Merge branch 'feature/ldap_refactor'

Conflicts:
	pam_yubico.c

README

@@ -20,7 +20,7 @@ later. This has introduced a dependency of libykpers-1 from the
 ykpersonalize package. Pass `--without-cr` to `configure` to avoid
 this dependency.
 
-The development community is co-ordinated via 
+The development community is co-ordinated via
 https://github.com/Yubico/yubico-pam[the GitHub project page].
 
 The project is licensed under a BSD license.  See the file COPYING for
@@ -150,7 +150,7 @@ service, go https://upgrade.yubico.com/getapikey[here].
 
 debug:: to enable debug output to stdout.
 
-alwaysok:: 
+alwaysok::
 to enable all authentication attempts to succeed
 (aka presentation mode).
 
@@ -310,10 +310,10 @@ information including the OTP and ID of your token to the shell -- copy the ID
 into your config file and you should be up and going.
 
 ------
-Yubikey for `youruser': 
+Yubikey for `youruser':
 [pam_yubico.c:pam_sm_authenticate(867)] conv returned 44 bytes
 [pam_yubico.c:pam_sm_authenticate(885)] Skipping first 0 bytes. Length is 44, token_id set to 12 and token OTP always 32.
-[pam_yubico.c:pam_sm_authenticate(892)] OTP: ccccccclabcabkhbdncicglfltnukadfoifadfhhhhfe ID: cccccclabcab 
+[pam_yubico.c:pam_sm_authenticate(892)] OTP: ccccccclabcabkhbdncicglfltnukadfoifadfhhhhfe ID: cccccclabcab
 ------
 
 
@@ -336,5 +336,27 @@ Examples
 If you want to use the YubiKey to authenticate you on Linux console
 logins, add the following to the top of `/etc/pam.d/login`:
 
- auth sufficient pam_yubico.so id=16 debug
+   auth sufficient pam_yubico.so id=16 debug
+
+OpenVPN and ActiveDirectory
+---------------------------
+
+create file '/etc/pam.d/openvpn':
+
+   auth  required  pam_yubico.so ldap_uri=ldap://ldap-srv debug id=19 yubi_attr=pager
+      ldapdn=dc=ad,dc=next-audience,dc=net
+      ldap_filter=(&(sAMAccountName=%u)(memberOf=CN=mygroup,OU=DefaultUser,DC=adivser,DC=net))
+      ldap_bind_user=bind_user ldap_bind_password=bind_password try_first_pass
+   account required  pam_yubico.so
+
+create file 'openvpn.conf'
+
+   plugin openvpn-plugin-auth-pam.so openvpn
+
+
+Feedback
+--------
+
+If you want to discuss anything related to the Yubico PAM module,
+please e-mail the mailing list yubico-devel@googlegroups.com.
 

pam_yubico.8.txt

@@ -57,10 +57,10 @@ This argument is used to show the OTP (One Time Password) when it is entered, i.
 Specify the LDAP server URI (e.g. ldap://localhost).
 
 *ldap_server*=_server_::
-Specify the LDAP server host (default LDAP port is used). *Deprecated.  Use "ldap_uri" instead.*
+Specify the LDAP server host (default LDAP port is used). *Deprecated.  Use 'ldap_uri' instead.*
 
 *ldapdn*=_dn_::
-The dn where the users are stored (eg: ou=users,dc=domain,dc=com).
+The dn where the users are stored (eg: ou=users,dc=domain,dc=com). If 'ldap_filter' is used this is the base from which the subtree search will be performed.
 
 *user_attr*=_attr_::
 The LDAP attribute used to store user names (eg:cn).
@@ -74,12 +74,26 @@ The prefix of the LDAP attribute's value, in case of a generic attribute, used t
 *token_id_length*=_length_::
 Length of ID prefixing the OTP (this is 12 if using the YubiCloud).
 
