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Massive Security Flaws Exposed At Google, eBay, PayPal, Amazon, and Yahoo

Discussion in 'BlackHat Lounge' started by The Scarlet Pimp, Oct 30, 2012.

  1. The Scarlet Pimp

    The Scarlet Pimp Jr. VIP Jr. VIP Premium Member

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    It was a strange e-mail, coming from a job recruiter at Google, asking
    Zachary Harris if he was interested in a position as a site-reliability engineer.

    "You obviously have a passion for Linux and programming," the e-mail
    from the Google recruiter read. "I wanted to see if you are open to
    confidentially exploring opportunities with Google?"

    Harris was intrigued, but skeptical. The e-mail had come to him last
    December completely out of the blue, and as a mathematician, he didn't
    seem the likeliest candidate for the job Google was pitching.

    So he wondered if the e-mail might have been spoofed ? something sent
    from a scammer to appear to come from the search giant. But when Harris examined the e-mail's header information, it all seemed legitimate.

    Then he noticed something strange. Google was using a weak cryptographic key to certify to recipients that its correspondence came from a legitimate Google corporate domain.

    Anyone who cracked the key could use it to impersonate an e-mail sender from Google, including Google founders Sergey Brin and Larry Page.

    The problem lay with the DKIM key (DomainKeys Identified Mail) Google
    used for its google.com e-mails. DKIM involves a cryptographic key that
    domains use to sign e-mail originating from them ? or passing through
    them ? to validate to a recipient that the domain in the header
    information on an e-mail is correct and that the correspondence indeed
    came from the stated domain.

    When e-mail arrives at its destination, the receiving server can look up
    the public key through the sender's DNS records and verify the validity
    of the signature.

    For security reasons, the DKIM standard calls for using keys that are at
    least 1,024 bits in length. But Google was using a 512-bit key ? which
    could be easily cracked with a little cloud-computing help.

    Harris thought there was no way Google would be so careless, so he
    concluded it must be a sly recruiting test to see if job applicants
    would spot the vulnerability.


    Perhaps the recruiter was in on the game; or perhaps it was set up by Google's tech team behind the scenes, with recruiters as unwitting accomplices.

    Harris wasn't interested in the job at Google, but he decided to crack
    the key and send an e-mail to Google founders Brin and Page, as each
    other, just to show them that he was onto their game.

    "I love factoring numbers," Harris says. "So I thought this was fun.
    I really wanted to solve their puzzle and prove I could do it."

    In the e-mail, he plugged his personal website:

    Hey Larry,

    Here's an interesting idea still being developed in its infancy:

    http://www.everythingwiki.net/index.php/What_Zach_wants_regarding_wiki_technology

    or, if the above gives you trouble try this instead:

    http://everythingwiki.sytes.net/index.php/What_Zach_wants_regarding_wiki_technology.

    I think we should look into whether Google could get involved with
    this guy in some way. What do you think?

    -Sergey

    Harris made sure the return path for the e-mails went to his own e-mail
    account, so that Brin and Page could ask him how he'd cracked their
    puzzle. But Harris never got a response from the Google founders.

    Instead, two days later, he noticed that Google's cryptographic key had
    suddenly changed to 2,048 bits. And he got a lot of sudden hits to his
    web site from Google IP addresses.

    Oops! Harris thought. It was a real vulnerability he'd found.

    "I assumed the e-mail got to some influential tech person who
    looked at it and said, ?Wait a second, how is this obviously
    spoofed e-mail getting through?'

    And they apparently figured it out on their own," he says.

    Harris started exploring other sites and noticed the same problem with
    the DKIM keys used by PayPal, Yahoo, Amazon, eBay, Apple, Dell,
    LinkedIn, Twitter, SBCGlobal, US Bank, HP, Match.com and HSBC.

    Send an e-mail as jeff.bezos@accounts.amazon.com? No problem!

    Spoof marissa.meyer@yahoo-inc.com? Piece of cake!

    Spoofing e-mail is one of the methods that attackers use in phishing
    attacks that trick users into opening malicious e-mails that appear to
    be legitimate messages from PayPal, eBay or a bank, in order to trick
    users into disclosing their account login credentials.

    Moreover, some of the most high-profile attacks in recent years --
    against Google, RSA and others -- have used spear-phishing attacks that
    involve targeting specific people at a company by sending them a
    malicious e-mail that appears to come from a trusted colleague or
    source, in order to trick the recipient into visiting a compromised
    website where malware is downloaded to their machine.

    A spoofed e-mail that is actually signed with a company's DKIM key can
    help attackers get their phishing attacks past filters set up to
    detect them.

    Finding the vulnerability in Google's own domain was ironic, since Google makes concerted efforts to block e-mails sent to Gmail users from other spoofed domains.

    A Google spokeswoman told Wired that the company took the problem very seriously and instituted a fix as soon as it became aware of the issue.

    She said the company has revoked the keys for all of its affected
    domains and re-issued new ones that are greater than 1,024 bits.

