00001 /* punycode.c --- Implementation of punycode used to ASCII encode IDN's. 00002 * Copyright (C) 2002, 2003, 2004 Simon Josefsson 00003 * 00004 * This file is part of GNU Libidn. 00005 * 00006 * GNU Libidn is free software; you can redistribute it and/or 00007 * modify it under the terms of the GNU Lesser General Public 00008 * License as published by the Free Software Foundation; either 00009 * version 2.1 of the License, or (at your option) any later version. 00010 * 00011 * GNU Libidn is distributed in the hope that it will be useful, 00012 * but WITHOUT ANY WARRANTY; without even the implied warranty of 00013 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 00014 * Lesser General Public License for more details. 00015 * 00016 * You should have received a copy of the GNU Lesser General Public 00017 * License along with GNU Libidn; if not, write to the Free Software 00018 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA 00019 * 00020 */ 00021 00022 /* 00023 * This file is derived from RFC 3492bis written by Adam M. Costello. 00024 * 00025 * Disclaimer and license: Regarding this entire document or any 00026 * portion of it (including the pseudocode and C code), the author 00027 * makes no guarantees and is not responsible for any damage resulting 00028 * from its use. The author grants irrevocable permission to anyone 00029 * to use, modify, and distribute it in any way that does not diminish 00030 * the rights of anyone else to use, modify, and distribute it, 00031 * provided that redistributed derivative works do not contain 00032 * misleading author or version information. Derivative works need 00033 * not be licensed under similar terms. 00034 * 00035 * Copyright (C) The Internet Society (2003). All Rights Reserved. 00036 * 00037 * This document and translations of it may be copied and furnished to 00038 * others, and derivative works that comment on or otherwise explain it 00039 * or assist in its implementation may be prepared, copied, published 00040 * and distributed, in whole or in part, without restriction of any 00041 * kind, provided that the above copyright notice and this paragraph are 00042 * included on all such copies and derivative works. However, this 00043 * document itself may not be modified in any way, such as by removing 00044 * the copyright notice or references to the Internet Society or other 00045 * Internet organizations, except as needed for the purpose of 00046 * developing Internet standards in which case the procedures for 00047 * copyrights defined in the Internet Standards process must be 00048 * followed, or as required to translate it into languages other than 00049 * English. 00050 * 00051 * The limited permissions granted above are perpetual and will not be 00052 * revoked by the Internet Society or its successors or assigns. 00053 * 00054 * This document and the information contained herein is provided on an 00055 * "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING 00056 * TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING 00057 * BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION 00058 * HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF 00059 * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 00060 */ 00061 00062 #include <string.h> 00063 00064 #include "punycode.h" 00065 00066 /*** Bootstring parameters for Punycode ***/ 00067 00068 enum 00069 { base = 36, tmin = 1, tmax = 26, skew = 38, damp = 700, 00070 initial_bias = 72, initial_n = 0x80, delimiter = 0x2D 00071 }; 00072 00073 /* basic(cp) tests whether cp is a basic code point: */ 00074 #define basic(cp) ((punycode_uint)(cp) < 0x80) 00075 00076 /* delim(cp) tests whether cp is a delimiter: */ 00077 #define delim(cp) ((cp) == delimiter) 00078 00079 /* decode_digit(cp) returns the numeric value of a basic code */ 00080 /* point (for use in representing integers) in the range 0 to */ 00081 /* base-1, or base if cp does not represent a value. */ 00082 00083 static punycode_uint 00084 decode_digit (punycode_uint cp) 00085 { 00086 return cp - 48 < 10 ? cp - 22 : cp - 65 < 26 ? cp - 65 : 00087 cp - 97 < 26 ? cp - 97 : base; 00088 } 00089 00090 /* encode_digit(d,flag) returns the basic code point whose value */ 00091 /* (when used for representing integers) is