's directory services client) expects a UID, not a DN, as is the POSIX standard for group members, and doesn't know how to parse usernames in groups that use DN's to identify their members. Instead, they expect UID's, and since there appears to be no way to do this client side with dscl (believe me, I did try to find one before resorting to this), I have constructed the above rewriteRule to do this for them. This should not impact my Linux clients either, as nslcd (a daemon created in a fork of nss_ldap by Arthur de Jong) only performs DN-to-UID translations if the group members are represented as DN-valued attribute values. My question wasn't whether or not the result is a valid DN - it's whether or not it would actually work, functionally speaking. Is that the case, regardless of how ugly or undesirable it might be?
You seem to be confusing LDAP groups (groupOfNames objectClass, member attribute) with POSIX groups (posixGroup objectClass, memberUid attribute). This has been sorted out long ago. Use the right object for each application. The rest of the discussion, at this point, seems moot.
p.
For reference, here is the back-meta database configuration I was going to use before I discovered that back-relay supported the searchResult rewriteContext:
database meta suffix "dc=example-proxy,dc=com"
overlay rwm rwm-rewriteEngine on uri "ldap://localhost/dc=example-proxy,dc=com" rwm-suffixmassage "dc=example-proxy,dc=com" "dc=example,dc=com" rwm-rewriteContext searchResult rwm-rewriteRule "^uid=([^,]+?),ou=Users,dc=example,dc=com$" "$1"
In either case, I have a few questions going forward from this point:
- Is it legal to rewrite the search result DN's as described in the
example above? I'm hoping that since the data being manipulated is going from server -> client and is not being stored in the directory, the attributes I'm rewriting would not be subjected to the syntax requirements of the entry that holds them.
- Are there any benefits or drawbacks to using a rewriteMap to
accomplish this task? In my mind, it just seems like another means to the same end, at least based on the following configuration I came up with:
rwm-rewriteMap ldap dn2uid "ldap://localhost/ou=Users,dc=example,dc=com?uid?sub" rwm-rewriteContext searchResult rwm-rewriteRule "^uid=([^,]+?),ou=Users,dc=example,dc=com$" "${dn2uid($1)}"
Same as above. You're performing an internal search to obtain information you already have, and cast it in invalid form.
If there was any other way at all to do this, I would, believe me. But, OS X's LDAPv3 plugin for dscl simply does not know how to utilize DN-valued group members, and provides no way to customize the way search results are parsed. So again, I understand that the information is not a valid DN, but again, if functionally speaking this works, then that's what I'll have to do to leverage my rfc2307bis-style dynamic groups on OS X.
- Is there a better way to go about doing this that I've failed to see
or consider?
Consider why you need it: broken client? Fix the client. Anything else? Perhaps LDAP is not what you need; in any case, move such mangling into the client.
LDAP is what I need, and unfortunately, "fixing the client" (as in hacking and recompiling dscl's LDAPv3 plugin) would potentially invalidate a warranty of service and support.
- Considering the slapd-meta man page, which mentions that some of its
features could potentially result in excessive overhead for some installations, are the features used in the aforementioned configuration(s) efficient enough to scale well in a very busy environment? I'm aware that's a pretty vague and loaded question with lots of variables, so I'm just looking for an educated opinion from a 10,000 foot view, assuming excellent hardware, high network capacity, and heavy - say, 5k, 10k, 15k queries per second - traffic. Performance will obviously be tested before implementing this, but it'd still be nice to have a rough idea of what to expect going in.
Pure rewriting may not impact too much; rewriteMaps that rewuire further internal lookups may yield significant overhead. Of course, if you setup things like ACL checking that involves significant internal searches on a database that makes extensive use of rewriting, things can get even worse.
Great, thanks so much for that assessment, Pierangelo.
