/* punycode.c --- Implementation of punycode used to ASCII encode IDN's. * Copyright (C) 2002, 2003, 2004 Simon Josefsson * * This file is part of GNU Libidn. * * GNU Libidn is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2.1 of the License, or (at your option) any later version. * * GNU Libidn is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with GNU Libidn; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA * */ /* * This file is derived from RFC 3492bis written by Adam M. Costello. * * Disclaimer and license: Regarding this entire document or any * portion of it (including the pseudocode and C code), the author * makes no guarantees and is not responsible for any damage resulting * from its use. The author grants irrevocable permission to anyone * to use, modify, and distribute it in any way that does not diminish * the rights of anyone else to use, modify, and distribute it, * provided that redistributed derivative works do not contain * misleading author or version information. Derivative works need * not be licensed under similar terms. * * Copyright (C) The Internet Society (2003). All Rights Reserved. * * This document and translations of it may be copied and furnished to * others, and derivative works that comment on or otherwise explain it * or assist in its implementation may be prepared, copied, published * and distributed, in whole or in part, without restriction of any * kind, provided that the above copyright notice and this paragraph are * included on all such copies and derivative works. However, this * document itself may not be modified in any way, such as by removing * the copyright notice or references to the Internet Society or other * Internet organizations, except as needed for the purpose of * developing Internet standards in which case the procedures for * copyrights defined in the Internet Standards process must be * followed, or as required to translate it into languages other than * English. * * The limited permissions granted above are perpetual and will not be * revoked by the Internet Society or its successors or assigns. * * This document and the information contained herein is provided on an * "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING * TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING * BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION * HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. */ #include <string.h> #include "punycode.h" /*** Bootstring parameters for Punycode ***/ enum { base = 36, tmin = 1, tmax = 26, skew = 38, damp = 700, initial_bias = 72, initial_n = 0x80, delimiter = 0x2D }; /* basic(cp) tests whether cp is a basic code point: */ #define basic(cp) ((punycode_uint)(cp) < 0x80) /* delim(cp) tests whether cp is a delimiter: */ #define delim(cp) ((cp) == delimiter) /* decode_digit(cp) returns the numeric value of a basic code */ /* point (for use in representing integers) in the range 0 to */ /* base-1, or base if cp does not represent a value. */ static punycode_uint decode_digit (punycode_uint cp) { return cp - 48 < 10 ? cp - 22 : cp - 65 < 26 ? cp - 65 : cp - 97 < 26 ? cp - 97 : base; } /* encode_digit(d,flag) returns the basic code point whose value */ /* (when used for representing integers) is d, which needs to be in */ /* the range 0 to base-1. The lowercase form is used unless flag is */ /* nonzero, in which case the uppercase form is used. The behavior */ /* is undefined if flag is nonzero and digit d has no uppercase form. */ static char encode_digit (punycode_uint d, int flag) { return d + 22 + 75 * (d < 26) - ((flag != 0) << 5); /* 0..25 map to ASCII a..z or A..Z */ /* 26..35 map to ASCII 0..9 */ } /* flagged(bcp) tests whether a basic code point is flagged */ /* (uppercase). The behavior is undefined if bcp is not a */ /* basic code point. */ #define flagged(bcp) ((punycode_uint)(bcp) - 65 < 26) /* encode_basic(bcp,flag) forces a basic code point to lowercase */ /* if flag is zero, uppercase if flag is nonzero, and returns */ /* the resulting code point. The code point is unchanged if it */ /* is caseless. The behavior is undefined if bcp is not a basic */ /* code point. */ static char encode_basic (punycode_uint bcp, int flag) { bcp -= (bcp - 97 < 26) << 5; return bcp + ((!flag && (bcp - 65 < 26)) << 5); } /*** Platform-specific constants ***/ /* maxint is the maximum value of a punycode_uint variable: */ static const punycode_uint maxint = -1; /* Because maxint is unsigned, -1 becomes the maximum value. */ /*** Bias adaptation function ***/ static punycode_uint adapt (punycode_uint delta, punycode_uint numpoints, int firsttime) { punycode_uint k; delta = firsttime ? delta / damp : delta >> 1; /* delta >> 1 is a faster way of doing delta / 2 */ delta += delta / numpoints; for (k = 0; delta > ((base - tmin) * tmax) / 2; k += base) { delta /= base - tmin; } return k + (base - tmin + 1) * delta / (delta + skew); } /*** Main encode function ***/ /** * punycode_encode - encode Unicode to Punycode * @input_length: The number of code points in the @input array and * the number of flags in the @case_flags array. * @input: An array of code points. They are presumed to be Unicode * code points, but that is not strictly REQUIRED. The array * contains code points, not code units. UTF-16 uses code units * D800 through DFFF to refer to code points 10000..10FFFF. The * code points D800..DFFF do not occur in any valid Unicode string. * The code points that can occur in Unicode strings (0..D7FF and * E000..10FFFF) are also called Unicode scalar values. * @case_flags: A %NULL pointer or an array of boolean values parallel * to the @input array. Nonzero (true, flagged) suggests that the * corresponding Unicode character be forced to uppercase after * being decoded (if possible), and zero (false, unflagged) suggests * that it be forced to lowercase (if possible). ASCII code points * (0..7F) are encoded literally, except that ASCII letters are * forced to uppercase or lowercase according to the corresponding * case flags. If @case_flags is a %NULL pointer then ASCII letters * are left as they are, and other code points are treated as * unflagged. * @output_length: The caller passes in the maximum number of ASCII * code points that it can receive. On successful return it will * contain the number of ASCII code points actually output. * @output: An array of ASCII code points. It is *not* * null-terminated; it will contain zeros if and only if the @input * contains zeros. (Of course the caller can leave room for a * terminator and add one if needed.) * * Converts a sequence of code points (presumed to be Unicode code * points) to Punycode. * * Return value: The return value can be any of the #Punycode_status * values defined above except %PUNYCODE_BAD_INPUT. If not * %PUNYCODE_SUCCESS, then @output_size and @output might contain * garbage. **/ int punycode_encode (size_t input_length, const punycode_uint input[], const unsigned char case_flags[], size_t * output_length, char output[]) { punycode_uint input_len, n, delta, h, b, bias, j, m, q, k, t; size_t out, max_out; /* The Punycode spec assumes that the input length is the same type */ /* of integer as a code point, so we need to convert the size_t to */ /* a punycode_uint, which could overflow. */ if (input_length > maxint) return punycode_overflow; input_len = (punycode_uint) input_length; /* Initialize the state: */ n = initial_n; delta = 0; out = 0; max_out = *output_length; bias = initial_bias; /* Handle the basic code points: */ for (j = 0; j < input_len; ++j) { if (basic (input[j])) { if (max_out - out < 2) return punycode_big_output; output[out++] = case_flags ? encode_basic (input[j], case_flags[j]) : (char) input[j]; } /* else if (input[j] < n) return punycode_bad_input; */ /* (not needed for Punycode with unsigned code points) */ } h = b = (punycode_uint) out; /* cannot overflow because out <= input_len <= maxint */ /* h is the number of code points that have been handled, b is the */ /* number of basic code points, and out is the number of ASCII code */ /* points that have been output. */ if (b > 0) output[out++] = delimiter; /* Main encoding loop: */ while (h < input_len) { /* All non-basic code points < n have been */ /* handled already. Find the next larger one: */ for (m = maxint, j = 0; j < input_len; ++j) { /* if (basic(input[j])) continue; */ /* (not needed for Punycode) */ if (input[j] >= n && input[j] < m) m = input[j]; } /* Increase delta enough to advance the decoder's */ /* <n,i> state to <m,0>, but guard against overflow: */ if (m - n > (maxint - delta) / (h + 1)) return punycode_overflow; delta += (m - n) * (h + 1); n = m; for (j = 0; j < input_len; ++j) { /* Punycode does not need to check whether input[j] is basic: */ if (input[j] < n /* || basic(input[j]) */ ) { if (++delta == 0) return punycode_overflow; } if (input[j] == n) { /* Represent delta as a generalized variable-length integer: */ for (q = delta, k = base;; k += base) { if (out >= max_out) return punycode_big_output; t = k <= bias /* + tmin */ ? tmin : /* +tmin not needed */ k >= bias + tmax ? tmax : k - bias; if (q < t) break; output[out++] = encode_digit (t + (q - t) % (base - t), 0); q = (q - t) / (base - t); } output[out++] = encode_digit (q, case_flags && case_flags[j]); bias = adapt (delta, h + 1, h == b); delta = 0; ++h; } } ++delta, ++n; } *output_length = out; return punycode_success; } /*** Main decode function ***/ /** * punycode_decode - decode Punycode to Unicode * @input_length: The number of ASCII code points in the @input array. * @input: An array of ASCII code points (0..7F). * @output_length: The caller passes in the maximum