From d3a18f06162b9585d2db936472b75fdbff37162d Mon Sep 17 00:00:00 2001
From: Sumit Bose <sbose@redhat.com>
Date: Oct 10 2018 21:02:54 +0000
Subject: pam_sss: add try_cert_auth option


With this new option pam_sss can be configured to only do Smartcard
authentication or return an error if this is not possible.

Related to https://pagure.io/SSSD/sssd/issue/3650

Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>

---

diff --git a/src/man/pam_sss.8.xml b/src/man/pam_sss.8.xml
index d8e6a20..ca2e8e2 100644
--- a/src/man/pam_sss.8.xml
+++ b/src/man/pam_sss.8.xml
@@ -50,6 +50,9 @@
             <arg choice='opt'>
                 <replaceable>prompt_always</replaceable>
             </arg>
+            <arg choice='opt'>
+                <replaceable>try_cert_auth</replaceable>
+            </arg>
         </cmdsynopsis>
     </refsynopsisdiv>
 
@@ -200,6 +203,26 @@ auth sufficient pam_sss.so allow_missing_name
                     </para>
                 </listitem>
             </varlistentry>
+            <varlistentry>
+                <term>
+                    <option>try_cert_auth</option>
+                </term>
+                <listitem>
+                    <para>
+                        Try to use certificate based authentication, i.e.
+                        authentication with a Smartcard or similar devices. If a
+                        Smartcard is available and the service is allowed for
+                        Smartcard authentication the use will be prompted for a
+                        PIN and the certificate based authentication will
+                        continue
+                    </para>
+                    <para>
+                        If no Smartcard is available or certificate based
+                        authentication is not allowed for the current service
+                        PAM_AUTHINFO_UNAVAIL is returned.
+                    </para>
+                </listitem>
+            </varlistentry>
         </variablelist>
     </refsect1>
 
diff --git a/src/sss_client/pam_sss.c b/src/sss_client/pam_sss.c
index b336d1f..96ff15a 100644
--- a/src/sss_client/pam_sss.c
+++ b/src/sss_client/pam_sss.c
@@ -1997,6 +1997,8 @@ static void eval_argv(pam_handle_t *pamh, int argc, const char **argv,
             *flags |= PAM_CLI_FLAGS_ALLOW_MISSING_NAME;
         } else if (strcmp(*argv, "prompt_always") == 0) {
             *flags |= PAM_CLI_FLAGS_PROMPT_ALWAYS;
+        } else if (strcmp(*argv, "try_cert_auth") == 0) {
+            *flags |= PAM_CLI_FLAGS_TRY_CERT_AUTH;
         } else {
             logger(pamh, LOG_WARNING, "unknown option: %s", *argv);
         }
@@ -2405,6 +2407,13 @@ static int pam_sss(enum sss_cli_command task, pam_handle_t *pamh,
                     }
                 }
 
+                if (flags & PAM_CLI_FLAGS_TRY_CERT_AUTH
+                        && pi.cert_list == NULL) {
+                    D(("No certificates for authentication available."));
+                    overwrite_and_free_pam_items(&pi);
+                    return PAM_AUTHINFO_UNAVAIL;
+                }
+
                 if (strcmp(pi.pam_service, "gdm-smartcard") == 0) {
                     ret = check_login_token_name(pamh, &pi, quiet_mode);
                     if (ret != PAM_SUCCESS) {
diff --git a/src/sss_client/sss_cli.h b/src/sss_client/sss_cli.h
index 3404715..38e3f99 100644
--- a/src/sss_client/sss_cli.h
+++ b/src/sss_client/sss_cli.h
@@ -373,6 +373,7 @@ enum pam_item_type {
 #define PAM_CLI_FLAGS_USE_2FA (1 << 5)
 #define PAM_CLI_FLAGS_ALLOW_MISSING_NAME (1 << 6)
 #define PAM_CLI_FLAGS_PROMPT_ALWAYS (1 << 7)
+#define PAM_CLI_FLAGS_TRY_CERT_AUTH (1 << 8)
 
 #define SSS_NSS_MAX_ENTRIES 256
 #define SSS_NSS_HEADER_SIZE (sizeof(uint32_t) * 4)