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suckless-quark/http.c
Laslo Hunhold c51b31d7ac
Refactor response-generation 
I wasn't happy with how responses were generated. HTTP-headers were
handled by hand and it was duplicated in multiple parts of the code.
Due to the duplication, some functions like timestamp() had really
ugly semantics.

The HTTP requests are parsed much better: We have an enum of fields
we care about that are automatically read into our request struct. This
commit adapts this idea to the response: We have an enum of fields
we might put into our response, and a response-struct holds the
content of these fields. A function http_send_header() automatically
sends a header based on the entries in response. In case we don't
use a field, we just leave the field in the response-struct empty.

With this commit, some logical changes came with it:

  - timestamp() now has a sane signature, TIMESTAMP_LEN is no more and
    it can now return proper errors and is also reentrant by using
    gmtime_r() instead of gmtime()
  - No more use of a static timestamp-array, making all the methods
    also reentrant
  - Better internal-error-reporting: Because the fields are filled
    before and not during sending the response-headers, we can better
    report any internal errors as status 500 instead of sending a
    partial non-500-header and then dying.

These improved data structures make it easier to read and hack the code
and implement new features, if desired.

Signed-off-by: Laslo Hunhold <dev@frign.de>
2020-08-05 13:41:44 +02:00

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/* See LICENSE file for copyright and license details. */
#include <arpa/inet.h>
#include <ctype.h>
#include <errno.h>
#include <limits.h>
#include <netinet/in.h>
#include <regex.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include <strings.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <time.h>
#include <unistd.h>
#include "config.h"
#include "http.h"
#include "resp.h"
#include "util.h"
const char *req_field_str[] = {
[REQ_HOST] = "Host",
[REQ_RANGE] = "Range",
[REQ_MOD] = "If-Modified-Since",
};
const char *req_method_str[] = {
[M_GET] = "GET",
[M_HEAD] = "HEAD",
};
const char *status_str[] = {
[S_OK] = "OK",
[S_PARTIAL_CONTENT] = "Partial Content",
[S_MOVED_PERMANENTLY] = "Moved Permanently",
[S_NOT_MODIFIED] = "Not Modified",
[S_BAD_REQUEST] = "Bad Request",
[S_FORBIDDEN] = "Forbidden",
[S_NOT_FOUND] = "Not Found",
[S_METHOD_NOT_ALLOWED] = "Method Not Allowed",
[S_REQUEST_TIMEOUT] = "Request Time-out",
[S_RANGE_NOT_SATISFIABLE] = "Range Not Satisfiable",
[S_REQUEST_TOO_LARGE] = "Request Header Fields Too Large",
[S_INTERNAL_SERVER_ERROR] = "Internal Server Error",
[S_VERSION_NOT_SUPPORTED] = "HTTP Version not supported",
};
const char *res_field_str[] = {
[RES_ACCEPT_RANGES] = "Accept-Ranges",
[RES_ALLOW] = "Allow",
[RES_LOCATION] = "Location",
[RES_LAST_MODIFIED] = "Last-Modified",
[RES_CONTENT_LENGTH] = "Content-Length",
[RES_CONTENT_RANGE] = "Content-Range",
[RES_CONTENT_TYPE] = "Content-Type",
};
enum status
http_send_header(int fd, const struct response *res)
{
char t[FIELD_MAX];
size_t i;
if (timestamp(t, sizeof(t), time(NULL))) {
return S_INTERNAL_SERVER_ERROR;
}
