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curl/lib/altsvc.c

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C
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/***************************************************************************
* _ _ ____ _
* Project ___| | | | _ \| |
* / __| | | | |_) | |
* | (__| |_| | _ <| |___
* \___|\___/|_| \_\_____|
*
* Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
*
* This software is licensed as described in the file COPYING, which
* you should have received as part of this distribution. The terms
* are also available at https://curl.se/docs/copyright.html.
*
* You may opt to use, copy, modify, merge, publish, distribute and/or sell
* copies of the Software, and permit persons to whom the Software is
* furnished to do so, under the terms of the COPYING file.
*
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
* KIND, either express or implied.
*
* SPDX-License-Identifier: curl
*
***************************************************************************/
/*
* The Alt-Svc: header is defined in RFC 7838:
* https://datatracker.ietf.org/doc/html/rfc7838
*/
#include "curl_setup.h"
#if !defined(CURL_DISABLE_HTTP) && !defined(CURL_DISABLE_ALTSVC)
#include <curl/curl.h>
#include "urldata.h"
#include "altsvc.h"
#include "curl_get_line.h"
#include "strcase.h"
#include "parsedate.h"
#include "sendf.h"
#include "warnless.h"
#include "fopen.h"
#include "rename.h"
#include "strdup.h"
#include "inet_pton.h"
/* The last 3 #include files should be in this order */
#include "curl_printf.h"
#include "curl_memory.h"
#include "memdebug.h"
#define MAX_ALTSVC_LINE 4095
#define MAX_ALTSVC_DATELENSTR "64"
#define MAX_ALTSVC_DATELEN 64
#define MAX_ALTSVC_HOSTLENSTR "512"
#define MAX_ALTSVC_HOSTLEN 512
#define MAX_ALTSVC_ALPNLENSTR "10"
#define MAX_ALTSVC_ALPNLEN 10
#define H3VERSION "h3"
static enum alpnid alpn2alpnid(char *name)
{
if(strcasecompare(name, "h1"))
return ALPN_h1;
if(strcasecompare(name, "h2"))
return ALPN_h2;
if(strcasecompare(name, H3VERSION))
return ALPN_h3;
return ALPN_none; /* unknown, probably rubbish input */
}
/* Given the ALPN ID, return the name */
const char *Curl_alpnid2str(enum alpnid id)
{
switch(id) {
case ALPN_h1:
return "h1";
case ALPN_h2:
return "h2";
case ALPN_h3:
return H3VERSION;
default:
return ""; /* bad */
}
}
static void altsvc_free(struct altsvc *as)
{
free(as->src.host);
free(as->dst.host);
free(as);
}
static struct altsvc *altsvc_createid(const char *srchost,
const char *dsthost,
enum alpnid srcalpnid,
enum alpnid dstalpnid,
unsigned int srcport,
unsigned int dstport)
{
struct altsvc *as = calloc(1, sizeof(struct altsvc));
size_t hlen;
size_t dlen;
if(!as)
return NULL;
hlen = strlen(srchost);
dlen = strlen(dsthost);
DEBUGASSERT(hlen);
DEBUGASSERT(dlen);
if(!hlen || !dlen) {
/* bad input */
free(as);
return NULL;
}
if((hlen > 2) && srchost[0] == '[') {
/* IPv6 address, strip off brackets */
srchost++;
hlen -= 2;
}
else if(srchost[hlen - 1] == '.')
