PostgreSQL 10 Installer For Windows DLL Hijacking
Posted on 11 October 2017
Hi @ll, the executable installers of PostgreSQL 10 for Windows, 1. PostgreSQL-10.0-1-win64-bigsql.exe, available from <https://www.openscg.com/bigsql/postgresql/installers.jsp/> via <https://www.postgresql.org/download/windows/>, 2. postgresql-10.0-1-windows.exe and postgresql-10.0-1-windows-x64.exe, available from <https://www.enterprisedb.com/downloads/postgres-postgresql-downloads#windows> via <https://www.postgresql.org/download/windows/>, are vulnerable and defective: Vulnerabilities ~~~~~~~~~~~~~~~ 1.a) They load (on a fully patched Windows 7) the system DLLs UXTheme.dll, SAMCli.dll, SchedCli.dll, LogonCli.dll and CryptSP.dll from their "application directory" instead Windows' "system directory" %SystemRoot%System32, resulting in arbitrary code execution. For software downloaded with a web browser the "application directory" is typically the user's "Downloads" directory: see <http://seclists.org/fulldisclosure/2015/Nov/101> and <http://seclists.org/fulldisclosure/2015/Dec/86> plus <https://insights.sei.cmu.edu/cert/2008/09/carpet-bombing-and-directory-poisoning.html>, <http://blog.acrossecurity.com/2012/02/downloads-folder-binary-planting.html>, <http://seclists.org/fulldisclosure/2012/Aug/134> and <http://blogs.technet.com/b/srd/archive/2014/05/13/load-library-safely.aspx> Also see <https://cwe.mitre.org/data/definitions/426.html>, <https://cwe.mitre.org/data/definitions/427.html>, <https://capec.mitre.org/data/definitions/471.html> and <https://skanthak.homepage.t-online.de/!execute.html> Thanks to the embedded application manifest which specifies "requireAdministrator" the installers will be started with administrative privileges ("protected" administrators are prompted for consent, unprivileged standard users are prompted for an administrator password), resulting in an escalation of privilege! If (one of) the DLLs named above get(s) planted in the users "Downloads" directory, for example per "drive-by download", this vulnerability becomes a remote code execution WITH escalation of privilege. Proof of concept: ~~~~~~~~~~~~~~~~~ 1. Visit <https://skanthak.homepage.t-online.de/sentinel.html>, download <https://skanthak.homepage.t-online.de/download/SENTINEL.DLL> and save it as UXTheme.dll in your "Downloads" directory, then copy it as SAMCli.dll, SchedCli.dll, LogonCli.dll and CryptSP.dll; 2. Download the executable installers <https://oscg-downloads.s3.amazonaws.com/packages/PostgreSQL-10.0-1-win64-bigsql.exe> <https://get.enterprisedb.com/postgresql/postgresql-10.0-1-windows-x64.exe> <https://get.enterprisedb.com/postgresql/postgresql-10.0-1-windows.exe> and save them in your "Downloads" directory; 3. Start the downloaded installers; notice the message boxes displayed from the "sentinels": PWNED! 1.b) They create about a dozen DLLs with names BR*.TMP (as generated by Windows GetTempFileName() API, see <https://msdn.microsoft.com/en-us/library/aa364991.aspx>) in the user's (unprotected) %TEMP% directory and loads them during execution. See <https://cwe.mitre.org/data/definitions/377.html> and <https://cwe.mitre.org/data/definitions/379.html> for this well-known and well-documented weakness. An unprivileged attacker can modify these DLLs between their creation and loading, for example using the following (trivial) batch script, again resulting in arbitrary code execution with escalation of privilege! --- BITROCK.CMD --- :WAIT If Not Exist "%TEMP%BR????.DLL" Goto :WAIT For %%! In ("%TEMP%BR????.DLL") Do Copy "%USERPROFILE%DownloadsUXTheme.dll" "%%!" --- EOF --- Defects ~~~~~~~ 2.a) they have INVALID PE (section) headers; Microsoft's DUMPBIN.EXE aborts with "access violation" (see below) due to the INVALID section name "/4"! From the PE/COFF specification, available via <https://www.microsoft.com/en-us/download/details.aspx?id=19509> | Offset Size Field Description | 0 8 Name An 8-byte, null-padded UTF-8 encoded string. | If the string is exactly 8 characters long, | there is no terminating null. For longer names, | this field contains a slash (/) that is followed | by an ASCII representation of a decimal number | that is an offset into the string table. | Executable images do not use a string table and do | not support section names longer than 8 characters. | Long names in object files are truncated if they | are emitted to an executable file. 2.b) their IMPORT directory contains 2 IMAGE_IMPORT_DESCRIPTOR entries for msvcrt.dll. It should but have only 1 IMAGE_IMPORT_DESCRIPTOR per DLL! See the PE/COFF specification: | Import Directory Table ... | The import directory table consists of an array of import directory | entries, one entry for each DLL to which the image refers. Mitigations: ~~~~~~~~~~~~ * Don't build executable installers, they are almost always vulnerable! Create native installation packages for the respective OS instead. For Windows these are .MSI or .INF with .CAB. * Don't use executable installers! * stay FAR away from PostgreSQL for Windows! stay tuned Stefan Kanthak Timeline: ~~~~~~~~~ 2017-02-17 vulnerability report sent to security@postgresql.org 2017-02-18 reply from vendor: "the installers are built using Bitrock InstallBuilder which generates the final executable that the user downloads. I have therefore escalated this report to Bitrock's support team, and as soon as they have a solution will initiate a set of update releases for affected packages." 2017-10-05 PostgreSQL releases version 10, again sporting this vulnerability. Obviously both PostgreSQL and BitRock are unwilling, unable or just too incompetent to provide installers without well-known, trivial to detect and trivial to exploit vulnerabilities. 2017-10-09 report published Evidence ~~~~~~~~ C:UsersStefanDownloads>link.exe /dump PostgreSQL-10.0-1-win64-bigsql.exe Microsoft (R) COFF/PE Dumper Version 8.00.50727.762 Copyright (C) Microsoft Corporation. All rights reserved. Dump of file PostgreSQL-10.0-1-win64-bigsql.exe File Type: EXECUTABLE IMAGE LINK : fatal error LNK1000: Internal error during DumpSections Version 8.00.50727.762 ExceptionCode = C0000005 ExceptionFlags = 00000000 ExceptionAddress = 00427362 (00400000) "C:Program Files...LINK.EXE" NumberParameters = 00000002 ExceptionInformation[ 0] = 00000000 ExceptionInformation[ 1] = 00000004
