Commit message: Fix infinite loop in LZMA decompression

Check the liblzma error code more thoroughly to avoid infinite loops.

Closes: https://gitlab.gnome.org/GNOME/libxml2/issues/13
Closes: https://bugzilla.gnome.org/show_bug.cgi?id=794914

This is CVE-2018-9251 and CVE-2018-14567.

Thanks to Dongliang Mu and Simon Wörner for the reports.
CVE: CVE-2018-9251
CWE: CWE-835
Vulnerability description: The xz_decomp function in xzlib.c in libxml2 2.9.8, if --with-lzma is used, allows remote attackers to cause a denial of service (infinite loop) via a crafted XML file that triggers LZMA_MEMLIMIT_ERROR, as demonstrated by xmllint, a different vulnerability than CVE-2015-8035.

Project: libxml2
File: xzlib.c

xz_load(xz_statep state, unsigned char *buf, unsigned int len,
        unsigned int *have)
{
    int ret;

    *have = 0;
    do {
        ret = read(state->fd, buf + *have, len - *have);
        if (ret <= 0)
            break;
        *have += ret;
    } while (*have < len);
    if (ret < 0) {
        xz_error(state, -1, strerror(errno));
        return -1;
    }
    if (ret == 0)
        state->eof = 1;
    return 0;
}

Project: libxml2
File: xzlib.c

__libxml2_xzcompressed(xzFile f) {
    return xz_compressed(f);
}

Project: libxml2
File: xzlib.c

xz_avail_zstrm(xz_statep state)
{
    int ret;
    state->strm.avail_in = state->zstrm.avail_in;
    state->strm.next_in = state->zstrm.next_in;
    ret = xz_avail(state);
    state->zstrm.avail_in = (uInt) state->strm.avail_in;
    state->zstrm.next_in = (Bytef *) state->strm.next_in;
    return ret;
}

Project: libxml2
File: xzlib.c

xz_reset(xz_statep state)
{
    state->have = 0;            /* no output data available */
    state->eof = 0;             /* not at end of file */
    state->how = LOOK;          /* look for gzip header */
    state->direct = 1;          /* default for empty file */
    state->seek = 0;            /* no seek request pending */
    xz_error(state, LZMA_OK, NULL);     /* clear error */
    state->pos = 0;             /* no uncompressed data yet */
    state->strm.avail_in = 0;   /* no input data yet */
#ifdef LIBXML_ZLIB_ENABLED
    state->zstrm.avail_in = 0;  /* no input data yet */
#endif
}

Project: libxml2
File: xzlib.c

xz_decomp(xz_statep state)
{
    int ret;
    unsigned had;
    unsigned long crc, len;
    lzma_stream *strm = &(state->strm);

    lzma_action action = LZMA_RUN;

    /* fill output buffer up to end of deflate stream */
    had = strm->avail_out;
    do {
        /* get more input for inflate() */
        if (strm->avail_in == 0 && xz_avail(state) == -1)
            return -1;
        if (strm->avail_in == 0) {
            xz_error(state, LZMA_DATA_ERROR, "unexpected end of file");
            return -1;
        }
        if (state->eof)
            action = LZMA_FINISH;

        /* decompress and handle errors */
#ifdef LIBXML_ZLIB_ENABLED
        if (state->how == GZIP) {
            state->zstrm.avail_in = (uInt) state->strm.avail_in;
            state->zstrm.next_in = (Bytef *) state->strm.next_in;
            state->zstrm.avail_out = (uInt) state->strm.avail_out;
            state->zstrm.next_out = (Bytef *) state->strm.next_out;
            ret = inflate(&state->zstrm, Z_NO_FLUSH);
            if (ret == Z_STREAM_ERROR || ret == Z_NEED_DICT) {
                xz_error(state, Z_STREAM_ERROR,
                         "internal error: inflate stream corrupt");
                return -1;
            }
            /*
             * FIXME: Remapping a couple of error codes and falling through
             * to the LZMA error handling looks fragile.
             */
            if (ret == Z_MEM_ERROR)
                ret = LZMA_MEM_ERROR;
            if (ret == Z_DATA_ERROR)
                ret = LZMA_DATA_ERROR;
            if (ret == Z_STREAM_END)
                ret = LZMA_STREAM_END;
            state->strm.avail_in = state->zstrm.avail_in;
            state->strm.next_in = state->zstrm.next_in;
            state->strm.avail_out = state->zstrm.avail_out;
            state->strm.next_out = state->zstrm.next_out;
        } else                  /* state->how == LZMA */
#endif
            ret = lzma_code(strm, action);
        if (ret == LZMA_MEM_ERROR) {
            xz_error(state, LZMA_MEM_ERROR, "out of memory");
            return -1;
        }
        if (ret == LZMA_DATA_ERROR) {
            xz_error(state, LZMA_DATA_ERROR, "compressed data error");
            return -1;
        }
        if (ret == LZMA_PROG_ERROR) {
            xz_error(state, LZMA_PROG_ERROR, "compression error");
            return -1;
        }
        if ((state->how != GZIP) &&
            (ret != LZMA_OK) && (ret != LZMA_STREAM_END)) {
            xz_error(state, ret, "lzma error");
            return -1;
        }
    } while (strm->avail_out && ret != LZMA_STREAM_END);

