Anecdotes about the Seine

([-]) Isn’t it just learning from scratch?

After a short break, the training of the technical team officially began.

Rather than calling it "training", it is more appropriate to say "training".Together with the recruits of the same period, Lu Ting started the study of basic safety courses in the computer room of the office building in the camp.Different from the undergraduate education received at school, the training here has no theory and is directly hands-on.The professor from the Imperial Military Academy wrote down an IP address on the blackboard and told the students: "The teaching content of the first week is binary analysis. The sample program is obtained from this server. There are three in total. The goal is to obtain the hidden password in the binary. There are You can ask me any questions."

Then he patted the chalk dust on his hands, walked to the side of the podium and sat down, and went to do his own thing in front of the notebook.

Lu Ting first looked at the screen in front of her. It was not the familiar Windows system, but the Linux interface.Well, Lu Ting thought to herself, she was starting to feel a little scared.When I was in school, almost all homework platforms were developed based on Windows. She is really not familiar with Linux, but at least she knows a few commands.

So she typed the two letters "ls" on the terminal and pressed Enter to view the files in the current directory.

Nothing is displayed on the screen.

She "cd" back and searched in her user directory for a long time, but there was nothing.There are no sample programs, no tutorials, no instructions, and no documentation of any kind.

Lu Ting remembered that the professor said that the sample program should be obtained from the server, so she looked at the IP address on the blackboard.Then she was worried, how to connect remotely?

Many years later, Lu Ting, who has become the deputy commander of the Imperial Army's cyber army, recalled the moment of worry in the first training class, and would shake her head with her head covered in pain, showing a painful expression: "I was too good at that time, The cooking is terrible. How can you be so good? You can’t do anything!”

But at that time, Lu Ting's shame and anxiety were only a lot more than many years later.Looking at the people around, they have already started staring at the screen and working hard, the keyboard is crackling, and the screen is full of flashing codes.

At this moment, that familiar voice appeared behind him unhurriedly: "How is it?"

Lu Ting looked back and saw that it was Feng Xinduo.Lu Ting didn't know why this genius team leader appeared here at this moment, and she couldn't care less to think about it at this moment, and she was too embarrassed to tell the truth, so she could only vaguely say: "Well, I'm still thinking about it, think about it..."

Feng Xinduo showed a kind smile, which made Lu Ting's heart beat. "There are many methods for remote connection and file transfer." Feng Xinduo said slowly, "NC, ssh, and scp are all available, depending on which one you are more familiar with."

Lu Ting's face turned red: "Ah, yes, I was just thinking about which one to use."

Don't be too obvious about her face-saving and self-defense in what she said, but Feng Xinduo smiled lightly and didn't expose it.Before leaving, she suddenly turned her head and said with a smile: "Make good use of search engines."

Lu Ting blushed even more.

After searching for a long time, she finally figured out how to use these Linux commands and downloaded the three ELF files.Lu Ting tried to run them one by one. Sure enough, after displaying some text information, each program needs to read a password from the file input, and only after the verification is successful can it continue to run.

For the rest of the day, Lu Ting almost kept searching various keywords: "binary analysis", "reverse engineering", "dynamic debugging" and so on.Two minutes before the end of the course, Lu Ting finally decided on what to do next: learn to read assembly code.

Then the bell rang for the end of get out of class, and looking at other people, someone had already submitted the password result of the first program.

That night, Lu Ting didn't go to dinner with the big team, but went straight back to the dormitory, threw herself on the bed, buried her head in the pillow, and let out a long and desperate sigh.

She had never experienced such a strong sense of frustration. Sitting in that bright and quiet computer room, she felt that she was the person with the lowest IQ in this place.In school before, her academic performance was the same, but it doesn't matter, she has other careers to fight for, and uses various achievements to satisfy herself.Throwing the [-]% exam paper aside, she can hang shoulders with her good buddies from the student union and go out to play and sing.But not anymore.Now she has no sense of accomplishment that she can use to make herself feel better, and no friends to relieve loneliness, like a person struggling alone in the water, no lifebuoy, no boat, no helpers of any kind.

In an instant, all self-confidence was gone, and there was only a hideous voice: "You can't do it".

She rubbed her face against the pillow, as if to wipe away the unseen tears.But when he raised his head, the determined expression returned to his face.She took off her military uniform and changed into a comfortable sportswear.While she was putting on her shoes, the roommate came back from dinner.

"Do you know that the computer room is open at night?" Lu Ting asked her roommate while tying her shoelaces.

"I don't know." The roommate replied, opening the alien notebook and clicking on Steam. "Why don't you ask Captain Feng, maybe she has the authority."

Ask Captain Feng?That really killed her.For some reason, Lu Ting had a strange feeling about Captain Feng.Maybe it was that calm demeanor that attracted her, maybe it was the genius experience that day that made her envious, or maybe it was the embarrassment she made in front of her today that made her heartbroken.But anyway, she was unwilling to expose any of her weaknesses in front of her.

Instead, deep in her heart, she had a small hope: I want to let her know that I can do it.

So she would rather ask than ask, and go to the computer room to try her luck.