if (dprintf(fd,
"HTTP/1.1 %d %s\r\n"
"Date: %s\r\n"
"Connection: close\r\n",
res->status, status_str[res->status], t) < 0) {
return S_REQUEST_TIMEOUT;
}
for (i = 0; i < NUM_RES_FIELDS; i++) {
if (res->field[i][0] != '\0') {
if (dprintf(fd, "%s: %s\r\n", res_field_str[i],
res->field[i]) < 0) {
return S_REQUEST_TIMEOUT;
}
}
}
if (dprintf(fd, "\r\n") < 0) {
return S_REQUEST_TIMEOUT;
}
return res->status;
}
enum status
http_send_status(int fd, enum status s)
{
enum status sendstatus;
struct response res = {
.status = s,
.field[RES_CONTENT_TYPE] = "text/html; charset=utf-8",
};
if (s == S_METHOD_NOT_ALLOWED) {
if (esnprintf(res.field[RES_ALLOW],
sizeof(res.field[RES_ALLOW]), "%s",
"Allow: GET, HEAD")) {
return S_INTERNAL_SERVER_ERROR;
}
}
if ((sendstatus = http_send_header(fd, &res)) != s) {
return sendstatus;
}
if (dprintf(fd,
"<!DOCTYPE html>\n<html>\n\t<head>\n"
"\t\t<title>%d %s</title>\n\t</head>\n\t<body>\n"
"\t\t<h1>%d %s</h1>\n\t</body>\n</html>\n",
s, status_str[s], s, status_str[s]) < 0) {
return S_REQUEST_TIMEOUT;
}
return s;
}
static void
decode(char src[PATH_MAX], char dest[PATH_MAX])
{
size_t i;
uint8_t n;
char *s;
for (s = src, i = 0; *s; s++, i++) {
if (*s == '%' && (sscanf(s + 1, "%2hhx", &n) == 1)) {
dest[i] = n;
s += 2;
} else {
dest[i] = *s;
}
}
dest[i] = '\0';
}
int
http_get_request(int fd, struct request *r)
{
struct in6_addr addr;
size_t hlen, i, mlen;
ssize_t off;
char h[HEADER_MAX], *p, *q;
/* empty all fields */
memset(r, 0, sizeof(*r));
/*
* receive header
*/
for (hlen = 0; ;) {
if ((off = read(fd, h + hlen, sizeof(h) - hlen)) < 0) {
return http_send_status(fd, S_REQUEST_TIMEOUT);
} else if (off == 0) {
break;
}
hlen += off;
if (hlen >= 4 && !memcmp(h + hlen - 4, "\r\n\r\n", 4)) {
break;
}
if (hlen == sizeof(h)) {
return http_send_status(fd, S_REQUEST_TOO_LARGE);
}
}
/* remove terminating empty line */
if (hlen < 2) {
return http_send_status(fd, S_BAD_REQUEST);
}
hlen -= 2;
/* null-terminate the header */
h[hlen] = '\0';
/*
* parse request line
*/
/* METHOD */
for (i = 0; i < NUM_REQ_METHODS; i++) {
mlen = strlen(req_method_str[i]);
if (!strncmp(req_method_str[i], h, mlen)) {
r->method = i;
break;
}
}
if (i == NUM_REQ_METHODS) {
return http_send_status(fd, S_METHOD_NOT_ALLOWED);
}
/* a single space must follow the method */
if (h[mlen] != ' ') {
return http_send_status(fd, S_BAD_REQUEST);
}
/* basis for next step */
p = h + mlen + 1;
/* TARGET */
if (!(q = strchr(p, ' '))) {
return http_send_status(fd, S_BAD_REQUEST);
}
*q = '\0';
if (q - p + 1 > PATH_MAX) {
return http_send_status(fd, S_REQUEST_TOO_LARGE);
}
memcpy(r->target, p, q - p + 1);
decode(r->target, r->target);
/* basis for next step */
p = q + 1;
/* HTTP-VERSION */
if (strncmp(p, "HTTP/", sizeof("HTTP/") - 1)) {
return http_send_status(fd, S_BAD_REQUEST);
}
p += sizeof("HTTP/") - 1;
if (strncmp(p, "1.0", sizeof("1.0") - 1) &&
strncmp(p, "1.1", sizeof("1.1") - 1)) {
return http_send_status(fd, S_VERSION_NOT_SUPPORTED);
}
p += sizeof("1.*") - 1;
/* check terminator */
if (strncmp(p, "\r\n", sizeof("\r\n") - 1)) {
return http_send_status(fd, S_BAD_REQUEST);
}
/* basis for next step */
p += sizeof("\r\n") - 1;
/*
* parse request-fields
*/
/* match field type */
for (; *p != '\0';) {
for (i = 0; i < NUM_REQ_FIELDS; i++) {
