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PostgreSQL 8.1.4 Released to Plug Injection Hole
alurkar writes to tell us that PostgreSQL released version 8.1.4 today in order to combat a security flaw allowing a SQL injection attack. From the article: "The vulnerability affects PostgreSQL servers exposed to untrusted input, such as input coming from Web forms, in conjunction with multi-byte encodings like (Shift-JIS (SJIS), 8-bit Unicode Transformation Format (UTF-8), 16-bit Unicode Transformation Format (UTF-16), and BIG5. In particular, Berkus says that applications using 'ad-hoc methods to "escape" strings going into the database, such as regexes, or PHP3's addslashes() and magic_quotes' are particularly unsafe. 'Since these bypass database-specific code for safe handling of strings, many such applications will need to be re-written to become secure.'"
If someone wants to try and help me with this problem, let me know, but I had trouble getting mysql to insert (actually doing COPY since it's about 10x faster) anywhere near what I can get with PG8.
I can understand how SJIS and BIG5 are vulnerable.
But in a UTF-8 string, no single byte will match a single quote besides the single quote character (0x27).
It seems to me that simply inserting a backslash before every single quote and backslash in a given string will have the desired effect, and that UTF-8 is not particularly vulnerable to this problem. (quite by design- it was invented by none other than Ken Thompson)
Either that article is misleading somehow, or else the postgres developers are simply putting in some safeguards for common errors in things such as php scripts.
PostgreSQL defaults to SQL-ASCII encoding, which is unaffected by this particular attack. Only clients which connect using a multibyte encoding would be affected.
Actually, this really isn't a vulnerability in the database server itself -- the update just intentionally breaks certain badly written applications in order to protect them from themselves. If PHP's addslashes() ends up creating valid multibyte characters that produce unexpected behavior, that's really PHP's problem -- Postgres is just doing what it's told.
People who don't use prepared queries doesn't deserve any better than having someone to fuck up your database!
Often such are combersome or impossible with dynamic query generation, such as Query-by-Example forms where the terms and sort options depend on user input.
Many "prepared" thingies also depend on positional parameters, which can get messy. Would you like to use and maintain a function with 19 positional parameters? That is what it can feel like.
Further, certain kinds of prepared statements seem to have the same flaw. The PS api may "check" the types, but still passes a string to the database such that if you can find a way past the syntactical type checkers, you can pull off the same thing.
I do wish that most database API's offered a "read-only" mode such that the query being sent to the database is designated read-only. That way the worse a hacker can do is grab table data but not change anything. If you have logins restricted only to necessary tables, then the damage exposure is further limited.
Table-ized A.I.
'He also notes that the addslashes function was deprecated in PHP 4.0 due to security risks, but a "distressing" number of PHP applications continue to use the function.'
How come the php documentation doesn't mention this?