idna.c

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/*
 * Copyright 2014 Chris Young <chris@unsatisfactorysoftware.co.uk>
 *
 * This file is part of NetSurf, http://www.netsurf-browser.org/
 *
 * NetSurf is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; version 2 of the License.
 *
 * NetSurf 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
/**
 * \file
 * NetSurf international domain name handling implementation.
 */
 
#include <assert.h>
#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
 
#include "netsurf/inttypes.h"
 
#include "utils/errors.h"
#include "utils/idna.h"
#include "utils/idna_props.h"
#include "utils/log.h"
#include "utils/punycode.h"
#include "utils/utf8.h"
#include "utils/utils.h"
 
 
/**
 * Convert punycode status into nserror.
 *
 * \param status The punycode status to convert.
 * \return The corresponding nserror code for the status.
 */
static nserror punycode_status_to_nserror(enum punycode_status status)
{
        nserror ret = NSERROR_NOMEM;
 
        switch (status) {
        case punycode_success:
                ret = NSERROR_OK;
                break;
 
        case punycode_bad_input:
                NSLOG(netsurf, INFO, "Bad input");
                ret = NSERROR_BAD_ENCODING;
                break;
 
        case punycode_big_output:
                NSLOG(netsurf, INFO, "Output too big");
                ret = NSERROR_BAD_SIZE;
                break;
 
        case punycode_overflow:
                NSLOG(netsurf, INFO, "Overflow");
                ret = NSERROR_NOSPACE;
                break;
 
        default:
                break;
        }
        return ret;
}
 
 
/**
 * Convert a host label in UCS-4 to an ACE version
 *
 * \param ucs4_label UCS-4 NFC string containing host label
 * \param len Length of host label (in characters/codepoints)
 * \param ace_label ASCII-compatible encoded version
 * \param out_len Length of ace_label
 * \return NSERROR_OK on success, appropriate error otherwise
 *
 * If return value != NSERROR_OK, output will be left untouched.
 */
static nserror
idna__ucs4_to_ace(int32_t *ucs4_label,
                  size_t len,
                  char **ace_label,
                  size_t *out_len)
{
        char punycode[65]; /* max length of host label + NULL */
        size_t output_length = 60; /* punycode length - 4 - 1 */
        nserror ret;
 
        punycode[0] = 'x';
        punycode[1] = 'n';
        punycode[2] = '-';
        punycode[3] = '-';
 
        ret = punycode_status_to_nserror(punycode_encode(len,
                        (const punycode_uint *)ucs4_label, NULL,
                        &output_length, punycode + 4));
        if (ret != NSERROR_OK) {
                return ret;
        }
 
        output_length += SLEN("xn--");
        punycode[output_length] = '\0';
 
        *ace_label = strdup(punycode);
        *out_len = output_length;
 
        return NSERROR_OK;
}
 
 
/**
 * Convert a host label in ACE format to UCS-4
 *
 * \param ace_label ASCII string containing host label
 * \param ace_len Length of host label
 * \param ucs4_label Pointer to hold UCS4 decoded version
 * \param ucs4_len Pointer to hold length of ucs4_label
 * \return NSERROR_OK on success, appropriate error otherwise
 *
 * If return value != NSERROR_OK, output will be left untouched.
 */
static nserror
idna__ace_to_ucs4(const char *ace_label,
                  size_t ace_len,
                  int32_t **ucs4_label,
                  size_t *ucs4_len)
{
        int32_t *ucs4;
        nserror ret;
        size_t output_length = ace_len; /* never exceeds input length */
 
        /* The header should always have been checked before calling */
        assert((ace_label[0] == 'x') && (ace_label[1] == 'n') &&
                (ace_label[2] == '-') && (ace_label[3] == '-'));
 
        ucs4 = malloc(output_length * 4);
        if (ucs4 == NULL) {
                return NSERROR_NOMEM;
        }
 
        ret = punycode_status_to_nserror(punycode_decode(ace_len - 4,
                ace_label + 4, &output_length, (punycode_uint *)ucs4, NULL));
        if (ret != NSERROR_OK) {
                free(ucs4);
                return ret;
        }
 
        ucs4[output_length] = '\0';
 
