Coding Blog

Language C Linux x86/ELF Difficulty: 1 - Very easy, for newbies Platform: Unix/Linux, etc. Language: C/C++ [Solving the Crackme] As usual, we have to run the file first. joset@kee:~/src/crackmes/mycrk$ ./mycrk Type cd-key: eve wrong! joset@kee:~/src/crackmes/mycrk$ From this point we already know what the file needs, a correct key . I immediately disassembled the file without even bothering about its characteristics. joset@kee:~/src/crackmes/mycrk$ objdump -d mycrk > temp.txt joset@kee:~/src/crackmes/mycrk$ less temp.txt The first trick, is to look for the disassembly of the main function. Here’s a portion of it. ... 80483d4: c7 45 fc 67 1e 01 00 movl $0x11e67,0xfffffffc(%ebp) 80483db: c7 45 f8 70 12 5b 00 movl $0x5b1270,0xfffffff8(%ebp) 80483e2: c7 45 f0 06 00 00 00 movl $0x6,0xfffffff0(%ebp) 80483e9: 83 ec 0c sub $0xc,%esp 80483ec: 68 14 85 04 08 push $0x8048514 80483f1: e8 ee f...

A good morning to start off is to get this simple program working. This is an improvement of the previous palindrome checker posted. What can we benefit from this anyway? ; palindrome checker start: mov ah, 0ah lea dx, strptr int 21h lea di, string lea si, strlen mov cl, [si] xor ch, ch mov bx, cx lea si, string shr cl, 1 check: mov dl, [si] mov dh, [di+bx-1] cmp dl, dh jne notpal inc si dec di loop check cmp dl, dh je pal notpal: mov ah, 09h lea dx, msg2 int 21h int 20h pal: mov ah, 09h lea dx, msg1 int 21h int 20h strptr label byte maxlen db 49 strlen db ? string db 50 dup ('$') msg1 db '',10,'string is a palindrome!$' msg2 db '',10,'string is not a palindrome!$' “If God’s people which are call...

This is a simple case inverter, if you want to try this out download the a86 assembler here . It works like a charm in dosemu-freedos . ; case inverter start: mov ah, 0ah lea dx, strptr int 21h lea si, string mov cl, [strlen] check: mov al, [si] cmp al, 'Z' ja lowercase cmp al, 'a' jb uppercase lowercase: cmp al, 'a' jb traverse cmp al, 'z' jbe toupper uppercase: cmp al, 'Z' ja traverse cmp al, 'A' jae tolower toupper: sub al, 32 mov [si], al jmp traverse tolower: add al, 32 mov [si], al traverse: inc si loop check mov ah, 02h mov dl, 10 int 21h mov ah, 09h lea dx, string int 21h int 20h strptr label byte maxlen db 49 strlen db ? string db 50 dup ('$') “Fo...

crackme will print text under certain conditions what are the conditions? sorry for my bad english - lord Difficulty: 1 - very easy, for newbies Platform: Unix/Linux, etc. Language: Assembler [Solving the Crackme] An initiative would be running the file: joset@kee:~/src/crackmes$ ./blah joset@kee:~/src/crackmes$ It didn’t print anything at all. So the conditions aren’t met. I’ve been using gdb and objdump for quite some time now. Since there is no form of corruption in the file, these tools will be more than enough. Here’s the disassembly of the file in objdump: blah: file format elf32-i386 Disassembly of section .text: 08048094 : 8048094: 31 c0 xor %eax,%eax 8048096: b8 2f 00 00 00 mov $0x2f,%eax 804809b: cd 80 int $0x80 804809d: 3d ad de 00 00 cmp $0xdead,%eax 80480a2: 75 16 jne 0x80480ba 80480a4: b8 04 00 00 ...

Making you feel loved was the easiest thing I have ever done before. It’s just sad to think that things just changed. I wish I could turn back those days. The times when we sat down under a tree, observed the fading horizon, held hands and stared at the crimsoning sun. I know how destiny fools us. If destiny asserts that we are not for each other, then I would fight destiny just to have you in my arms forever. I love you my everdearest. I’m sorry for what had happened to the rose. It’s not too late though, I can still take care another bud for you.

Simple programming stuffs save me from insanity. This a86 assembly program tells if str1 is a palindrome. start: cld mov cx, 7 lea si, str1 lea di, temp reverse: mov al, [si+6] mov [di], al inc di dec si loop reverse mov ah, 09h lea dx, temp int 21h cld mov cx, 4 compare: lea di, temp lea si, str1 repe cmpsb jne exit mov ah, 09h lea dx, yes int 21h exit: mov ah, 4Ch mov al, 00 int 21h int 20h str1 db 'racecar$' yes db '',10,'string is a palindrome!$' temp db 8 dup ('$') [Middle-East Crisis] Israel, known as the chosen people of God called a thousand reservists in a possible prelude to a ground offensive against Lebanon. Accordingly, they have to clean up bunkers and tunnels that are invulnerable to air attacks. Isn’t it ironic...

I can still remember way back then, I was five years old when I had my primary hobbies, hunting, fishing, and shooting-range. Today, we went to Sinubung, a semi-dangerous place located in the far west coast of Zamboanga City and is known for its shore having huge waves and numerous sea urchins. We have gone fishing. It was fun riding my grandfather’s motor-operated vinta again though I am deeply saddened with what had happened today. The last time I set foot on that vinta was 15 years ago. I can still remember my grandfather pulling the nylon with a huge squid hooked up. Of course, the squid fired up a black tint. Because of that black tint, and the times when I threw up while riding the vinta, I have something now which I call memories worth remembering. Awhile ago, we did the same but no squid and from what I have observed fishes are already scarce! We spent almost three hours, changing position from time to time on the sea. I was the one throwing and pulling the anchor everyt...