Lastly, on a somewhat tangential note, given that there's no documentation with respect to cn=config for setting up slapo-rwm (or doing it in conjunction with a proxy backend), is there any way to discover the cn=config attributes and objectclasses for those backend and overlays that's better or more efficient than creating a standard slapd.conf configuration and converting it with slapd using -f and -F? Perhaps an official or unofficial bit of documentation floating around out there other than a few miscellaneous postings on the mailing lists and some ITS contents? On a similar note in the same vein, as far as I can tell, none of the man pages, admin guide sections, or FAQ-O-Matic entries on slapd-relay mention which rewrite contexts are available with it, and I didn't realize that slapd-relay accepted the searchResult rewrite context until I read the servers/slapd/back-relay/README file (while searching for code that might reveal slapo-rwm's cn=config attribute equivalents). Would it be objectionable to update these reference points with said information? I'd be happy to file an ITS and submit patches and/or content for updating the documentation, if Gavin is too busy, unavailable, or would like some help.
None that I'm aware of. The FAQ is interactive; if by extensive experimenting, or by looking at the code, you want to contribute, it'd be more than welcome. Please note that 2.4.22 contains some improvements to slapo-rwm cn=config handling; you may want to stick with that release.
p.
Duly noted, and thanks again for your advice here, and any future advice on this topic.
Respectfully, Ryan
masarati@aero.polimi.it wrote:
masarati@aero.polimi.it wrote:
In this case, dscl (Mac OS X's directory services client) expects a UID, not a DN, as is the POSIX standard for group members, and doesn't know how to parse usernames in groups that use DN's to identify their members. Instead, they expect UID's, and since there appears to be no way to do this client side with dscl (believe me, I did try to find one before resorting to this), I have constructed the above rewriteRule to do this for them. This should not impact my Linux clients either, as nslcd (a daemon created in a fork of nss_ldap by Arthur de Jong) only performs DN-to-UID translations if the group members are represented as DN-valued attribute values. My question wasn't whether or not the result is a valid DN - it's whether or not it would actually work, functionally speaking. Is that the case, regardless of how ugly or undesirable it might be?
You seem to be confusing LDAP groups (groupOfNames objectClass, member attribute) with POSIX groups (posixGroup objectClass, memberUid attribute). This has been sorted out long ago. Use the right object for each application. The rest of the discussion, at this point, seems moot.
p.
No, I know the difference. What I'm saying is that the OS X clients aren't translating DN-valued LDAP group membership attributes to UID-valued POSIX group memberships. On Linux, this is done with nss_ldap/nss_ldapd/nslcd by either:
a) parsing the group membership attributes, which are listed as DN's, and returning just the portion between the 'uid=' and the next comma (e.g., if the DN was 'uid=jdoe,ou=Users,dc=example,dc=org', nslcd would translate that to 'jdoe', for use as a POSIX group member), or
b) issuing a second lookup to map the UID corresponding to that particular DN (kind of the way slapo-rwm can if configured to).
In other words, I'm what I'm proposing to do is exactly what nss_ldapd/nslcd does, only in a proxy database on the server side in the server's response to the client, instead of on the client side of that response.
The *only* reason I'm doing this is because it's not being done on OS X machines by Directory Service's LDAPv3 plugin (the equivalent to Linux's nss_ldap plugin for NSS), and I cannot change the way the LDAPv3 plugin works by hacking its code, as doing so could void the warranty and support and all that other proprietary nonsense. So my only choice is to do it in the response on the server side, instead of in the response on the client side.
And, since this is going to be done by means of a virtual naming context with slapd-meta and slapo-rwm, only the OS X clients will be using that virtual naming context. Everybody else, who does it properly on the client side, will use the real naming context. The main reason for the OP was to verify whether or not the implementation I proposed would actually *work*, regardless of whether or not it was advisable from a policy standpoint. If by "invalid", you mean "will not work" (and not "it is not advisable to do so"), then that is fine and I'll find some other way around this problem (somehow...) - so if you wouldn't mind clarifying your response, I would be appreciative.
