Comparing a Password

When Directory Server calls a password storage scheme plug-in compare function, it passes that function an input password char * and a stored, encoded password char * from the directory. The compare function returns zero, 0, if the input password matches the password from the directory. The function returns 1 otherwise. The prototype for the example compare function, xorcmp(), is therefore as follows:

static int xorcmp(char * userpwd, char * dbpwd);

Here, userpwd is the input password. dbpwd is the password from the directory. The compare function must encode the input password to compare the result to the password from the directory.

Example 11–2 Comparing a userPassword Value (testpwdstore.c)

#include "slapi-plugin.h"

static int
xorcmp(char * userpwd, char * dbpwd)
{
    /* Check the correspondence of the two char by char       */       
    int i, len = strlen(userpwd);
    for (i = 0; i < len; i++) {
        if ((userpwd[i] ^ 42) != dbpwd[i])
            return 1;                  /* Different passwords */
    }
    return 0;                          /* Identical passwords */
}

Notice that Directory Server strips the prefix from the password before passing the value to the compare function. In other words, you need not account for {XOR} in this case.

Not all encoding algorithms have such a trivial compare function.