From b6545b83f94c5fb7aec1478b8d458a1393f479c8 Mon Sep 17 00:00:00 2001
From: "Maxin B. John" <maxin.john@intel.com>
Date: Wed, 25 May 2016 14:12:25 +0300
Subject: [PATCH] pam_unix: support 'nullok_secure' option

Debian patch to add a new 'nullok_secure' option to pam_unix,
which accepts users with null passwords only when the applicant is
connected from a tty listed in /etc/securetty.

Authors: Sam Hartman <hartmans@debian.org>,
         Steve Langasek <vorlon@debian.org>

Upstream-Status: Pending

Signed-off-by: Ming Liu <ming.liu@windriver.com>
Signed-off-by: Amarnath Valluri <amarnath.valluri@intel.com>
Signed-off-by: Maxin B. John <maxin.john@intel.com>
---
 modules/pam_unix/Makefile.am    |  3 ++-
 modules/pam_unix/pam_unix.8.xml | 19 ++++++++++++++++++-
 modules/pam_unix/support.c      | 40 +++++++++++++++++++++++++++++++++++-----
 modules/pam_unix/support.h      |  8 ++++++--
 4 files changed, 61 insertions(+), 9 deletions(-)

diff --git a/modules/pam_unix/Makefile.am b/modules/pam_unix/Makefile.am
index 56df178..2bba460 100644
--- a/modules/pam_unix/Makefile.am
+++ b/modules/pam_unix/Makefile.am
@@ -30,7 +30,8 @@ if HAVE_VERSIONING
   pam_unix_la_LDFLAGS += -Wl,--version-script=$(srcdir)/../modules.map
 endif
 pam_unix_la_LIBADD = $(top_builddir)/libpam/libpam.la \
-	@LIBCRYPT@ @LIBSELINUX@ @TIRPC_LIBS@ @NSL_LIBS@
+	@LIBCRYPT@ @LIBSELINUX@ @TIRPC_LIBS@ @NSL_LIBS@ \
+	../pam_securetty/tty_secure.lo
 
 securelib_LTLIBRARIES = pam_unix.la
 
diff --git a/modules/pam_unix/pam_unix.8.xml b/modules/pam_unix/pam_unix.8.xml
index 1b318f1..be0330e 100644
--- a/modules/pam_unix/pam_unix.8.xml
+++ b/modules/pam_unix/pam_unix.8.xml
@@ -159,7 +159,24 @@
           <para>
             The default action of this module is to not permit the
             user access to a service if their official password is blank.
-            The <option>nullok</option> argument overrides this default.
+            The <option>nullok</option> argument overrides this default
+            and allows any user with a blank password to access the
+            service.
+          </para>
+        </listitem>
+      </varlistentry>
+      <varlistentry>
+        <term>
+          <option>nullok_secure</option>
+        </term>
+        <listitem>
+          <para>
+            The default action of this module is to not permit the
+            user access to a service if their official password is blank.
+            The <option>nullok_secure</option> argument overrides this
+            default and allows any user with a blank password to access
+            the service as long as the value of PAM_TTY is set to one of
+            the values found in /etc/securetty.
           </para>
         </listitem>
       </varlistentry>
diff --git a/modules/pam_unix/support.c b/modules/pam_unix/support.c
index fc8595e..29e3341 100644
--- a/modules/pam_unix/support.c
+++ b/modules/pam_unix/support.c
@@ -183,13 +183,22 @@ int _set_ctrl(pam_handle_t *pamh, int flags, int *remember, int *rounds,
 	/* now parse the arguments to this module */
 
 	for (; argc-- > 0; ++argv) {
+		int sl;
 
 		D(("pam_unix arg: %s", *argv));
 
 		for (j = 0; j < UNIX_CTRLS_; ++j) {
-			if (unix_args[j].token
-			    && !strncmp(*argv, unix_args[j].token, strlen(unix_args[j].token))) {
-				break;
+			if (unix_args[j].token) {
+				sl = strlen(unix_args[j].token);
+				if (unix_args[j].token[sl-1] == '=') {
+					/* exclude argument from comparison */
+					if (!strncmp(*argv, unix_args[j].token, sl))
+						break;
+				} else {
+				/* compare full strings */
+					if (!strcmp(*argv, unix_args[j].token))
+						break;
+				}
 			}
 		}
 
@@ -560,6 +569,7 @@ static int _unix_run_helper_binary(pam_handle_t *pamh, const char *passwd,
     if (child == 0) {
 	static char *envp[] = { NULL };
 	const char *args[] = { NULL, NULL, NULL, NULL };
+	int nullok = off(UNIX__NONULL, ctrl);
 
