PHP 内核源码 session_id 生成算法初入

PHP7 session_id 生成算法与 5.X 版本有很大区别

/*
 * Note that we cannot use the BASE64 alphabet here, because
 * it contains "/" and "+": both are unacceptable for simple inclusion
 * into URLs.
 */

static char hexconvtab[] = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ,-";

static void bin_to_readable(unsigned char *in, size_t inlen, char *out, size_t outlen, char nbits) /* {{{ */
{
    unsigned char *p, *q;
    unsigned short w;
    int mask;
    int have;

    p = (unsigned char *)in;
    q = (unsigned char *)in + inlen;

    w = 0;
    have = 0;
    mask = (1 << nbits) - 1;

    while (outlen--) {
        if (have < nbits) {
            if (p < q) {
                w |= *p++ << have;
                have += 8;
            } else {
                /* Should never happen. Input must be large enough. */
                ZEND_ASSERT(0);
                break;
            }
        }

        /* consume nbits */
        *out++ = hexconvtab[w & mask];
        w >>= nbits;
        have -= nbits;
    }

    *out = '\0';
}
/* }}} */

#define PS_EXTRA_RAND_BYTES 60

PHPAPI zend_string *php_session_create_id(PS_CREATE_SID_ARGS) /* {{{ */
{
    unsigned char rbuf[PS_MAX_SID_LENGTH + PS_EXTRA_RAND_BYTES];
    zend_string *outid;

    /* It would be enough to read ceil(sid_length * sid_bits_per_character / 8) bytes here.
     * We read sid_length bytes instead for simplicity. */
    /* Read additional PS_EXTRA_RAND_BYTES just in case CSPRNG is not safe enough */
    if (php_random_bytes_throw(rbuf, PS(sid_length) + PS_EXTRA_RAND_BYTES) == FAILURE) {
        return NULL;
    }

    outid = zend_string_alloc(PS(sid_length), 0);
    bin_to_readable(
        rbuf, PS(sid_length),
        ZSTR_VAL(outid), ZSTR_LEN(outid),
        (char)PS(sid_bits_per_character));

    return outid;
}
/* }}} */

php5.6 实现：MD5 / SHA1 / HASH

PHPAPI char *php_session_create_id(PS_CREATE_SID_ARGS) /* {{{ */
{
    PHP_MD5_CTX md5_context;
    PHP_SHA1_CTX sha1_context;
#if defined(HAVE_HASH_EXT) && !defined(COMPILE_DL_HASH)
    void *hash_context = NULL;
#endif
    unsigned char *digest;
    int digest_len;
    int j;
    char *buf, *outid;
    struct timeval tv;
    zval **array;
    zval **token;
    char *remote_addr = NULL;

    gettimeofday(&tv, NULL);

    if (zend_hash_find(&EG(symbol_table), "_SERVER", sizeof("_SERVER"), (void **) &array) == SUCCESS &&
        Z_TYPE_PP(array) == IS_ARRAY &&
        zend_hash_find(Z_ARRVAL_PP(array), "REMOTE_ADDR", sizeof("REMOTE_ADDR"), (void **) &token) == SUCCESS &&
        Z_TYPE_PP(token) == IS_STRING
    ) {
        remote_addr = Z_STRVAL_PP(token);
    }

    /* maximum 15+19+19+10 bytes */
    spprintf(&buf, 0, "%.15s%ld%ld%0.8F", remote_addr ? remote_addr : "", tv.tv_sec, (long int)tv.tv_usec, php_combined_lcg(TSRMLS_C) * 10);

    switch (PS(hash_func)) {
        case PS_HASH_FUNC_MD5:
            PHP_MD5Init(&md5_context);
            PHP_MD5Update(&md5_context, (unsigned char *) buf, strlen(buf));
            digest_len = 16;
            break;
        case PS_HASH_FUNC_SHA1:
            PHP_SHA1Init(&sha1_context);
            PHP_SHA1Update(&sha1_context, (unsigned char *) buf, strlen(buf));
            digest_len = 20;
            break;
#if defined(HAVE_HASH_EXT) && !defined(COMPILE_DL_HASH)
        case PS_HASH_FUNC_OTHER:
            if (!PS(hash_ops)) {
                php_error_docref(NULL TSRMLS_CC, E_ERROR, "Invalid session hash function");
                efree(buf);
                return NULL;
            }

