Speaker 1: Welcome back to the deep Dive. Today we are we're
Speaker 1: not just looking at a technical glitch. We are staring
Speaker 1: into the abyss of one of the most enduring, dangerous,
Speaker 1: and honestly philosophically fascinating concepts in computer security.
Speaker 2: It really is it's the vulnerability that just refuses to die,
Speaker 2: the classic boogeyman.
Speaker 1: We are talking about buffer overflows. And if that term
Speaker 1: makes you think of, I don't know, a plumbing disaster,
Speaker 1: You're not entirely.
Speaker 2: Wrong, not at all. It's just that the pipes are
Speaker 2: memory and the water is malicious coat. And to guide
Speaker 2: us through this, we're digging into a really foundational.
Speaker 1: Text, right the book Buffer Overflow Attacks, Detect, Exploit, Prevent
Speaker 1: by James C. Foster.
Speaker 2: It's a technical book, for sure, but it gets surprisingly
Speaker 2: deep on the why of it all.
Speaker 1: And we're pairing that with a really striking forward by
Speaker 1: Dave Tell, who frames this whole topic in a way
Speaker 1: I just did not expect. It's less like computer science
Speaker 1: and more like a martial art, and.
Speaker 2: That's exactly where we're talking about this. It's so easy
Speaker 2: to dismiss buffer overflows as the you know, old school
Speaker 2: bug from the nineties.
Speaker 1: Yeah, something we should have solved by now.
Speaker 2: But the source material makes this compelling case. If you
Speaker 2: want to understand security, you have to understand the overflow.
Speaker 2: It is the fundamental proof that the software community still
Speaker 2: doesn't fully get how to design secure code.
Speaker 1: That is a heavy statement, proof we don't know how
Speaker 1: to write secure code. It is so our mission today
Speaker 1: is to dig into that. We want to move past
Speaker 1: the buzzwords and really understand the mechanics, the stack, the heap,
Speaker 1: the shell code, and figure out.
Speaker 2: Why on earth writing an exploit is described as a
Speaker 2: statement of truth.
Speaker 1: Okay, but before we get into the you know, truth
Speaker 1: and beauty of it all, let's ground this in reality,
Speaker 1: because when these things go wrong, they go wrong in public.
Speaker 1: And my favorite example from the book involves Madonna.
Speaker 2: Oh, this story is incredible. It's this perfect collision of celebrity,
Speaker 2: copyright and hackers with way too much time on their hands.
Speaker 1: So let's set the scene. It's April two thousand and
Speaker 1: three and napster is gone, but file sharing is just exploding.
Speaker 1: Everyone's on Khaza LimeWire.
Speaker 2: Right, and Madonna is about to release her new album,
Speaker 2: American Life, and she decides no, the parrots are not
Speaker 2: gonna win.
Speaker 1: She's taking a stand, so her team floods these networks
Speaker 1: with decoy files.
Speaker 2: Exactly, you think you're downloading her new single, you wait
Speaker 2: an hour on your dial up modem, I remember that pain,
Speaker 2: and when you finally play it, it's not the song.
Speaker 2: It's just a loop of Madonna's voice saying what the
Speaker 2: fuck do you think you're doing.
Speaker 1: Which honestly is a pretty punk rock move for a
Speaker 1: pop star. What do you think you're doing? It's so direct,
Speaker 1: it is.
Speaker 2: But you just don't poke the internet bear like that
Speaker 2: and expect nothing to happen.
Speaker 1: No, the retaliation was swift.
Speaker 2: A group of hackers, rumored to be the editors of
Speaker 2: Frag magazine, though they denied it, decided to target Madonna
Speaker 2: dot com itself.
Speaker 1: And this wasn't social engineering, right. They didn't just guess
Speaker 1: her pastorng No.
Speaker 2: No, no, this is a pure technical takedown. They found
Speaker 2: a buffer overflow of vulnerability in her web server software.
Speaker 2: They didn't just crash the site, They exploited it, took
Speaker 2: it over, and the defacement was so personal, extremely They
Speaker 2: wiped the site and posted the actual MP three's of
Speaker 2: her new album for free download.
