I'm trying to secure a login endpoint by attempting to bypass the login that uses LDAP.
It employs a search query of "cn=" + username + ", dc=example, dc=com" with a filter of "(objectClass=*)".
Is an LDAP injection attack possible here with username? Obviously, I will eventually escape all the queries and filters.
LDAP injection attacks can't do anything useful.
In your case, you're injecting the user input into the base DN (also called "search root") of the search. The base DN must be a valid DN (distinguished name). Any attempt at injecting some clever value there will likely result in something that is not a valid DN, and the search will fail (or return nothing). Even if it did result in a valid DN, I assume you are still asking for the user's password, so they'd have to know the password for that account.
But if you want to prevent that, just replace , in the input to \,. That's likely something you should do anyway, since if the account has a comma in the name, it will be escaped like that in the DN. This is an odd way of doing it though. Usually the base DN would always be the same and you would use the search filter to find the right account (i.e. (&(objectClass=user)(cn={whatever})))
If you are injecting user input into the search filter, the end user could change the query, but there is still nothing useful that can be done since the query can only read values. (although you can still protect against that if you want by escaping ( and ) with \28 and \29)
LDAP queries are not like SQL, where an injection attack can end the SELECT statement and begin another statement.
Related
in order to implement a custom sql function named getUserName and getPassword from an input url, im trying to find a way to extract the user name and password from a given url using regex.
the code will be executing on snowflake sql flavor language so my coding tools are limited to sql functions and regex supported by snowflake.
i can find the url scheme and the domain/host, get their indexes and length, and extract as substring every thing in between to get the user name and password, the problem is that it wont work with many edge cases, can you suggest better methods/code execution?
this is an example url:
http://UserName123:P#$$:\/\/0rd#domain.co.uk:34567/3.0.1/file_name.txt?pn1:pv1&pn2:pv2#ref
this is the current regex used to identify the url scheme and domain:
(^[a-z0-9.-]+:\/\/)|((?:#)([a-z0-9.-]+))
this is an sql example of getting the scheme:
SPLIT_PART(REGEXP_SUBSTR(A, '^[a-z0-9.-]+://', 1, 1, 'c'), ':', 0) as split
Username and password in a URL are bad practice. URLs, along with the query string (and thus the passwords) will show up in server log files or it can leak/get stolen another way.
So, redesign is needed and not a solution to this problem.
I hope you find it good to know now instead of after solving the problem.
I understand you can't simply filter on dn, but I have something like this:
dc=lvl3,dc=lvl2,dc=lvl1, and someone could have a dn like this:
CN=Last, First,OU=ou1,OU=retired,OU=ou1,DC=lvl3,DC=lvl2,DC=lvl1.
Is there a way I can filter results for those who do not have 'retired' in any ou?
No. Not as an LDAP filter.
You could of course do a search and then sort on the CLient-side.
Generally organization of "characteristics" of users should be done using Attributes and not by the Directory Structure.
Something like:
employeeType=Active
employeeType=Retired
employeeType=etc
To avoid these conditions.
Maybe, but it depends on the server's LDAP implementation.
There is a filter syntax which allows matching against DN attributes (in addition to entry attributes):
(ou:dn:=Retired)
(Within the LDAP specification this is known as the 'dnAttributes' field, part of the 'extensibleMatch' filter type. See RFC 4511 section 4.5.1.7.7)
Not all directory servers support this. For example, OpenLDAP handles it correctly, but Active Directory (MS AD and Samba) will ignore it, behaving as if you used (ou=Retired) instead.
If your server supports this, then a negative match is simply done by wrapping the filter in (!(...)) as you would normally do.
However, in other cases you should either a) use a custom attribute, or b) perhaps check for membership in a global "Active employees" group or something similar.
I want to retrieve a user DN as stored in the LDAP server, keeping the original characters case. For example, let's assume the DN in my server is "cn=Bob, o=MyOrg". I want to query the server using "cn=bob, o=myorg" and retrieve the original "cn=Bob, o=MyOrg", as a result.
The DirContext.getAttributes(dn) method can return a set of attributes but this does not include the DN itself. On the other hand, DirContext.search() returns a SearchResult that has this information using getNameInNamespace(). Unfortunately, search expressions do not seem to allow search on DN, which is what I have.
I understand that I might achieve this by first retrieving a unique attribute using getAttributes(), and then use this attribute value in search(). But this leads to 2 connections. Plus I need to make sure that I have a unique, not null, attribute I can search() on.
Let me reply to my question with the solution I found.
It involves the search() function, where the name parameter (search context) should be the DN, and the query filter is empty or like (objectClass=*). It then returns one row, corresponding to the DN being searched. The original DN is then available in the SearchResult.
Just do a lookup of the DN. The resulting DirContext should have its getNameInNamespace() in the correct case.
A search will also work but it's less efficient and more code.
I have a series of users and groups. Users' DNs can be added to the group's uniquemember attribute. How can I query LDAP such that I send a user dn and it returns to me the OU of the group that user belongs to?
I am doing this based on the LDAP at ldap.forumsys.com.
See the screenshot below:
Thanks.
What you want is a pretty common equality match filter, for example:
(uniquemember=uid=einstein,dc=example,dc=com)
Note, that the value is not quoted. You only need to escape / replace special characters (e.g. parenthesis). More information about LDAP filter syntax can be found in RFC 4515.
Also keep in mind that LDAP filters are very simple and provide only simple value matching (this can be confusing to people used to SQL and complex queries with joins, subselects, functions, etc.).
When using SQL in conjunction with another language what data must be escaped? I was just reading the question here and it was my understanding that only data from the user must be escaped.
Also must all SQL statements be escaped? e.g. INSERT, UPDATE and SELECT
EVERY type of query in SQL must be properly escaped. And not only "user" data. It's entirely possible to inject YOURSELF if you're not careful.
e.g. in pseudo-code:
$name = sql_get_query("SELECT lastname FROM sometable");
sql_query("INSERT INTO othertable (badguy) VALUES ('$name')");
That data never touched the 'user', it was never submitted by the user, but it's still a vulnerability - consider what happens if the user's last name is O'Brien.
Most programming languages provide code for connecting to databases in a uniform way (for example JDBC in Java and DBI in Perl). These provide automatic techniques for doing any necessary escaping using Prepared Statements.
All SQL queries should be properly sanitized and there are various ways of doing it.
You need to prevent the user from trying to exploit your code using SQL Injection.
Injections can be made in various ways, for example through user input, server variables and cookie modifications.
Given a query like:
"SELECT * FROM tablename WHERE username= <user input> "
If the user input is not escaped, the user could do something like
' or '1'='1
Executing the query with this input will actually make it always true, possibly exposing sensitive data to the attacker. But there are many other, much worse scenarios injection can be used for.
You should take a look at the OWASP SQL Injection Guide. They have a nice overview of how to prevent those situations and various ways of dealing with it.
I also think it largely depends on what you consider 'user data' to be or indeed orignate from. I personally consider user data as data available (even if this is only through exploitations) in the public domain, i.e. can be changed by 'a' user even if it's not 'the' user.
Marc B makes a good point however that in certain circumstances you may dirty your own data, so I guess it's always better to be safer than sorry in regards to sql data.
I would note that in regards to direct user input (i.e. from web forms, etc) you should always have an additional layer server side validation before the data even gets near a sql query.