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My question is inspired by apples goto fail; bug.

I am wondering if the bug is really as dangerous as it is propagated everywhere. The reason I am in doubt about that is that there is a MITM attack required to abuse the bug, isn't it? And if this is the case then the only point this becomes dangerous is in public WIFI's or hotspots or anything like this. Or I understand this wrong and there are possibilities to be MITM-attacked from outside, that means in between two ISP routers for for instance?

Don't get me wrong, of course I know this is very dangerous, but is it still dangerous if I am only connected to the Internet through my private LAN?

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Yes it can be. Since i do not use MAC or i-Phone or anything i'm not sure about how it is exploited but i'm sure you don't have to be a coding genius to understand this code So here's the Apple bug:

static OSStatus
SSLVerifySignedServerKeyExchange(SSLContext *ctx, bool isRsa, SSLBuffer signedParams,
                                 uint8_t *signature, UInt16 signatureLen)
{
    OSStatus        err;
    ...

    if ((err = SSLHashSHA1.update(&hashCtx, &serverRandom)) != 0)
        goto fail;
    if ((err = SSLHashSHA1.update(&hashCtx, &signedParams)) != 0)
        goto fail;
        goto fail;
    if ((err = SSLHashSHA1.final(&hashCtx, &hashOut)) != 0)
        goto fail;
    ...

fail:
    SSLFreeBuffer(&signedHashes);
    SSLFreeBuffer(&hashCtx);
    return err;
}

Source: So it is a mistake by not commenting the second goto fail; so this can be a really dangerous loophole if you are on an open network (It lets you make a secure connection to an IP without considering the signature) . Not much danger in private LAN if you trust the others in the network.

  • Thanks, I am aware of the code's vulnerability. But there is no chance to bypass or corrupt any data by being a Man in the middle anywhere in the routing path, right? Well, this is rather a question about Man in the middle than about goto error;. – exilit Mar 4 '14 at 13:04
  • If an attacker installed the certificate without the public key on their own server and then hijacked the global DNS to point the domain to their own server, would an attack be theoretically possible? – SilverlightFox Mar 5 '14 at 9:28

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