if (!strncasecmp(p, req_field_str[i],
strlen(req_field_str[i]))) {
break;
}
}
if (i == NUM_REQ_FIELDS) {
/* unmatched field, skip this line */
if (!(q = strstr(p, "\r\n"))) {
return http_send_status(fd, S_BAD_REQUEST);
}
p = q + (sizeof("\r\n") - 1);
continue;
}
p += strlen(req_field_str[i]);
/* a single colon must follow the field name */
if (*p != ':') {
return http_send_status(fd, S_BAD_REQUEST);
}
/* skip whitespace */
for (++p; *p == ' ' || *p == '\t'; p++)
;
/* extract field content */
if (!(q = strstr(p, "\r\n"))) {
return http_send_status(fd, S_BAD_REQUEST);
}
*q = '\0';
if (q - p + 1 > FIELD_MAX) {
return http_send_status(fd, S_REQUEST_TOO_LARGE);
}
memcpy(r->field[i], p, q - p + 1);
/* go to next line */
p = q + (sizeof("\r\n") - 1);
}
/*
* clean up host
*/
p = strrchr(r->field[REQ_HOST], ':');
q = strrchr(r->field[REQ_HOST], ']');
/* strip port suffix but don't interfere with IPv6 bracket notation
* as per RFC 2732 */
if (p && (!q || p > q)) {
/* port suffix must not be empty */
if (*(p + 1) == '\0') {
return http_send_status(fd, S_BAD_REQUEST);
}
*p = '\0';
}
/* strip the brackets from the IPv6 notation and validate the address */
if (q) {
/* brackets must be on the outside */
if (r->field[REQ_HOST][0] != '[' || *(q + 1) != '\0') {
return http_send_status(fd, S_BAD_REQUEST);
}
/* remove the right bracket */
*q = '\0';
p = r->field[REQ_HOST] + 1;
/* validate the contained IPv6 address */
if (inet_pton(AF_INET6, p, &addr) != 1) {
return http_send_status(fd, S_BAD_REQUEST);
}
/* copy it into the host field */
memmove(r->field[REQ_HOST], p, q - p + 1);
}
return 0;
}
static void
encode(char src[PATH_MAX], char dest[PATH_MAX])
{
size_t i;
char *s;
for (s = src, i = 0; *s && i < (PATH_MAX - 4); s++) {
if (iscntrl(*s) || (unsigned char)*s > 127) {
i += snprintf(dest + i, PATH_MAX - i, "%%%02X",
(unsigned char)*s);
} else {
dest[i] = *s;
i++;
}
}
dest[i] = '\0';
}
static int
normabspath(char *path)
{
size_t len;
int last = 0;
char *p, *q;
/* require and skip first slash */
if (path[0] != '/') {
return 1;
}
p = path + 1;
/* get length of path */
len = strlen(p);
for (; !last; ) {
/* bound path component within (p,q) */
if (!(q = strchr(p, '/'))) {
q = strchr(p, '\0');
last = 1;
}
if (p == q || (q - p == 1 && p[0] == '.')) {
/* "/" or "./" */
goto squash;
} else if (q - p == 2 && p[0] == '.' && p[1] == '.') {
/* "../" */
if (p != path + 1) {
/* place p right after the previous / */
for (p -= 2; p > path && *p != '/'; p--);
p++;
}
goto squash;
} else {
/* move on */
p = q + 1;
continue;
}
squash:
/* squash (p,q) into void */
if (last) {
*p = '\0';
len = p - path;
} else {
memmove(p, q + 1, len - ((q + 1) - path) + 2);
len -= (q + 1) - p;
}
}
return 0;
}
static enum status
parse_range(char *s, off_t size, off_t *lower, off_t *upper)
{
char *p, *q;
const char *err;
/* default to the complete range */
*lower = 0;
*upper = size - 1;
/* done if no range-string is given */
if (s == NULL || *s == '\0') {
return 0;
}
/* skip opening statement */
if (strncmp(s, "bytes=", sizeof("bytes=") - 1)) {
return S_BAD_REQUEST;
}
p = s + (sizeof("bytes=") - 1);
/* find hyphen and replace with \0 */
if (!(q = strchr(p, '-'))) {
return S_BAD_REQUEST;
}
*(q++) = '\0';
/*
* byte-range=first\0last...
