Can any user bind port <1024

[KapilRaj]

Chaps,

I hv a doubt & it goes as follows,

-- Can any user bind port number less than 1024
-- If i start an application (tomcat-servelett engine) to listen on port 80 by a normal user, Is that going to fail ?

Kapil Raj

[Jordan Bean]

Only superuser can bind port < 1024.

[KapilRaj]

Are you sure on that ?. I hv an application called OAS (Oracle application Server) listening on port 80. It is started by a normal user.

Kapil

[Jordan Bean]

Yes. Only superuser can bind port < 1024.

OAS is either invoked by root to bind the port before it changes to another user, or the application uses setuid execution.

[James R. Ferguson]

Hi:

The so-called "well-known-ports" fall into the range below 1024 and cannot be bound unless the *effective* uid of the process is root's.

Regards!

...JRF...

[KapilRaj]

ok guys,

if u masters are so confident on it . I still hv to convince myself & the only way to accomplish that is to check up how OAS is started in my environment.

kaps

[Christopher Caldwell]

Yup. He's right.

From /usr/include/netinet/in.h


/*
* Ports < IPPORT_RESERVED are reserved for
* privileged processes (e.g. root).
* Ports > IPPORT_USERRESERVED are reserved
* for servers, not necessarily privileged.
*/
#define IPPORT_RESERVED 1024

Make sure your effective UID isn't really root (e.g. is the program setuid?).

[Anil C. Sedha]

Kapil

Only superuser binds ports less than 1024.

Now, do you have any entry for OAS in your /etc/inetd.conf file for a lower port number.

I believe your OAS application is executed using super user rights while startup if it doesn't start using inetd.

Regards,
Anil

[Sean OB_1]

All ports below 1024 are reserved for root processes.

No user can bind to a port below that unless they use setuid.