/* strip off trailing dot */
hlen--;
if((dlen > 2) && dsthost[0] == '[') {
/* IPv6 address, strip off brackets */
dsthost++;
dlen -= 2;
}
as->src.host = Curl_memdup0(srchost, hlen);
if(!as->src.host)
goto error;
as->dst.host = Curl_memdup0(dsthost, dlen);
if(!as->dst.host)
goto error;
as->src.alpnid = srcalpnid;
as->dst.alpnid = dstalpnid;
as->src.port = curlx_ultous(srcport);
as->dst.port = curlx_ultous(dstport);
return as;
error:
altsvc_free(as);
return NULL;
}
static struct altsvc *altsvc_create(char *srchost,
char *dsthost,
char *srcalpn,
char *dstalpn,
unsigned int srcport,
unsigned int dstport)
{
enum alpnid dstalpnid = alpn2alpnid(dstalpn);
enum alpnid srcalpnid = alpn2alpnid(srcalpn);
if(!srcalpnid || !dstalpnid)
return NULL;
return altsvc_createid(srchost, dsthost, srcalpnid, dstalpnid,
srcport, dstport);
}
/* only returns SERIOUS errors */
static CURLcode altsvc_add(struct altsvcinfo *asi, char *line)
{
/* Example line:
h2 example.com 443 h3 shiny.example.com 8443 "20191231 10:00:00" 1
*/
char srchost[MAX_ALTSVC_HOSTLEN + 1];
char dsthost[MAX_ALTSVC_HOSTLEN + 1];
char srcalpn[MAX_ALTSVC_ALPNLEN + 1];
char dstalpn[MAX_ALTSVC_ALPNLEN + 1];
char date[MAX_ALTSVC_DATELEN + 1];
unsigned int srcport;
unsigned int dstport;
unsigned int prio;
unsigned int persist;
int rc;
rc = sscanf(line,
"%" MAX_ALTSVC_ALPNLENSTR "s %" MAX_ALTSVC_HOSTLENSTR "s %u "
"%" MAX_ALTSVC_ALPNLENSTR "s %" MAX_ALTSVC_HOSTLENSTR "s %u "
"\"%" MAX_ALTSVC_DATELENSTR "[^\"]\" %u %u",
srcalpn, srchost, &srcport,
dstalpn, dsthost, &dstport,
date, &persist, &prio);
if(9 == rc) {
struct altsvc *as;
time_t expires = Curl_getdate_capped(date);
as = altsvc_create(srchost, dsthost, srcalpn, dstalpn, srcport, dstport);
if(as) {
as->expires = expires;
as->prio = prio;
as->persist = persist ? 1 : 0;
Curl_llist_append(&asi->list, as, &as->node);
}
}
return CURLE_OK;
}
/*
* Load alt-svc entries from the given file. The text based line-oriented file
* format is documented here: https://curl.se/docs/alt-svc.html
*
* This function only returns error on major problems that prevent alt-svc
* handling to work completely. It will ignore individual syntactical errors
* etc.
*/
static CURLcode altsvc_load(struct altsvcinfo *asi, const char *file)
{
CURLcode result = CURLE_OK;
FILE *fp;
/* we need a private copy of the filename so that the altsvc cache file
name survives an easy handle reset */
free(asi->filename);
asi->filename = strdup(file);
if(!asi->filename)
return CURLE_OUT_OF_MEMORY;
fp = fopen(file, FOPEN_READTEXT);
if(fp) {
struct dynbuf buf;
Curl_dyn_init(&buf, MAX_ALTSVC_LINE);
while(Curl_get_line(&buf, fp)) {
char *lineptr = Curl_dyn_ptr(&buf);
while(*lineptr && ISBLANK(*lineptr))
lineptr++;
if(*lineptr == '#')
/* skip commented lines */
continue;
altsvc_add(asi, lineptr);
}
Curl_dyn_free(&buf); /* free the line buffer */
fclose(fp);
}
return result;
}
/*
* Write this single altsvc entry to a single output line
*/
static CURLcode altsvc_out(struct altsvc *as, FILE *fp)
{
struct tm stamp;
const char *dst6_pre = "";
const char *dst6_post = "";
const char *src6_pre = "";
const char *src6_post = "";
CURLcode result = Curl_gmtime(as->expires, &stamp);
if(result)
return result;
#ifdef USE_IPV6
else {
char ipv6_unused[16];
if(1 == Curl_inet_pton(AF_INET6, as->dst.host, ipv6_unused)) {
dst6_pre = "[";
dst6_post = "]";
}
if(1 == Curl_inet_pton(AF_INET6, as->src.host, ipv6_unused)) {
src6_pre = "[";
src6_post = "]";
}
}
#endif
fprintf(fp,
"%s %s%s%s %u "
"%s %s%s%s %u "
"\"%d%02d%02d "
"%02d:%02d:%02d\" "
"%u %u\n",
Curl_alpnid2str(as->src.alpnid),
src6_pre, as->src.host, src6_post,
as->src.port,
Curl_alpnid2str(as->dst.alpnid),
dst6_pre, as->dst.host, dst6_post,
as->dst.port,
stamp.tm_year + 1900, stamp.tm_mon + 1, stamp.tm_mday,
stamp.tm_hour, stamp.tm_min, stamp.tm_sec,
as->persist, as->prio);
return CURLE_OK;
}
/* ---- library-wide functions below ---- */
/*
* Curl_altsvc_init() creates a new altsvc cache.