Speaker 1: Basically saying you want to hide it here It is
Speaker 1: for everybody but the kicker.
Speaker 2: The real chef's kiss was the message they left on
Speaker 2: the homepage.
Speaker 1: This is the best part.
Speaker 2: They changed the headline to mimic her decoy file. It
Speaker 2: just read this is what the fuck I think I'm doing.
Speaker 1: That is brutal, such a specific clap back.
Speaker 2: And then, just for good measure, they added a marriage
Speaker 2: proposal to Morgan Webb from tech TV.
Speaker 1: It was just this perfect storm of technical skill and
Speaker 1: internet trolling.
Speaker 2: But the real takeaway for us is the access. This
Speaker 2: wasn't a glitch. This was total control. They owned that machine.
Speaker 1: That distinction is so key. So let's peel back the layers.
Speaker 1: How do you get from sending too much data to
Speaker 1: owning the machine? Let's define the beast. What is actually overflowing?
Speaker 2: Okay, so let's break this down. A buffer is really
Speaker 2: just a fancy name for a container in the computer's memory.
Speaker 2: Think of it like a bucket and ram set aside
Speaker 2: to hold say a username.
Speaker 1: Okay, so a bucket designed to hold ten characters exactly.
Speaker 2: And overflow is just trying to pour one hundred characters
Speaker 2: into that ten character bucket. In the real world, it
Speaker 2: spills on the floor. In computer memory, there is no floor.
Speaker 1: There's no empty space.
Speaker 2: No, everything is packed in right next to everything else.
Speaker 2: When you spill over, you're not spilling onto the floor.
Speaker 2: You're spilling into the next bucket over. You're physically overriding
Speaker 2: whatever data was sitting there.
Speaker 1: And that data could be anything. It could be part
Speaker 1: of a picture, or it could be a critical system instruction.
Speaker 2: Precisely, and this is where the geography of memory really matters.
Speaker 2: The source breaks it down into two main types, stack
Speaker 2: overflows and heap corruption.
Speaker 1: Let's start with the stack. That's the one you always
Speaker 1: hear about movies.
Speaker 2: It is because it's the most common. The stack is
Speaker 2: this very neat organized part of memory for temporary stuff
Speaker 2: like a stack of plates. But buried in that stack
Speaker 2: of plates is something incredibly important called the return address.
Speaker 1: The return address that's the bookmark, right. It tells the
Speaker 1: program where to go back to.
Speaker 2: That's a perfect analogy. When a program runs a little
Speaker 2: side task like check password, it needs to know where
Speaker 2: to return to. When it's done, it writes that location,
Speaker 2: that return address, onto the stack.
Speaker 1: So it's like, okay, I'm going to go do this,
Speaker 1: and when I'm finished. I'll come right back to this
Speaker 1: line of code exactly.
Speaker 2: Now, imagine your buffer, your bucket is sitting right next
Speaker 2: to that return address on the stack. If you pour
Speaker 2: too much data in, you overflow and physically overwrite that bookmark.
Speaker 1: You're erasing their map and drawing your own.
Speaker 2: Yes, you replace the go back to the main program
Speaker 2: instruction with go to this specific address where I've hidden
Speaker 2: my own malicious code. The function finishes. The computer blindly
Speaker 2: follows your new map and executes your code.
Speaker 1: That's the hijack. You've turned the program into your puppet.
Speaker 2: That's it. Now the heap is different. It's messier, more
Speaker 2: dynamic exploiting. It is harder because it's not as predictable,
Speaker 2: but still possible.
Speaker 1: And the book it also mentions format strings. Is that
Speaker 1: the same thing.
Speaker 2: It's related. It comes from lazy programming. If you let
Speaker 2: a user type in special characters like a PRESANX into
Speaker 2: a function that prints text, you can trick it into
Speaker 2: reading from memory or even writing to it. It's a
Speaker 2: different door to the same room.
Speaker 1: Okay, so we've got the mechanism, But I want to
Speaker 1: go back to what Davi Tell said in the forward.
Speaker 1: He talks about this whole process like it's almost spiritual.
