1 /*
2  * Copyright (c) 2020 Omar Polo <op@omarpolo.com>
3  *
4  * Permission to use, copy, modify, and distribute this software for any
5  * purpose with or without fee is hereby granted, provided that the above
6  * copyright notice and this permission notice appear in all copies.
7  *
8  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
15  */
16 
17 #include <ctype.h>
18 #include <string.h>
19 
20 #include "gmid.h"
21 
22 /*
23  * Notes from RFC3986
24  *
25  * => gemini://tanso.net/rfc/rfc3986.txt
26  *
27  *
28  * ABNF
29  * ====
30  *
31  * pct-encoded	"%" HEXDIG HEXDIG
32  *
33  * reserved	= gen-delims / sub-delimis
34  * gen-delims	= ":" / "/" / "?" / "#" / "[" / "]" / "@"
35  * sub-delims	= "!" / "$" / "&" / "'" / "(" / ")"
36  * 		/ "*" / "+" / "," / ";" / "="
37  *
38  * unreserved	= ALPHA / DIGIT / "-" / "." / "_" / "~"
39  *
40  * URI		= scheme ":" hier-part [ "?" query ] [ "#" fragment ]
41  *
42  * hier-part	= "//" authority path-abempty
43  * 		/ path-absolute
44  * 		/ path-rootless
45  * 		/ path-empty
46  *
47  * scheme	= ALPHA *( ALPHA / DIGIT / "+" / "-" / "." )
48  *
49  * authority	= [ userinfo "@" ] host [ ":" port ]
50  *
51  * (note that userinfo isn't used for Gemini URL)
52  *
53  * host		= IP-literal / IPv4address / reg-name
54  * reg-name	= *( unreserved / pct-encoded / sub-delims )
55  *
56  * port		= *DIGIT
57  *
58  * path		= path-abemty	; begins with "/" or is empty
59  * 		/ path-absolute	; begins with "/" but not "//"
60  * 		/ path-noscheme	; begins with a non-colon segment
61  * 		/ path-rootless ; begins with a segment
62  * 		/ path-empty	; zero characters
63  *
64  * path-abemty		= *( "/" segment )
65  * path-absolute	= "/" [ segment-nz *( "/" segment ) ]
66  * path-noscheme	= ; not used
67  * path-rootless	= ; not used
68  * path-empty		= ; not used
69  *
70  * segment		= *pchar
71  * segment-nz	= 1*pchar
72  * segment-nz-nc	= 1*( unreserved / pct-encoded / sub-delims / "@" )
73  * pchar		= unreserved / pct-encoded / sub-delims / ":" / "@"
74  *
75  * query		= *( pchar / "/" / "?" )
76  *
77  * fragment		= *( pchar / "/" / "?" )
78  *
79  *
80  * EXAMPLE
81  * =======
82  *
83  *    foo://example.com:8042/over/there?name=ferret#nose
84  *    \_/   \______________/\_________/ \_________/ \__/
85  *     |           |            |            |        |
86  *  scheme     authority       path        query   fragment
87  *
88  */
89 
90 /* XXX: these macros will expand multiple times their argument */
91 
92 #define UNRESERVED(p)				\
93 	(isalnum(p)				\
94 	    || p == '-'				\
95 	    || p == '.'				\
96 	    || p == '_'				\
97 	    || p == '~')
98 
99 #define SUB_DELIMITERS(p)			\
100 	(p == '!'				\
101 	    || p == '$'				\
102 	    || p == '&'				\
103 	    || p == '\''			\
104 	    || p == '('				\
105 	    || p == ')'				\
106 	    || p == '*'				\
107 	    || p == '+'				\
108 	    || p == ','				\
109 	    || p == ';'				\
110 	    || p == '=')
111 
112 static int
113 parse_pct_encoded(struct parser *p)
114 {
115 	if (*p->uri != '%')
116 		return 0;
117 
118 	if (!isxdigit(*(p->uri+1)) || !isxdigit(*(p->uri+2))) {
119 		p->err = "illegal percent-encoding";
120 		return 0;
121 	}
122 
123 	sscanf(p->uri+1, "%2hhx", p->uri);
124 	memmove(p->uri+1, p->uri+3, strlen(p->uri+3)+1);
125 	if (*p->uri == '\0') {
126 		p->err = "illegal percent-encoding";
127 		return 0;
128 	}
129 
130 	return 1;
131 }
132 
133 /* ALPHA *( ALPHA / DIGIT / "+" / "-" / "." ) "://" */
134 static int
135 parse_scheme(struct parser *p)
136 {
137 	p->parsed->schema = p->uri;
138 
139 	if (!isalpha(*p->uri)) {
140 		p->err = "illegal character in scheme";
141 		return 0;
142 	}
143 
144 	p->uri++;
145 	while (isalnum(*p->uri)
146 	    || *p->uri == '+'
147 	    || *p->uri == '-'
148 	    || *p->uri == '.')