Respectfully, Ryan
masarati@aero.polimi.it wrote:
masarati@aero.polimi.it wrote:
In this case, dscl (Mac OS X's directory services client) expects a UID, not a DN, as is the POSIX standard for group members, and doesn't know how to parse usernames in groups that use DN's to identify their members. Instead, they expect UID's, and since there appears to be no way to do this client side with dscl (believe me, I did try to find one before resorting to this), I have constructed the above rewriteRule to do this for them. This should not impact my Linux clients either, as nslcd (a daemon created in a fork of nss_ldap by Arthur de Jong) only performs DN-to-UID translations if the group members are represented as DN-valued attribute values. My question wasn't whether or not the result is a valid DN - it's whether or not it would actually work, functionally speaking. Is that the case, regardless of how ugly or undesirable it might be?
You seem to be confusing LDAP groups (groupOfNames objectClass, member attribute) with POSIX groups (posixGroup objectClass, memberUid attribute). This has been sorted out long ago. Use the right object for each application. The rest of the discussion, at this point, seems moot.
p.
No, I know the difference. What I'm saying is that the OS X clients aren't translating DN-valued LDAP group membership attributes to UID-valued POSIX group memberships. On Linux, this is done with nss_ldap/nss_ldapd/nslcd by either:
a) parsing the group membership attributes, which are listed as DN's, and returning just the portion between the 'uid=' and the next comma (e.g., if the DN was 'uid=jdoe,ou=Users,dc=example,dc=org', nslcd would translate that to 'jdoe', for use as a POSIX group member), or
b) issuing a second lookup to map the UID corresponding to that particular DN (kind of the way slapo-rwm can if configured to).
In other words, I'm what I'm proposing to do is exactly what nss_ldapd/nslcd does, only in a proxy database on the server side in the server's response to the client, instead of on the client side of that response.
The *only* reason I'm doing this is because it's not being done on OS X machines by Directory Service's LDAPv3 plugin (the equivalent to Linux's nss_ldap plugin for NSS), and I cannot change the way the LDAPv3 plugin works by hacking its code, as doing so could void the warranty and support and all that other proprietary nonsense. So my only choice is to do it in the response on the server side, instead of in the response on the client side.
And, since this is going to be done by means of a virtual naming context with slapd-meta and slapo-rwm, only the OS X clients will be using that virtual naming context. Everybody else, who does it properly on the client side, will use the real naming context. The main reason for the OP was to verify whether or not the implementation I proposed would actually *work*, regardless of whether or not it was advisable from a policy standpoint. If by "invalid", you mean "will not work" (and not "it is not advisable to do so"), then that is fine and I'll find some other way around this problem (somehow...) - so if you wouldn't mind clarifying your response, I would be appreciative.
Well, perhaps you should then have a look at slapo-nssov (contrib/slapd-modules/nssov/); someone else on this list may give you better support than I could in setting it up appropriately.
p.
masarati@aero.polimi.it wrote:
masarati@aero.polimi.it wrote:
masarati@aero.polimi.it wrote:
No, I know the difference. What I'm saying is that the OS X clients aren't translating DN-valued LDAP group membership attributes to UID-valued POSIX group memberships. On Linux, this is done with nss_ldap/nss_ldapd/nslcd by either:
a) parsing the group membership attributes, which are listed as DN's, and returning just the portion between the 'uid=' and the next comma (e.g., if the DN was 'uid=jdoe,ou=Users,dc=example,dc=org', nslcd would translate that to 'jdoe', for use as a POSIX group member), or
b) issuing a second lookup to map the UID corresponding to that particular DN (kind of the way slapo-rwm can if configured to).
In other words, I'm what I'm proposing to do is exactly what nss_ldapd/nslcd does, only in a proxy database on the server side in the server's response to the client, instead of on the client side of that response.
The *only* reason I'm doing this is because it's not being done on OS X machines by Directory Service's LDAPv3 plugin (the equivalent to Linux's nss_ldap plugin for NSS), and I cannot change the way the LDAPv3 plugin works by hacking its code, as doing so could void the warranty and support and all that other proprietary nonsense. So my only choice is to do it in the response on the server side, instead of in the response on the client side.