Speaker 1: He compares it to judo.
Speaker 2: He does, and it fits so well. In judo, you
Speaker 2: use your opponent's weight against them in a buffer overflow.
Speaker 2: You're not breaking the system from the outside. You are
Speaker 2: using its own software, its own memory, its own rules
Speaker 2: against it. You're flipping the system with its own momentum.
Speaker 1: He also says it's like weightlifting, something you have to
Speaker 1: constantly practice.
Speaker 2: Right. You can't just learn this once. The whole landscape
Speaker 2: is a treadmill. Microsoft adds a protection hackers find a bypass,
Speaker 2: a new protection, a new bypass. ATel says, if you
Speaker 2: stop writing exploits for three months, your skills are basically
Speaker 2: ancient history.
Speaker 1: That's intense. It's not just notledge, it's performance. You have
Speaker 1: to stay fit.
Speaker 2: And that leads to the mindset. He describes never be afraid.
Speaker 2: It sound like a motivational poster, but he means it.
Speaker 2: When you're deep in assembly, code and memory addresses, it's
Speaker 2: easy to get lost. He says, you have to fantasize
Speaker 2: about the success, visualize getting that rootshell to push through.
Speaker 1: I love that quote, and exploit is a complex statement
Speaker 1: of truth.
Speaker 2: What you're saying, is this is possible, and saying it
Speaker 2: truthfully makes it beautiful.
Speaker 1: That completely reframes it. The hacker isn't a vandal, they're
Speaker 1: a realist. They're proving that the code as it exists
Speaker 1: isn't what the developer imagined exactly.
Speaker 2: It's the code as imagined versus the code as it
Speaker 2: actually is. In silicon, the exploit proves the reality.
Speaker 1: So let's get into that truth. We've overslowed the buffer,
Speaker 1: we've hijacked the return address. Now we need to actually
Speaker 1: do something. We need a payload and or shell code.
Speaker 1: This was the part of the book that really just
Speaker 1: blew my mind. Shell code is the actual set of
Speaker 1: instructions you inject.
Speaker 2: Yeah, the goal is usually to launch a shell a
Speaker 2: command prompt so you can take over. But writing shell
Speaker 2: code is like building a ship in a bottle while
Speaker 2: wearing ofnmits. The constraints are just insane, And.
Speaker 1: The biggest one is the addressing problem. Can you break
Speaker 1: that down?
Speaker 2: Sure? So, imagine you're dropped into a forest with a map,
Speaker 2: but you have no idea where you are on that map.
Speaker 2: The shell code is injected into memory, but it doesn't
Speaker 2: know its own address.
Speaker 1: It doesn't know where it lives right, and.
Speaker 2: To run it needs to find its own data, like
Speaker 2: the text string binch to start the command line. But
Speaker 2: how can it point to its own feet if it
Speaker 2: doesn't know where it's standing?
Speaker 1: So how does it find itself?
Speaker 2: There's this brilliant, almost beautiful trick mentioned in the text,
Speaker 2: the jmpcl trick.
Speaker 1: Okay, walk me through it.
Speaker 2: The code starts, the very first instruction is jump. It
Speaker 2: jumps all the way to the very end of its own.
Speaker 1: Code, skips everything, goes to the end.
Speaker 2: At the end is a calible instruction which says go
Speaker 2: back to the beginning.
Speaker 1: Wait, why jump to the end just to call back
Speaker 1: to the start? That sounds pointless.
Speaker 2: It's all about the side effects assembly language. When you
Speaker 2: use the call instruction, the CPU automatically does something helpful.
Speaker 2: It pushes the return address onto the stack.
Speaker 1: Ah. So by calling itself, the code forces the CPU
Speaker 1: to write down I was just here exactly.
Speaker 2: The shell code then just pops that address off the
Speaker 2: stack and boom. It now knows its own location in memory.
Speaker 2: It located itself by using the CPU's own bookmarking system
Speaker 2: against it.
Speaker 1: That is unbelievably clever. It's like throwing a boomerang just
Speaker 1: to see where it comes back from.
