login: optional support for PAM

3 files changed, 71 insertions, 10 deletions

diff --git a/Makefile.flags b/Makefile.flags
index d8817bed6..c64a5c838 100644
--- a/Makefile.flags
+++ b/Makefile.flags
@@ -60,18 +60,20 @@ LDFLAGS += -static
 endif
 
 BBOX_LIB_LIST = m crypt
+
+ifeq ($(CONFIG_PAM),y)
+BBOX_LIB_LIST += pam pam_misc
+endif
+
 ifeq ($(CONFIG_SELINUX),y)
-#LDLIBS += -lselinux -lsepol
 BBOX_LIB_LIST += selinux sepol
 endif
 
 ifeq ($(CONFIG_EFENCE),y)
-#LDLIBS += -lefence
 BBOX_LIB_LIST += efence
 endif
 
 ifeq ($(CONFIG_DMALLOC),y)
-#LDLIBS += -ldmalloc
 BBOX_LIB_LIST += dmalloc
 endif
 
diff --git a/loginutils/Config.in b/loginutils/Config.in
index 63ae9b4db..6f2702e95 100644
--- a/loginutils/Config.in
+++ b/loginutils/Config.in
@@ -128,6 +128,13 @@ config LOGIN
           Note that Busybox binary must be setuid root for this applet to
           work properly.
 
+config PAM
+        bool "Support for PAM (Pluggable Authentication Modules)"
+        default n
+        depends on LOGIN
+        help
+          Use PAM in login(1) instead of direct access to password database.
+
 config LOGIN_SCRIPTS
         bool "Support for login scripts"
         depends on LOGIN
diff --git a/loginutils/login.c b/loginutils/login.c
index 7b60fd017..b633a7feb 100644
--- a/loginutils/login.c
+++ b/loginutils/login.c
@@ -14,6 +14,15 @@
 #include <selinux/flask.h> /* for security class definitions  */
 #endif
 
+#if ENABLE_PAM
+#include <pam/pam_appl.h>
+#include <pam/pam_misc.h>
+static const struct pam_conv conv = {
+        misc_conv,
+        NULL
+};
+#endif
+
 enum {
         TIMEOUT = 60,
         EMPTY_USERNAME_COUNT = 10,
@@ -125,7 +134,7 @@ static void die_if_nologin_and_non_root(int amroot)
 static ALWAYS_INLINE void die_if_nologin_and_non_root(int amroot) {}
 #endif
 
-#if ENABLE_FEATURE_SECURETTY
+#if ENABLE_FEATURE_SECURETTY && !ENABLE_PAM
 static int check_securetty(void)
 {
         FILE *fp;
@@ -214,7 +223,7 @@ int login_main(int argc, char **argv)
                 LOGIN_OPT_h = (1<<1),
                 LOGIN_OPT_p = (1<<2),
         };
-        char fromhost[512];
+        char *fromhost;
         char username[USERNAME_SIZE];
         const char *tmp;
         int amroot;
@@ -226,6 +235,9 @@ int login_main(int argc, char **argv)
         char full_tty[TTYNAME_SIZE];
         USE_SELINUX(security_context_t user_sid = NULL;)
         USE_FEATURE_UTMP(struct utmp utent;)
+        USE_PAM(pam_handle_t *pamh;)
+        USE_PAM(int pamret;)
+        USE_PAM(const char *failed_msg;)
 
         short_tty = full_tty;
         username[0] = '\0';
@@ -265,13 +277,12 @@ int login_main(int argc, char **argv)
                 USE_FEATURE_UTMP(
                         safe_strncpy(utent.ut_host, opt_host, sizeof(utent.ut_host));
                 )
-                snprintf(fromhost, sizeof(fromhost)-1, " on '%.100s' from "
-                                        "'%.200s'", short_tty, opt_host);
+                fromhost = xasprintf(" on '%s' from '%s'", short_tty, opt_host);
         } else
-                snprintf(fromhost, sizeof(fromhost)-1, " on '%.100s'", short_tty);
+                fromhost = xasprintf(" on '%s'", short_tty);
 
-        // Was breaking "login <username>" from shell command line:
-        // bb_setpgrp();
+        /* Was breaking "login <username>" from shell command line: */
+        /*bb_setpgrp();*/
 
         openlog(applet_name, LOG_PID | LOG_CONS | LOG_NOWAIT, LOG_AUTH);
 
@@ -279,6 +290,46 @@ int login_main(int argc, char **argv)
                 if (!username[0])
                         get_username_or_die(username, sizeof(username));
 
+#if ENABLE_PAM
+                pamret = pam_start("login", username, &conv, &pamh);
+                if (pamret != PAM_SUCCESS) {
+                        failed_msg = "pam_start";
+                        goto pam_auth_failed;
+                }
+                /* set TTY (so things like securetty work) */
+                pamret = pam_set_item(pamh, PAM_TTY, short_tty);
+                if (pamret != PAM_SUCCESS) {
+                        failed_msg = "pam_set_item(TTY)";
+                        goto pam_auth_failed;
+                }
+                pamret = pam_authenticate(pamh, 0);
+                if (pamret == PAM_SUCCESS) {
+                        char *pamuser;
+                        /* check that the account is healthy. */
+                        pamret = pam_acct_mgmt(pamh, 0);
+                        if (pamret != PAM_SUCCESS) {
+                                failed_msg = "account setup";
+                                goto pam_auth_failed;
+                        }
+                        /* read user back */
+                        /* gcc: "dereferencing type-punned pointer breaks aliasing rules..."
+                         * thus we use double cast */
+                        if (pam_get_item(pamh, PAM_USER, (const void **)(void*)&pamuser) != PAM_SUCCESS) {
+                                failed_msg = "pam_get_item(USER)";
+                                goto pam_auth_failed;
+                        }
+                        safe_strncpy(username, pamuser, sizeof(username));
+                }
+                /* If we get here, the user was authenticated, and is
+                 * granted access. */
+                pw = getpwnam(username);
+                if (pw)
+                        break;
+                goto auth_failed;
+ pam_auth_failed:
+                bb_error_msg("%s failed: %s", failed_msg, pam_strerror(pamh, pamret));
+                safe_strncpy(username, "UNKNOWN", sizeof(username));
+#else /* not PAM */
                 pw = getpwnam(username);
                 if (!pw) {
                         strcpy(username, "UNKNOWN");
@@ -301,6 +352,7 @@ int login_main(int argc, char **argv)
                 /* authorization takes place here */
                 if (correct_password(pw))
                         break;
+#endif /* ENABLE_PAM */
  auth_failed:
                 opt &= ~LOGIN_OPT_f;
                 bb_do_delay(FAIL_DELAY);