mirror of
https://github.com/omar-polo/gmid.git
synced 2024-09-07 03:49:24 +02:00
Some particularly crafted IRIs can cause a denial of service (DOS). IRIs which have a trailing `..' segment and resolve to a valid IRI (i.e. a .. that's not escaping the root directory) will make the server process loop forever. This is """just""" an DOS vulnerability, it doesn't expose anything sensitive or give an attacker anything else.
463 lines
8.5 KiB
C
463 lines
8.5 KiB
C
/*
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* Copyright (c) 2020 Omar Polo <op@omarpolo.com>
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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#include "gmid.h"
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#include <ctype.h>
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#include <string.h>
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static inline int
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unreserved(int p)
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{
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return isalnum(p)
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|| p == '-'
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|| p == '.'
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|| p == '_'
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|| p == '~';
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}
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static inline int
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sub_delimiters(int p)
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{
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return p == '!'
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|| p == '$'
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|| p == '&'
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|| p == '\''
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|| p == '('
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|| p == ')'
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|| p == '*'
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|| p == '+'
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|| p == ','
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|| p == ';'
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|| p == '=';
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}
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static int
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valid_pct_enc_string(char *s)
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{
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if (*s != '%')
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return 1;
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if (!isxdigit(s[1]) || !isxdigit(s[2]))
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return 0;
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if (s[1] == '0' && s[2] == '0')
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return 0;
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return 1;
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}
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static int
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valid_pct_encoded(struct parser *p)
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{
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if (p->iri[0] != '%')
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return 0;
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if (!valid_pct_enc_string(p->iri)) {
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p->err = "illegal percent-encoding";
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return 0;
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}
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p->iri += 2;
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return 1;
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}
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static void
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pct_decode(char *s)
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{
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sscanf(s+1, "%2hhx", s);
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memmove(s+1, s+3, strlen(s+3)+1);
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}
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static int
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parse_pct_encoded(struct parser *p)
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{
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if (p->iri[0] != '%')
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return 0;
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if (!valid_pct_enc_string(p->iri)) {
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p->err = "illegal percent-encoding";
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return 0;
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}
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pct_decode(p->iri);
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if (*p->iri == '\0') {
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p->err = "illegal percent-encoding";
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return 0;
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}
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return 1;
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}
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/* ALPHA *( ALPHA / DIGIT / "+" / "-" / "." ) "://" */
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static int
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parse_scheme(struct parser *p)
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{
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p->parsed->schema = p->iri;
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if (!isalpha(*p->iri)) {
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p->err = "illegal character in scheme";
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return 0;
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}
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do {
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/* normalize the scheme (i.e. lowercase it)
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*
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* XXX: since we cannot have good things, tolower
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* behaviour depends on the LC_CTYPE locale. The good
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* news is that we're sure p->iri points to something
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* that's in the ASCII range, so tolower can't
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* mis-behave on some systems due to the locale. */
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*p->iri = tolower(*p->iri);
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p->iri++;
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} while (isalnum(*p->iri)
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|| *p->iri == '+'
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|| *p->iri == '-'
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|| *p->iri == '.');
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if (*p->iri != ':') {
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p->err = "illegal character in scheme";
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return 0;
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}
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*p->iri = '\0';
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if (p->iri[1] != '/' || p->iri[2] != '/') {
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p->err = "invalid marker after scheme";
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return 0;
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}
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p->iri += 3;
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return 1;
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}
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/* *DIGIT */
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static int
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parse_port(struct parser *p)
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{
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uint32_t i = 0;
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p->parsed->port = p->iri;
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for (; isdigit(*p->iri); p->iri++) {
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i = i * 10 + *p->iri - '0';
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if (i > UINT16_MAX) {
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p->err = "port number too large";
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return 0;
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}
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}
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if (*p->iri != '/' && *p->iri != '\0') {
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p->err = "illegal character in port number";
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return 0;
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}
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p->parsed->port_no = i;
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if (*p->iri != '\0') {
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*p->iri = '\0';
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p->iri++;
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}
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return 1;
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}
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/* TODO: add support for ip-literal and ipv4addr ? */
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/* *( unreserved / sub-delims / pct-encoded ) */
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static int
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parse_authority(struct parser *p)
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{
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p->parsed->host = p->iri;
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while (unreserved(*p->iri)
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|| sub_delimiters(*p->iri)
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|| parse_pct_encoded(p)
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|| valid_multibyte_utf8(p)) {
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/* normalize the host name. */
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if (*p->iri < 0x7F)
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*p->iri = tolower(*p->iri);
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p->iri++;
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}
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if (p->err != NULL)
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return 0;
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if (*p->iri == ':') {
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*p->iri = '\0';
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p->iri++;
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return parse_port(p);
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} else
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p->parsed->port_no = 1965;
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if (*p->iri == '/') {
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*p->iri = '\0';
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p->iri++;
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return 1;
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}
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if (*p->iri == '\0')
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return 1;
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p->err = "illegal character in authority section";
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return 0;
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}
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/* Routine for path_clean. Elide the pointed .. with the preceding
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* element. Return 0 if it's not possible. incr is the length of
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* the increment, 3 for ../ and 2 for .. */
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static int
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path_elide_dotdot(char *path, char *i, int incr)
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{
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char *j;
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if (i == path)
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return 0;
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for (j = i-2; j != path && *j != '/'; j--)
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/* noop */ ;
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if (*j == '/')
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j++;
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i += incr;
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memmove(j, i, strlen(i)+1);
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return 1;
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}
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/*
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* Use an algorithm similar to the one implemented in go' path.Clean:
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*
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* 1. Replace multiple slashes with a single slash
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* 2. Eliminate each . path name element
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* 3. Eliminate each inner .. along with the non-.. element that precedes it
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* 4. Eliminate trailing .. if possible or error (go would only discard)
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*
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* Unlike path.Clean, this function return the empty string if the
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* original path is equivalent to "/".