Speaker 2: It's elegant. But that's not even the hardest part. You
Speaker 2: also have the NLL byte problem.
Speaker 1: The nl byte. This sounded like the absolute villain of
Speaker 1: the story.
Speaker 2: It's the nemesis. Remember we're injecting our code through a
Speaker 2: function that handles text strings. In the C programming language,
Speaker 2: a string ends with the NLL byte. The value zero.
Speaker 1: It's the period at the end of the sentence tells
Speaker 1: the program to stop reading.
Speaker 2: Correct. So if your malicious shell code has a single
Speaker 2: zero byte anywhere in it, the copy function just stopped ops.
Speaker 2: It cuts your attack off before it's even fully loaded.
Speaker 1: But zeros have to be everywhere in code. If I
Speaker 1: want to set a register to zero, then instruction contains
Speaker 1: zero exactly.
Speaker 2: So you have to figure out how to command the
Speaker 2: processor to use the value zero without ever actually writing
Speaker 2: a zero in your code. It's like writing a novel
Speaker 2: without using the letter E.
Speaker 1: How is that even possible?
Speaker 2: Use math, specifically the xor.
Speaker 1: Operation xor exclusive or R.
Speaker 2: Right, it's a basic logic gate. If you xr any
Speaker 2: value with itself, the result is always zero. Everything cancels out.
Speaker 1: So instead of telling the computer move zero into register A,
Speaker 1: you tell it xor register A with register A and
Speaker 1: the result is zero.
Speaker 2: The result is zero, but the instruction itself, the actual
Speaker 2: bytes you injected, contains no zeros. You've completely bypassed the filter.
Speaker 1: That is the art form, that's the Judo move. It's
Speaker 1: this incredible constraint based creativity.
Speaker 2: It really is. You're navigating this minefield where one wrong
Speaker 2: bite just crashes everything before you can get control.
Speaker 1: So we've navigated the minefield, we have our shell code.
Speaker 1: Where are we running this? The book distinguishes between remote
Speaker 1: and local attack right.
Speaker 2: Remote is the classic hacker movie, you're attacking a server
Speaker 2: across the internet. Local is when you're already inside with
Speaker 2: a low level account and you want to become the
Speaker 2: administrator or route.
Speaker 1: Let's do remote first, you launch the exploit. How do
Speaker 1: you actually talk to the shell you just spawned?
Speaker 2: The simple way is port binding. Your shell code tells
Speaker 2: the victim machine to open a new door, say port one, two, three,
Speaker 2: four five and listen. Then you just connect to that
Speaker 2: new port.
Speaker 1: But firewalls would hate that, oh they do.
Speaker 2: A random new port opening up is a gigantic red
Speaker 2: flag it gets blocked immediately. This sophisticated method is socket reus.
Speaker 1: How does that work?
Speaker 2: It's parasitic. The shell code looks for the connection that's
Speaker 2: already open, the very one you use to send the exploit.
Speaker 2: It finds that connections handle in.
Speaker 1: Memory, and it just takes it over.
Speaker 2: It duplicates it. It redirects the shell's input and output
Speaker 2: to that existing connection. So from the firewalls perspective, there's
Speaker 2: no new connection. You send the exploit, and suddenly your
Speaker 2: existing terminal window is the command prompt on their server.
Speaker 1: That is terrifyingly stealthy.
Speaker 2: It is now for local attacks, the goal is usually
Speaker 2: escaping some kind of jail. The book talks about the
Speaker 2: crup jail.
Speaker 1: A creup jail sounds like a timeout corner for software.
Speaker 2: It's a pretty good analogy. It's a security feature that
Speaker 2: locks a program into a specific directory. As far as
Speaker 2: that program knows that folders the entire universe. It can't
Speaker 2: see the real system files outside.
Speaker 1: So if you hack the program, you're still stuck in jail.
Speaker 1: How do you break out?
Speaker 2: The technique in the book is shockingly simple. If you
Speaker 2: have root powers inside the jail, you create a new folder,
Speaker 2: and then you use the fruit command again to move
Speaker 2: into that new folder.