        *ucs4_label = ucs4;
        *ucs4_len = output_length;
 
        return NSERROR_OK;
}
 
 
#ifdef WITH_UTF8PROC
 
#include <libutf8proc/utf8proc.h>
 
int32_t idna_contexto[] = {
        /* CONTEXTO codepoints which have a rule defined */
        0x00b7, 0x0375, 0x05f3, 0x05f4, 0x30fb, 0x0660, 0x0661,
        0x0662, 0x0663, 0x0664, 0x0665, 0x0666, 0x0667, 0x0668,
        0x0669, 0x06f0, 0x06f1, 0x06f2, 0x06f3, 0x06f4, 0x06f5,
        0x06f6, 0x06f7, 0x06f8, 0x06f9, 0
};
 
/**
 * Find the IDNA property of a UCS-4 codepoint
 *
 * \param cp    Unicode codepoint
 * \return IDNA property
 */
static idna_property idna__cp_property(int32_t cp)
{
        const idna_table *t;
 
        t = idna_derived;
        while (t->p.property) {
                if ((cp >= t->start) && (cp <= t->end)) {
                        return t->p.property;
                }
                t++;
        };
 
        return IDNA_P_DISALLOWED;
}
 
 
/**
 * Find the Joining_Type property of a UCS-4 codepoint
 *
 * \param cp    Unicode codepoint
 * \return JT property
 */
static idna_unicode_jt idna__jt_property(int32_t cp)
{
        const idna_table *t;
 
        t = idna_joiningtype;
        while (t->p.jt) {
                if ((cp >= t->start) && (cp <= t->end)) {
                        return t->p.jt;
                }
                t++;
        };
 
        return IDNA_UNICODE_JT_U;
}
 
 
/**
 * Check if a CONTEXTO codepoint has a rule defined
 *
 * \param cp    Unicode codepoint
 * \return true if a rule is defined
 */
static bool idna__contexto_rule(int32_t cp)
{
        int32_t *t;
        for (t = idna_contexto; *t != 0; t++) {
                if (*t == cp) {
                        return true;
                }
        }
 
        return false;
}
 
 
/**
 * Check if a CONTEXTJ codepoint has a rule defined,
 * and conforms to that rule.
 *
 * \param label UCS-4 string
 * \param index character in the string which is CONTEXTJ
 * \param len The length of the label
 * \return true if conforming
 */
static bool idna__contextj_rule(int32_t *label, int index, size_t len)
{
        const utf8proc_property_t *unicode_props;
        idna_unicode_jt joining_type;
        int i;
        bool match;
 
        /* These CONTEXTJ rules are defined at
         * http://www.iana.org/assignments/idna-tables-5.2.0/idna-tables-5.2.0.xml
         */
 
        if (label[index] == 0x200c) {
                if (index == 0) {
                        return false; /* No previous character */
                }
                unicode_props = utf8proc_get_property(label[index - 1]);
                if (unicode_props->combining_class == IDNA_UNICODE_CCC_VIRAMA) {
                        return true;
                }
 
                match = false;
                for (i = 0; i < (index - 1); i++) {
                        joining_type = idna__jt_property(label[i]);
                        if (((joining_type == IDNA_UNICODE_JT_L) ||
                             (joining_type == IDNA_UNICODE_JT_D)) &&
                            (idna__jt_property(label[i+1]) == IDNA_UNICODE_JT_T)) {
                                match = true;
                                break;
                        }
                }
 
                if (match == false) {
                        return false;
                }
 
                if (idna__jt_property(label[index+1]) != IDNA_UNICODE_JT_T) {
                        return false;
                }
 
                for (i = (index + 1); i < (int)len; i++) {
                        joining_type = idna__jt_property(label[i]);
 
                        if ((joining_type == IDNA_UNICODE_JT_R) ||
                            (joining_type == IDNA_UNICODE_JT_D)) {
                                return true;
                        }
                }
 
                return false;
 