+*ldap_bind_user*=_user_::
+The user to attempt a LDAP bind as.
+
+*ldap_bind_password*=_password_::
+The password to use on LDAP bind.
+
+*ldap_filter*=_filter_::
+An ldap filter to use for attempting to find the correct object in LDAP. In this string %u will be replaced with the username.
+
+*ldap_cacertfile*=_cacertfile_::
+Ca certfile for the LDAP connection.
+
 == EXAMPLES
 
   auth sufficient pam_yubico.so id=16 debug
 
   auth required pam_yubico.so mode=challenge-response
 
+  auth required pam_yubico.so id=16 ldap_uri=ldaps://ldap.example.com ldap_filter=(uid=%u) yubi_attr=yubiKeyId
+
 == BUGS
 Report yubico-pam bugs in the issue tracker: https://github.com/Yubico/yubico-pam/issues
 

pam_yubico.c

@@ -113,6 +113,10 @@ struct cfg
   const char *urllist;
   const char *ldapserver;
   const char *ldap_uri;
+  const char *ldap_bind_user;
+  const char *ldap_bind_password;
+  const char *ldap_filter;
+  const char *ldap_cacertfile;
   const char *ldapdn;
   const char *user_attr;
   const char *yubi_attr;
@@ -193,8 +197,10 @@ free_out:
  * This function will look in ldap id the token correspond to the
  * requested user. It will returns 0 for failure and 1 for success.
  *
- * For the moment ldaps is not supported. ldap serve can be on a
+ * ldaps is only supported for ldap_uri based connections.
- * remote host.
+ * ldap_cacertfile usually needs to be set for this to work.
+ *
+ * ldap serve can be on a remote host.
  *
  * You need the following parameters in you pam config:
  * ldapserver=  OR ldap_uri=
@@ -202,6 +208,9 @@ free_out:
  * user_attr=
  * yubi_attr=
  *
+ * If using ldap_uri, you can specify multiple failover hosts
+ * eg.
+ * ldap_uri=ldaps://host1.fqdn.example.com,ldaps://host2.fqdn.example.com
  */
 static int
 authorize_user_token_ldap (struct cfg *cfg,
@@ -222,21 +231,18 @@ authorize_user_token_ldap (struct cfg *cfg,
   struct berval **vals;
   int i, rc;
 
+  char *filter = NULL;
   char *find = NULL;
+  int scope = LDAP_SCOPE_BASE;
 #endif
   DBG(("called"));
 #ifdef HAVE_LIBLDAP
-
-  if (cfg->user_attr == NULL) {
-    DBG (("Trying to look up user to YubiKey mapping in LDAP, but user_attr not set!"));
-    return 0;
-  }
   if (cfg->yubi_attr == NULL) {
     DBG (("Trying to look up user to YubiKey mapping in LDAP, but yubi_attr not set!"));
     return 0;
   }
-  if (cfg->ldapdn == NULL) {
+  if (cfg->user_attr && cfg->ldapdn == NULL) {
-    DBG (("Trying to look up user to YubiKey mapping in LDAP, but ldapdn not set!"));
+    DBG (("Trying to look up user to YubiKey mapping in LDAP, user_attr set but ldapdn not set!"));
     return 0;
   }
 
@@ -246,7 +252,7 @@ authorize_user_token_ldap (struct cfg *cfg,
       rc = ldap_initialize (&ld, cfg->ldap_uri);
       if (rc != LDAP_SUCCESS)
 	{
-	  DBG (("ldap_init: %s", ldap_err2string (rc)));
+	  DBG (("ldap_initialize: %s", ldap_err2string (rc)));
 	  retval = 0;
 	  goto done;
 	}
@@ -261,10 +267,21 @@ authorize_user_token_ldap (struct cfg *cfg,
 	}
     }
 
+  ldap_set_option(ld, LDAP_OPT_REFERRALS, LDAP_OPT_OFF);
   ldap_set_option (ld, LDAP_OPT_PROTOCOL_VERSION, &protocol);
 
+  if (cfg->ldap_uri && cfg->ldap_cacertfile) {
+    /* Set CA CERTFILE.  This makes ldaps work when using ldap_uri */
+    ldap_set_option (0, LDAP_OPT_X_TLS_CACERTFILE, cfg->ldap_cacertfile);
+  }
   /* Bind anonymously to the LDAP server. */
-  rc = ldap_simple_bind_s (ld, NULL, NULL);
+  if (cfg->ldap_bind_user && cfg->ldap_bind_password) {
+    DBG (("try bind with: %s:[%s]", cfg->ldap_bind_user, cfg->ldap_bind_password));
+    rc = ldap_simple_bind_s (ld, cfg->ldap_bind_user, cfg->ldap_bind_password);
+  } else {
+    DBG (("try bind anonymous"));
+    rc = ldap_simple_bind_s (ld, NULL, NULL);
+  }
   if (rc != LDAP_SUCCESS)
     {
       DBG (("ldap_simple_bind_s: %s", ldap_err2string (rc)));
@@ -273,22 +290,30 @@ authorize_user_token_ldap (struct cfg *cfg,
     }
 
