decode.cc

/*
 * ModSecurity, http://www.modsecurity.org/
 * Copyright (c) 2015 - 2021 Trustwave Holdings, Inc. (http://www.trustwave.com/)
 *
 * You may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * If any of the files related to licensing are missing or if you have any
 * other questions related to licensing please contact Trustwave Holdings, Inc.
 * directly using the email address security@modsecurity.org.
 *
 */

#include "src/utils/decode.h"
#include "modsecurity/modsecurity.h"
#include "src/utils/string.h"


namespace modsecurity {
namespace utils {


int urldecode_nonstrict_inplace(unsigned char *input,
    uint64_t input_len, int *invalid_count, int *changed) {
    unsigned char *d = (unsigned char *)input;
    uint64_t i, count;

    *changed = 0;

    if (input == NULL) {
        return -1;
    }

    i = count = 0;
    while (i < input_len) {
        if (input[i] == '%') {
            /* Character is a percent sign. */

            /* Are there enough bytes available? */
            if (i + 2 < input_len) {
                char c1 = input[i + 1];
                char c2 = input[i + 2];
                if (VALID_HEX(c1) && VALID_HEX(c2)) {
                    uint64_t uni = string::x2c(&input[i + 1]);

                    *d++ = (wchar_t)uni;
                    count++;
                    i += 3;
                    *changed = 1;
                } else {
                    /* Not a valid encoding, skip this % */
                    *d++ = input[i++];
                    count++;
                    (*invalid_count)++;
                }
            } else {
                /* Not enough bytes available, copy the raw bytes. */
                *d++ = input[i++];
                count++;
                (*invalid_count)++;
            }
        } else {
            /* Character is not a percent sign. */
            if (input[i] == '+') {
                *d++ = ' ';
                *changed = 1;
            } else {
                *d++ = input[i];
            }
            count++;
            i++;
        }
    }

#if 0
    *d = '\0';
#endif

    return count;
}


std::string uri_decode(const std::string & sSrc) {
    // Note from RFC1630: "Sequences which start with a percent
    // sign but are not followed by two hexadecimal characters
    // (0-9, A-F) are reserved for future extension"

    const unsigned char * pSrc = (const unsigned char *)sSrc.c_str();
    const int SRC_LEN = sSrc.length();
    const unsigned char * const SRC_END = pSrc + SRC_LEN;
    // last decodable '%'
    const unsigned char * const SRC_LAST_DEC = SRC_END - 2;

    char * const pStart = new char[SRC_LEN];
    char * pEnd = pStart;

    while (pSrc < SRC_LAST_DEC) {
        if (*pSrc == '%') {
            char dec1, dec2;
            if (-1 != (dec1 = string::HEX2DEC[*(pSrc + 1)])
                && -1 != (dec2 = string::HEX2DEC[*(pSrc + 2)])) {
                *pEnd++ = (dec1 << 4) + dec2;
                pSrc += 3;
                continue;
            }
        }
        *pEnd++ = *pSrc++;
    }

    // the last 2- chars
    while (pSrc < SRC_END) {
        *pEnd++ = *pSrc++;
    }

    std::string sResult(pStart, pEnd);
    delete [] pStart;
    return sResult;
}


}  // namespace utils
}  // namespace modsecurity