        } else if (label[index] == 0x200d) {
                if (index == 0) {
                        return false; /* No previous character */
                }
                unicode_props = utf8proc_get_property(label[index - 1]);
                if (unicode_props->combining_class == IDNA_UNICODE_CCC_VIRAMA) {
                        return true;
                }
                return false;
        }
 
        /* No rule defined */
        return false;
}
 
 
/**
 * Convert a UTF-8 string to UCS-4
 *
 * \param utf8_label    UTF-8 string containing host label
 * \param len   Length of host label (in bytes)
 * \param ucs4_label    Pointer to update with the output
 * \param ucs4_len      Pointer to update with the length
 * \return NSERROR_OK on success, appropriate error otherwise
 *
 * If return value != NSERROR_OK, output will be left untouched.
 */
static nserror
idna__utf8_to_ucs4(const char *utf8_label,
                   size_t len,
                   int32_t **ucs4_label,
                   size_t *ucs4_len)
{
        int32_t *nfc_label;
        ssize_t nfc_size;
 
        nfc_label = malloc(len * 4);
        if (nfc_label == NULL) {
                return NSERROR_NOMEM;
        }
 
        nfc_size = utf8proc_decompose((const uint8_t *)utf8_label, len,
                nfc_label, len * 4, UTF8PROC_STABLE | UTF8PROC_COMPOSE);
        if (nfc_size < 0) {
                return NSERROR_NOMEM;
        }
 
        nfc_size = utf8proc_normalize_utf32(nfc_label, nfc_size,
                UTF8PROC_STABLE | UTF8PROC_COMPOSE);
        if (nfc_size < 0) {
                return NSERROR_NOMEM;
        }
 
        *ucs4_label = nfc_label;
        *ucs4_len = nfc_size;
 
        return NSERROR_OK;
}
 
 
/**
 * Convert a UCS-4 string to UTF-8
 *
 * \param ucs4_label    UCS-4 string containing host label
 * \param ucs4_len      Length of host label (in bytes)
 * \param utf8_label    Pointer to update with the output
 * \param utf8_len      Pointer to update with the length
 * \return NSERROR_OK on success, appropriate error otherwise
 *
 * If return value != NSERROR_OK, output will be left untouched.
 */
static nserror
idna__ucs4_to_utf8(const int32_t *ucs4_label,
                   size_t ucs4_len,
                   char **utf8_label,
                   size_t *utf8_len)
{
        int32_t *nfc_label;
        ssize_t nfc_size = ucs4_len;
 
        nfc_label = malloc(1 + ucs4_len * 4);
        if (nfc_label == NULL) {
                return NSERROR_NOMEM;
        }
        memcpy(nfc_label, ucs4_label, ucs4_len * 4);
 
        nfc_size = utf8proc_reencode(nfc_label, ucs4_len,
                UTF8PROC_STABLE | UTF8PROC_COMPOSE);
        if (nfc_size < 0) {
                return NSERROR_NOMEM;
        }
 
        *utf8_label = (char *)nfc_label;
        *utf8_len = nfc_size;
 
        return NSERROR_OK;
}
 
 
/**
 * Check if a host label is valid for IDNA2008
 *
 * \param label Host label to check (UCS-4)
 * \param len   Length of host label (in characters/codepoints)
 * \return true if compliant, false otherwise
 */
static bool idna__is_valid(int32_t *label, size_t len)
{
        const utf8proc_property_t *unicode_props;
        idna_property idna_prop;
        size_t i = 0;
 
        /* 1. Check that the string is NFC.
         * This check is skipped as the conversion to Unicode
         * does normalisation as part of the conversion.
         */
 
        /* 2. Check characters 3 and 4 are not '--'. */
        if ((len >= 4) && (label[2] == 0x002d) && (label[3] == 0x002d)) {
                NSLOG(netsurf, INFO,
                      "Check failed: characters 2 and 3 are '--'");
                return false;
        }
 