* It returns the new instance or NULL if something goes wrong.
*/
struct altsvcinfo *Curl_altsvc_init(void)
{
struct altsvcinfo *asi = calloc(1, sizeof(struct altsvcinfo));
if(!asi)
return NULL;
Curl_llist_init(&asi->list, NULL);
/* set default behavior */
asi->flags = CURLALTSVC_H1
#ifdef USE_HTTP2
| CURLALTSVC_H2
#endif
#ifdef USE_HTTP3
| CURLALTSVC_H3
#endif
;
return asi;
}
/*
* Curl_altsvc_load() loads alt-svc from file.
*/
CURLcode Curl_altsvc_load(struct altsvcinfo *asi, const char *file)
{
CURLcode result;
DEBUGASSERT(asi);
result = altsvc_load(asi, file);
return result;
}
/*
* Curl_altsvc_ctrl() passes on the external bitmask.
*/
CURLcode Curl_altsvc_ctrl(struct altsvcinfo *asi, const long ctrl)
{
DEBUGASSERT(asi);
asi->flags = ctrl;
return CURLE_OK;
}
/*
* Curl_altsvc_cleanup() frees an altsvc cache instance and all associated
* resources.
*/
void Curl_altsvc_cleanup(struct altsvcinfo **altsvcp)
{
if(*altsvcp) {
struct Curl_llist_node *e;
struct Curl_llist_node *n;
struct altsvcinfo *altsvc = *altsvcp;
for(e = Curl_llist_head(&altsvc->list); e; e = n) {
struct altsvc *as = Curl_node_elem(e);
n = Curl_node_next(e);
altsvc_free(as);
}
free(altsvc->filename);
free(altsvc);
*altsvcp = NULL; /* clear the pointer */
}
}
/*
* Curl_altsvc_save() writes the altsvc cache to a file.
*/
CURLcode Curl_altsvc_save(struct Curl_easy *data,
struct altsvcinfo *altsvc, const char *file)
{
CURLcode result = CURLE_OK;
FILE *out;
char *tempstore = NULL;
if(!altsvc)
/* no cache activated */
return CURLE_OK;
/* if not new name is given, use the one we stored from the load */
if(!file && altsvc->filename)
file = altsvc->filename;
if((altsvc->flags & CURLALTSVC_READONLYFILE) || !file || !file[0])
/* marked as read-only, no file or zero length filename */
return CURLE_OK;
result = Curl_fopen(data, file, &out, &tempstore);
if(!result) {
struct Curl_llist_node *e;
struct Curl_llist_node *n;
fputs("# Your alt-svc cache. https://curl.se/docs/alt-svc.html\n"
"# This file was generated by libcurl! Edit at your own risk.\n",
out);
for(e = Curl_llist_head(&altsvc->list); e; e = n) {
struct altsvc *as = Curl_node_elem(e);
n = Curl_node_next(e);
result = altsvc_out(as, out);
if(result)
break;
}
fclose(out);
if(!result && tempstore && Curl_rename(tempstore, file))
result = CURLE_WRITE_ERROR;
if(result && tempstore)
unlink(tempstore);
}
free(tempstore);
return result;
}
static CURLcode getalnum(const char **ptr, char *alpnbuf, size_t buflen)
{
size_t len;
const char *protop;
const char *p = *ptr;
while(*p && ISBLANK(*p))
p++;
protop = p;
while(*p && !ISBLANK(*p) && (*p != ';') && (*p != '='))
p++;
len = p - protop;
*ptr = p;
if(!len || (len >= buflen))
return CURLE_BAD_FUNCTION_ARGUMENT;
memcpy(alpnbuf, protop, len);
alpnbuf[len] = 0;
return CURLE_OK;
}
/* hostcompare() returns true if 'host' matches 'check'. The first host
* argument may have a trailing dot present that will be ignored.