    /* update available output and crc check value */
    state->have = had - strm->avail_out;
    state->next = strm->next_out - state->have;
#ifdef LIBXML_ZLIB_ENABLED
    state->zstrm.adler =
        crc32(state->zstrm.adler, state->next, state->have);
#endif

    if (ret == LZMA_STREAM_END) {
#ifdef LIBXML_ZLIB_ENABLED
        if (state->how == GZIP) {
            if (gz_next4(state, &crc) == -1 || gz_next4(state, &len) == -1) {
                xz_error(state, LZMA_DATA_ERROR, "unexpected end of file");
                return -1;
            }
            if (crc != state->zstrm.adler) {
                xz_error(state, LZMA_DATA_ERROR, "incorrect data check");
                return -1;
            }
            if (len != (state->zstrm.total_out & 0xffffffffL)) {
                xz_error(state, LZMA_DATA_ERROR, "incorrect length check");
                return -1;
            }
            state->strm.avail_in = 0;
            state->strm.next_in = NULL;
            state->strm.avail_out = 0;
            state->strm.next_out = NULL;
        } else
#endif
        if (strm->avail_in != 0 || !state->eof) {
            xz_error(state, LZMA_DATA_ERROR, "trailing garbage");
            return -1;
        }
        state->how = LOOK;      /* ready for next stream, once have is 0 (leave
                                 * state->direct unchanged to remember how) */
    }

    /* good decompression */
    return 0;
}

Project: libxml2
File: xzlib.c

xz_error(xz_statep state, int err, const char *msg)
{
    /* free previously allocated message and clear */
    if (state->msg != NULL) {
        if (state->err != LZMA_MEM_ERROR)
            xmlFree(state->msg);
        state->msg = NULL;
    }

    /* set error code, and if no message, then done */
    state->err = err;
    if (msg == NULL)
        return;

    /* for an out of memory error, save as static string */
    if (err == LZMA_MEM_ERROR) {
        state->msg = (char *) msg;
        return;
    }

    /* construct error message with path */
    if ((state->msg =
         xmlMalloc(strlen(state->path) + strlen(msg) + 3)) == NULL) {
        state->err = LZMA_MEM_ERROR;
        state->msg = (char *) "out of memory";
        return;
    }
    strcpy(state->msg, state->path);
    strcat(state->msg, ": ");
    strcat(state->msg, msg);
    return;
}

Project: libxml2
File: xzlib.c

xz_open(const char *path, int fd, const char *mode ATTRIBUTE_UNUSED)
{
    xz_statep state;

    /* allocate xzFile structure to return */
    state = xmlMalloc(sizeof(xz_state));
    if (state == NULL)
        return NULL;
    state->size = 0;            /* no buffers allocated yet */
    state->want = BUFSIZ;       /* requested buffer size */
    state->msg = NULL;          /* no error message yet */
    state->init = 0;            /* initialization of zlib data */

    /* save the path name for error messages */
    state->path = xmlMalloc(strlen(path) + 1);
    if (state->path == NULL) {
        xmlFree(state);
        return NULL;
    }
    strcpy(state->path, path);

    /* open the file with the appropriate mode (or just use fd) */
    state->fd = fd != -1 ? fd : open(path,
#ifdef O_LARGEFILE
                                     O_LARGEFILE |
#endif
#ifdef O_BINARY
                                     O_BINARY |
#endif
                                     O_RDONLY, 0666);
    if (state->fd == -1) {
        xmlFree(state->path);
        xmlFree(state);
        return NULL;
    }

    /* save the current position for rewinding (only if reading) */
    state->start = lseek(state->fd, 0, SEEK_CUR);
    if (state->start == (uint64_t) - 1)
        state->start = 0;