149 		p->uri++;
150 
151 	if (*p->uri != ':') {
152 		p->err = "illegal character in scheme";
153 		return 0;
154 	}
155 
156 	*p->uri = '\0';
157 	if (*(++p->uri) != '/' || *(++p->uri) != '/') {
158 		p->err = "invalid marker after scheme";
159 		return 0;
160 	}
161 
162 	p->uri++;
163 	return 1;
164 }
165 
166 /* *DIGIT */
167 static int
168 parse_port(struct parser *p)
169 {
170 	uint32_t i = 0;
171 
172 	p->parsed->port = p->uri;
173 
174 	for (; isdigit(*p->uri); p->uri++) {
175 		i = i * 10 + *p->uri - '0';
176 		if (i > UINT16_MAX) {
177 			p->err = "port number too large";
178 			return 0;
179 		}
180 	}
181 
182 	if (*p->uri != '/' && *p->uri != '\0') {
183 		p->err = "illegal character in port number";
184 		return 0;
185 	}
186 
187 	p->parsed->port_no = i;
188 
189 	if (*p->uri != '\0') {
190 		*p->uri = '\0';
191 		p->uri++;
192 	}
193 
194 	return 1;
195 }
196 
197 /* TODO: add support for ip-literal and ipv4addr ? */
198 /* *( unreserved / sub-delims / pct-encoded ) */
199 static int
200 parse_authority(struct parser *p)
201 {
202 	p->parsed->host = p->uri;
203 
204 	while (UNRESERVED(*p->uri)
205 	    || SUB_DELIMITERS(*p->uri)
206 	    || parse_pct_encoded(p))
207 		p->uri++;
208 
209 	if (p->err != NULL)
210 		return 0;
211 
212 	if (*p->uri == ':') {
213 		*p->uri = '\0';
214 		p->uri++;
215 		return parse_port(p);
216 	}
217 
218 	if (*p->uri == '/') {
219 		*p->uri = '\0';
220 		p->uri++;
221 		return 1;
222 	}
223 
224 	if (*p->uri == '\0')
225 		return 1;
226 
227 	p->err = "illegal character in authority section";
228 	return 0;
229 }
230 
231 /* Routine for path_clean.  Elide the pointed .. with the preceding
232  * element.  Return 0 if it's not possible.  incr is the length of
233  * the increment, 3 for ../ and 2 for .. */
234 static int
235 path_elide_dotdot(char *path, char *i, int incr)
236 {
237 	char *j;
238 
239 	if (i == path)
240 		return 0;
241 	for (j = i-2; j != path && *j != '/'; j--)
242                 /* noop */ ;
243 	if (*j == '/')
244 		j++;
245 	i += incr;
246 	memmove(j, i, strlen(i)+1);
247 	return 1;
248 }
249 
250 /*
251  * Use an algorithm similar to the one implemented in go' path.Clean:
252  *
253  * 1. Replace multiple slashes with a single slash
254  * 2. Eliminate each . path name element
255  * 3. Eliminate each inner .. along with the non-.. element that precedes it
256  * 4. Eliminate trailing .. if possible or error (go would only discard)
257  *
258  * Unlike path.Clean, this function return the empty string if the
259  * original path is equivalent to "/".