   /* Allocation of memory for search strings depending on input size */
-  i = (strlen(cfg->user_attr) + strlen(cfg->ldapdn) + strlen(user) + 3) * sizeof(char);
+  if (cfg->user_attr && cfg->yubi_attr && cfg->ldapdn) {
-  if ((find = malloc(i)) == NULL) {
+    i = (strlen(cfg->user_attr) + strlen(cfg->ldapdn) + strlen(user) + 3) * sizeof(char);
-    DBG (("Failed allocating %i bytes", i));
+    if ((find = malloc(i)) == NULL) {
-    retval = 0;
+      DBG (("Failed allocating %i bytes", i));
-    goto done;
+      retval = 0;
+      goto done;
+    }
+    sprintf (find, "%s=%s,%s", cfg->user_attr, user, cfg->ldapdn);
+    filter = NULL;
+  } else if (cfg->ldapdn) {
+    find = strdup(cfg->ldapdn); /* allow free later */
+  }
+  if (cfg->ldap_filter) {
+    filter = filter_printf(cfg->ldap_filter, user);
+    scope = LDAP_SCOPE_SUBTREE;
   }
-
-  sprintf (find, "%s=%s,%s", cfg->user_attr, user, cfg->ldapdn);
-
   attrs[0] = (char *) cfg->yubi_attr;
 
-  DBG(("LDAP : look up object '%s', ask for attribute '%s'", find, cfg->yubi_attr));
+  DBG(("LDAP : look up object base='%s' filter='%s', ask for attribute '%s'", find,
+      filter ? filter:"(null)", cfg->yubi_attr));
 
   /* Search for the entry. */
-  if ((rc = ldap_search_ext_s (ld, find, LDAP_SCOPE_BASE,
+  if ((rc = ldap_search_ext_s (ld, find, scope,
-			       NULL, attrs, 0, NULL, NULL, LDAP_NO_LIMIT,
+			       filter, attrs, 0, NULL, NULL, LDAP_NO_LIMIT,
 			       LDAP_NO_LIMIT, &result)) != LDAP_SUCCESS)
     {
       DBG (("ldap_search_ext_s: %s", ldap_err2string (rc)));
@@ -312,16 +337,16 @@ authorize_user_token_ldap (struct cfg *cfg,
 	{
 	  if ((vals = ldap_get_values_len (ld, e, a)) != NULL)
 	    {
-	      DBG(("LDAP : Found %i values - checking if any of them match '%s%s'",
-		   ldap_count_values_len(vals),
-		   cfg->yubi_attr_prefix ? cfg->yubi_attr_prefix : "",
-		   token_id));
-
 	      yubi_attr_prefix_len = cfg->yubi_attr_prefix ? strlen(cfg->yubi_attr_prefix) : 0;
 
 	      /* Compare each value for the attribute against the token id. */
 	      for (i = 0; vals[i] != NULL; i++)
 		{
+	          DBG(("LDAP : Found %i values - checking if any of them match '%s:%s:%s'",
+		       ldap_count_values_len(vals),
+		       vals[i]->bv_val,
+		       cfg->yubi_attr_prefix ? cfg->yubi_attr_prefix : "", token_id));
+
 		  /* Only values containing this prefix are considered. */
 		  if ((!cfg->yubi_attr_prefix || !strncmp (cfg->yubi_attr_prefix, vals[i]->bv_val, yubi_attr_prefix_len)))
 		    {
@@ -349,6 +374,8 @@ authorize_user_token_ldap (struct cfg *cfg,
   /* free memory allocated for search strings */
   if (find != NULL)
     free(find);
+  if (filter != NULL)
+    free(filter);
 
