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SQL Server Forum / General / Security / November 2007sa password
Let's say that you create an instance - and I'd be curious of the answers for both 2000 and 2005 - in Mixed Mode. If I remember right, the sa password is stored on disk but is encrypted. Is that encryption really that powerful? Isn't this a huge security risk? Given a few days, couldn't any decent cracker break one password that is decrypted? The password hash is stored on the master database and only sysadmin has access to it. You can use some tools to find out the password but depending on its complexity it can take days or weeks. But you need to have the password hash first. Hope this helps, Ben Nevarez Senior Database Administrator AIG SunAmerica > Let's say that you create an instance - and I'd be curious of the answers for > both 2000 and 2005 - in Mixed Mode. If I remember right, the sa password is > stored on disk but is encrypted. Is that encryption really that powerful? > Isn't this a huge security risk? Given a few days, couldn't any decent > cracker break one password that is decrypted? In addition, in SQL Server 2005 , 'sa' login is disabled by default > The password hash is stored on the master database and only sysadmin has > access to it. [quoted text clipped - 18 lines] >> Isn't this a huge security risk? Given a few days, couldn't any decent >> cracker break one password that is decrypted? Sorry, but what do you mean by password hash?? > The password hash is stored on the master database and only sysadmin has > access to it. [quoted text clipped - 14 lines] > > Isn't this a huge security risk? Given a few days, couldn't any decent > > cracker break one password that is decrypted? Nevermind. I just found this sobering article all about it! http://www.nextgenss.com/papers/cracking-sql-passwords.pdf > Sorry, but what do you mean by password hash?? > [quoted text clipped - 16 lines] > > > Isn't this a huge security risk? Given a few days, couldn't any decent > > > cracker break one password that is decrypted? A hash function converts a variable length input stream (a password in this case) to a fixed length value. The function is sometimes called one-way, which means it should be easy to create the hash but very difficult to determine the input (in this case a password) from the hash. It should be easier to do a brute force search of all passwords to find one that produces the same hash. A good hash function produces very different hashes even if the input is only slightly different, and has few collisions, meaning cases where two inputs produce the same hash value, and produces values that appear random. The SHA algorithm referred to in the article you link produces a 160-bit hash, hence the 40 character hash strings (actually 20 hexidecimal characters). This is better than MD5 which produces a 128-bit hash. A brute force attach of an MD5 hash would require 2^64 operations, which is feasible, but a brute force attach of an SHA hash would require 2^80 operations, which is more difficult. The article you linked is disturbing. Knowing that the second hash is limited to uppercase characters makes a brute force attach much easier. Does anyone know why an upper case version of the password should be saved? Are there any cases where the password is not case sensitive? Note the article only applies to SQL Server 2000.  SignatureRichard Mueller Microsoft MVP Scripting and ADSI Hilltop Lab - http://www.rlmueller.net -- > Nevermind. I just found this sobering article all about it! > [quoted text clipped - 26 lines] >> > > decent >> > > cracker break one password that is decrypted? First I mispelled attack as attach throughout my previous post. I also mispoke a bit. The 2^64 and 2^80 I referred to is the number of trial input strings that must be hashed in order to expect to find any two that match. This is the so called "birthday" attack. This is much easier than finding an input that hashes to one specific hash value. The number of input strings you would expect to have to try is closer to 2^128 and 2^160. Except that the universe of possible passwords is greatly reduced if you know that all characters are uppercase. SignatureRichard Mueller Microsoft MVP Scripting and ADSI Hilltop Lab - http://www.rlmueller.net -- >A hash function converts a variable length input stream (a password in this >case) to a fixed length value. The function is sometimes called one-way, [quoted text clipped - 51 lines] >>> > > decent >>> > > cracker break one password that is decrypted? Guys, Thx for the clarification and the information. > First I mispelled attack as attach throughout my previous post. I also > mispoke a bit. The 2^64 and 2^80 I referred to is the number of trial input [quoted text clipped - 60 lines] > >>> > > decent > >>> > > cracker break one password that is decrypted? The size of this number causes an arithmetic overflow. There must be something interesting in the mechanics if the number to crunch it must be bigger than the system can handle. select POWER(2,128) (over 340 undecillion) That's a big number. It would seem the system would be unable to handle the number internally. Just curious, how big a system would be required to crack the hash, and on what order of magnitude would something like that cost? SignatureRegards, Jamie > First I mispelled attack as attach throughout my previous post. I also > mispoke a bit. The 2^64 and 2^80 I referred to is the number of trial input [quoted text clipped - 60 lines] > >>> > > decent > >>> > > cracker break one password that is decrypted? I have not attempted to crack hashes, although the article linked earlier claims it can be done. My point was not that you must handle numbers of that size, but that in theory it could require that many operations. Actually, that many brute force guesses. Per Bruce Schneier in "Applied Cryptography" (Chapter on "One-Way Hash Functions"): ===== quote ========== Assume that a one-way hash function follows all of the properties listed above and the best way to attack it is by using brute force. It produces an m-bit output. Finding a message that hashes to a give hash value would require hashing 2^m random messages. Finding two messages that hash to the same value would only require hashing 2^(m/2) random messages. A machine that hashes a million messages per second would take 600,000 years to find a second message that matched a given 64-bit hash. The same machine could find a pair of messages that hashed to the same value in about an hour. ===== quote ========== Do the math, it works out. All of this assumes that all messages are equally likely. If we reduce the universe of possible messages to all upper case, this can make an attack easier. The article linked before claims this makes the task possible. However, the SQL Server 2000 hashes are 160-bit. A brute force attach, even if we know the password is all upper case, is not feasible. However, the article linked (now that I read it more carefully) uses a dictionary attack. It assumes a file of possible upper case passwords. My recollection is that passwords can be up to 128 characters. If your password is in the dictionary file you're toast. But with a long enough secure password (letters, numbers, symbols, no words) I doubt it could be cracked in a reasonable time. SignatureRichard Mueller Microsoft MVP Scripting and ADSI Hilltop Lab - http://www.rlmueller.net -- > The size of this number causes an arithmetic overflow. There must be > something interesting in the mechanics if the number to crunch it must be [quoted text clipped - 81 lines] >> >>> > > decent >> >>> > > cracker break one password that is decrypted? Richard and others, SQL Server 2000 uses the second hash to support making the passwords Case Insensitive (by turning them to all uppercase) and checking against that also. Is it needed? No, not in SQL Server 2005, which no longer supports that back-level behaviour. One side effect of an upgrade to SQL Server 2005 is that some SQL Logins will have problems since the users (or some application's proxy account password) did not know the proper capitalization of their passwords. RLF >A hash function converts a variable length input stream (a password in this >case) to a fixed length value. The function is sometimes called one-way, [quoted text clipped - 51 lines] >>> > > decent >>> > > cracker break one password that is decrypted? |
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