Directory traversal vulnerability in zziplib 0.13.69

[92wyunchao]

Directory traversal vulnerability in zziplib 0.13.69 allows attackers to overwrite arbitrary files via a .. (dot dot) in an zip file. $unzzip-mem evil.zip evil.zip

Relevant code in function unzzip_cat in Unzzipcat-mem.c: static int unzzip_cat (int argc, char argv, int extract) { ...... if (argc == 2) { / print directory list / ZZIP_MEM_ENTRY* entry = zzip_mem_disk_findfirst(disk); DBG2("findfirst %p\n", entry); for (; entry ; entry = zzip_mem_disk_findnext(disk, entry)) { *char name = zzip_mem_entry_to_name (entry); FILE* out = stdout; if (extract) out = create_fopen(name, "wb", 1); //no checkout here if (! out) { if (errno != EISDIR) { DBG3("can not open output file %i %s", errno, strerror(errno)); done = EXIT_ERRORS; } continue; } unzzip_mem_disk_cat_file (disk, name, out); if (extract) fclose(out); } } ...... }

static FILE create_fopen(char name, char mode, int subdirs) { if (subdirs) { char p = strrchr(name, '/'); if (p) { char* dir_name = _zzip_strndup(name, p-name); makedirs(dir_name); free (dir_name); } } return fopen(name, mode);
}

static void unzzip_mem_disk_cat_file(ZZIP_MEM_DISK disk, char name, FILE out) { ZZIP_DISK_FILE file = zzip_mem_disk_fopen (disk, name); if (file) { char buffer[1025]; int len; while ((len = zzip_mem_disk_fread (buffer, 1, 1024, file))) { fwrite (buffer, 1, len, out); } zzip_mem_disk_fclose (file); } }

[jmoellers]

Other "zip/unzip" programs just delete any "../" components from the path. Should zziplib do the same? Added note: I'm not sure about this, as this would then unintendedly over-write yet another file! Simply drop any pathname containing "../" or add an option to allow "../" in extracted pathnames? NB This issue also exists in the other unzzipcat-*.c files!

[jmoellers]

Proposed solution: static inline void remove_dotdotslash(char path) { / Note: removing "../" from the path ALWAYS shortens the path, never adds to it! / char dotdotslash; int warned = 0;

dotdotslash = path;
while ((dotdotslash = strstr("../", dotdotslash)) != NULL)
{
    /*
     * Remove only if at the beginning of the pathname ("../path/name")
     * or when preceded by a slash ("path/../name"),
     * otherwise not ("path../name..")!
     */
    if (dotdotslash == path || dotdotslash[-1] == '/')
    {
        char *src, *dst;
        if (!warned)
        {
            /* Note: the first time through the pathname is still intact */
            fprintf(stderr, "Removing \"../\" path component(s) in %s\n", path);
            warned = 1;
        }
        /* We cannot use strcpy(), as there "The strings may not overlap" */
        for (src = dotdotslash+3, dst=dotdotslash; (*dst = *src) != '\0'; src+, dst++)
            ;
    }
    else
        dotdotslash +=3;    /* skip this instance to prevent infinite loop */
}

} then insert "remove_dotdotslash(dir_name);" before "makedirs(dir_name)".

[jmoellers]

https://github.com/gdraheim/zziplib/pull/63

[jamartis]

Hey, unzip-mem (single z) seems to have the same problem. patch.txt

[0-wiz-0]

https://nvd.nist.gov/vuln/detail/CVE-2018-17828 points to this ticket, and it seems to have open questions. Can you please fix this?