Blind SQL Injection in Gogs label search
========================================
Researcher: Timo Schmid <tschmid@ernw.de>


Description
===========
Gogs(Go Git Service) is a painless self-hosted Git Service written in Go. (taken
 from [1])

It is very similiar to the github hosting plattform. Multiple users can create
multiple repositories and share code with others with the git version control
system. Repositories can be marked as public or private to prevent access from
 unauthorized users.

Gogs provides a view to filter issues by labels. This view is accessible at
/<username>/<repository>/issues?labels=&type=&state=

The labels Parameter of this view is vulnerable to a blind SQL injection.


Exploitation Technique:
=======================
Remote


Severity Level:
===============
Critical


CVSS Base Score
===============
6.6 (AV:N / AC:H / Au:N / C:C / I:P / A:P)


CVE-ID
======
CVE-2014-8681


Impact
======
The vulnerability results at least in a complete compromise of the database.
Depending on the particular database configuration a compromise of the system
is also possible.


Status
======
Fixed by Vendor


Vulnerable Code Section
=======================
models/issue.go:
[...]
// GetIssues returns a list of issues by given conditions.
func GetIssues(uid, rid, pid, mid int64, page int, isClosed bool, labelIds,
sortType string) ([]Issue, error) {
    sess := x.Limit(20, (page-1)*20)

    if rid > 0 {
        sess.Where("repo_id=?", rid).And("is_closed=?", isClosed)
    } else {
        sess.Where("is_closed=?", isClosed)
    }

    if uid > 0 {
        sess.And("assignee_id=?", uid)
    } else if pid > 0 {
        sess.And("poster_id=?", pid)
    }

    if mid > 0 {
        sess.And("milestone_id=?", mid)
    }

    if len(labelIds) > 0 {
        for _, label := range strings.Split(labelIds, ",") {
            sess.And("label_ids like '%$" + label + "|%'")
        }
    }
[...]

The vulnerability exists because of a string concatination in the SQL query with
user supplied data. A attacker is restricted to not use commas in the injection
string as the program splits input at commas.


Proof of Concept
================
Test of version string contains at least 10 characters:
http://www.example.com/user/repos/issues?label=' or char_length(@@version) > 10
and '|%'='&type=all&state=

Returns all issues if true, non if false.

This could be used to extract data with a binary search.


Solution
========
This vulnerability could easily be fixed by using prepared statements:

sess.And("label_ids like ?", "%$" + label + "|%")

Update to Version 0.5.6.1025.

Affected Versions
=================
>= v0.3.1-9-g49dc57e
<= v0.5.6.1024-gf1d8746


Timeline
========
2014-09-25: Developer informed
2014-10-16: Contact of developer regarding fix
2014-10-25: Working together with developer on fix
2014-10-25: Fixed by ensuring datatype of user input
2014-11-14: CVE-ID assigned


Credits
=======
Pascal Turbing <pturbing@ernw.de>
Jiahua (Joe) Chen <u@gogs.io>


References
==========
[1] https://github.com/gogits/gogs
[2] http://gogs.io/
[3] http://www.insinuator.net/2012/05/sql-injection-testing-for-business-purposes-part-1/
[4] http://www.insinuator.net/2012/05/sql-injection-testing-for-business-purposes-part-2/
[5] http://www.insinuator.net/2012/06/sql-injection-testing-for-business-purposes-part-3/
[6] https://www.ernw.de/download/BC-1401.txt


Advisory-ID
===========
BC-1401


Disclaimer
==========
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