    Harris found three classes of key lengths used by vulnerable domains ?
    384 bits, 512 bits, and 768 bits.

    "A 384-bit key I can factor on my laptop in 24 hours," he says. "The 512-bit keys I can factor in about 72 hours using Amazon Web Services for $75. And I did do a number of those.

    Then there are the 768-bit keys. Those are not factorable by a normal
    person like me with my resources alone. But the government of Iran
    probably could, or a large group with sufficient computing resources
    could pull it off."

    In addition to Google, he found that eBay, Yahoo, Twitter and
    Amazon
    were all using 512-bit keys.

    PayPal, LinkedIn, US Bank and HSBC were using 768-bit keys.

    "It was good that PayPal and the banks were in the 768 category, but
    still, for domains that are as heavily phished as PayPal, 768 is really
    not okay," Harris says.

    "They really should have been at 1024, and they have heeded the message and said they really should have had stronger keys all along."

    Most of the companies Harris contacted over the last few months have
    fixed their keys, though some are still dragging their feet, he notes.

    After contacting CERT Coordination Center at Carnegie Mellon University
    to report the vulnerability in August, Harris decided to go public to
    warn other domains about the need to check their DKIM keys.

    Michael Orlando, vulnerability analyst with CERT, said his group planned
    to release an announcement about the issue this week to spread the word.

    The fix is an easy one ? companies simply need to generate a new key at
    the stronger length and place it in their DNS records. But they also
    need to remember to revoke their old key, Harris says.

    "As long as the old one is still in the DNS record, even if you're not
    using it, an attacker can still use it," he says.

    Harris thinks the problem is that many companies set their keys once and
    then forget about them, despite advances in cryptographic breakthroughs
    that make their keys obsolete.

    "People who use cryptographic tools need to realize that local
    configurations need to be maintained just like software updates need to
    be maintained." he says.

    "In 1998 it was an academic breakthrough of great concerted effort to
    crack a 512 bit key. Today little old me can do it by myself in 72
    hours on AWS.

    The field of cryptography keeps developing and breaking new ground just like everything else, and you can't just install a private key, or
    select a hash algorithm, and expect it to be good forever."

    But Harris says the problem isn't just with the sender domains; he found
    that receiving domains also created vulnerabilities by accepting DKIM
    keys that were clearly marked as tests.

    In some cases, sender domains had generated test keys when they set up their systems, but never revoked them. Although Harris found keys that were clearly flagged as being test keys, recipient domains that saw these flags accepted the emails as being verified instead of considering them unsigned, as they should have done.

    "So that's a problem on both sides; the senders are having these testing
    keys that they're leaving in DNS records long after the period of
    testing is completed, and then the verifiers are ignoring the testing
    flag." he says.

    Harris isn't a security researcher, and he didn't even know what DKIM
    was before he started investigating the authenticity of the Google email
    he received.

    "The fact that I went into this not knowing what a DKIM header was
    illustrates that somebody with enough technical background can figure
    this out as they go along." he says.
     
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  2. Dagreyon

    Dagreyon Jr. VIP Jr. VIP

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    Great read. Obviously he's very smart....
     
  3. jazzc

    jazzc Moderator Staff Member Moderator Jr. VIP

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    Or a cryptologist ;) j/k indeed you have to be very smart to be a good one :)
     
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  4. IamNRE

    IamNRE Jr. VIP Jr. VIP Premium Member

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    Tl;dr .....
     
  5. acotut

    acotut Elite Member

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    Verry interesting read,thanks for sharing with us!
     
  6. ./v3xr

    ./v3xr Newbie

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    It's about time someone brings these flaws to light; this has been well-known info in the hacking communities for ages... almost as long as they've been employing DKIM!

    Thanks for the share OP, gave my quite the chuckle. :rolleyes:
     
  7. TrevorB

    TrevorB Jr. VIP Jr. VIP Premium Member

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    Find the flaw to get into Googles servers and find the code for ranking sites. lol
     
  8. madoctopus

    madoctopus Supreme Member

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    I'd rather be a gynecologist than a cryptologist... just saying...
    Oh, nice sig banner btw :)

    Nice read. I bet they fluffed the article a bit compared to reality, magazines do that.
     
  9. CosmicSoundz

    CosmicSoundz BANNED BANNED

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    source?
     
  10. ./v3xr

    ./v3xr Newbie

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    From a cryptographic and security standpoint, everything in the article is believable, and I can attest to at least the crappy DKIMs xD
     
  11. 67731

    67731 Regular Member

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    Good read and lucky for them a person wanted to have fun with this info!
     
  12. dubious

    dubious Regular Member

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    The thing about these stories in which some random professor or random cryptologist discovers a security flaw, it is almost a certainty that the vulnerability was discovered by someone of more... diabolic intent several months, perhaps years, earlier. They just don't have the appropriate motivation to actually notify the big boys of said flaws.
     
  13. silentthunder

    silentthunder Jr. VIP Jr. VIP Premium Member

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    Reads like a mystery very near this life!