And, since this is going to be done by means of a virtual naming context with slapd-meta and slapo-rwm, only the OS X clients will be using that virtual naming context. Everybody else, who does it properly on the client side, will use the real naming context. The main reason for the OP was to verify whether or not the implementation I proposed would actually *work*, regardless of whether or not it was advisable from a policy standpoint. If by "invalid", you mean "will not work" (and not "it is not advisable to do so"), then that is fine and I'll find some other way around this problem (somehow...) - so if you wouldn't mind clarifying your response, I would be appreciative.
Well, perhaps you should then have a look at slapo-nssov (contrib/slapd-modules/nssov/); someone else on this list may give you better support than I could in setting it up appropriately.
p.
No; nssov is irrelevant here - that would only work for Linux clients, and they're the ones who perform the DN-to-UID translations appropriately. I know that this isn't just an issue for me; O'Reilly have even made passing references in their books about the fact that Apple's LDAPv3 Directory Services plugin does not handle DN-valued group memberships appropriately (third paragraph from the bottom): http://macdevcenter.com/pub/a/mac/2003/08/26/active_directory.html?page=2
That was 7 years ago, and they still haven't fixed it. Wonder what the odds are that they'll have a change of heart? :P
Thanks anyways, though, for taking a gander at this. I'm going to try and implement the workaround I mentioned above for those OS X hosts, as a stopgap (hopefully a stopgap and not permanent, anyways...) until and if Apple updates the plugin to allow DN-valued group memberships, as they do for Active Directory. Hopefully it works. I wish I could say that I find it ironic that they would get it right with AD and not with *nix, but I digress...
Respectfully, Ryan
masarati@aero.polimi.it wrote:
masarati@aero.polimi.it wrote:
masarati@aero.polimi.it wrote:
No, I know the difference. What I'm saying is that the OS X clients aren't translating DN-valued LDAP group membership attributes to UID-valued POSIX group memberships. On Linux, this is done with nss_ldap/nss_ldapd/nslcd by either:
a) parsing the group membership attributes, which are listed as DN's, and returning just the portion between the 'uid=' and the next comma (e.g., if the DN was 'uid=jdoe,ou=Users,dc=example,dc=org', nslcd would translate that to 'jdoe', for use as a POSIX group member), or
b) issuing a second lookup to map the UID corresponding to that particular DN (kind of the way slapo-rwm can if configured to).
In other words, I'm what I'm proposing to do is exactly what nss_ldapd/nslcd does, only in a proxy database on the server side in the server's response to the client, instead of on the client side of that response.
The *only* reason I'm doing this is because it's not being done on OS X machines by Directory Service's LDAPv3 plugin (the equivalent to Linux's nss_ldap plugin for NSS), and I cannot change the way the LDAPv3 plugin works by hacking its code, as doing so could void the warranty and support and all that other proprietary nonsense. So my only choice is to do it in the response on the server side, instead of in the response on the client side.
And, since this is going to be done by means of a virtual naming context with slapd-meta and slapo-rwm, only the OS X clients will be using that virtual naming context. Everybody else, who does it properly on the client side, will use the real naming context. The main reason for the OP was to verify whether or not the implementation I proposed would actually *work*, regardless of whether or not it was advisable from a policy standpoint. If by "invalid", you mean "will not work" (and not "it is not advisable to do so"), then that is fine and I'll find some other way around this problem (somehow...) - so if you wouldn't mind clarifying your response, I would be appreciative.
Well, perhaps you should then have a look at slapo-nssov (contrib/slapd-modules/nssov/); someone else on this list may give you better support than I could in setting it up appropriately.
p.
