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-rw-r--r--src/cerberus.c44
-rw-r--r--src/cerberus.h4
-rw-r--r--src/pam.c123
-rw-r--r--src/pam.h10
-rw-r--r--src/passphrase.c1
5 files changed, 167 insertions, 15 deletions
diff --git a/src/cerberus.c b/src/cerberus.c
index 06b83df..d18b690 100644
--- a/src/cerberus.c
+++ b/src/cerberus.c
@@ -22,13 +22,26 @@
#ifdef USE_TTY_GROUP
+/**
+ * The group ID for the `tty` group
+ */
static gid_t tty_group = 0;
#endif
+
+/**
+ * The user's entry in the password file
+ */
static struct passwd* entry;
-static pid_t child_pid;
+/**
+ * The process ID of the child process, 0 if none
+ */
+pid_t child_pid = 0;
-void do_login(int argc, char** argv);
+/**
+ * The passphrase
+ */
+char* passphrase = NULL;
/**
@@ -70,7 +83,6 @@ void do_login(int argc, char** argv)
{
char* username = NULL;
char* hostname = NULL;
- char* passphrase = NULL;
char preserve_env = 0;
char skip_auth = 0;
int ret;
@@ -202,18 +214,15 @@ void do_login(int argc, char** argv)
username = entry->pw_name;
- /* Get the passphrase, if -f has not been used */
- if (skip_auth == 0)
- {
- passphrase = get_passphrase();
- printf("\n");
- }
+
+ /* Verify passphrase or other token, if -f has not been used */
+ initialise_pam(hostname, username, read_passphrase);
+ if ((skip_auth == 0) && authenticate_pam())
+ printf("(auto-authenticated)\n");
/* Passphrase entered, turn off timeout */
alarm(0);
- /* TODO verify passphrase */
-
/* Wipe and free the passphrase from the memory */
if ((skip_auth == 0) && passphrase)
{
@@ -223,7 +232,6 @@ void do_login(int argc, char** argv)
free(passphrase);
}
-
/* Reset terminal settings */
reenable_echo();
@@ -282,3 +290,15 @@ void do_login(int argc, char** argv)
exec_shell(entry);
}
+
+/**
+ * Read passphrase from the terminal
+ *
+ * @return The entered passphrase
+ */
+char* read_passphrase(void)
+{
+ passphrase = get_passphrase();
+ return passphrase;
+}
+
diff --git a/src/cerberus.h b/src/cerberus.h
index 38d9acb..5c5a240 100644
--- a/src/cerberus.h
+++ b/src/cerberus.h
@@ -47,5 +47,9 @@
#endif
+void do_login(int argc, char** argv);
+char* read_passphrase(void);
+
+
#endif
diff --git a/src/pam.c b/src/pam.c
index 5332d7f..f85e741 100644
--- a/src/pam.c
+++ b/src/pam.c
@@ -18,6 +18,8 @@
*/
#include <stdio.h>
#include <unistd.h>
+#include <signal.h>
+#include <string.h>
#include <security/pam_appl.h>
#include <security/pam_misc.h>
@@ -29,6 +31,26 @@
#define __failed(RC) ((RC) != PAM_SUCCESS)
+void quit_pam(int sig);
+
+int conv_pam(int num_msg, const struct pam_message** msg, struct pam_response** resp, void* appdata_ptr);
+
+
+/**
+ * Old signal action for SIGHUP
+ */
+struct sigaction signal_action_hup;
+
+/**
+ * Old signal action for SIGTERM
+ */
+struct sigaction signal_action_term;
+
+/**
+ * The process ID of the child process, 0 if none
+ */
+extern pid_t child_pid;
+
/**
* The PAM handle
*/
@@ -37,7 +59,17 @@ static pam_handle_t* handle = NULL;
/**
* The PAM convention
*/
-static struct pam_conv conv = { misc_conv, NULL };
+static struct pam_conv conv = { conv_pam, NULL };
+
+/**
+ * Whether the user was auto-authenticated
+ */
+static char auto_authenticated = 1;
+
+/**
+ * Function that can be used to read a passphrase from the terminal
+ */
+static char* (*passphrase_reader)(void) = NULL;
/**
@@ -64,9 +96,12 @@ static void do_pam(int rc)
*
* @param remote The remote computer, {@code NULL} for local login
* @param username The username of the user to log in to
+ * @param reader Function that can be used to read a passphrase from the terminal
*/
-void initialise_pam(char* remote, char* username)