 #else
   DBG (("Trying to use LDAP, but this function is not compiled in pam_yubico!!"));
@@ -671,6 +698,14 @@ parse_cfg (int flags, int argc, const char **argv, struct cfg *cfg)
 	cfg->ldapserver = argv[i] + 11;
       if (strncmp (argv[i], "ldap_uri=", 9) == 0)
 	cfg->ldap_uri = argv[i] + 9;
+      if (strncmp (argv[i], "ldap_bind_user=", 15) == 0)
+	cfg->ldap_bind_user = argv[i] + 15;
+      if (strncmp (argv[i], "ldap_bind_password=", 19) == 0)
+	cfg->ldap_bind_password = argv[i] + 19;
+      if (strncmp (argv[i], "ldap_filter=", 12) == 0)
+	cfg->ldap_filter = argv[i] + 12;
+      if (strncmp (argv[i], "ldap_cacertfile=", 16) == 0)
+        cfg->ldap_cacertfile = argv[i] + 16;
       if (strncmp (argv[i], "ldapdn=", 7) == 0)
 	cfg->ldapdn = argv[i] + 7;
       if (strncmp (argv[i], "user_attr=", 10) == 0)
@@ -705,6 +740,10 @@ parse_cfg (int flags, int argc, const char **argv, struct cfg *cfg)
       D (("authfile=%s", cfg->auth_file ? cfg->auth_file : "(null)"));
       D (("ldapserver=%s", cfg->ldapserver ? cfg->ldapserver : "(null)"));
       D (("ldap_uri=%s", cfg->ldap_uri ? cfg->ldap_uri : "(null)"));
+      D (("ldap_bind_user=%s", cfg->ldap_bind_user ? cfg->ldap_bind_user : "(null)"));
+      D (("ldap_bind_password=%s", cfg->ldap_bind_password ? cfg->ldap_bind_password : "(null)"));
+      D (("ldap_filter=%s", cfg->ldap_filter ? cfg->ldap_filter : "(null)"));
+      D (("ldap_cacertfile=%s", cfg->ldap_cacertfile ? cfg->ldap_cacertfile : "(null)"));
       D (("ldapdn=%s", cfg->ldapdn ? cfg->ldapdn : "(null)"));
       D (("user_attr=%s", cfg->user_attr ? cfg->user_attr : "(null)"));
       D (("yubi_attr=%s", cfg->yubi_attr ? cfg->yubi_attr : "(null)"));
@@ -741,6 +780,7 @@ pam_sm_authenticate (pam_handle_t * pamh,
   size_t templates = 0;
   char *urls[10];
   char *tmpurl = NULL;
+  char *onlypasswd = NULL;
 
   parse_cfg (flags, argc, argv, cfg);
 
@@ -936,7 +976,7 @@ pam_sm_authenticate (pam_handle_t * pamh,
   /* user entered their system password followed by generated OTP? */
   if (password_len > TOKEN_OTP_LEN + cfg->token_id_length)
     {
-      char *onlypasswd = strdup (password);
+      onlypasswd = strdup (password);
 
       if (! onlypasswd) {
 	retval = PAM_BUF_ERR;
@@ -949,7 +989,6 @@ pam_sm_authenticate (pam_handle_t * pamh,
 	    "setting item PAM_AUTHTOK"));
 
       retval = pam_set_item (pamh, PAM_AUTHTOK, onlypasswd);
-      free (onlypasswd);
       if (retval != PAM_SUCCESS)
 	{
 	  DBG (("set_item returned error: %s", pam_strerror (pamh, retval)));
@@ -1008,6 +1047,8 @@ pam_sm_authenticate (pam_handle_t * pamh,
     }
 
 done:
+  if (onlypasswd)
+    free(onlypasswd);
   if (templates > 0)
     {
       size_t i;
@@ -1029,7 +1070,7 @@ done:
       retval = PAM_SUCCESS;
     }
   DBG (("done. [%s]", pam_strerror (pamh, retval)));
-  pam_set_data (pamh, "yubico_setcred_return", (void*) (intptr_t) retval, NULL);
+  pam_set_data (pamh, "yubico_setcred_return", (void*)(intptr_t)retval, NULL);
 
   if (resp)
     {
@@ -1047,16 +1088,55 @@ pam_sm_setcred (pam_handle_t * pamh, int flags, int argc, const char **argv)
   return PAM_SUCCESS;
 }
 
+PAM_EXTERN int
+pam_sm_acct_mgmt(pam_handle_t *pamh, int flags, int argc, const char **argv)
+{
+  int retval;
+  int rc = pam_get_data(pamh, "yubico_setcred_return", (const void**)&retval);
+  if (rc == PAM_SUCCESS && retval == PAM_SUCCESS) {
+    D (("pam_sm_acct_mgmt returing PAM_SUCCESS"));
+    return PAM_SUCCESS;
+  }
+  D (("pam_sm_acct_mgmt returing PAM_AUTH_ERR:%d", rc));
+  return PAM_AUTH_ERR;
+}
+
+PAM_EXTERN int
+pam_sm_open_session(pam_handle_t *pamh, int flags,
+	int argc, const char *argv[])
+{
+
+  D(("pam_sm_open_session"));
+  return (PAM_SUCCESS);
+}
+
+PAM_EXTERN int
+pam_sm_close_session(pam_handle_t *pamh, int flags,
+	int argc, const char *argv[])
+{
+  D(("pam_sm_close_session"));
+  return (PAM_SUCCESS);
+}
+
+PAM_EXTERN int
+pam_sm_chauthtok(pam_handle_t *pamh, int flags,
+	int argc, const char *argv[])
+{
+  D(("pam_sm_chauthtok"));
+  return (PAM_SERVICE_ERR);
+}
+
+
 #ifdef PAM_STATIC
 