 	/* XXX - should really tidy up PAM here too */
 
@@ -587,7 +597,16 @@ static int _unix_run_helper_binary(pam_handle_t *pamh, const char *passwd,
 	/* exec binary helper */
 	args[0] = CHKPWD_HELPER;
 	args[1] = user;
-	if (off(UNIX__NONULL, ctrl)) {	/* this means we've succeeded */
+	if (on(UNIX_NULLOK_SECURE, ctrl)) {
+		const void *uttyname;
+		retval = pam_get_item(pamh, PAM_TTY, &uttyname);
+		if (retval != PAM_SUCCESS || uttyname == NULL
+			|| _pammodutil_tty_secure(pamh, (const char *)uttyname) != PAM_SUCCESS) {
+			nullok = 0;
+		}
+	}
+
+	if (nullok) {
 	  args[2]="nullok";
 	} else {
 	  args[2]="nonull";
@@ -672,6 +691,17 @@ _unix_blankpasswd (pam_handle_t *pamh, unsigned int ctrl, const char *name)
 	if (on(UNIX__NONULL, ctrl))
 		return 0;	/* will fail but don't let on yet */
 
+	if (on(UNIX_NULLOK_SECURE, ctrl)) {
+		int retval2;
+		const void *uttyname;
+		retval2 = pam_get_item(pamh, PAM_TTY, &uttyname);
+		if (retval2 != PAM_SUCCESS || uttyname == NULL)
+			return 0;
+
+		if (_pammodutil_tty_secure(pamh, (const char *)uttyname) != PAM_SUCCESS)
+			return 0;
+	}
+
 	/* UNIX passwords area */
 
 	retval = get_pwd_hash(pamh, name, &pwd, &salt);
@@ -758,7 +788,7 @@ int _unix_verify_password(pam_handle_t * pamh, const char *name
 			}
 		}
 	} else {
-		retval = verify_pwd_hash(p, salt, off(UNIX__NONULL, ctrl));
+		retval = verify_pwd_hash(p, salt, _unix_blankpasswd(pamh, ctrl, name));
 	}
 
 	if (retval == PAM_SUCCESS) {
diff --git a/modules/pam_unix/support.h b/modules/pam_unix/support.h
index b4c279c..8da4a8e 100644
--- a/modules/pam_unix/support.h
+++ b/modules/pam_unix/support.h
@@ -98,8 +98,9 @@ typedef struct {
 #define UNIX_QUIET		 28	/* Don't print informational messages */
 #define UNIX_NO_PASS_EXPIRY      29     /* Don't check for password expiration if not used for authentication */
 #define UNIX_DES                 30     /* DES, default */
+#define UNIX_NULLOK_SECURE       31     /* NULL passwords allowed only on secure ttys */
 /* -------------- */
-#define UNIX_CTRLS_              31	/* number of ctrl arguments defined */
+#define UNIX_CTRLS_              32	/* number of ctrl arguments defined */
 
 #define UNIX_DES_CRYPT(ctrl)	(off(UNIX_MD5_PASS,ctrl)&&off(UNIX_BIGCRYPT,ctrl)&&off(UNIX_SHA256_PASS,ctrl)&&off(UNIX_SHA512_PASS,ctrl)&&off(UNIX_BLOWFISH_PASS,ctrl))
 
@@ -117,7 +118,7 @@ static const UNIX_Ctrls unix_args[UNIX_CTRLS_] =
 /* UNIX_AUTHTOK_TYPE */    {"authtok_type=",   _ALL_ON_,                0100, 0},
 /* UNIX__PRELIM */         {NULL,              _ALL_ON_^(0600),         0200, 0},
 /* UNIX__UPDATE */         {NULL,              _ALL_ON_^(0600),         0400, 0},
-/* UNIX__NONULL */         {NULL,              _ALL_ON_,               01000, 0},
+/* UNIX__NONULL */         {NULL,              _ALL_ON_^(02000000000), 01000, 0},
 /* UNIX__QUIET */          {NULL,              _ALL_ON_,               02000, 0},
 /* UNIX_USE_AUTHTOK */     {"use_authtok",     _ALL_ON_,               04000, 0},
 /* UNIX_SHADOW */          {"shadow",          _ALL_ON_,              010000, 0},
@@ -139,6 +140,7 @@ static const UNIX_Ctrls unix_args[UNIX_CTRLS_] =
 /* UNIX_QUIET */           {"quiet",           _ALL_ON_,         01000000000, 0},
 /* UNIX_NO_PASS_EXPIRY */  {"no_pass_expiry",  _ALL_ON_,         02000000000, 0},
 /* UNIX_DES */             {"des",             _ALL_ON_^(0260420000),      0, 1},
+/* UNIX_NULLOK_SECURE */   {"nullok_secure",   _ALL_ON_^(01000), 02000000000, 0},
 };
 
 #define UNIX_DEFAULTS  (unix_args[UNIX__NONULL].flag)
@@ -172,6 +174,8 @@ extern int _unix_read_password(pam_handle_t * pamh
 			,const char *data_name
 			,const void **pass);
 
+extern int _pammodutil_tty_secure(const pam_handle_t *pamh, const char *uttyname);
+
 extern int _unix_run_verify_binary(pam_handle_t *pamh,
 			unsigned int ctrl, const char *user, int *daysleft);
 #endif /* _PAM_UNIX_SUPPORT_H */
-- 
2.4.0