d, which needs to be in */ 00092 /* the range 0 to base-1. The lowercase form is used unless flag is */ 00093 /* nonzero, in which case the uppercase form is used. The behavior */ 00094 /* is undefined if flag is nonzero and digit d has no uppercase form. */ 00095 00096 static char 00097 encode_digit (punycode_uint d, int flag) 00098 { 00099 return d + 22 + 75 * (d < 26) - ((flag != 0) << 5); 00100 /* 0..25 map to ASCII a..z or A..Z */ 00101 /* 26..35 map to ASCII 0..9 */ 00102 } 00103 00104 /* flagged(bcp) tests whether a basic code point is flagged */ 00105 /* (uppercase). The behavior is undefined if bcp is not a */ 00106 /* basic code point. */ 00107 00108 #define flagged(bcp) ((punycode_uint)(bcp) - 65 < 26) 00109 00110 /* encode_basic(bcp,flag) forces a basic code point to lowercase */ 00111 /* if flag is zero, uppercase if flag is nonzero, and returns */ 00112 /* the resulting code point. The code point is unchanged if it */ 00113 /* is caseless. The behavior is undefined if bcp is not a basic */ 00114 /* code point. */ 00115 00116 static char 00117 encode_basic (punycode_uint bcp, int flag) 00118 { 00119 bcp -= (bcp - 97 < 26) << 5; 00120 return bcp + ((!flag && (bcp - 65 < 26)) << 5); 00121 } 00122 00123 /*** Platform-specific constants ***/ 00124 00125 /* maxint is the maximum value of a punycode_uint variable: */ 00126 static const punycode_uint maxint = -1; 00127 /* Because maxint is unsigned, -1 becomes the maximum value. */ 00128 00129 /*** Bias adaptation function ***/ 00130 00131 static punycode_uint 00132 adapt (punycode_uint delta, punycode_uint numpoints, int firsttime) 00133 { 00134 punycode_uint k; 00135 00136 delta = firsttime ? delta / damp : delta >> 1; 00137 /* delta >> 1 is a faster way of doing delta / 2 */ 00138 delta += delta / numpoints; 00139 00140 for (k = 0; delta > ((base - tmin) * tmax) / 2; k += base) 00141 { 00142 delta /= base - tmin; 00143 } 00144 00145 return k + (base - tmin + 1) * delta / (delta + skew); 00146 } 00147 00148 /*** Main encode function ***/ 00149 00187 int 00188 punycode_encode (size_t input_length, 00189 const punycode_uint input[], 00190 const unsigned char case_flags[], 00191 size_t * output_length, char output[]) 00192 { 00193 punycode_uint input_len, n, delta, h, b, bias, j, m, q, k, t; 00194 size_t out, max_out; 00195 00196 /* The Punycode spec assumes that the input length is the same type */ 00197 /* of integer as a code point, so we need to convert the size_t to */ 00198 /* a punycode_uint, which could overflow. */ 00199 00200 if (input_length > maxint) 00201 return punycode_overflow; 00202 input_len = (punycode_uint) input_length; 00203 00204 /* Initialize the state: */ 00205 00206 n = initial_n; 00207 delta = 0; 00208 out = 0; 00209 max_out = *output_length; 00210 bias = initial_bias; 00211 00212 /* Handle the basic code points: */ 00213 00214 for (j = 0; j < input_len; ++j) 00215 { 00216 if (basic (input[j])) 00217 { 00218 if (max_out - out < 2) 00219 return punycode_big_output; 00220 output[out++] = case_flags ? 00221 encode_basic (input[j], case_flags[j]) : (char) input[j]; 00222 } 00223 /* else if (input[j] < n) return punycode_bad_input; */ 00224 /* (not needed for Punycode with unsigned code points) */ 00225 } 00226 00227 h = b = (punycode_uint) out; 00228 /* cannot overflow because out <= input_len <= maxint */ 00229 00230 /* h is the number of code points that have been handled, b is the */ 00231 /* number of basic code points, and out is the number of ASCII code */ 00232 /* points that have been output. */ 00233 00234 if (b > 0) 00235 output[out++] = delimiter; 00236 00237 /* Main encoding loop: */ 00238 00239 while (h < input_len) 00240 { 00241 /* All non-basic code points < n have been */ 00242 /* handled already. Find the next larger one: */ 00243 00244 for (m = maxint, j = 0; j < input_len; ++j) 00245 { 00246 /* if (basic(input[j])) continue; */ 00247 /* (not needed for Punycode) */ 00248 if (input[j] >= n && input[j] < m) 00249 m = input[j]; 00250 } 00251 00252 /* Increase delta enough to advance the decoder's */ 00253 /* <n,i> state to <m,0>, but guard against overflow: */ 00254 00255 if (m - n > (maxint - delta) / (h + 1)) 00256 return punycode_overflow; 00257 delta += (m - n) * (h + 1); 00258 n = m; 00259 