        /* 3. Check the first character is not a combining mark */
        unicode_props = utf8proc_get_property(label[0]);
 
        if ((unicode_props->category == UTF8PROC_CATEGORY_MN) ||
                (unicode_props->category == UTF8PROC_CATEGORY_MC) ||
                (unicode_props->category == UTF8PROC_CATEGORY_ME)) {
                NSLOG(netsurf, INFO,
                      "Check failed: character 0 is a combining mark");
                return false;
        }
 
        for (i = 0; i < len; i++) {
                idna_prop = idna__cp_property(label[i]);
 
                /* 4. Check characters not DISALLOWED by RFC5892 */
                if (idna_prop == IDNA_P_DISALLOWED) {
                        NSLOG(netsurf, INFO,
                              "Check failed: character %"PRIsizet" (%"PRIx32") is DISALLOWED",
                              i,
                              label[i]);
                        return false;
                }
 
                /* 5. Check CONTEXTJ characters conform to defined rules */
                if (idna_prop == IDNA_P_CONTEXTJ) {
                        if (idna__contextj_rule(label, i, len) == false) {
                                NSLOG(netsurf, INFO,
                                      "Check failed: character %"PRIsizet" (%"PRIx32") does not conform to CONTEXTJ rule",
                                      i,
                                      label[i]);
                                return false;
                        }
                }
 
                /* 6. Check CONTEXTO characters have a rule defined */
                /** \todo optionally we can check conformance to this rule */
                if (idna_prop == IDNA_P_CONTEXTO) {
                        if (idna__contexto_rule(label[i]) == false) {
                                NSLOG(netsurf, INFO,
                                      "Check failed: character %"PRIsizet" (%"PRIx32") has no CONTEXTO rule defined",
                                      i,
                                      label[i]);
                                return false;
                        }
                }
 
                /* 7. Check characters are not UNASSIGNED */
                if (idna_prop == IDNA_P_UNASSIGNED) {
                        NSLOG(netsurf, INFO,
                              "Check failed: character %"PRIsizet" (%"PRIx32") is UNASSIGNED",
                              i,
                              label[i]);
                        return false;
                }
 
                /** \todo 8. (optionally) check Bidi compliance */
        }
 
        return true;
}
 
 
/**
 * Verify an ACE label is valid
 *
 * \param label Host label to check
 * \param len   Length of label
 * \return true if valid, false otherwise
 */
static bool idna__verify(const char *label, size_t len)
{
        nserror error;
        int32_t *ucs4;
        char *ace;
        ssize_t ucs4_len;
        size_t u_ucs4_len, ace_len;
 
        /* Convert our ACE label back to UCS-4 */
        error = idna__ace_to_ucs4(label, len, &ucs4, &u_ucs4_len);
        if (error != NSERROR_OK) {
                return false;
        }
 
        /* Perform NFC normalisation */
        ucs4_len = utf8proc_normalize_utf32(ucs4, u_ucs4_len,
                UTF8PROC_STABLE | UTF8PROC_COMPOSE);
        if (ucs4_len < 0) {
                free(ucs4);
                return false;
        }
 
        /* Convert the UCS-4 label back to ACE */
        error = idna__ucs4_to_ace(ucs4, (size_t)ucs4_len,
                                &ace, &ace_len);
        free(ucs4);
        if (error != NSERROR_OK) {
                return false;
        }
 
        /* Check if it matches the input */
        if ((len == ace_len) && (strncmp(label, ace, len) == 0)) {
                free(ace);
                return true;
        }
 
        NSLOG(netsurf, INFO, "Re-encoded ACE label %s does not match input",
              ace);
        free(ace);
 
        return false;
}
 
 
#else /* WITH_UTF8PROC */
 
 
/**
 * Convert a UTF-8 string to UCS-4
 *
 * \param utf8_label    UTF-8 string containing host label
 * \param len   Length of host label (in bytes)
 * \param ucs4_label    Pointer to update with the output
 * \param ucs4_len      Pointer to update with the length
 * \return NSERROR_OK on success, appropriate error otherwise
 *
 * If return value != NSERROR_OK, output will be left untouched.
 */
static nserror
idna__utf8_to_ucs4(const char *utf8_label,
                   size_t len,
                   int32_t **ucs4_label,
                   size_t *ucs4_len)
{
        return NSERROR_NOT_IMPLEMENTED;
}
 
