I looked at several of the krb5 related modules and it appears that none of them provide a means for a user to change their own password.

The following demonstrates that it is possible to change an AD password from linux using the krb5 library. This code is crude and minimally tested - you should use it with caution except as a basis for discovery.

#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;
use Inline (
    C   => 'DATA',
    LIBS    => '-lkrb5',
);

my $oldpw = shift or die "USAGE: test.pl oldpw newpw";
my $newpw = shift or die "USAGE: test.pl oldpw newpw";

my $ret = change_password($oldpw, $newpw);
$oldpw = $newpw = "";
undef($oldpw);
undef($newpw);
print "change_password returned $ret\n";
print  "  :" . change_password_error($ret) . "\n";

__DATA__
__C__
#include <stdio.h>
#include <krb5.h>
#include <et/com_err.h>

static krb5_error_code error_code = 0;
static char error_text[1024] = "";

char *change_password_error(int error_number) {
    static char buf[1024];
    char *text[] = {
        /* 0 */ "success",
        /* 1 */ "krb5_init_context failed",
        /* 2 */ "krb5_parse_name failed",
        /* 3 */ "krb5_get_init_creds_opt_alloc failed",
        /* 4 */ "krb5_get_init_creds failed",
        /* 5 */ "krb5_change_password failed",
        /* 6 */ "krb5_change_password failed",
    };

    if(error_number > 6) {
        sprintf(buf, "Unknown error code: %d", error_number);
    } else {
        if(error_code) {
            sprintf(buf, "%s: %s",
                text[error_number],
                error_message(error_code)
            );
        } else if(strlen(error_text)) {
            sprintf(buf, "%s: %s",
                text[error_number],
                error_text
            );
        } else {
            sprintf(buf, "%s", text[error_number]);
        }
    }

    return(buf);
}

int change_password(char* oldpw, char* newpw) {
    krb5_context context;
    krb5_principal princ;
    krb5_get_init_creds_opt *opts = NULL;
    krb5_creds creds;
    int result_code;
    krb5_data result_code_string;
    krb5_data result_string;

    error_code = krb5_init_context(&context);
    if ( error_code ) return(1);

    error_code = krb5_parse_name(context, "billyb", &princ);
    if ( error_code ) return(2);

    error_code = krb5_get_init_creds_password(
        context, &creds, princ, oldpw,
        NULL, NULL,
        0, "kadmin/changepw", NULL
    );
    if ( error_code ) return(4);

    error_code = krb5_change_password(context, &creds, newpw,
        &result_code, &result_code_string, &result_string);

    if ( error_code ) return(5);

    if(result_code) {
        if(
            result_code_string.length + result_string.length + 5 >
                sizeof(error_text)
        ) {
            sprintf(error_text, "buffer overrun");
        } else {
            printf("setting error_text\n");
            sprintf(error_text, "%.*s%s%.*s",
                (int) result_code_string.length, result_code_string.da
+ta,
                result_string.length?": ":"",
                (int) result_string.length,
                result_string.data ? result_string.data : ""
            );
        }
        return(6);
    }

    if (result_string.data != NULL) free(result_string.data);
    if (result_code_string.data != NULL) free(result_code_string.data)
+;

    return(0);
}
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