    /* initialize stream */
    xz_reset(state);

    /* return stream */
    return (xzFile) state;
}

Project: libxml2
File: xzlib.c

__libxml2_xzopen(const char *path, const char *mode)
{
    return xz_open(path, -1, mode);
}

Project: libxml2
File: xzlib.c

xz_make(xz_statep state)
{
    lzma_stream *strm = &(state->strm);

    if (state->how == LOOK) {   /* look for lzma / gzip header */
        if (xz_head(state) == -1)
            return -1;
        if (state->have)        /* got some data from xz_head() */
            return 0;
    }
    if (state->how == COPY) {   /* straight copy */
        if (xz_load(state, state->out, state->size << 1, &(state->have)) ==
            -1)
            return -1;
        state->next = state->out;
    } else if (state->how == LZMA || state->how == GZIP) {      /* decompress */
        strm->avail_out = state->size << 1;
        strm->next_out = state->out;
        if (xz_decomp(state) == -1)
            return -1;
    }
    return 0;
}

Project: libxml2
File: xzlib.c

is_format_lzma(xz_statep state)
{
    lzma_stream *strm = &(state->strm);

    lzma_filter filter;
    lzma_options_lzma *opt;
    uint32_t dict_size;
    uint64_t uncompressed_size;
    size_t i;

    if (strm->avail_in < 13)
        return 0;

    filter.id = LZMA_FILTER_LZMA1;
    if (lzma_properties_decode(&filter, NULL, state->in, 5) != LZMA_OK)
        return 0;

    opt = filter.options;
    dict_size = opt->dict_size;
    free(opt); /* we can't use xmlFree on a string returned by zlib */

    /* A hack to ditch tons of false positives: We allow only dictionary
     * sizes that are 2^n or 2^n + 2^(n-1) or UINT32_MAX. LZMA_Alone
     * created only files with 2^n, but accepts any dictionary size.
     * If someone complains, this will be reconsidered.
     */
    if (dict_size != UINT32_MAX) {
        uint32_t d = dict_size - 1;

        d |= d >> 2;
        d |= d >> 3;
        d |= d >> 4;
        d |= d >> 8;
        d |= d >> 16;
        ++d;
        if (d != dict_size || dict_size == 0)
            return 0;
    }

    /* Another hack to ditch false positives: Assume that if the
     * uncompressed size is known, it must be less than 256 GiB.
     * Again, if someone complains, this will be reconsidered.
     */
    uncompressed_size = 0;
    for (i = 0; i < 8; ++i)
        uncompressed_size |= (uint64_t) (state->in[5 + i]) << (i * 8);

    if (uncompressed_size != UINT64_MAX
        && uncompressed_size > (UINT64_C(1) << 38))
        return 0;

    return 1;
}

Project: libxml2
File: xzlib.c

__libxml2_xzdopen(int fd, const char *mode)
{
    char *path;                 /* identifier for error messages */
    xzFile xz;

    if (fd == -1 || (path = xmlMalloc(7 + 3 * sizeof(int))) == NULL)
        return NULL;
    sprintf(path, "<fd:%d>", fd);       /* for debugging */
    xz = xz_open(path, fd, mode);
    xmlFree(path);
    return xz;
}

Project: libxml2
File: xzlib.c

xz_avail(xz_statep state)
{
    lzma_stream *strm = &(state->strm);

    if (state->err != LZMA_OK)
        return -1;
    if (state->eof == 0) {
        /* avail_in is size_t, which is not necessary sizeof(unsigned) */
        unsigned tmp = strm->avail_in;

        if (xz_load(state, state->in, state->size, &tmp) == -1) {
            strm->avail_in = tmp;
            return -1;
        }
        strm->avail_in = tmp;
        strm->next_in = state->in;
    }
    return 0;
}

Project: libxml2
File: xzlib.c

xz_head(xz_statep state)
{
    lzma_stream *strm = &(state->strm);
    lzma_stream init = LZMA_STREAM_INIT;
    int flags;
    unsigned len;

    /* allocate read buffers and inflate memory */
    if (state->size == 0) {
        /* allocate buffers */
        state->in = xmlMalloc(state->want);
        state->out = xmlMalloc(state->want << 1);
        if (state->in == NULL || state->out == NULL) {
            if (state->out != NULL)
                xmlFree(state->out);
            if (state->in != NULL)
                xmlFree(state->in);
            xz_error(state, LZMA_MEM_ERROR, "out of memory");
            return -1;
        }
        state->size = state->want;