 
/**
 * Convert a UCS-4 string to UTF-8
 *
 * \param ucs4_label    UCS-4 string containing host label
 * \param ucs4_len      Length of host label (in bytes)
 * \param utf8_label    Pointer to update with the output
 * \param utf8_len      Pointer to update with the length
 * \return NSERROR_OK on success, appropriate error otherwise
 *
 * If return value != NSERROR_OK, output will be left untouched.
 */
static nserror
idna__ucs4_to_utf8(const int32_t *ucs4_label,
                   size_t ucs4_len,
                   char **utf8_label,
                   size_t *utf8_len)
{
        return NSERROR_NOT_IMPLEMENTED;
}
 
 
/**
 * Check if a host label is valid for IDNA2008
 *
 * \param label Host label to check (UCS-4)
 * \param len   Length of host label (in characters/codepoints)
 * \return true if compliant, false otherwise
 */
static bool idna__is_valid(int32_t *label, size_t len)
{
        return true;
}
 
 
/**
 * Verify an ACE label is valid
 *
 * \param label Host label to check
 * \param len   Length of label
 * \return true if valid, false otherwise
 */
static bool idna__verify(const char *label, size_t len)
{
        return true;
}
 
 
#endif /* WITH_UTF8PROC */
 
 
/**
 * Find the length of a host label
 *
 * \param host  String containing a host or FQDN
 * \param max_length    Length of host string to search (in bytes)
 * \return Distance to next separator character or end of string
 */
static size_t idna__host_label_length(const char *host, size_t max_length)
{
        const char *p = host;
        size_t length = 0;
 
        while (length < max_length) {
                if ((*p == '.') || (*p == ':') || (*p == '\0')) {
                        break;
                }
                length++;
                p++;
        }
 
        return length;
}
 
 
/**
 * Check if a host label is LDH
 *
 * \param label Host label to check
 * \param len   Length of host label
 * \return true if LDH compliant, false otherwise
 */
static bool idna__is_ldh(const char *label, size_t len)
{
        const char *p = label;
        size_t i = 0;
 
        /* Check for leading or trailing hyphens */
        if ((p[0] == '-') || (p[len - 1] == '-'))
                return false;
 
        /* Check for non-alphanumeric, non-hyphen characters */
        for (i = 0; i < len; p++) {
                i++;
                if (*p == '-') continue;
                if ((*p >= '0') && (*p <= '9')) continue;
                if ((*p >= 'a') && (*p <= 'z')) continue;
                if ((*p >= 'A') && (*p <= 'Z')) continue;
 
                return false;
        }
 
        return true;
}
 
 
/**
 * Check if a host label appears to be ACE
 *
 * \param label Host label to check
 * \param len   Length of host label
 * \return true if ACE compliant, false otherwise
 */
static bool idna__is_ace(const char *label, size_t len)
{
        /* Check it is a valid DNS string */
        if (idna__is_ldh(label, len) == false) {
                return false;
        }
 
        /* Check the ACE prefix is present */
        if ((label[0] == 'x') && (label[1] == 'n') &&
            (label[2] == '-') && (label[3] == '-')) {
                return true;
        }
 
        return false;
}
 
/* This is the maximum length of a full DNS name */
#define FQDN_MAX 256
 
/* A "no action" action for FQDN_APPEND */
#define NO_ACTION (void)0
 
#define FQDN_APPEND(s, len, action)                                            \
        do {                                                                   \
                if ((FQDN_MAX - fqdn_len) <= len) {                            \
                        /* Not enough room to append this element */           \
                        action;                                                \
                        return NSERROR_BAD_URL;                                \
                } else {                                                       \
                        memcpy(fqdn_p, s, len);                                \
                        fqdn_p += len;                                         \
                        fqdn_len += len;                                       \
                        action;                                                \
                }                                                              \
        } while (0)
 