* ^ ^
* | |
* p q
*/
/*
* make sure we only have a single range, and not a comma
* separated list, which we will refuse to accept out of spite
* towards this horrible part of the spec
*/
if (strchr(q, ',')) {
return S_RANGE_NOT_SATISFIABLE;
}
if (p[0] != '\0') {
/*
* Range has format "first-last" or "first-",
* i.e. return bytes 'first' to 'last' (or the
* last byte if 'last' is not given),
* inclusively, and byte-numbering beginning at 0
*/
*lower = strtonum(p, 0, LLONG_MAX, &err);
if (!err) {
if (q[0] != '\0') {
*upper = strtonum(q, 0, LLONG_MAX, &err);
} else {
*upper = size - 1;
}
}
if (err) {
/* one of the strtonum()'s failed */
return S_BAD_REQUEST;
}
/* check ranges */
if (*lower > *upper || *lower >= size) {
return S_RANGE_NOT_SATISFIABLE;
}
/* adjust upper limit to be at most the last byte */
*upper = MIN(*upper, size - 1);
} else {
/*
* Range has format "-num", i.e. return the 'num'
* last bytes
*/
/*
* use upper as a temporary storage for 'num',
* as we know 'upper' is size - 1
*/
*upper = strtonum(q, 0, LLONG_MAX, &err);
if (err) {
return S_BAD_REQUEST;
}
/* determine lower */
if (*upper > size) {
/* more bytes requested than we have */
*lower = 0;
} else {
*lower = size - *upper;
}
/* set upper to the correct value */
*upper = size - 1;
}
/* reset \0 to the hyphen */
*(q - 1) = '-';
return 0;
}
#undef RELPATH
#define RELPATH(x) ((!*(x) || !strcmp(x, "/")) ? "." : ((x) + 1))
enum status
http_send_response(int fd, struct request *r)
{
struct in6_addr addr;
struct response res = { 0 };
struct stat st;
struct tm tm = { 0 };
size_t len, i;
off_t lower, upper;
int hasport, ipv6host;
static char realtarget[PATH_MAX], tmptarget[PATH_MAX];
char *p, *mime;
const char *vhostmatch, *targethost;
/* make a working copy of the target */
memcpy(realtarget, r->target, sizeof(realtarget));
/* match vhost */
vhostmatch = NULL;
if (s.vhost) {
for (i = 0; i < s.vhost_len; i++) {
/* switch to vhost directory if there is a match */
if (!regexec(&s.vhost[i].re, r->field[REQ_HOST], 0,
NULL, 0)) {
if (chdir(s.vhost[i].dir) < 0) {
return http_send_status(fd, (errno == EACCES) ?
S_FORBIDDEN : S_NOT_FOUND);
}
vhostmatch = s.vhost[i].chost;
break;
}
}
if (i == s.vhost_len) {
return http_send_status(fd, S_NOT_FOUND);
}
/* if we have a vhost prefix, prepend it to the target */
if (s.vhost[i].prefix) {
if (esnprintf(tmptarget, sizeof(tmptarget), "%s%s",
s.vhost[i].prefix, realtarget)) {
return http_send_status(fd, S_REQUEST_TOO_LARGE);
}
memcpy(realtarget, tmptarget, sizeof(realtarget));
}
}
/* apply target prefix mapping */
for (i = 0; i < s.map_len; i++) {
len = strlen(s.map[i].from);
if (!strncmp(realtarget, s.map[i].from, len)) {
/* match canonical host if vhosts are enabled and
* the mapping specifies a canonical host */
if (s.vhost && s.map[i].chost &&
strcmp(s.map[i].chost, vhostmatch)) {
continue;
}
/* swap out target prefix */
if (esnprintf(tmptarget, sizeof(tmptarget), "%s%s",
s.map[i].to, realtarget + len)) {
return http_send_status(fd, S_REQUEST_TOO_LARGE);
}
memcpy(realtarget, tmptarget, sizeof(realtarget));
break;
}
}
/* normalize target */
if (normabspath(realtarget)) {
return http_send_status(fd, S_BAD_REQUEST);
}
/* reject hidden target */
if (realtarget[0] == '.' || strstr(realtarget, "/.")) {
return http_send_status(fd, S_FORBIDDEN);
}
/* stat the target */
if (stat(RELPATH(realtarget), &st) < 0) {
return http_send_status(fd, (errno == EACCES) ?
