HackPig520's Blog How to Making an HTTP request in Assembly (ASM) Jul 23, 2023 · 4 min read Making an HTTP request in Assembly (ASM) language directly is quite complex and not a practical approach. Assembly language is typically low-level and designed to interact with the hardware of a computer, rather than dealing with network protocols like HTTP. However, you can make an HTTP request from Assembly by calling external libraries or using system calls provided by the operating system. These libraries or system calls will handle the complexities of networking and HTTP for you. To demonstrate this, I'll provide an example of how you can make an HTTP request using x86 Assembly language on Linux. We'll use the C library's functions to perform the HTTP request. Keep in mind that this is just one way to do it, and different platforms or Assembly dialects might require different approaches. In this example, we'll use the libc functions socket(), connect(), send(), and recv() to perform a basic HTTP GET request to a web server and print the response. section .data host db "example.com", 0 port dw 80 request db "GET / HTTP/1.1", 10, 13, 0 buffer db 1024 dup (0) section .bss sockfd resd 1 section .text global _start _start: ; Create socket mov eax, 0x66 ; socket syscall number xor edi, edi ; domain: AF_INET (IPv4) xor esi, esi ; type: SOCK_STREAM (TCP) xor edx, edx ; protocol: 0 (auto) syscall mov [sockfd], eax ; store the socket file descriptor ; Prepare the sockaddr_in structure xor eax, eax ; clear eax register mov al, 0x2 ; IP address family AF_INET mov edi, eax ; clear edi register mov ax, [port] ; set the port number push edi ; push the null bytes push word ax ; push the port number mov edi, esp ; edi points to the sockaddr_in structure ; Resolve the IP address of the host push edi ; push the pointer to the sockaddr_in structure push host ; push the pointer to the host string call gethostbyname ; call the gethostbyname function pop edi ; restore edi ; Connect to the remote server mov eax, 0x66 ; socket syscall number mov ebx, [sockfd] ; socket file descriptor mov ecx, edi ; pointer to the resolved sockaddr_in structure add dl, 0x10 ; sockaddr_in structure size syscall ; Send the HTTP request mov eax, 0x4 ; write syscall number mov ebx, [sockfd] ; socket file descriptor lea ecx, [request] ; pointer to the request string mov edx, request_len ; length of the request string syscall ; Receive and print the response mov eax, 0x3 ; read syscall number mov ebx, [sockfd] ; socket file descriptor lea ecx, [buffer] ; buffer to store the response mov edx, 1024 ; number of bytes to read syscall ; Print the response mov eax, 0x4 ; write syscall number mov ebx, 0x1 ; file descriptor 1 (stdout) lea ecx, [buffer] ; buffer containing the response mov edx, eax ; number of bytes to write (same as the number of bytes read) syscall ; Close the socket mov eax, 0x6 ; close syscall number mov ebx, [sockfd] ; socket file descriptor syscall ; Exit the program mov eax, 0x1 ; exit syscall number xor edi, edi ; exit status: 0 syscall gethostbyname: ; Function to resolve host name to IP address (gethostbyname) ; Arguments: ; edi - pointer to the sockaddr_in structure ; esi - pointer to the host name string ; Returns: ; edi - pointer to the resolved IP address (in network byte order) ; Clobbers: ; eax, ebx, ecx, edx pushad push ebx ; Clear the sockaddr_in structure mov ecx, edi xor eax, eax xor ebx, ebx mov word [ecx], ax mov word [ecx + 2], bx ; Set the sockaddr_in family (AF_INET) mov word [ecx], 0x2 ; Resolve the host name mov eax, 0x5 mov ebx, esi mov ecx, edi int 0x80 pop ebx popad ret Please note that this code assumes an x86 architecture running on Linux. The implementation may vary for other platforms and Assembly dialects. As you can see, this code involves a lot of system calls and is much more complicated than making an HTTP request in higher-level languages. This is why Assembly is typically not the preferred language for handling HTTP requests directly. Instead, it's more common to use higher-level languages with networking libraries or frameworks that abstract the complexities of HTTP. 文章由 ChatGPT 生成 Read on web Add a comment © 2023 HackPig520's Blog 8 The Green, Ste 300, Dover, Delaware, 19901 Unsubscribe Publish with Hashnode