        /* allocate decoder memory */
        state->strm = init;
        state->strm.avail_in = 0;
        state->strm.next_in = NULL;
        if (lzma_auto_decoder(&state->strm, 100000000, 0) != LZMA_OK) {
            xmlFree(state->out);
            xmlFree(state->in);
            state->size = 0;
            xz_error(state, LZMA_MEM_ERROR, "out of memory");
            return -1;
        }
#ifdef LIBXML_ZLIB_ENABLED
        /* allocate inflate memory */
        state->zstrm.zalloc = Z_NULL;
        state->zstrm.zfree = Z_NULL;
        state->zstrm.opaque = Z_NULL;
        state->zstrm.avail_in = 0;
        state->zstrm.next_in = Z_NULL;
        if (state->init == 0) {
            if (inflateInit2(&(state->zstrm), -15) != Z_OK) {/* raw inflate */
                xmlFree(state->out);
                xmlFree(state->in);
                state->size = 0;
                xz_error(state, LZMA_MEM_ERROR, "out of memory");
                return -1;
            }
            state->init = 1;
        }
#endif
    }

    /* get some data in the input buffer */
    if (strm->avail_in == 0) {
        if (xz_avail(state) == -1)
            return -1;
        if (strm->avail_in == 0)
            return 0;
    }

    /* look for the xz magic header bytes */
    if (is_format_xz(state) || is_format_lzma(state)) {
        state->how = LZMA;
        state->direct = 0;
        return 0;
    }
#ifdef LIBXML_ZLIB_ENABLED
    /* look for the gzip magic header bytes 31 and 139 */
    if (strm->next_in[0] == 31) {
        strm->avail_in--;
        strm->next_in++;
        if (strm->avail_in == 0 && xz_avail(state) == -1)
            return -1;
        if (strm->avail_in && strm->next_in[0] == 139) {
            /* we have a gzip header, woo hoo! */
            strm->avail_in--;
            strm->next_in++;

            /* skip rest of header */
            if (NEXT() != 8) {  /* compression method */
                xz_error(state, LZMA_DATA_ERROR,
                         "unknown compression method");
                return -1;
            }
            flags = NEXT();
            if (flags & 0xe0) { /* reserved flag bits */
                xz_error(state, LZMA_DATA_ERROR,
                         "unknown header flags set");
                return -1;
            }
            NEXT();             /* modification time */
            NEXT();
            NEXT();
            NEXT();
            NEXT();             /* extra flags */
            NEXT();             /* operating system */
            if (flags & 4) {    /* extra field */
                len = (unsigned) NEXT();
                len += (unsigned) NEXT() << 8;
                while (len--)
                    if (NEXT() < 0)
                        break;
            }
            if (flags & 8)      /* file name */
                while (NEXT() > 0) ;
            if (flags & 16)     /* comment */
                while (NEXT() > 0) ;
            if (flags & 2) {    /* header crc */
                NEXT();
                NEXT();
            }
            /* an unexpected end of file is not checked for here -- it will be
             * noticed on the first request for uncompressed data */

            /* set up for decompression */
            inflateReset(&state->zstrm);
            state->zstrm.adler = crc32(0L, Z_NULL, 0);
            state->how = GZIP;
            state->direct = 0;
            return 0;
        } else {
            /* not a gzip file -- save first byte (31) and fall to raw i/o */
            state->out[0] = 31;
            state->have = 1;
        }
    }
#endif

    /* doing raw i/o, save start of raw data for seeking, copy any leftover
     * input to output -- this assumes that the output buffer is larger than
     * the input buffer, which also assures space for gzungetc() */
    state->raw = state->pos;
    state->next = state->out;
    if (strm->avail_in) {
        memcpy(state->next + state->have, strm->next_in, strm->avail_in);
        state->have += strm->avail_in;
        strm->avail_in = 0;
    }
    state->how = COPY;
    state->direct = 1;
    return 0;
}

Project: libxml2
File: xzlib.c

__libxml2_xzclose(xzFile file)
{
    int ret;
    xz_statep state;

    /* get internal structure */
    if (file == NULL)
        return LZMA_DATA_ERROR;
    state = (xz_statep) file;

    /* free memory and close file */
    if (state->size) {
        lzma_end(&(state->strm));
#ifdef LIBXML_ZLIB_ENABLED
        if (state->init == 1)
            inflateEnd(&(state->zstrm));
        state->init = 0;
#endif
        xmlFree(state->out);
        xmlFree(state->in);
    }
    xmlFree(state->path);
    if ((state->msg != NULL) && (state->err != LZMA_MEM_ERROR))
        xmlFree(state->msg);
    ret = close(state->fd);
    xmlFree(state);
    return ret ? ret : LZMA_OK;
}