number of code * points that it can receive into the @output array (which is also * the maximum number of flags that it can receive into the * @case_flags array, if @case_flags is not a %NULL pointer). On * successful return it will contain the number of code points * actually output (which is also the number of flags actually * output, if case_flags is not a null pointer). The decoder will * never need to output more code points than the number of ASCII * code points in the input, because of the way the encoding is * defined. The number of code points output cannot exceed the * maximum possible value of a punycode_uint, even if the supplied * @output_length is greater than that. * @output: An array of code points like the input argument of * punycode_encode() (see above). * @case_flags: A %NULL pointer (if the flags are not needed by the * caller) or an array of boolean values parallel to the @output * array. Nonzero (true, flagged) suggests that the corresponding * Unicode character be forced to uppercase by the caller (if * possible), and zero (false, unflagged) suggests that it be forced * to lowercase (if possible). ASCII code points (0..7F) are output * already in the proper case, but their flags will be set * appropriately so that applying the flags would be harmless. * * Converts Punycode to a sequence of code points (presumed to be * Unicode code points). * * Return value: The return value can be any of the #Punycode_status * values defined above. If not %PUNYCODE_SUCCESS, then * @output_length, @output, and @case_flags might contain garbage. * **/ int punycode_decode (size_t input_length, const char input[], size_t * output_length, punycode_uint output[], unsigned char case_flags[]) { punycode_uint n, out, i, max_out, bias, oldi, w, k, digit, t; size_t b, j, in; /* Initialize the state: */ n = initial_n; out = i = 0; max_out = *output_length > maxint ? maxint : (punycode_uint) * output_length; bias = initial_bias; /* Handle the basic code points: Let b be the number of input code */ /* points before the last delimiter, or 0 if there is none, then */ /* copy the first b code points to the output. */ for (b = j = 0; j < input_length; ++j) if (delim (input[j])) b = j; if (b > max_out) return punycode_big_output; for (j = 0; j < b; ++j) { if (case_flags) case_flags[out] = flagged (input[j]); if (!basic (input[j])) return punycode_bad_input; output[out++] = input[j]; } /* Main decoding loop: Start just after the last delimiter if any */ /* basic code points were copied; start at the beginning otherwise. */ for (in = b > 0 ? b + 1 : 0; in < input_length; ++out) { /* in is the index of the next ASCII code point to be consumed, */ /* and out is the number of code points in the output array. */ /* Decode a generalized variable-length integer into delta, */ /* which gets added to i. The overflow checking is easier */ /* if we increase i as we go, then subtract off its starting */ /* value at the end to obtain delta. */ for (oldi = i, w = 1, k = base;; k += base) { if (in >= input_length) return punycode_bad_input; digit = decode_digit (input[in++]); if (digit >= base) return punycode_bad_input; if (digit > (maxint - i) / w) return punycode_overflow; i += digit * w; t = k <= bias /* + tmin */ ? tmin : /* +tmin not needed */ k >= bias + tmax ? tmax : k - bias; if (digit < t) break; if (w > maxint / (base - t)) return punycode_overflow; w *= (base - t); } bias = adapt (i - oldi, out + 1, oldi == 0); /* i was supposed to wrap around from out+1 to 0, */ /* incrementing n each time, so we'll fix that now: */ if (i / (out + 1) > maxint - n) return punycode_overflow; n += i / (out + 1); i %= (out + 1); /* Insert n at position i of the output: */ /* not needed for Punycode: */ /* if (basic(n)) return punycode_invalid_input; */ if (out >= max_out) return punycode_big_output; if (case_flags) { memmove (case_flags + i + 1, case_flags + i, out - i); /* Case of last ASCII code point determines case flag: */ case_flags[i] = flagged (input[in - 1]); } memmove (output + i + 1, output + i, (out - i) * sizeof *output); output[i++] = n; } *output_length = (size_t) out; /* cannot overflow because out <= old value of *output_length */ return punycode_success; } /** * punycode_uint * * Unicode code point data type, this is always a 32 bit unsigned * integer. */ /** * Punycode_status * @PUNYCODE_SUCCESS: Successful operation. This value is guaranteed * to always be zero, the remaining ones are only guaranteed to hold * non-zero values, for logical comparison purposes. * @PUNYCODE_BAD_INPUT: Input is invalid. * @PUNYCODE_BIG_OUTPUT: Output would exceed the space provided. * @PUNYCODE_OVERFLOW: Input needs wider integers to process. * * Enumerated return codes of punycode_encode() and punycode_decode(). * The value 0 is guaranteed to always correspond to success. */