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ftp.c
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ftp.c
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#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <poll.h>
#include "ftpscan.h"
#define CRLF "\r\n"
#define CRLF_LEN 2
static void set_last_message(char *response);
static int ftp_read_banner(int fd);
static char *ftp_read_line(int fd);
static char *ftp_read_line_timeout(int fd, int timeout);
static void strip(char *string);
static int response2code(const char *response);
static char *last_server_message;
int
ftp_login(int fd, const char *username, const char *password)
{
char buffer[256];
if(ftp_read_banner(fd))
return -1;
snprintf(buffer, sizeof(buffer), "USER %s", username);
int code = ftp_exchange_command(fd, buffer);
if(ftp_code_okay(code))
return 0;
if(code != 331)
return -1;
snprintf(buffer, sizeof(buffer), "PASS %s", password);
if(!ftp_code_okay(ftp_exchange_command(fd, buffer)))
return -1;
return 0;
}
int
ftp_anon_login(int fd)
{
return ftp_login(fd, "ftp", "IEUser@");
}
int
ftp_code_okay(int code)
{
return code >= 200 && code < 300;
}
int
ftp_exchange_command(int fd, const char *command)
{
debug("--> %s", command);
write_all(fd, command, strlen(command));
write_all(fd, CRLF, CRLF_LEN);
return ftp_command_response(fd);
}
int
ftp_command_response(int fd)
{
char *response = ftp_read_line(fd);
debug("<-- %s", response);
set_last_message(response);
return response2code(response);
}
void
ftp_drain_extra_responses(int fd)
{
while(1) {
char *extra_response = ftp_read_line_timeout(fd, 500);
if(extra_response == NULL)
return;
debug("<-- %s", extra_response);
}
}
static void
set_last_message(char *response)
{
if(strlen(response) <= 4) {
last_server_message = "";
return;
}
if(response[3] == ' ')
last_server_message = response + 4;
else
last_server_message = response + 3;
}
char *
ftp_get_last_server_message()
{
return last_server_message;
}
static char *
ftp_read_line_timeout(int fd, int timeout)
{
struct pollfd pfd;
pfd.fd = fd;
pfd.events = POLLIN;
pfd.revents = 0;
if(poll(&pfd, 1, timeout) == 0)
return NULL;
if((pfd.revents & POLLIN) == 0)
return NULL;
return ftp_read_line(fd);
}
static char *
ftp_read_line(int fd)
{
static char line_buffer[1024];
char c;
int n;
size_t count = 0;
size_t remaining = sizeof(line_buffer) - 1;
while(remaining > 0) {
if((n = recv(fd, &c, 1, 0)) < 0)
fatal("recv() failed reading line from server.");
if(n == 0)
fatal("EOF reading line from server.");
if(c == '\r')
continue;
if(c == '\n')
break;
line_buffer[count] = c;
count++;
remaining--;
}
if(remaining == 0)
warn("No newline found in response after reading %d bytes.", count);
line_buffer[count] = 0;
strip(line_buffer);
return line_buffer;
}
static int
ftp_read_banner(int fd)
{
while(1) {
char *banner = ftp_read_line_timeout(fd, 1000);
if(banner == NULL)
return 0;
info("%s", banner);
}
}
static void
strip(char *string)
{
while(1) {
int len = strlen(string);
if(len > 0 && isspace(string[len - 1]))
string[len - 1] = 0;
else
return;
}
}
static int
response2code(const char *response)
{
int code = 0;
int i;
for(i = 0; i < 3; i++) {
code *= 10;
if(!isdigit(response[i]))
return -1;
code += response[i] - '0';
}
return code;
}