Project: libxml2
File: xzlib.c

xz_skip(xz_statep state, uint64_t len)
{
    unsigned n;

    /* skip over len bytes or reach end-of-file, whichever comes first */
    while (len)
        /* skip over whatever is in output buffer */
        if (state->have) {
            n = (uint64_t) state->have > len ?
                (unsigned) len : state->have;
            state->have -= n;
            state->next += n;
            state->pos += n;
            len -= n;
        }

    /* output buffer empty -- return if we're at the end of the input */
        else if (state->eof && state->strm.avail_in == 0)
            break;

    /* need more data to skip -- load up output buffer */
        else {
            /* get more output, looking for header if required */
            if (xz_make(state) == -1)
                return -1;
        }
    return 0;
}

Project: libxml2
File: xzlib.c

is_format_xz(xz_statep state)
{
    lzma_stream *strm = &(state->strm);

    return strm->avail_in >= 6 && memcmp(state->in, "\3757zXZ", 6) == 0;
}

Project: libxml2
File: xzlib.c

gz_next4(xz_statep state, unsigned long *ret)
{
    int ch;
    unsigned long val;
    z_streamp strm = &(state->zstrm);

    val = NEXTZ();
    val += (unsigned) NEXTZ() << 8;
    val += (unsigned long) NEXTZ() << 16;
    ch = NEXTZ();
    if (ch == -1)
        return -1;
    val += (unsigned long) ch << 24;
    *ret = val;
    return 0;
}

Project: libxml2
File: xzlib.c

xz_compressed(xzFile f) {
    xz_statep state;

    if (f == NULL)
        return(-1);
    state = (xz_statep) f;
    if (state->init <= 0)
        return(-1);

    switch (state->how) {
        case COPY:
	    return(0);
	case GZIP:
	case LZMA:
	    return(1);
    }
    return(-1);
}

Project: libxml2
File: xzlib.c

__libxml2_xzread(xzFile file, void *buf, unsigned len)
{
    unsigned got, n;
    xz_statep state;
    lzma_stream *strm;

    /* get internal structure */
    if (file == NULL)
        return -1;
    state = (xz_statep) file;
    strm = &(state->strm);

    /* check that we're reading and that there's no error */
    if (state->err != LZMA_OK)
        return -1;

    /* since an int is returned, make sure len fits in one, otherwise return
     * with an error (this avoids the flaw in the interface) */
    if ((int) len < 0) {
        xz_error(state, LZMA_BUF_ERROR,
                 "requested length does not fit in int");
        return -1;
    }

    /* if len is zero, avoid unnecessary operations */
    if (len == 0)
        return 0;

    /* process a skip request */
    if (state->seek) {
        state->seek = 0;
        if (xz_skip(state, state->skip) == -1)
            return -1;
    }

    /* get len bytes to buf, or less than len if at the end */
    got = 0;
    do {
        /* first just try copying data from the output buffer */
        if (state->have) {
            n = state->have > len ? len : state->have;
            memcpy(buf, state->next, n);
            state->next += n;
            state->have -= n;
        }

        /* output buffer empty -- return if we're at the end of the input */
        else if (state->eof && strm->avail_in == 0)
            break;

        /* need output data -- for small len or new stream load up our output
         * buffer */
        else if (state->how == LOOK || len < (state->size << 1)) {
            /* get more output, looking for header if required */
            if (xz_make(state) == -1)
                return -1;
            continue;           /* no progress yet -- go back to memcpy() above */
            /* the copy above assures that we will leave with space in the
             * output buffer, allowing at least one gzungetc() to succeed */
        }

        /* large len -- read directly into user buffer */
        else if (state->how == COPY) {  /* read directly */
            if (xz_load(state, buf, len, &n) == -1)
                return -1;
        }

        /* large len -- decompress directly into user buffer */
        else {                  /* state->how == LZMA */
            strm->avail_out = len;
            strm->next_out = buf;
            if (xz_decomp(state) == -1)
                return -1;
            n = state->have;
            state->have = 0;
        }

        /* update progress */
        len -= n;
        buf = (char *) buf + n;
        got += n;
        state->pos += n;
    } while (len);

    /* return number of bytes read into user buffer (will fit in int) */
    return (int) got;
}