Lu Ting quietly walked to the door of the office building.In fact, she didn't need to "quietly" at all, because the doorman obviously remembered her face and said kindly, "Are you here to work overtime?"

Lu Ting was a little embarrassed, and nodded: "Uh, yes."

She swiped her ID card, entered the main building, and came to the door of the computer room.Everything is dark, no lights, no people.According to the guard, there should be people who often come to work overtime, but obviously she is the only one among the new recruits.She pushed the door carefully, but it was unlocked, and then she walked in, turned on her computer, and continued her unfinished self-study during the day.

Since the foundation is too poor, let's work hard to make up for it.she thought.Anyway, don't others learn from nothing?

The faint screen light in the computer room kept flickering throughout the night.On the other side of the dormitory building in the camp area, a person stood in front of the window of the room, watching the flash of the window in the computer room of the office building, showing an elusive smile.

Lu Ting just worked overtime and studied hard for a week.On Friday afternoon, with huge dark circles under her eyes, she felt that her eyes were about to go blind. Finally, she found the password of the last program and submitted it before the end of the course.Seeing the satisfied expression on the professor's face, she ticked Lu Ting's name. She finally felt relieved, and her whole body relaxed from the tension.

There was a hand holding her, and the touch was very gentle.After Lu Ting stood still, she turned around and saw that it was Feng Xinduo.For a moment, she was so happy that she seemed to fly, and she just wanted to grab her and say: Look, I succeeded!I successfully completed the task of the first week!But she was still very thin-skinned after all, and the thought only flashed for a moment.Then she got up seriously, stood up quickly, and said to Feng Xinduo: "Captain, I have completed this week's task."

She originally thought that the other party would praise her, and she was polite anyway.But Feng Xinduo didn't.She still had that calm expression and said, "Oh? How did you do it?"

So Lu Ting began to talk about her experience this week: first, she was familiar with the assembly code, and then used IdaPro to disassemble, and by reading the operands of the cmp instruction in the assembly code, she determined each key of the password for verification in the code. byte.Of course, there are also some small methods she found herself proud of - dynamic debugging and verification through gdb.

After she finished chirping, she looked at Feng Xinduo with expectant eyes, thinking that I have solved the problem by self-study in such a short time, how is it, is it okay?

However, Feng Xinduo shook his head, frowned and said: "Your method is too stupid, and it is not universal. This time the binary is not encrypted, and the password is also directly compared. What if the binary program is confused? What if the password is passed two times?" What should I do if I encrypt it for the second time? One xor operation will kill you, and you can’t see it just by reading the code.”

Lu Ting was suddenly stunned by such an attack, she was speechless and speechless.

Feng Xinduo didn't notice the change in her expression at all, and continued: "Have you used pdb? You should know how to write Python code, right? Go back and have a look, and write an automated script to process it, it will be much faster than this."

Lu Ting didn't expect that this person not only didn't affirm herself, but also assigned homework.

For a moment, Lu Ting felt a burst of anger, and the anger rushed straight to the top of her head.But that fire quickly died down, replaced by a cooling sense of failure.But she was already used to this feeling.If there is anything in this world that can control her spiritual lifeline, it is probably "other people's affirmation".But that was okay, she already knew how to deal with the constant frustration.

She gritted her teeth, tried to maintain a calm expression, and said, "Okay, I'll go back and have a look."

So Friday night was another sleepless night.With the previous foundation, it is not difficult to write automated scripts as long as you master the usage of the library interface.Lu Ting had to admit that Feng Xinduo was right, this method was indeed much faster.For a moment, she felt that she had been struggling to read the compilation line by line before, acting like a fool.But she comforted herself, it doesn't matter, at least she is familiar with compilation.She has always been good at comforting herself.

After Lu Ting handed over the automation script code to Feng Xinduo, she thought that the difficult time had passed.But it is not.She didn't know that there were more difficult things ahead.

I don't know why, in the subsequent training, Feng Xinduo always flashed behind Lu Ting from time to time, or pointed out the problems in her code, or dropped a hint lightly when she got stuck.Lu Ting knew that what she said was right, but every time she helped, she felt a sense of shame at what to do.I don't need your help, Lu Ting thought.She never needed anyone's help, she helped others.This hateful Feng Xinduo took away the last bit of her poor sense of accomplishment.

But that's not the worst.The worst thing is that Feng Xinduo always has to add some burdens to her already heavy learning tasks.For example, in the recent vulnerability exploitation course, Lu Ting has successfully solved the buffer overflow and format string, but when she learned the heap exploitation, she couldn't figure it out.At this moment, Feng Xinduo appeared again, and said to her in a commanding tone: "I will send you a detailed implementation document of gmalloc. You can take a look and implement a heap allocator yourself."

Lu Ting almost spit out a mouthful of old blood, sister, I haven't finished the task in front of me, why are you giving me more weight?But how could she refuse to say that she couldn't do it?No way, just bite the bullet.After several sleepless nights, Lu Ting was pleasantly surprised to find that after writing a heap allocator, she knew all the heap allocators like the back of her hand.That being the case, the heap utilization that relies on the principle of the heap allocator to attack has naturally become extremely simple.

Lu Ting had to admit that Feng Xinduo really had something.