opening accounts from a non-root account ..

[Peter Holzer]

lubkt at spectrum.CC.Lehigh.EDU (Binod K. Taterway) writes:


>All of this works fine for root; but -F option of passwd(1) does not
>work with non-root. So, I thought I might get around by generating
>encrypted password in the first place.

Good idea.

>Here begins my journey to the wonderous land of crypt(3), login(1),
>DES, and a host of other programs. I realize crypt cannot generate
>initial encrypted password because it doesn't have the right seed. Let
>EPW be the encrypted password of the clear-text password, PW. Then,

>	EPW = crypt(PW, EPW)

>The second parameter of crypt is the seed: if the seed is same as EPW,
>then the result of crypt is same EPW. This is what is presumably used
>by login programs to validate a user.

>But, my problem is to generate EPW without initial seed.

The manual [crypt(3), makekey(8)] states that the salt are two
characters from the set [A-Za-z0-9./]. The salt is stored together with
the password so we can just use some random salt:

[...]
char saltchars [] = "AB...YZab...yz0123456789./";
char salt[2];

srand ((int)(time ((time_t *)0) + getpid()));
salt[0] = saltchars[rand() % 64];
salt[1] = saltchars[rand() % 64];
epw = crypt(pw, salt);
[...]

--
|    _  | Peter J. Holzer                       | Think of it   |
| |_|_) | Technical University Vienna           | as evolution  |
| | |   | Dept. for Real-Time Systems           | in action!    |
| __/   | hp at vmars.tuwien.ac.at                 |     Tony Rand |