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Author: XlogicX

ASM_x86/LinuxAPI_08_mkdir.asm

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+;Simple example of creating a directory with the mkdir API call. API calls found in this example program:
+; 	mkdir, exit
+; High level description of what theis example program does:
+;	Create a new directroy called 'newdir' using the mkdir API call
+;	exits gracefully with exit().
+
+section .text
+global _start
+
+_start:
+
+; Create a new directroy called 'newdir' using the mkdir API call
+;------------------------------------------------------------------------------
+	mov		eax, 39				;mkdir
+	mov		ebx, newdir			;pointer to the directory name
+	mov		ecx, 600o			;Read/Write for Owner
+	int		0x80
+
+
+; Exit program
+;------------------------------------------------------------------------------
+	mov		eax, 1
+	int		0x80
+
+section .data
+	newdir db 'newdir', 0x00
+
+; ------------------------------
+; | Some bitfield explanations |
+; ------------------------------
+
+; Mode Octal codes
+;------------------------------------------------------------------------------
+;	Read	4
+;	Write	2
+;	Execute	1

ASM_x86/LinuxAPI_09_rmdir.asm

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+;Simple example of removing a directory with the rmdir API call. API calls found in this example program:
+; 	rmdir, exit
+; High level description of what theis example program does:
+;	Attempts ot remove the directory 'newdir' if it exists, using the rmdir API
+;	exits gracefully with exit().
+
+section .text
+global _start
+
+_start:
+
+; Attempts ot remove the directory 'newdir' if it exists, using the rmdir API
+;------------------------------------------------------------------------------
+	mov		eax, 40				;rmdir
+	mov		ebx, newdir			;pointer to the directory name
+	int		0x80
+
+
+; Exit program
+;------------------------------------------------------------------------------
+	mov		eax, 1
+	int		0x80
+
+section .data
+	newdir db 'newdir', 0x00
+
+; ------------------------------
+; | Some bitfield explanations |
+; ------------------------------
+
+; Mode Octal codes
+;------------------------------------------------------------------------------
+;	Read	4
+;	Write	2
+;	Execute	1

ASM_x86/LinuxAPI_10_getdents.asm

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+;Example of reading the contents of a directory using the getdents API call. API calls found in this example program:
+; 	open, getdents, exit
+; High level description of what theis example program does:
+;	Opens a directory in readonly mode for the file descriptor with open API
+;	Reads data structure for directory and places in memory buffer with getdents API
+;	Closes fd for directory with close API
+;	exits gracefully with exit().
+
+section .text
+global _start
+
+_start:
+
+; Open dir with open() call and a dir specified at 'dir' buffer
+;------------------------------------------------------------------------------
+	mov		eax, 5				;open
+	mov		ebx, dir			;pointer to the directory
+	xor		ecx, ecx			;readonly
+	xor		edx, edx			;permissions not relevant
+	int		0x80
+	mov		[filehandle], eax	;save filehandle
+
+; Get directroy contents into dirbuffer memory location
+;------------------------------------------------------------------------------
+	mov		eax, 141				;getdents
+	mov		ebx, [filehandle]		;pointer to the directory fd
+	mov		ecx, dirbuffer			;where we want the results
+	mov		edx, 300				;size of buffer for results
+	int		0x80
+
+; Close the file with close().
+;------------------------------------------------------------------------------
+	mov		ebx, [filehandle]	;get filehandle return value
+	mov		eax, 6				;close
+	int		0x80
+
+; Exit program
+;------------------------------------------------------------------------------
+	mov		eax, 1
+	int		0x80
+
+section .data
+	dir db '.', 0x00
+
+section .bss
+	filehandle resb 4
+	dirbuffer resb 300
+
+; Seems simple right? Oh...you wanted something inteligible as far as the
+; directory listing results, and you wanted them printed out, not just a data
+; blob in a memory buffer? Aint nobody got time for that, below is some
+; documentation for the datastructure, parse it (with your brain) from memory
+; yourself. This is just a quick PoC for getdents, not a PoC for parsing a
+; complex data structure and displaying it to a human (that program would be 
+; bigger).
+; ------------------------------
+; | Some bitfield explanations |
+; ------------------------------
+
+; Data Structure for the directory results that show up in the provided buffer
+;------------------------------------------------------------------------------
+; struct linux_dirent {
+;     unsigned long  d_ino;     /* Inode number */
+;     unsigned long  d_off;     /* Offset to next linux_dirent */
+;     unsigned short d_reclen;  /* Length of this linux_dirent */
+;     char           d_name[];  /* Filename (null-terminated) */
+;                       /* length is actually (d_reclen - 2 -
+;                          offsetof(struct linux_dirent, d_name)) */
+;     /*
+;     char           pad;       // Zero padding byte
+;     char           d_type;    // File type (only since Linux
+;                               // 2.6.4); offset is (d_reclen - 1)
+;     
+; }