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/*
* Support functions for pam_krb5.
*
* Some general utility functions used by multiple PAM groups that aren't
* associated with any particular chunk of functionality.
*
* Copyright 2005, 2006, 2007, 2009 Russ Allbery <rra@stanford.edu>
* Copyright 2005 Andres Salomon <dilinger@debian.org>
* Copyright 1999, 2000 Frank Cusack <fcusack@fcusack.com>
*
* See LICENSE for licensing terms.
*/
#include <config.h>
#include <portable/pam.h>
#include <krb5.h>
#include <pwd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <internal.h>
/*
* Given the PAM arguments and the user we're authenticating, see if we should
* ignore that user because they're root or have a low-numbered UID and we
* were configured to ignore such users. Returns true if we should ignore
* them, false otherwise.
*/
int
pamk5_should_ignore(struct pam_args *args, PAM_CONST char *username)
{
struct passwd *pwd;
if (args->ignore_root && strcmp("root", username) == 0) {
pamk5_debug(args, "ignoring root user");
return 1;
}
if (args->minimum_uid > 0) {
pwd = pam_modutil_getpwnam(args->pamh, username);
if (pwd != NULL && pwd->pw_uid < (unsigned long) args->minimum_uid) {
pamk5_debug(args, "ignoring low-UID user (%lu < %d)",
(unsigned long) pwd->pw_uid, args->minimum_uid);
return 1;
}
}
return 0;
}
/*
* Map the user to a Kerberos principal according to alt_auth_map. Returns
* PAM_SUCCESS on success, storing the mapped principal name in newly
* allocated memory in principal. The caller is responsible for freeing.
* Returns PAM_SERVICE_ERROR on any error.
*/
int
pamk5_map_principal(struct pam_args *args, const char *username,
char **principal)
{
char *user = NULL;
char *realm;
const char *i;
size_t needed, offset;
/* Makes no sense if alt_auth_map isn't set. */
if (args->alt_auth_map == NULL)
return PAM_SERVICE_ERR;
/* Need to split off the realm if it is present. */
realm = strchr(username, '@');
if (realm == NULL)
user = (char *) username;
else {
user = strdup(username);
if (user == NULL)
return PAM_SERVICE_ERR;
realm = strchr(user, '@');
if (realm == NULL)
goto fail;
*realm = '\0';
realm++;
}
/* Now, allocate a string and build the principal. */
needed = 0;
for (i = args->alt_auth_map; *i != '\0'; i++) {
if (i[0] == '%' && i[1] == 's') {
needed += strlen(user);
i++;
} else {
needed++;
}
}
if (realm != NULL)
needed += 1 + strlen(realm);
needed++;
*principal = malloc(needed);
if (*principal == NULL)
goto fail;
offset = 0;
for (i = args->alt_auth_map; *i != '\0'; i++) {
if (i[0] == '%' && i[1] == 's') {
memcpy(*principal + offset, user, strlen(user));
offset += strlen(user);
i++;
} else {
(*principal)[offset] = *i;
offset++;
}
}
(*principal)[offset] = '\0';
return PAM_SUCCESS;
fail:
if (user != NULL && user != username)
free(user);
return PAM_SERVICE_ERR;
}
/*
* Verify the user authorization. Call krb5_kuserok if this is a local
* account, or do the krb5_aname_to_localname verification if ignore_k5login
* was requested. For non-local accounts, the principal must match the
* authentication identity.
*/
int
pamk5_authorized(struct pam_args *args)
{
struct context *ctx;
krb5_context c;
struct passwd *pwd;
char kuser[65]; /* MAX_USERNAME == 65 (MIT Kerberos 1.4.1). */
if (args == NULL || args->ctx == NULL || args->ctx->context == NULL)
return PAM_SERVICE_ERR;
ctx = args->ctx;
if (ctx->name == NULL)
return PAM_SERVICE_ERR;
c = ctx->context;
/*
* If alt_auth_map was set, authorize the user if the authenticated
* principal matches the mapped principal. alt_auth_map essentially
* serves as a supplemental .k5login.
*/
if (args->alt_auth_map != NULL) {
char *mapped;
char *authed;
int retval;
krb5_principal princ;
if (pamk5_map_principal(args, ctx->name, &mapped) != PAM_SUCCESS)
return PAM_SERVICE_ERR;
retval = krb5_parse_name(c, mapped, &princ);
if (retval != 0) {
free(mapped);
return PAM_SERVICE_ERR;
}
free(mapped);
retval = krb5_unparse_name(c, princ, &mapped);
if (retval != 0)
return PAM_SERVICE_ERR;
retval = krb5_unparse_name(c, ctx->princ, &authed);
if (retval != 0) {
free(mapped);
return PAM_SERVICE_ERR;
}
if (strcmp(authed, mapped) == 0) {
free(authed);
free(mapped);
return PAM_SUCCESS;
}
free(authed);
free(mapped);
}
/*
* If the name to which we're authenticating contains @ (is fully
* qualified), it must match the principal exactly.
*/
if (strchr(ctx->name, '@') != NULL) {
char *principal;
int retval;
retval = krb5_unparse_name(c, ctx->princ, &principal);
if (retval != 0)
return PAM_SERVICE_ERR;
if (strcmp(principal, ctx->name) != 0) {
free(principal);
return PAM_AUTH_ERR;
}
return PAM_SUCCESS;
}
/*
* Otherwise, apply either krb5_aname_to_localname or krb5_kuserok
* depending on the situation.
*/
pwd = pam_modutil_getpwnam(args->pamh, ctx->name);
if (args->ignore_k5login || pwd == NULL) {
if (krb5_aname_to_localname(c, ctx->princ, sizeof(kuser), kuser) != 0)
return PAM_AUTH_ERR;
if (strcmp(kuser, ctx->name) != 0)
return PAM_AUTH_ERR;
} else {
if (!krb5_kuserok(c, ctx->princ, ctx->name))
return PAM_AUTH_ERR;
}
return PAM_SUCCESS;
}
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