 struct pam_module _pam_yubico_modstruct = {
   "pam_yubico",
   pam_sm_authenticate,
   pam_sm_setcred,
-  NULL,
+  pam_sm_acct_mgmt,
-  NULL,
+  pam_sm_open_session,
-  NULL,
+  pam_sm_close_session,
-  NULL
+  pam_sm_chauthtok
 };
 
 #endif

tests/aux/ldap.pl

@@ -43,8 +43,9 @@ use constant RESULT_OK => {
 };
 
 my %objects = (
-  'uid=foo,ou=users,dc=example,dc=com' => ['vvincredible'],
+  'base=uid=foo,ou=users,dc=example,dc=com' => {keys => ['vvincredible']},
-  'uid=test,ou=users,dc=example,dc=com' =>['cccccccfhcbe', 'ccccccbchvth'],
+  'base=uid=test,ou=users,dc=example,dc=com' => {keys => ['cccccccfhcbe', 'ccccccbchvth']},
+  'sub:base=:(uid=test)' => {keys => ['cccccccfhcbe', 'ccccccbchvth'], dn => 'uid=test,out=users,dc=example,dc=com'},
 );
 
 sub bind {
@@ -56,14 +57,22 @@ sub bind {
 sub search {
   my $self = shift;
   my $reqData = shift;
-  my $base = $reqData->{'baseObject'};
+  my $id;
-  my $id = $objects{$base};
+  my $base;
+  if($reqData->{'scope'} == 0) {
+    $base = $reqData->{'baseObject'};
+    $id = $objects{'base=' . $base};
+  } elsif($reqData->{'scope'} == 2) {
+    my $match = $reqData->{'filter'}->{'equalityMatch'};
+    $id = $objects{'sub:base=' . $reqData->{'baseObject'} . ':(' . $match->{'attributeDesc'} . '=' . $match->{'assertionValue'} . ')'};
+    $base = $id->{'dn'};
+  }
   my @entries;
   if($id) {
     my $entry = Net::LDAP::Entry->new;
     $entry->dn($base);
     $entry->add(objectClass => [ "person" ]);
-    $entry->add(yubiKeyId => $id);
+    $entry->add(yubiKeyId => $id->{'keys'});
     push @entries, $entry;
   }
   return RESULT_OK, @entries;

tests/pam_test.c

@@ -63,7 +63,6 @@ static struct data {
 static const char *ldap_cfg[] = {
   "id=1",
   "urllist=http://localhost:"YKVAL_PORT2"/wsapi/2/verify;http://localhost:"YKVAL_PORT1"/wsapi/2/verify",
-  "authfile="AUTHFILE,
   "ldap_uri=ldap://localhost:"LDAP_PORT,
   "ldapdn=ou=users,dc=example,dc=com",
   "user_attr=uid",
@@ -71,6 +70,15 @@ static const char *ldap_cfg[] = {
   "debug"
 };
 
+static const char *ldap_cfg2[] = {
+  "id=1",
+  "urllist=http://localhost:"YKVAL_PORT1"/wsapi/2/verify;http://localhost:"YKVAL_PORT2"/wsapi/2/verify",
+  "ldap_uri=ldap://localhost:"LDAP_PORT,
+  "ldap_filter=(uid=%u)",
+  "yubi_attr=yubiKeyId",
+  "debug"
+};
+
 static const struct data *test_get_data(void *id) {
   return &_data[(long)id];
 }
@@ -212,6 +220,10 @@ static int test_authenticate_ldap2(void) {
   return pam_sm_authenticate(4, 0, sizeof(ldap_cfg) / sizeof(char*), ldap_cfg);
 }
 