No; nssov is irrelevant here - that would only work for Linux clients, and they're the ones who perform the DN-to-UID translations appropriately. I know that this isn't just an issue for me; O'Reilly have even made passing references in their books about the fact that Apple's LDAPv3 Directory Services plugin does not handle DN-valued group memberships appropriately (third paragraph from the bottom): http://macdevcenter.com/pub/a/mac/2003/08/26/active_directory.html?page=2
That was 7 years ago, and they still haven't fixed it. Wonder what the odds are that they'll have a change of heart? :P
Thanks anyways, though, for taking a gander at this. I'm going to try and implement the workaround I mentioned above for those OS X hosts, as a stopgap (hopefully a stopgap and not permanent, anyways...) until and if Apple updates the plugin to allow DN-valued group memberships, as they do for Active Directory. Hopefully it works. I wish I could say that I find it ironic that they would get it right with AD and not with *nix, but I digress...
Slapo-rwm (and back-meta, which mimics it) by design only rewrite DN-valued attrs, and only rewrite them to DN values. This is for two reasons:
1) DN-rewriting makes sense in distributed directories, virtual views and so on
2) otherwise, people would abuse it, opening too many cans of worms, or would use it, like in your case, to workaround broken clients, thus allowing those clients to live forever shifting to the DSA all the burden of working around their issues.
In any case, hacking slapo-rwm for your purpose shouldn't be very difficult: you should simply hack where, after rewriting, the syntax of the rewritten attrs is checked. In the case of searchResult this occurs in rwm_dnattr_result_rewrite() by calling rwm_dn_massage_pretty_normalize(). You can replace that call simply by rwm_dn_massage() (with some memory bookkeeping, possibly).
If you succeed, please do not submit patches, as they'll likely be rejected. The "right" way to solve the issue would be to design a "slapo-apple" overlay that hides all the hacks required by that client.
p.
masarati@aero.polimi.it wrote:
masarati@aero.polimi.it wrote:
No; nssov is irrelevant here - that would only work for Linux clients, and they're the ones who perform the DN-to-UID translations appropriately. I know that this isn't just an issue for me; O'Reilly have even made passing references in their books about the fact that Apple's LDAPv3 Directory Services plugin does not handle DN-valued group memberships appropriately (third paragraph from the bottom): http://macdevcenter.com/pub/a/mac/2003/08/26/active_directory.html?page=2
That was 7 years ago, and they still haven't fixed it. Wonder what the odds are that they'll have a change of heart? :P
Thanks anyways, though, for taking a gander at this. I'm going to try and implement the workaround I mentioned above for those OS X hosts, as a stopgap (hopefully a stopgap and not permanent, anyways...) until and if Apple updates the plugin to allow DN-valued group memberships, as they do for Active Directory. Hopefully it works. I wish I could say that I find it ironic that they would get it right with AD and not with *nix, but I digress...
Slapo-rwm (and back-meta, which mimics it) by design only rewrite DN-valued attrs, and only rewrite them to DN values.
Bummer for me.
This is for two reasons:
- DN-rewriting makes sense in distributed directories, virtual views and
so on
Agreed; I saw a lot of other practical uses for it during my research.
- otherwise, people would abuse it, opening too many cans of worms, or
would use it, like in your case, to workaround broken clients, thus allowing those clients to live forever shifting to the DSA all the burden of working around their issues.
Agreed here as well. I can completely understand the justifications.
In any case, hacking slapo-rwm for your purpose shouldn't be very difficult: you should simply hack where, after rewriting, the syntax of the rewritten attrs is checked. In the case of searchResult this occurs in rwm_dnattr_result_rewrite() by calling rwm_dn_massage_pretty_normalize(). You can replace that call simply by rwm_dn_massage() (with some memory bookkeeping, possibly).
I may give this a shot, thanks for the tip.
If you succeed, please do not submit patches, as they'll likely be rejected. The "right" way to solve the issue would be to design a "slapo-apple" overlay that hides all the hacks required by that client.
p.
I think this is a good idea, given the speed with which Apple usually addresses things like this. But it will probably have to wait until I've had a chance to resolve some other outstanding issues, such as ITS#6540, before I can take the time to write an overlay from scratch.
Again, many thanks for the advice.
Respectfully, Ryan
openldap-software@openldap.org
-
masarati＠aero.polimi.it -
Ryan Steele