1/* punycode.c Implementation of punycode used to ASCII encode IDN's.
2 * Copyright (C) 2002, 2003 Simon Josefsson
3 *
4 * This file is part of GNU Libidn.
5 *
6 * GNU Libidn is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
9 * version 2.1 of the License, or (at your option) any later version.
10 *
11 * GNU Libidn is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Lesser General Public License for more details.
15 *
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with GNU Libidn; if not, see <http://www.gnu.org/licenses/>.
18 */
19
20/*
21 * This file is derived from RFC 3492bis written by Adam M. Costello.
22 *
23 * Disclaimer and license: Regarding this entire document or any
24 * portion of it (including the pseudocode and C code), the author
25 * makes no guarantees and is not responsible for any damage resulting
26 * from its use. The author grants irrevocable permission to anyone
27 * to use, modify, and distribute it in any way that does not diminish
28 * the rights of anyone else to use, modify, and distribute it,
29 * provided that redistributed derivative works do not contain
30 * misleading author or version information. Derivative works need
31 * not be licensed under similar terms.
32 *
33 * Copyright (C) The Internet Society (2003). All Rights Reserved.
34 *
35 * This document and translations of it may be copied and furnished to
36 * others, and derivative works that comment on or otherwise explain it
37 * or assist in its implementation may be prepared, copied, published
38 * and distributed, in whole or in part, without restriction of any
39 * kind, provided that the above copyright notice and this paragraph are
40 * included on all such copies and derivative works. However, this
41 * document itself may not be modified in any way, such as by removing
42 * the copyright notice or references to the Internet Society or other
43 * Internet organizations, except as needed for the purpose of
44 * developing Internet standards in which case the procedures for
45 * copyrights defined in the Internet Standards process must be
46 * followed, or as required to translate it into languages other than
47 * English.
48 *
49 * The limited permissions granted above are perpetual and will not be
50 * revoked by the Internet Society or its successors or assigns.
51 *
52 * This document and the information contained herein is provided on an
53 * "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
54 * TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
55 * BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
56 * HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
57 * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
58 */
59
60#include <string.h>
61
62#include "punycode.h"
63
64/*** Bootstring parameters for Punycode ***/
65
66enum
67{ base = 36, tmin = 1, tmax = 26, skew = 38, damp = 700,
68 initial_bias = 72, initial_n = 0x80, delimiter = 0x2D
69};
70
71/* basic(cp) tests whether cp is a basic code point: */
72#define basic(cp) ((punycode_uint)(cp) < 0x80)
73
74/* delim(cp) tests whether cp is a delimiter: */
75#define delim(cp) ((cp) == delimiter)
76
77/* decode_digit(cp) returns the numeric value of a basic code */
78/* point (for use in representing integers) in the range 0 to */
79/* base-1, or base if cp does not represent a value. */
80
81static punycode_uint
82decode_digit (punycode_uint cp)
83{
84 return cp - 48 < 10 ? cp - 22 : cp - 65 < 26 ? cp - 65 :
85 cp - 97 < 26 ? cp - 97 : base;
86}
87
88/* encode_digit(d,flag) returns the basic code point whose value */
89/* (when used for representing integers) is d, which needs to be in */
90/* the range 0 to base-1. The lowercase form is used unless flag is */
91/* nonzero, in which case the uppercase form is used. The behavior */
92/* is undefined if flag is nonzero and digit d has no uppercase form. */
93
94static char
95encode_digit (punycode_uint d, int flag)
96{
97 return d + 22 + 75 * (d < 26) - ((flag != 0) << 5);
98 /* 0..25 map to ASCII a..z or A..Z */
99 /* 26..35 map to ASCII 0..9 */
100}
101
102/* flagged(bcp) tests whether a basic code point is flagged */
103/* (uppercase). The behavior is undefined if bcp is not a */
104/* basic code point. */
105