*/
static bool hostcompare(const char *host, const char *check)
{
size_t hlen = strlen(host);
size_t clen = strlen(check);
if(hlen && (host[hlen - 1] == '.'))
hlen--;
if(hlen != clen)
/* they cannot match if they have different lengths */
return FALSE;
return strncasecompare(host, check, hlen);
}
/* altsvc_flush() removes all alternatives for this source origin from the
list */
static void altsvc_flush(struct altsvcinfo *asi, enum alpnid srcalpnid,
const char *srchost, unsigned short srcport)
{
struct Curl_llist_node *e;
struct Curl_llist_node *n;
for(e = Curl_llist_head(&asi->list); e; e = n) {
struct altsvc *as = Curl_node_elem(e);
n = Curl_node_next(e);
if((srcalpnid == as->src.alpnid) &&
(srcport == as->src.port) &&
hostcompare(srchost, as->src.host)) {
Curl_node_remove(e);
altsvc_free(as);
}
}
}
#ifdef DEBUGBUILD
/* to play well with debug builds, we can *set* a fixed time this will
return */
static time_t altsvc_debugtime(void *unused)
{
char *timestr = getenv("CURL_TIME");
(void)unused;
if(timestr) {
long val = strtol(timestr, NULL, 10);
return (time_t)val;
}
return time(NULL);
}
#undef time
#define time(x) altsvc_debugtime(x)
#endif
#define ISNEWLINE(x) (((x) == '\n') || (x) == '\r')
/*
* Curl_altsvc_parse() takes an incoming alt-svc response header and stores
* the data correctly in the cache.
*
* 'value' points to the header *value*. That is contents to the right of the
* header name.
*
* Currently this function rejects invalid data without returning an error.
* Invalid hostname, port number will result in the specific alternative
* being rejected. Unknown protocols are skipped.
*/
CURLcode Curl_altsvc_parse(struct Curl_easy *data,
struct altsvcinfo *asi, const char *value,
enum alpnid srcalpnid, const char *srchost,
unsigned short srcport)
{
const char *p = value;
size_t len;
char namebuf[MAX_ALTSVC_HOSTLEN] = "";
char alpnbuf[MAX_ALTSVC_ALPNLEN] = "";
struct altsvc *as;
unsigned short dstport = srcport; /* the same by default */
CURLcode result = getalnum(&p, alpnbuf, sizeof(alpnbuf));
size_t entries = 0;
#ifdef CURL_DISABLE_VERBOSE_STRINGS
(void)data;
#endif
if(result) {
infof(data, "Excessive alt-svc header, ignoring.");
return CURLE_OK;
}
DEBUGASSERT(asi);
/* "clear" is a magic keyword */
if(strcasecompare(alpnbuf, "clear")) {
/* Flush cached alternatives for this source origin */
altsvc_flush(asi, srcalpnid, srchost, srcport);
return CURLE_OK;
}
do {
if(*p == '=') {
/* [protocol]="[host][:port]" */
enum alpnid dstalpnid = alpn2alpnid(alpnbuf); /* the same by default */
p++;
if(*p == '\"') {
const char *dsthost = "";
const char *value_ptr;
char option[32];
unsigned long num;
char *end_ptr;
bool quoted = FALSE;
time_t maxage = 24 * 3600; /* default is 24 hours */
bool persist = FALSE;
bool valid = TRUE;
p++;
if(*p != ':') {
/* hostname starts here */
const char *hostp = p;
if(*p == '[') {
/* pass all valid IPv6 letters - does not handle zone id */
len = strspn(++p, "0123456789abcdefABCDEF:.");
if(p[len] != ']')
/* invalid host syntax, bail out */
break;
/* we store the IPv6 numerical address *with* brackets */
len += 2;
p = &p[len-1];
}
else {
while(*p && (ISALNUM(*p) || (*p == '.') || (*p == '-')))
p++;
len = p - hostp;
}
if(!len || (len >= MAX_ALTSVC_HOSTLEN)) {