00260 for (j = 0; j < input_len; ++j) 00261 { 00262 /* Punycode does not need to check whether input[j] is basic: */ 00263 if (input[j] < n /* || basic(input[j]) */ ) 00264 { 00265 if (++delta == 0) 00266 return punycode_overflow; 00267 } 00268 00269 if (input[j] == n) 00270 { 00271 /* Represent delta as a generalized variable-length integer: */ 00272 00273 for (q = delta, k = base;; k += base) 00274 { 00275 if (out >= max_out) 00276 return punycode_big_output; 00277 t = k <= bias /* + tmin */ ? tmin : /* +tmin not needed */ 00278 k >= bias + tmax ? tmax : k - bias; 00279 if (q < t) 00280 break; 00281 output[out++] = encode_digit (t + (q - t) % (base - t), 0); 00282 q = (q - t) / (base - t); 00283 } 00284 00285 output[out++] = encode_digit (q, case_flags && case_flags[j]); 00286 bias = adapt (delta, h + 1, h == b); 00287 delta = 0; 00288 ++h; 00289 } 00290 } 00291 00292 ++delta, ++n; 00293 } 00294 00295 *output_length = out; 00296 return punycode_success; 00297 } 00298 00299 /*** Main decode function ***/ 00300 00336 int 00337 punycode_decode (size_t input_length, 00338 const char input[], 00339 size_t * output_length, 00340 punycode_uint output[], unsigned char case_flags[]) 00341 { 00342 punycode_uint n, out, i, max_out, bias, oldi, w, k, digit, t; 00343 size_t b, j, in; 00344 00345 /* Initialize the state: */ 00346 00347 n = initial_n; 00348 out = i = 0; 00349 max_out = *output_length > maxint ? maxint 00350 : (punycode_uint) * output_length; 00351 bias = initial_bias; 00352 00353 /* Handle the basic code points: Let b be the number of input code */ 00354 /* points before the last delimiter, or 0 if there is none, then */ 00355 /* copy the first b code points to the output. */ 00356 00357 for (b = j = 0; j < input_length; ++j) 00358 if (delim (input[j])) 00359 b = j; 00360 if (b > max_out) 00361 return punycode_big_output; 00362 00363 for (j = 0; j < b; ++j) 00364 { 00365 if (case_flags) 00366 case_flags[out] = flagged (input[j]); 00367 if (!basic (input[j])) 00368 return punycode_bad_input; 00369 output[out++] = input[j]; 00370 } 00371 00372 /* Main decoding loop: Start just after the last delimiter if any */ 00373 /* basic code points were copied; start at the beginning otherwise. */ 00374 00375 for (in = b > 0 ? b + 1 : 0; in < input_length; ++out) 00376 { 00377 00378 /* in is the index of the next ASCII code point to be consumed, */ 00379 /* and out is the number of code points in the output array. */ 00380 00381 /* Decode a generalized variable-length integer into delta, */ 00382 /* which gets added to i. The overflow checking is easier */ 00383 /* if we increase i as we go, then subtract off its starting */ 00384 /* value at the end to obtain delta. */ 00385 00386 for (oldi = i, w = 1, k = base;; k += base) 00387 { 00388 if (in >= input_length) 00389 return punycode_bad_input; 00390 digit = decode_digit (input[in++]); 00391 if (digit >= base) 00392 return punycode_bad_input; 00393 if (digit > (maxint - i) / w) 00394 return punycode_overflow; 00395 i += digit * w; 00396 t = k <= bias /* + tmin */ ? tmin : /* +tmin not needed */ 00397 k >= bias + tmax ? tmax : k - bias; 00398 if (digit < t) 00399 break; 00400 if (w > maxint / (base - t)) 00401 return punycode_overflow; 00402 w *= (base - t); 00403 } 00404 00405 bias = adapt (i - oldi, out + 1, oldi == 0); 00406 00407 /* i was supposed to wrap around from out+1 to 0, */ 00408 /* incrementing n each time, so we'll fix that now: */ 00409 00410 if (i / (out + 1) > maxint - n) 00411 return punycode_overflow; 00412 n += i / (out + 1); 00413 i %= (out + 1); 00414 00415 /* Insert n at position i of the output: */ 00416 00417 /* not needed for Punycode: */ 00418 /* if (basic(n)) return punycode_invalid_input; */ 00419 if (out >= max_out) 00420 return punycode_big_output; 00421 00422 if (case_flags) 00423 { 00424 memmove (case_flags + i + 1, case_flags + i, out - i); 00425 /* Case of last ASCII code point determines case flag: */ 00426 case_flags[i] = flagged (input[in - 1]); 00427 } 00428 00429 memmove (output + i + 1, output + i, (out - i) * sizeof *output); 00430 output[i++] = n; 00431 } 00432 00433 *output_length = (size_t) out; 00434 /* cannot overflow because out <= old value of *output_length */ 00435 return punycode_success; 00436 } 00437