106#define flagged(bcp) ((punycode_uint)(bcp) - 65 < 26)
107
108/* encode_basic(bcp,flag) forces a basic code point to lowercase */
109/* if flag is zero, uppercase if flag is nonzero, and returns */
110/* the resulting code point. The code point is unchanged if it */
111/* is caseless. The behavior is undefined if bcp is not a basic */
112/* code point. */
113
114static char
115encode_basic (punycode_uint bcp, int flag)
116{
117 bcp -= (bcp - 97 < 26) << 5;
118 return bcp + ((!flag && (bcp - 65 < 26)) << 5);
119}
120
121/*** Platform-specific constants ***/
122
123/* maxint is the maximum value of a punycode_uint variable: */
124static const punycode_uint maxint = -1;
125/* Because maxint is unsigned, -1 becomes the maximum value. */
126
127/*** Bias adaptation function ***/
128
129static punycode_uint
130adapt (punycode_uint delta, punycode_uint numpoints, int firsttime)
131{
132 punycode_uint k;
133
134 delta = firsttime ? delta / damp : delta >> 1;
135 /* delta >> 1 is a faster way of doing delta / 2 */
136 delta += delta / numpoints;
137
138 for (k = 0; delta > ((base - tmin) * tmax) / 2; k += base)
139 {
140 delta /= base - tmin;
141 }
142
143 return k + (base - tmin + 1) * delta / (delta + skew);
144}
145
146/*** Main encode function ***/
147
148/**
149 * punycode_encode:
150 * @input_length: The number of code points in the @input array and
151 * the number of flags in the @case_flags array.
152 * @input: An array of code points. They are presumed to be Unicode
153 * code points, but that is not strictly REQUIRED. The array
154 * contains code points, not code units. UTF-16 uses code units
155 * D800 through DFFF to refer to code points 10000..10FFFF. The
156 * code points D800..DFFF do not occur in any valid Unicode string.
157 * The code points that can occur in Unicode strings (0..D7FF and
158 * E000..10FFFF) are also called Unicode scalar values.
159 * @case_flags: A %NULL pointer or an array of boolean values parallel
160 * to the @input array. Nonzero (true, flagged) suggests that the
161 * corresponding Unicode character be forced to uppercase after
162 * being decoded (if possible), and zero (false, unflagged) suggests
163 * that it be forced to lowercase (if possible). ASCII code points
164 * (0..7F) are encoded literally, except that ASCII letters are
165 * forced to uppercase or lowercase according to the corresponding
166 * case flags. If @case_flags is a %NULL pointer then ASCII letters
167 * are left as they are, and other code points are treated as
168 * unflagged.
169 * @output_length: The caller passes in the maximum number of ASCII
170 * code points that it can receive. On successful return it will
171 * contain the number of ASCII code points actually output.
172 * @output: An array of ASCII code points. It is *not*
173 * null-terminated; it will contain zeros if and only if the @input
174 * contains zeros. (Of course the caller can leave room for a
175 * terminator and add one if needed.)
176 *
177 * Converts a sequence of code points (presumed to be Unicode code
178 * points) to Punycode.
179 *
180 * Return value: The return value can be any of the punycode_status
181 * values defined above except %punycode_bad_input. If not
182 * %punycode_success, then @output_size and @output might contain
183 * garbage.
184 **/
185int
186punycode_encode (size_t input_length,
187 const punycode_uint input[],
188 const unsigned char case_flags[],
189 size_t * output_length, char output[])
190{
191 punycode_uint input_len, n, delta, h, b, bias, j, m, q, k, t;
192 size_t out, max_out;
193
194 /* The Punycode spec assumes that the input length is the same type */
195 /* of integer as a code point, so we need to convert the size_t to */
196 /* a punycode_uint, which could overflow. */
197
198 if (input_length > maxint)
199 return punycode_overflow;
200 input_len = (punycode_uint) input_length;
201
202 /* Initialize the state: */
203
204 n = initial_n;
205 delta = 0;
206 out = 0;
207 max_out = *output_length;
208 bias = initial_bias;
209
210 /* Handle the basic code points: */
211
212 for (j = 0; j < input_len; ++j)
213 {
214 if (basic (input[j]))
215 {
216 if (max_out - out < 2)
217 return punycode_big_output;
218 output[out++] = case_flags ?