infof(data, "Excessive alt-svc hostname, ignoring.");
valid = FALSE;
}
else {
memcpy(namebuf, hostp, len);
namebuf[len] = 0;
dsthost = namebuf;
}
}
else {
/* no destination name, use source host */
dsthost = srchost;
}
if(*p == ':') {
unsigned long port = 0;
p++;
if(ISDIGIT(*p))
/* a port number */
port = strtoul(p, &end_ptr, 10);
else
end_ptr = (char *)p; /* not left uninitialized */
if(!port || port > USHRT_MAX || end_ptr == p || *end_ptr != '\"') {
infof(data, "Unknown alt-svc port number, ignoring.");
valid = FALSE;
}
else {
dstport = curlx_ultous(port);
p = end_ptr;
}
}
if(*p++ != '\"')
break;
/* Handle the optional 'ma' and 'persist' flags. Unknown flags
are skipped. */
for(;;) {
while(ISBLANK(*p))
p++;
if(*p != ';')
break;
p++; /* pass the semicolon */
if(!*p || ISNEWLINE(*p))
break;
result = getalnum(&p, option, sizeof(option));
if(result) {
/* skip option if name is too long */
option[0] = '\0';
}
while(*p && ISBLANK(*p))
p++;
if(*p != '=')
return CURLE_OK;
p++;
while(*p && ISBLANK(*p))
p++;
if(!*p)
return CURLE_OK;
if(*p == '\"') {
/* quoted value */
p++;
quoted = TRUE;
}
value_ptr = p;
if(quoted) {
while(*p && *p != '\"')
p++;
if(!*p++)
return CURLE_OK;
}
else {
while(*p && !ISBLANK(*p) && *p!= ';' && *p != ',')
p++;
}
num = strtoul(value_ptr, &end_ptr, 10);
if((end_ptr != value_ptr) && (num < ULONG_MAX)) {
if(strcasecompare("ma", option))
maxage = (time_t)num;
else if(strcasecompare("persist", option) && (num == 1))
persist = TRUE;
}
}
if(dstalpnid && valid) {
if(!entries++)
/* Flush cached alternatives for this source origin, if any - when
this is the first entry of the line. */
altsvc_flush(asi, srcalpnid, srchost, srcport);
as = altsvc_createid(srchost, dsthost,
srcalpnid, dstalpnid,
srcport, dstport);
if(as) {
/* The expires time also needs to take the Age: value (if any) into
account. [See RFC 7838 section 3.1] */
as->expires = maxage + time(NULL);
as->persist = persist;
Curl_llist_append(&asi->list, as, &as->node);
infof(data, "Added alt-svc: %s:%d over %s", dsthost, dstport,
Curl_alpnid2str(dstalpnid));
}
}
}
else
break;
/* after the double quote there can be a comma if there is another
string or a semicolon if no more */
if(*p == ',') {
/* comma means another alternative is presented */
p++;
result = getalnum(&p, alpnbuf, sizeof(alpnbuf));
if(result)
break;
}
}
else
break;
} while(*p && (*p != ';') && (*p != '\n') && (*p != '\r'));
return CURLE_OK;
}
/*
* Return TRUE on a match
*/
bool Curl_altsvc_lookup(struct altsvcinfo *asi,
enum alpnid srcalpnid, const char *srchost,
int srcport,
struct altsvc **dstentry,
const int versions) /* one or more bits */
{
struct Curl_llist_node *e;
struct Curl_llist_node *n;
time_t now = time(NULL);
DEBUGASSERT(asi);
DEBUGASSERT(srchost);
DEBUGASSERT(dstentry);
for(e = Curl_llist_head(&asi->list); e; e = n) {
struct altsvc *as = Curl_node_elem(e);
n = Curl_node_next(e);
if(as->expires < now) {
/* an expired entry, remove */
Curl_node_remove(e);
altsvc_free(as);
continue;
}
if((as->src.alpnid == srcalpnid) &&
hostcompare(srchost, as->src.host) &&
(as->src.port == srcport) &&
(versions & (int)as->dst.alpnid)) {
/* match */
*dstentry = as;
return TRUE;
}
}
return FALSE;
}
#endif /* !CURL_DISABLE_HTTP && !CURL_DISABLE_ALTSVC */
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