/* exported interface documented in idna.h */
nserror
idna_encode(const char *host, size_t len, char **ace_host, size_t *ace_len)
{
        nserror error;
        int32_t *ucs4_host;
        size_t label_len, output_len, ucs4_len, fqdn_len = 0;
        char fqdn[FQDN_MAX];
        char *output, *fqdn_p = fqdn;
 
        label_len = idna__host_label_length(host, len);
        if (label_len == 0) {
                return NSERROR_BAD_URL;
        }
 
        while (label_len != 0) {
                if (idna__is_ldh(host, label_len) == false) {
                        /* This string is IDN or invalid */
 
                        /* Convert to Unicode */
                        error = idna__utf8_to_ucs4(host, label_len,
                                                   &ucs4_host, &ucs4_len);
                        if (error != NSERROR_OK) {
                                return error;
                        }
 
                        /* Check this is valid for conversion */
                        if (idna__is_valid(ucs4_host, ucs4_len) == false) {
                                free(ucs4_host);
                                return NSERROR_BAD_URL;
                        }
 
                        /* Convert to ACE */
                        error = idna__ucs4_to_ace(ucs4_host, ucs4_len,
                                                &output, &output_len);
                        free(ucs4_host);
                        if (error != NSERROR_OK) {
                                return error;
                        }
                        FQDN_APPEND(output, output_len, free(output));
                } else {
                        /* This is already a DNS-valid ASCII string */
                        if ((idna__is_ace(host, label_len) == true) &&
                            (idna__verify(host, label_len) == false)) {
                                NSLOG(netsurf, INFO,
                                      "Cannot verify ACE label %s", host);
                                return NSERROR_BAD_URL;
                        }
                        FQDN_APPEND(host, label_len, NO_ACTION);
                }
 
                FQDN_APPEND(".", 1, NO_ACTION);
 
                host += label_len;
                if ((*host == '\0') || (*host == ':')) {
                        break;
                }
                host++;
                len = len - label_len - 1;
 
                label_len = idna__host_label_length(host, len);
        }
 
        fqdn_p--;
        *fqdn_p = '\0';
        *ace_host = strdup(fqdn);
        *ace_len = fqdn_len - 1; /* last character is NULL */
 
        return NSERROR_OK;
}
 
 
/* exported interface documented in idna.h */
nserror
idna_decode(const char *ace_host, size_t ace_len, char **host, size_t *host_len)
{
        nserror error;
        int32_t *ucs4_host;
        size_t label_len, output_len, ucs4_len, fqdn_len = 0;
        char fqdn[FQDN_MAX];
        char *output, *fqdn_p = fqdn;
 
        label_len = idna__host_label_length(ace_host, ace_len);
        if (label_len == 0) {
                return NSERROR_BAD_URL;
        }
 
        while (label_len != 0) {
                if (idna__is_ace(ace_host, label_len) == true) {
                        /* This string is DNS-valid and (probably) encoded */
 
                        /* Decode to Unicode */
                        error = idna__ace_to_ucs4(ace_host, label_len,
                                                  &ucs4_host, &ucs4_len);
                        if (error != NSERROR_OK) {
                                return error;
                        }
 
                        /* Convert to UTF-8 */
                        error = idna__ucs4_to_utf8(ucs4_host, ucs4_len,
                                                   &output, &output_len);
                        free(ucs4_host);
                        if (error != NSERROR_OK) {
                                return error;
                        }
                        FQDN_APPEND(output, output_len, free(output));
                } else {
                        /* Not ACE */
                        FQDN_APPEND(ace_host, label_len, NO_ACTION);
                }
 
                FQDN_APPEND(".", 1, NO_ACTION);
 
                ace_host += label_len;
                if ((*ace_host == '\0') || (*ace_host == ':')) {
                        break;
                }
                ace_host++;
                ace_len = ace_len - label_len - 1;
 
                label_len = idna__host_label_length(ace_host, ace_len);
        }
 
        fqdn_p--;
        *fqdn_p = '\0';
        *host = strdup(fqdn);
        *host_len = fqdn_len - 1; /* last character is NULL */
 
        return NSERROR_OK;
}