219 encode_basic (input[j], case_flags[j]) : (char) input[j];
220 }
221 /* else if (input[j] < n) return punycode_bad_input; */
222 /* (not needed for Punycode with unsigned code points) */
223 }
224
225 h = b = (punycode_uint) out;
226 /* cannot overflow because out <= input_len <= maxint */
227
228 /* h is the number of code points that have been handled, b is the */
229 /* number of basic code points, and out is the number of ASCII code */
230 /* points that have been output. */
231
232 if (b > 0)
233 output[out++] = delimiter;
234
235 /* Main encoding loop: */
236
237 while (h < input_len)
238 {
239 /* All non-basic code points < n have been */
240 /* handled already. Find the next larger one: */
241
242 for (m = maxint, j = 0; j < input_len; ++j)
243 {
244 /* if (basic(input[j])) continue; */
245 /* (not needed for Punycode) */
246 if (input[j] >= n && input[j] < m)
247 m = input[j];
248 }
249
250 /* Increase delta enough to advance the decoder's */
251 /* <n,i> state to <m,0>, but guard against overflow: */
252
253 if (m - n > (maxint - delta) / (h + 1))
254 return punycode_overflow;
255 delta += (m - n) * (h + 1);
256 n = m;
257
258 for (j = 0; j < input_len; ++j)
259 {
260 /* Punycode does not need to check whether input[j] is basic: */
261 if (input[j] < n /* || basic(input[j]) */ )
262 {
263 if (++delta == 0)
264 return punycode_overflow;
265 }
266
267 if (input[j] == n)
268 {
269 /* Represent delta as a generalized variable-length integer: */
270
271 for (q = delta, k = base;; k += base)
272 {
273 if (out >= max_out)
274 return punycode_big_output;
275 t = k <= bias /* + tmin */ ? tmin : /* +tmin not needed */
276 k >= bias + tmax ? tmax : k - bias;
277 if (q < t)
278 break;
279 output[out++] = encode_digit (t + (q - t) % (base - t), 0);
280 q = (q - t) / (base - t);
281 }
282
283 output[out++] = encode_digit (q, case_flags && case_flags[j]);
284 bias = adapt (delta, h + 1, h == b);
285 delta = 0;
286 ++h;
287 }
288 }
289
290 ++delta, ++n;
291 }
292
293 *output_length = out;
294 return punycode_success;
295}
296
297/*** Main decode function ***/
298
299/**
300 * punycode_decode:
301 * @input_length: The number of ASCII code points in the @input array.
302 * @input: An array of ASCII code points (0..7F).
303 * @output_length: The caller passes in the maximum number of code
304 * points that it can receive into the @output array (which is also
305 * the maximum number of flags that it can receive into the
306 * @case_flags array, if @case_flags is not a %NULL pointer). On
307 * successful return it will contain the number of code points
308 * actually output (which is also the number of flags actually
309 * output, if case_flags is not a null pointer). The decoder will
310 * never need to output more code points than the number of ASCII
311 * code points in the input, because of the way the encoding is
312 * defined. The number of code points output cannot exceed the
313 * maximum possible value of a punycode_uint, even if the supplied
314 * @output_length is greater than that.
315 * @output: An array of code points like the input argument of
316 * punycode_encode() (see above).
317 * @case_flags: A %NULL pointer (if the flags are not needed by the
318 * caller) or an array of boolean values parallel to the @output
319 * array. Nonzero (true, flagged) suggests that the corresponding
320 * Unicode character be forced to uppercase by the caller (if
321 * possible), and zero (false, unflagged) suggests that it be forced
322 * to lowercase (if possible). ASCII code points (0..7F) are output
323 * already in the proper case, but their flags will be set
324 * appropriately so that applying the flags would be harmless.
325 *
326 * Converts Punycode to a sequence of code points (presumed to be
327 * Unicode code points).
328 *
329 * Return value: The return value can be any of the punycode_status
330 * values defined above. If not %punycode_success, then
331 * @output_length, @output, and @case_flags might contain garbage.