Speaker 1: Jail inside of jail, Yes.
Speaker 2: But because of a quirk in older systems, doing that
Speaker 2: nested crude breaks the link to the original jail. And
Speaker 2: then you just spam dot slash.
Speaker 1: Go up one folder commandment over and over.
Speaker 2: You just climb the directory tree until you pop out
Speaker 2: at the top of the real file system. You've escaped.
Speaker 1: That feels like a video game cheat code, just running
Speaker 1: against a wall until you clip through the map.
Speaker 2: It basically is. And it just goes to show that
Speaker 2: even security features are just code, and if you understand
Speaker 2: the logic better than the person who wrote it, you
Speaker 2: can bypass it.
Speaker 1: Hearing all of this, the complexity, the creativity, the sheer
Speaker 1: fragility of memory, it brings us back to the big question,
Speaker 1: why why does the still work? We've known about this
Speaker 1: for decades.
Speaker 2: Yeah, the micro data in the book says buffer overflows
Speaker 2: account for a huge percentage of vulnerabilities. That number goes
Speaker 2: up and down, but the principle holds.
Speaker 1: So what's the root cause it's.
Speaker 2: Almost always the same thing. Poor input validation.
Speaker 1: We trust the user too much.
Speaker 2: We assume the user will send a username. That's eight
Speaker 2: characters long. We don't plan for them sending ten thousand
Speaker 2: characters of malicious assembly. We code for the happy path,
Speaker 2: not the psychopathic one.
Speaker 1: But surely big companies like Microsoft and Oracle are checking
Speaker 1: for this stuff.
Speaker 2: They are. But the source makes a great point about
Speaker 2: the myth of bug free software. It calls out Oracle,
Speaker 2: who once famously claimed their software was unbreakable.
Speaker 1: That's just asking for trouble. It's like naming your ship
Speaker 1: the Titanic.
Speaker 2: It is and they were proven wrong immediately. The book
Speaker 2: argues something that sounds a bit controversial, complete security should
Speaker 2: not be a sought after goal.
Speaker 1: Wait, really, we shouldn't try to be completely secure.
Speaker 2: His point is that it's unrealistic. It's an impossible goal.
Speaker 2: Software is just too complex. The goal should be risk management.
Speaker 2: You aim for realistic milestones like no user provided input vulnerabilities.
Speaker 2: You manage the flaws. You don't pretend you can eliminate
Speaker 2: them entirely.
Speaker 1: Because they're written by humans, and humans make mistakes, and.
Speaker 2: Buffer overflows are the digital version of that. It's what
Speaker 2: happens when our creations get away from us.
Speaker 1: So after all this, what's the takeaway? We've gone from
Speaker 1: this scary boogeyman to the beautiful truth of the code.
Speaker 2: I think it just changes how you look at the
Speaker 2: digital world. It's not this solid, reliable thing. It's this fragile,
Speaker 2: intricate dance of memory, and we can run it.
Speaker 1: That keeps changing shape. And I want to leave our
Speaker 1: listeners with that one final thought from Itel's forward that
Speaker 1: honestly just gave me chills.
Speaker 2: I think I know which one you mean.
Speaker 1: He writes that somewhere right now, there's a fifteen year
Speaker 1: old in Sweden working twenty hours a day to be
Speaker 1: better than you at this.
Speaker 2: It's a very sobering thought.
Speaker 1: He says. It's not just about learning a skill, it's
Speaker 1: about fiddling until the code is clean, until it's perfect.
Speaker 1: While security professionals are in meetings, that kid is staring
Speaker 1: at a heck stump trying to find one extra bite
Speaker 1: of space for their shell code.
Speaker 2: And that applies to the defenders too. Security isn't a
Speaker 2: product you buy, it's a process. It's the process of
Speaker 2: understanding the deepest flaws in what we build. Hopefully before
Speaker 2: that fifteen year old does.
Speaker 1: On that note, maybe it's time for all of us
Speaker 1: to go update our systems and maybe stop trusting user
Speaker 1: infally quite so much. Thanks for diving deep with us,
Speaker 1: Take curious, See you next time.