260  */
261 static int
262 path_clean(char *path)
263 {
264 	char *i;
265 
266 	/* 1. replace multiple slashes with a single one */
267 	for (i = path; *i; ++i) {
268 		if (*i == '/' && *(i+1) == '/') {
269 			memmove(i, i+1, strlen(i)); /* move also the \0 */
270 			i--;
271 		}
272 	}
273 
274 	/* 2. eliminate each . path name element */
275 	for (i = path; *i; ++i) {
276 		if ((i == path || *i == '/') && *(i+1) == '.' &&
277 		    *(i+2) == '/') {
278 			/* move also the \0 */
279 			memmove(i, i+2, strlen(i)-1);
280 			i--;
281 		}
282 	}
283 	if (!strcmp(path, ".") || !strcmp(path, "/.")) {
284 		*path = '\0';
285 		return 1;
286 	}
287 
288 	/* 3. eliminate each inner .. along with the preceding non-.. */
289 	for (i = strstr(path, "../"); i != NULL; i = strstr(path, ".."))
290 		if (!path_elide_dotdot(path, i, 3))
291 			return 0;
292 
293 	/* 4. eliminate trailing ..*/
294 	if ((i = strstr(path, "..")) != NULL)
295 		if (!path_elide_dotdot(path, i, 2))
296 			return 0;
297 
298 	return 1;
299 }
300 
301 static int
302 parse_query(struct parser *p)
303 {
304 	p->parsed->query = p->uri;
305 	if (*p->uri == '\0')
306 		return 1;
307 
308 	while (UNRESERVED(*p->uri)
309 	    || SUB_DELIMITERS(*p->uri)
310 	    || *p->uri == '/'
311 	    || *p->uri == '?'
312 	    || parse_pct_encoded(p)
313 	    || valid_multibyte_utf8(p))
314 		p->uri++;
315 
316 	if (p->err != NULL)
317 		return 0;
318 
319 	if (*p->uri != '\0' && *p->uri != '#') {
320 		p->err = "illegal character in query";
321 		return 0;
322 	}
323 
324 	if (*p->uri != '\0') {
325 		*p->uri = '\0';
326 		p->uri++;
327 	}
328 
329 	return 1;
330 }
331 
332 /* don't even bother */
333 static int
334 parse_fragment(struct parser *p)
335 {
336 	p->parsed->fragment = p->uri;
337 	return 1;
338 }
339 
340 /* XXX: is it too broad? */
341 /* *(pchar / "/") */
342 static int
343 parse_path(struct parser *p)
344 {
345 	char c;
346 
347 	p->parsed->path = p->uri;
348 	if (*p->uri == '\0') {
349 		p->parsed->query = p->parsed->fragment = p->uri;
350 		return 1;
351 	}
352 
353 	while (UNRESERVED(*p->uri)
354 	    || SUB_DELIMITERS(*p->uri)
355 	    || *p->uri == '/'
356 	    || parse_pct_encoded(p)
357 	    || valid_multibyte_utf8(p))
358 		p->uri++;
359 
360 	if (p->err != NULL)
361 		return 0;
362 
363 	if (*p->uri != '\0' && *p->uri != '?' && *p->uri != '#') {
364 		p->err = "illegal character in path";
365 		return 0;
366 	}
367 
368 	if (*p->uri != '\0') {
369 		c = *p->uri;
370 		*p->uri = '\0';
371 		p->uri++;
372 
373 		if (c == '#') {
374 			if (!parse_fragment(p))
375 				return 0;
376 		} else
377 			if (!parse_query(p) || !parse_fragment(p))
378 				return 0;
379 	}
380 
381 	if (!path_clean(p->parsed->path)) {
382 		p->err = "illegal path";
383 		return 0;
384 	}
385 
386 	return 1;
387 }
388 
389 int
390 parse_uri(char *uri, struct uri *ret, const char **err_ret)
391 {
392 	char *end;
393 	struct parser p = {uri, ret, NULL};
394 
395 	bzero(ret, sizeof(*ret));
396 
397 	/* initialize optional stuff to the empty string */
398 	end = uri + strlen(uri);
399 	p.parsed->port = end;
400 	p.parsed->path = end;
401 	p.parsed->query = end;
402 	p.parsed->fragment = end;
403 
404 	if (!parse_scheme(&p) || !parse_authority(&p) || !parse_path(&p)) {
405 		*err_ret = p.err;
406 		return 0;
407 	}
408 
409 	*err_ret = NULL;
410 	return 1;
411 }
412 
413 int
414 trim_req_uri(char *uri)
415 {
416 	char *i;
417 
418 	if ((i = strstr(uri, "\r\n")) == NULL)
419 		return 0;
420 	*i = '\0';
421 	return 1;
422 }