332 *
333 **/
334int
335punycode_decode (size_t input_length,
336 const char input[],
337 size_t * output_length,
338 punycode_uint output[], unsigned char case_flags[])
339{
340 punycode_uint n, out, i, max_out, bias, oldi, w, k, digit, t;
341 size_t b, j, in;
342
343 /* Initialize the state: */
344
345 n = initial_n;
346 out = i = 0;
347 max_out = *output_length > maxint ? maxint
348 : (punycode_uint) * output_length;
349 bias = initial_bias;
350
351 /* Handle the basic code points: Let b be the number of input code */
352 /* points before the last delimiter, or 0 if there is none, then */
353 /* copy the first b code points to the output. */
354
355 for (b = j = 0; j < input_length; ++j)
356 if (delim (input[j]))
357 b = j;
358 if (b > max_out)
359 return punycode_big_output;
360
361 for (j = 0; j < b; ++j)
362 {
363 if (case_flags)
364 case_flags[out] = flagged (input[j]);
365 if (!basic (input[j]))
366 return punycode_bad_input;
367 output[out++] = input[j];
368 }
369
370 /* Main decoding loop: Start just after the last delimiter if any */
371 /* basic code points were copied; start at the beginning otherwise. */
372
373 for (in = b > 0 ? b + 1 : 0; in < input_length; ++out)
374 {
375
376 /* in is the index of the next ASCII code point to be consumed, */
377 /* and out is the number of code points in the output array. */
378
379 /* Decode a generalized variable-length integer into delta, */
380 /* which gets added to i. The overflow checking is easier */
381 /* if we increase i as we go, then subtract off its starting */
382 /* value at the end to obtain delta. */
383
384 for (oldi = i, w = 1, k = base;; k += base)
385 {
386 if (in >= input_length)
387 return punycode_bad_input;
388 digit = decode_digit (input[in++]);
389 if (digit >= base)
390 return punycode_bad_input;
391 if (digit > (maxint - i) / w)
392 return punycode_overflow;
393 i += digit * w;
394 t = k <= bias /* + tmin */ ? tmin : /* +tmin not needed */
395 k >= bias + tmax ? tmax : k - bias;
396 if (digit < t)
397 break;
398 if (w > maxint / (base - t))
399 return punycode_overflow;
400 w *= (base - t);
401 }
402
403 bias = adapt (i - oldi, out + 1, oldi == 0);
404
405 /* i was supposed to wrap around from out+1 to 0, */
406 /* incrementing n each time, so we'll fix that now: */
407
408 if (i / (out + 1) > maxint - n)
409 return punycode_overflow;
410 n += i / (out + 1);
411 i %= (out + 1);
412
413 /* Insert n at position i of the output: */
414
415 /* not needed for Punycode: */
416 /* if (basic(n)) return punycode_invalid_input; */
417 if (out >= max_out)
418 return punycode_big_output;
419
420 if (case_flags)
421 {
422 memmove (case_flags + i + 1, case_flags + i, out - i);
423 /* Case of last ASCII code point determines case flag: */
424 case_flags[i] = flagged (input[in - 1]);
425 }
426
427 memmove (output + i + 1, output + i, (out - i) * sizeof *output);
428 output[i++] = n;
429 }
430
431 *output_length = (size_t) out;
432 /* cannot overflow because out <= old value of *output_length */
433 return punycode_success;
434}
435
436/**
437 * punycode_uint
438 *
439 * Unicode code point data type, this is always a 32 bit unsigned
440 * integer.
441 */
442
443/**
444 * Punycode_status
445 * @PUNYCODE_SUCCESS: Successful operation. This value is guaranteed
446 * to always be zero, the remaining ones are only guaranteed to hold
447 * non-zero values, for logical comparison purposes.
448 * @PUNYCODE_BAD_INPUT: Input is invalid.
449 * @PUNYCODE_BIG_OUTPUT: Output would exceed the space provided.
450 * @PUNYCODE_OVERFLOW: Input needs wider integers to process.
451 *
452 * Enumerated return codes of punycode_encode() and punycode_decode().
453 * The value 0 is guaranteed to always correspond to success.
454 */
455