Transcript Unix Wars I
mid 1960’s - Multics - proposed by AT&T, Honeywell, GE & MIT; funded by DARPA 1969 - Thompson & Ritchie create Unix 1978 to 84 - Bill Joy & Chuck Haley (Berkeley U.) create BSD Unix Unix Wars I - BSD 4.2 versus System V Unix Wars II - SVR4 versus OSF ISO Standard - POSIX 1991 - Linus Torvalds creates Linux Mach BSD System V OSF/1 NeXTStep SunOS Free BSD Linux OS X Solaris AIX HP-UX Authentication Admin File Systems Network-related Audit UID • 16-bits • ID 0 - 99 reserved • ID 0 is root GID • 16 or 32 bits • /etc/group stores local groups • wheel group for system administrators /etc/passwd • entry: UserName:*:UID:GID:FullName:UserDir:UserShell • passwords encrypted via crypt() • salt Standard Users root - superuser account daemon - executes as background process - handles system events such as print spooling lp - print server process guest - generic visitor account nobody - default user for unprivileged access - user owns no files mail - system account for email processing sshd - for running secure shell tasks www - for running a web server shell • command line interface • Born (sh), c-shell (csh), tc-shell (tcsh) commands • ls -- list directory information • cd -- set current directory • pwd -- display current directory • cat -- display contents of textfile • whoami -- display current user • su -- log in as a different user (will be prompted for password) • man -- give help on command • sudo -- execute a single command as root (must specify password) ufs ffs original Unix File System first tree-structured directory system Fast File System allows longer file names (255 chars rather than 14) supports symbolic links inodes separate inode (index node) per file/directory an inode has an address (index) but no name each inode resides on the disk contents: • address of associated item (file/directory) • item type • item size (in bytes) • time of last inode modification • time of last modification of item (mtime) • time of last item access (atime) • reference count (number of names for this inode) • item’s UID • item’s primary GID • item’s mode bits (permissions) directory ...consists of a list of pairs: name - inode index standard directory entries . refers to this directory’s inode .. refers to inode of the parent of this directory shell commands • cp -- copy (duplicate) file • mv -- move file from one directory to another • mkdir -- create new directory • ln -- create new link (use -s flag for symbolic link) • rm -- remove one name • rmdir -- log in as a different user (will be prompted for password) • chown -- change owner of file/directory • chmod -- change mode (permissions) for a file • umask -- set default mode (permissions) for this user t “sticky” bit - rwx r-x --- t owner group world - file d directory c character device (tty, printer) b block device (disk, CD) l symbolic link s socket Mode: Example r w x s read write execute set (in place of x) 1000 2000 4000 400 200 100 - sticky bit - set GID - set UID - read (owner) - write (owner) - execute (owner) TCP Wrappers • a common way to secure network transmissions on some Unix versions • when tcp wrappers are turned on... a) look in /etc/hosts.allow file for allowed firewall access b) look in /etc/hosts.deny file for denied firewall access c) if no rules apply, then access is granted • results logged to syslog • optionally sends banners to clients • can transfer access to “jail” or “faux” host-based firewalls • Free BSD • OS X • varies with Linux echo (UDP Port 7) ping command sends datagram to test connectivity systat (TCP Port 11) netstat command returns user names, login times, and so forth ftp (TCP Ports 20 & 21) file transfer protocol ftp transmits in plaintext - sftp encrypts anonymous ftp is a vulnerability ssh (TCP Port 2) secure shell for remote login uses symmetric encryption (ssh.config) requires that client have public key telnet (TCP Port 23) original remote login shell - uses plaintext smtp (TCP Port 25) Simple Mail Transfer Protocol - Internet standard for email transfer dns (TCP & UDP Port 53) Domain Name System (stay tuned) dhcp (UDP Ports 67 & 68) Dynamic Host Configuration Protocol IP address leasing utility finger (TCP Port 79) retrieves user info (name, location, login, telephone, and so forth http (TCP Ports 80 & 443) HypterText Transfer Protocol (WWW protocol) POP, POPS, IMAP, IMAPS (TCP Ports 109, 110, 143, 993 & 995) Post Office Protocol -- Internet Message Access Protocol snmp (UDP Ports 161 & 162) Simple Network Management Protocol remote system management tool rlogin & rsh (TCP Ports 513 & 514) more insecure login shells empty /etc/hosts.equiv