S_FORBIDDEN : S_NOT_FOUND);
}
if (S_ISDIR(st.st_mode)) {
/* add / to target if not present */
len = strlen(realtarget);
if (len >= PATH_MAX - 2) {
return http_send_status(fd, S_REQUEST_TOO_LARGE);
}
if (len && realtarget[len - 1] != '/') {
realtarget[len] = '/';
realtarget[len + 1] = '\0';
}
}
/* redirect if targets differ, host is non-canonical or we prefixed */
if (strcmp(r->target, realtarget) || (s.vhost && vhostmatch &&
strcmp(r->field[REQ_HOST], vhostmatch))) {
res.status = S_MOVED_PERMANENTLY;
/* encode realtarget */
encode(realtarget, tmptarget);
/* determine target location */
if (s.vhost) {
/* absolute redirection URL */
targethost = r->field[REQ_HOST][0] ? vhostmatch ?
vhostmatch : r->field[REQ_HOST] : s.host ?
s.host : "localhost";
/* do we need to add a port to the Location? */
hasport = s.port && strcmp(s.port, "80");
/* RFC 2732 specifies to use brackets for IPv6-addresses
* in URLs, so we need to check if our host is one and
* honor that later when we fill the "Location"-field */
if ((ipv6host = inet_pton(AF_INET6, targethost,
&addr)) < 0) {
return http_send_status(fd,
S_INTERNAL_SERVER_ERROR);
}
/* write location to response struct */
if (esnprintf(res.field[RES_LOCATION],
sizeof(res.field[RES_LOCATION]),
"//%s%s%s%s%s%s",
ipv6host ? "[" : "",
targethost,
ipv6host ? "]" : "", hasport ? ":" : "",
hasport ? s.port : "", tmptarget)) {
return http_send_status(fd, S_REQUEST_TOO_LARGE);
}
} else {
/* write relative redirection URL to response struct */
if (esnprintf(res.field[RES_LOCATION],
sizeof(res.field[RES_LOCATION]),
tmptarget)) {
return http_send_status(fd, S_REQUEST_TOO_LARGE);
}
}
return http_send_header(fd, &res);
}
if (S_ISDIR(st.st_mode)) {
/* append docindex to target */
if (esnprintf(realtarget, sizeof(realtarget), "%s%s",
r->target, s.docindex)) {
return http_send_status(fd, S_REQUEST_TOO_LARGE);
}
/* stat the docindex, which must be a regular file */
if (stat(RELPATH(realtarget), &st) < 0 || !S_ISREG(st.st_mode)) {
if (s.listdirs) {
/* remove index suffix and serve dir */
realtarget[strlen(realtarget) -
strlen(s.docindex)] = '\0';
return resp_dir(fd, RELPATH(realtarget), r);
} else {
/* reject */
if (!S_ISREG(st.st_mode) || errno == EACCES) {
return http_send_status(fd, S_FORBIDDEN);
} else {
return http_send_status(fd, S_NOT_FOUND);
}
}
}
}
/* modified since */
if (r->field[REQ_MOD][0]) {
/* parse field */
if (!strptime(r->field[REQ_MOD], "%a, %d %b %Y %T GMT", &tm)) {
return http_send_status(fd, S_BAD_REQUEST);
}
/* compare with last modification date of the file */
if (difftime(st.st_mtim.tv_sec, timegm(&tm)) <= 0) {
res.status = S_NOT_MODIFIED;
return http_send_header(fd, &res);
}
}
/* range */
switch (parse_range(r->field[REQ_RANGE], st.st_size, &lower, &upper)) {
case S_RANGE_NOT_SATISFIABLE:
res.status = S_RANGE_NOT_SATISFIABLE;
if (esnprintf(res.field[RES_CONTENT_RANGE],
sizeof(res.field[RES_CONTENT_RANGE]),
"bytes */%zu", st.st_size)) {
return http_send_status(fd, S_INTERNAL_SERVER_ERROR);
}
return http_send_header(fd, &res);
case S_BAD_REQUEST:
return http_send_status(fd, S_BAD_REQUEST);
default:
;
}
/* mime */
mime = "application/octet-stream";
if ((p = strrchr(realtarget, '.'))) {
for (i = 0; i < sizeof(mimes) / sizeof(*mimes); i++) {
if (!strcmp(mimes[i].ext, p + 1)) {
mime = mimes[i].type;
break;
}
}
}
return resp_file(fd, RELPATH(realtarget), r, &st, mime, lower, upper);
}
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