            hash_context = emalloc(PS(hash_ops)->context_size);
            PS(hash_ops)->hash_init(hash_context);
            PS(hash_ops)->hash_update(hash_context, (unsigned char *) buf, strlen(buf));
            digest_len = PS(hash_ops)->digest_size;
            break;
#endif /* HAVE_HASH_EXT */
        default:
            php_error_docref(NULL TSRMLS_CC, E_ERROR, "Invalid session hash function");
            efree(buf);
            return NULL;
    }
    efree(buf);

    if (PS(entropy_length) > 0) {
#ifdef PHP_WIN32
        unsigned char rbuf[2048];
        size_t toread = PS(entropy_length);

        if (php_win32_get_random_bytes(rbuf, MIN(toread, sizeof(rbuf))) == SUCCESS){

            switch (PS(hash_func)) {
                case PS_HASH_FUNC_MD5:
                    PHP_MD5Update(&md5_context, rbuf, toread);
                    break;
                case PS_HASH_FUNC_SHA1:
                    PHP_SHA1Update(&sha1_context, rbuf, toread);
                    break;
# if defined(HAVE_HASH_EXT) && !defined(COMPILE_DL_HASH)
                case PS_HASH_FUNC_OTHER:
                    PS(hash_ops)->hash_update(hash_context, rbuf, toread);
                    break;
# endif /* HAVE_HASH_EXT */
            }
        }
#else
        int fd;

        fd = VCWD_OPEN(PS(entropy_file), O_RDONLY);
        if (fd >= 0) {
            unsigned char rbuf[2048];
            int n;
            int to_read = PS(entropy_length);

            while (to_read > 0) {
                n = read(fd, rbuf, MIN(to_read, sizeof(rbuf)));
                if (n <= 0) break;

                switch (PS(hash_func)) {
                    case PS_HASH_FUNC_MD5:
                        PHP_MD5Update(&md5_context, rbuf, n);
                        break;
                    case PS_HASH_FUNC_SHA1:
                        PHP_SHA1Update(&sha1_context, rbuf, n);
                        break;
#if defined(HAVE_HASH_EXT) && !defined(COMPILE_DL_HASH)
                    case PS_HASH_FUNC_OTHER:
                        PS(hash_ops)->hash_update(hash_context, rbuf, n);
                        break;
#endif /* HAVE_HASH_EXT */
                }
                to_read -= n;
            }
            close(fd);
        }
#endif
    }

    digest = emalloc(digest_len + 1);
    switch (PS(hash_func)) {
        case PS_HASH_FUNC_MD5:
            PHP_MD5Final(digest, &md5_context);
            break;
        case PS_HASH_FUNC_SHA1:
            PHP_SHA1Final(digest, &sha1_context);
            break;
#if defined(HAVE_HASH_EXT) && !defined(COMPILE_DL_HASH)
        case PS_HASH_FUNC_OTHER:
            PS(hash_ops)->hash_final(digest, hash_context);
            efree(hash_context);
            break;
#endif /* HAVE_HASH_EXT */
    }

    if (PS(hash_bits_per_character) < 4
            || PS(hash_bits_per_character) > 6) {
        PS(hash_bits_per_character) = 4;

        php_error_docref(NULL TSRMLS_CC, E_WARNING, "The ini setting hash_bits_per_character is out of range (should be 4, 5, or 6) - using 4 for now");
    }

    outid = emalloc((size_t)((digest_len + 2) * ((8.0f / PS(hash_bits_per_character)) + 0.5)));
    j = (int) (bin_to_readable((char *)digest, digest_len, outid, (char)PS(hash_bits_per_character)) - outid);
    efree(digest);

    if (newlen) {
        *newlen = j;
    }

    return outid;
}
/* }}} */