+static int test_authenticate_ldap3(void) {
+  return pam_sm_authenticate(4, 0, sizeof(ldap_cfg2) / sizeof(char*), ldap_cfg2);
+}
+
 static pid_t run_mock(const char *port, const char *type) {
   pid_t pid = fork();
   if(pid == 0) {
@@ -251,28 +263,32 @@ int main(void) {
     ret = 5;
     goto out;
   }
-#ifdef HAVE_LIBLDAP
+  if(test_authenticate3() != PAM_SUCCESS) {
-  if(test_authenticate_ldap1() != PAM_SUCCESS) {
     ret = 6;
     goto out;
   }
+#ifdef HAVE_LIBLDAP
+  if(test_authenticate_ldap1() != PAM_SUCCESS) {
+    ret = 1001;
+    goto out;
+  }
   if(test_authenticate_ldap_fail1() != PAM_USER_UNKNOWN) {
-    ret = 7;
+    ret = 1002;
     goto out;
   }
   if(test_authenticate_ldap_fail2() != PAM_AUTH_ERR) {
-    ret = 8;
+    ret = 1003;
     goto out;
   }
   if(test_authenticate_ldap2() != PAM_SUCCESS) {
-    ret = 9;
+    ret = 1004;
+    goto out;
+  }
+  if(test_authenticate_ldap3() != PAM_SUCCESS) {
+    ret = 1005;
     goto out;
   }
 #endif
-  if(test_authenticate3() != PAM_SUCCESS) {
-    ret = 10;
-    goto out;
-  }
 
 out:
   kill(child, 9);

tests/util_test.c

@@ -125,7 +125,27 @@ static void test_load_chalresp_state(void) {
 
 #endif /* HAVE_CR */
 
+static void test_filter_printf(void) {
+    assert(filter_result_len("meno %u", "doof", NULL) == 10);
+    assert(filter_result_len("meno %u %u", "doof", NULL) == 15);
+    assert(filter_result_len("%u meno %u", "doof", NULL) == 15);
+    assert(filter_result_len("%u me %u no %u", "doof", NULL) == 21);
+    assert(filter_result_len("meno %w %%u", "doof", NULL) == 14);
+    assert(filter_result_len("meno %w %%u meno", "doof", NULL) == 19);
+    assert(filter_result_len("meno ", "doof", NULL) == 6);
+
+    assert(!strcmp(filter_printf("meno %u", "doof"), "meno doof"));
+    assert(!strcmp(filter_printf("meno %u %u", "doof"), "meno doof doof"));
+    assert(!strcmp(filter_printf("%u meno %u", "doof"), "doof meno doof"));
+    assert(!strcmp(filter_printf("%u me %u no %u", "doof"), "doof me doof no doof"));
+    assert(!strcmp(filter_printf("meno %w %%u", "doof"), "meno %w %doof"));
+    assert(!strcmp(filter_printf("meno %w %%u meno", "doof"), "meno %w %doof meno"));
+    assert(!strcmp(filter_printf("meno ", "doof"), "meno "));
+    printf("test_filter_printf OK\n");
+}
+
 int main (void) {
+  test_filter_printf();
   test_get_user_cfgfile_path();
   test_check_user_token();
 #if HAVE_CR

util.c

@@ -35,6 +35,9 @@
 #include <stdlib.h>
 #include <string.h>
 #include <sys/types.h>
+#include <sys/stat.h>
+#include <errno.h>
+#include <fcntl.h>
 #include <pwd.h>
 #include <unistd.h>
 
@@ -461,3 +464,44 @@ write_chalresp_state(FILE *f, CR_STATE *state)
   return 0;
 }
 #endif /* HAVE_CR */
+
+size_t filter_result_len(const char *filter, const char *user, char *output) {
+  const char *part = NULL;
+  size_t result = 0;
+  do
+    {
+      size_t len;
+      part = strstr(filter, "%u");
+      if(part)
+        len = part - filter;
+      else
+        len = strlen(filter);
+      if (output)
+        {
+          strncpy(output, filter, len);
+          output += len;
+        }
+      result += len;
+      filter += len + 2;
+      if(part)
+        {
+          if(output)
+            {
+              strncpy(output, user, strlen(user));
+              output += strlen(user);
+            }
+          result += strlen(user);
+        }
+    }
+  while(part);
+
+  if(output)
+    *output = '\0';
+  return(result + 1);
+}
+
+char *filter_printf(const char *filter, const char *user) {
+  char *result = malloc(filter_result_len(filter, user, NULL));
+  filter_result_len(filter, user, result);
+  return result;
+}

util.h

@@ -96,4 +96,7 @@ int challenge_response(YK_KEY *yk, int slot,
 
 #endif /* HAVE_CR */
 
+size_t filter_result_len(const char *filter, const char *user, char *output);
+char *filter_printf(const char *filter, const char *user);
+
 #endif /* __PAM_YUBICO_UTIL_H_INCLUDED__ */