+void initialise_pam(char* remote, char* username, char* (*reader)(void))
{
+ passphrase_reader = reader;
+
if (pam_start(remote ? "remote" : "local", username, &conv, &handle) != PAM_SUCCESS)
{
fprintf(stderr, "Cannot initialise PAM\n");
@@ -97,6 +132,8 @@ void verify_account_pam(void)
void open_session_pam(void)
{
int rc;
+ struct sigaction signal_action;
+
do_pam(pam_setcred(handle, PAM_ESTABLISH_CRED));
if (__failed(rc = pam_open_session(handle, 0)))
@@ -110,6 +147,14 @@ void open_session_pam(void)
pam_close_session(handle, 0);
do_pam(rc);
}
+
+ memset(&signal_action, 0, sizeof(signal_action));
+ signal_action.sa_handler = SIG_IGN;
+ sigaction(SIGINT, &signal_action, NULL);
+ sigaction(SIGHUP, &signal_action, &signal_action_hup);
+ signal_action.sa_handler = quit_pam;
+ sigaction(SIGHUP, &signal_action, NULL);
+ sigaction(SIGTERM, &signal_action, &signal_action_term);
}
@@ -118,7 +163,81 @@ void open_session_pam(void)
*/
void close_session_pam(void)
{
+ sigaction(SIGHUP, &signal_action_hup, NULL);
+ sigaction(SIGTERM, &signal_action_term, NULL);
+
pam_setcred(handle, PAM_DELETE_CRED);
pam_end(handle, pam_close_session(handle, 0));
}
+
+/**
+ * Signal handler for cleanly exit PAM session
+ *
+ * @param sig The received signal
+ */
+void quit_pam(int sig)
+{
+ if (child_pid)
+ kill(-child_pid, sig);
+ if (sig == SIGTERM)
+ kill(-child_pid, SIGHUP);
+
+ pam_setcred(handle, PAM_DELETE_CRED);
+ pam_end(handle, pam_close_session(handle, 0));
+
+ _exit(sig);
+}
+
+
+/**
+ * Perform token authentication
+ *
+ * @return Whether the user got automatically authenticated
+ */
+char authenticate_pam(void)
+{
+ int rc;
+
+ if (__failed(rc = pam_authenticate(handle, 0)))
+ {
+ printf("Incorrect passphrase\n");
+ pam_end(handle, rc);
+ sleep(FAILURE_SLEEP);
+ _exit(1);
+ }
+
+ return auto_authenticated;
+}
+
+
+/**
+ * Callback function for converation between PAM this application
+ *
+ * @param num_msg Number of pointers in the array `msg`
+ * @param msg Message from PAM
+ * @param resp Responses to PAM for by index corresponding messages
+ * @param appdata_ptr (Not used)
+ * @return `PAM_SUCCESS`, `PAM_CONV_ERR` or `PAM_BUF_ERR`
+ */
+int conv_pam(int num_msg, const struct pam_message** msg, struct pam_response** resp, void* appdata_ptr)
+{
+ int i;
+
+ (void) appdata_ptr;
+
+ for (i = 0; i < num_msg; i++)
+ {
+ ((*resp) + i)->resp = NULL;
+ ((*resp) + i)->resp_retcode = 0;
+
+ if ((**(msg + i)).msg_style == PAM_PROMPT_ECHO_OFF)
+ {
+ (*resp + i)->resp = passphrase_reader();
+ auto_authenticated = 0;
+ }
+ }
+
+ return PAM_SUCCESS;
+}
+
diff --git a/src/pam.h b/src/pam.h
index 4c793d3..ee766df 100644
--- a/src/pam.h
+++ b/src/pam.h
@@ -25,8 +25,9 @@
*
* @param remote The remote computer, {@code NULL} for local login
* @param username The username of the user to log in to
+ * @param reader Function that can be used to read a passphrase from the terminal
*/
-void initialise_pam(char* remote, char* username);
+void initialise_pam(char* remote, char* username, char* (*reader)(void));
/**
* Verify that the account may be used
@@ -43,6 +44,13 @@ void open_session_pam(void);
*/
void close_session_pam(void);
+/**
+ * Perform token authentication
+ *
+ * @return Whether the user got automatically authenticated
+ */
+char authenticate_pam(void);
+
#endif
diff --git a/src/passphrase.c b/src/passphrase.c
index c508b85..599d5ff 100644
--- a/src/passphrase.c
+++ b/src/passphrase.c
@@ -82,6 +82,7 @@ char* get_passphrase(void)
/* NUL-terminate passphrase */
*(rc + len) = 0;
+ printf("\n");
return rc;
}
generated by cgit v1.2.3-70-g09d2 (git 2.51.0) at 2025-10-31 19:59:53 +0000