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*/
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static int
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path_clean(char *path)
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{
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char *i;
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/* 1. replace multiple slashes with a single one */
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for (i = path; *i; ++i) {
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if (*i == '/' && *(i+1) == '/') {
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memmove(i, i+1, strlen(i)); /* move also the \0 */
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i--;
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}
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}
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/* 2. eliminate each . path name element */
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for (i = path; *i; ++i) {
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if ((i == path || *i == '/') &&
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*i != '.' && i[1] == '.' && i[2] == '/') {
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/* move also the \0 */
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memmove(i, i+2, strlen(i)-1);
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i--;
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}
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}
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if (!strcmp(path, ".") || !strcmp(path, "/.")) {
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*path = '\0';
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return 1;
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}
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/* 3. eliminate each inner .. along with the preceding non-.. */
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for (i = strstr(path, "../"); i != NULL; i = strstr(path, "..")) {
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/* break if we've found a trailing .. */
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if (i[2] == '\0')
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break;
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if (!path_elide_dotdot(path, i, 3))
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return 0;
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}
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/* 4. eliminate trailing ..*/
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if ((i = strstr(path, "..")) != NULL)
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if (!path_elide_dotdot(path, i, 2))
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return 0;
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return 1;
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}
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static int
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parse_query(struct parser *p)
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{
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p->parsed->query = p->iri;
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if (*p->iri == '\0')
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return 1;
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while (unreserved(*p->iri)
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|| sub_delimiters(*p->iri)
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|| *p->iri == '/'
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|| *p->iri == '?'
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|| *p->iri == ':'
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|| *p->iri == '@'
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|| valid_pct_encoded(p)
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|| valid_multibyte_utf8(p))
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p->iri++;
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if (p->err != NULL)
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return 0;
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if (*p->iri != '\0' && *p->iri != '#') {
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p->err = "illegal character in query";
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return 0;
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}
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if (*p->iri != '\0') {
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*p->iri = '\0';
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p->iri++;
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}
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return 1;
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}
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/* don't even bother */
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static int
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parse_fragment(struct parser *p)
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{
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p->parsed->fragment = p->iri;
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return 1;
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}
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/* XXX: is it too broad? */
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/* *(pchar / "/") */
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static int
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parse_path(struct parser *p)
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{
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char c;
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/* trim initial slashes */
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while (*p->iri == '/')
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p->iri++;
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p->parsed->path = p->iri;
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if (*p->iri == '\0') {
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p->parsed->query = p->parsed->fragment = p->iri;
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return 1;
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}
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while (unreserved(*p->iri)
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|| sub_delimiters(*p->iri)
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|| *p->iri == '/'
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|| parse_pct_encoded(p)
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|| valid_multibyte_utf8(p))
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p->iri++;
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if (p->err != NULL)
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return 0;
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if (*p->iri != '\0' && *p->iri != '?' && *p->iri != '#') {
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p->err = "illegal character in path";
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return 0;
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}
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if (*p->iri != '\0') {
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c = *p->iri;
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*p->iri = '\0';
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p->iri++;
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if (c == '#') {
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if (!parse_fragment(p))
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return 0;
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} else
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if (!parse_query(p) || !parse_fragment(p))
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return 0;
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}
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if (!path_clean(p->parsed->path)) {
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p->err = "illegal path";
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return 0;
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}
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return 1;
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}
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int
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parse_iri(char *iri, struct iri *ret, const char **err_ret)
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{
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char *end;
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struct parser p = {iri, ret, NULL};
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bzero(ret, sizeof(*ret));
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/* initialize optional stuff to the empty string */
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end = iri + strlen(iri);
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p.parsed->host = end;
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p.parsed->port = end;
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p.parsed->path = end;
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p.parsed->query = end;
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p.parsed->fragment = end;
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if (!parse_scheme(&p) || !parse_authority(&p) || !parse_path(&p)) {
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*err_ret = p.err;
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return 0;
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}
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*err_ret = NULL;
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return 1;
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}
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int
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trim_req_iri(char *iri, const char **err)
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{
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char *i;
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if ((i = strstr(iri, "\r\n")) == NULL) {
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*err = "missing CRLF";
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return 0;
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}
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*i = '\0';
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return 1;
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}
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int
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serialize_iri(struct iri *i, char *buf, size_t len)
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{
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size_t l;
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/* in ex.c we receive empty "" strings as NULL */
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if (i->schema == NULL || i->host == NULL) {
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memset(buf, 0, len);
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return 0;
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}
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strlcpy(buf, i->schema, len);
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strlcat(buf, "://", len);
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strlcat(buf, i->host, len);
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strlcat(buf, "/", len);
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if (i->path != NULL)
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l = strlcat(buf, i->path, len);
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if (i->query != NULL && *i->query != '\0') {
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strlcat(buf, "?", len);
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l = strlcat(buf, i->query, len);
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}
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return l < len;
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}
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char *
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pct_decode_str(char *s)
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{
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char *t;
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for (t = s; *t; ++t) {
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if (*t == '%' && valid_pct_enc_string(t))
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pct_decode(t);
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}
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return s;
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}
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