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#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
#include <assert.h>
#include <errno.h>
#include <unistd.h>
#include <sys/stat.h>
#include "plugin.h"
#include "util.h"
static char *static_file_dir = NULL;
static bool path_allowed(const char *path) {
char last = '\0';
for (size_t i = 0; path[i]; i++) {
// no unprintable characters
if (path[i] < 32 || path[i] >= 127) return false;
// no hidden files or magic directory items like ".."
if (last == '/' && path[i] == '.') return false;
last = path[i];
}
return true;
}
// Returns pointer to internal buffer, don't free
static const char* make_relative_path(const char *path) {
static char *rel = NULL;
static size_t rel_cap = 0;
size_t necessary = strlen(static_file_dir) + 1 + strlen(path) + 1;
if (necessary >= rel_cap) {
rel_cap = necessary;
rel = realloc(rel, rel_cap);
assert(rel);
}
sprintf(rel, "%s/%s", static_file_dir, path);
return rel;
}
// If an error occurs, returns -1 and sets errno
static ssize_t query_file_size(const char *path) {
struct stat st;
memset(&st, 0, sizeof st);
if (stat(path, &st) < 0) {
return -1;
}
if (st.st_mode & S_IFREG) {
return st.st_size;
} else {
errno = EISDIR;
return -1;
}
}
struct Buffer {
char *buf;
size_t cap, len;
};
static struct Buffer buffer_make(size_t capacity) {
struct Buffer buffer = (struct Buffer){malloc(capacity), capacity + 1, 0};
assert(buffer.buf);
return buffer;
}
static void buffer_free(struct Buffer buffer) {
free(buffer.buf);
}
static void buffer_append_mem(struct Buffer *buffer, const char *str, size_t len) {
if (buffer->len + len >= buffer->cap) {
do buffer->cap *= 2; while (buffer->len + len >= buffer->cap);
buffer->buf = realloc(buffer->buf, buffer->cap);
assert(buffer->buf);
}
memcpy(buffer->buf + buffer->len, str, len);
buffer->len += len;
buffer->buf[buffer->len] = 0;
}
static void buffer_append_str(struct Buffer *buffer, const char *str) {
buffer_append_mem(buffer, str, strlen(str));
}
// returns whether successful
static bool buffer_append_file(struct Buffer *buffer, const char *path) {
FILE *f = fopen(path, "rb");
if (!f) return false;
char block[4096];
while (true) {
size_t nr = fread(block, 1, sizeof block, f);
if (nr > 0) buffer_append_mem(buffer, block, nr);
if (nr < sizeof block) break;
}
bool has_error = ferror(f);
fclose(f);
return !has_error;
}
static struct Buffer build_response_headers(const char *status, const char *content_type, size_t body_len) {
struct Buffer buffer = buffer_make(200 + body_len);
buffer_append_str(&buffer, "HTTP/1.1 ");
buffer_append_str(&buffer, status);
buffer_append_str(&buffer, "\r\n");
if (content_type) {
buffer_append_str(&buffer, "Content-Type: ");
buffer_append_str(&buffer, content_type);
buffer_append_str(&buffer, "\r\n");
}
char tempbuf[128]; // size_t is at most 20 chars long
sprintf(tempbuf, "Content-Length: %zu\r\n", body_len);
buffer_append_str(&buffer, tempbuf);
buffer_append_str(&buffer, "Server: cserver\r\n\r\n");
return buffer;
}
static void send_404(int sock) {
const char *body = "404 Not found";
struct Buffer buffer = build_response_headers("404 Not found", NULL, strlen(body));
buffer_append_str(&buffer, body);
sendall(sock, buffer.buf, buffer.len);
}
static void send_500(int sock) {
const char *body = "500 Internal server error";
struct Buffer buffer = build_response_headers("500 Internal server error", NULL, strlen(body));
buffer_append_str(&buffer, body);
sendall(sock, buffer.buf, buffer.len);
}
static Handler_ret_t connection_handler(int sock, Headers *headers) {
if (!path_allowed(headers->url)) {
send_404(sock);
return HR_HANDLED;
}
const char *path = make_relative_path(headers->url);
ssize_t size = query_file_size(path);
if (size < 0) {
if (errno == ENOENT || errno == EISDIR) {
send_404(sock);
return HR_HANDLED;
} else {
send_500(sock);
return HR_HANDLED;
}
}
struct Buffer buffer = build_response_headers("200 OK", "text/plain; charset=UTF-8", size);
if (!buffer_append_file(&buffer, path)) {
buffer_free(buffer);
send_500(sock);
return HR_HANDLED;
}
sendall(sock, buffer.buf, buffer.len);
buffer_free(buffer);
return HR_HANDLED;
}
void plugin_register_yourself(register_callback_t callback) {
static_file_dir = getenv("STATIC_DIR");
if (!static_file_dir || access(static_file_dir, R_OK | X_OK) < 0) {
fprintf(stderr, "cserver: static: Environment variable $STATIC_DIR not set or directory not readable\n");
exit(1);
}
callback("static", &connection_handler);
}
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