confd: add support for $0$cleartext password

Finalize support for IETF System YANG incl. all IANA crypt-hash types.

This patch builds on the earlier work adding yescrypt and $factory$ key
word.  The YANG description for the crypt-hash type override has been
significantly udpated to discourage use of $0$cleartext passwords.

Signed-off-by: Joachim Wiberg <[email protected]>

package/confd/Config.in

@@ -11,3 +11,39 @@ config BR2_PACKAGE_CONFD
 	  either the on-system CLI or using NETCONF.
 
 	  https://github.com/kernelkit/infix
+
+if BR2_PACKAGE_CONFD
+
+choice
+	prompt "Default password crypt"
+	default BR2_PACKAGE_CONFD_YESCRYPT
+	help
+	  When users set $0$cleartext-password as their password confd
+	  salts and encrypts the "cleartext-password" with this selected
+	  hash algorithm.
+
+	  Infix defaults to yescrypt.
+
+config BR2_PACKAGE_CONFD_MD5CRYPT
+	bool "md5crypt"
+	help
+
+config BR2_PACKAGE_CONFD_SHA256CRYPT
+	bool "sha256crypt"
+
+config BR2_PACKAGE_CONFD_SHA512CRYPT
+	bool "sha512crypt"
+
+config BR2_PACKAGE_CONFD_YESCRYPT
+	bool "yescrypt"
+
+endchoice
+
+config BR2_PACKAGE_CONFD_DEFAULT_CRYPT
+	string
+	default "md5crypt"    if BR2_PACKAGE_CONFD_MD5CRYPT
+	default "sha256crypt" if BR2_PACKAGE_CONFD_SHA256CRYPT
+	default "sha512crypt" if BR2_PACKAGE_CONFD_SHA512CRYPT
+	default "yescrypt"    if BR2_PACKAGE_CONFD_YESCRYPT
+
+endif

package/confd/confd.mk

@@ -12,7 +12,7 @@ CONFD_LICENSE_FILES = LICENSE
 CONFD_REDISTRIBUTE = NO
 CONFD_DEPENDENCIES = host-sysrepo sysrepo netopeer2 jansson libite sysrepo libsrx libglib2
 CONFD_AUTORECONF = YES
-CONFD_CONF_OPTS += --disable-silent-rules
+CONFD_CONF_OPTS += --disable-silent-rules --with-crypt=$(BR2_PACKAGE_CONFD_DEFAULT_CRYPT)
 CONFD_SYSREPO_SHM_PREFIX = sr_buildroot$(subst /,_,$(CONFIG_DIR))_confd
 
 define CONFD_CONF_ENV

src/confd/configure.ac

@@ -36,6 +36,10 @@ AC_ARG_WITH(login-shell,
         AS_HELP_STRING([--with-login-shell=shell], [Login shell for new users, default: /bin/false]),
 	[login_shell=$withval], [login_shell=yes])
 
+AC_ARG_WITH(crypt,
+        AS_HELP_STRING([--with-crypt=crypt], [Default crypt for $0$cleartext, default: yescrypt]),
+	[crypt=$withval], [crypt="yescrypt"])
+
 AS_IF([test "x$enable_containers" = "xyes"], [
         AC_DEFINE(CONTAINERS, 1, [Built with container support])])
 
@@ -44,9 +48,15 @@ AS_IF([test "x$with_login_shell" != "xno"], [
 	AC_DEFINE_UNQUOTED(LOGIN_SHELL, "$login_shell", [Default: /bin/false])],[
 	AC_DEFINE_UNQUOTED(LOGIN_SHELL, "/bin/false")])
 
+AS_IF([test "x$with_crypt" != "xno"], [
+	AS_IF([test "x$crypt" = "xyes"], [crypt=yescrypt])
+	AC_DEFINE_UNQUOTED(DEFAULT_CRYPT, "$crypt", [Default: yescrypt])],[
+	AC_DEFINE_UNQUOTED(DEFAULT_CRYPT, "yescrypt")])
+
 # Check for pkg-config first, warn if it's not installed
 PKG_PROG_PKG_CONFIG
 
+PKG_CHECK_MODULES([crypt],   [libxcrypt >= 4.4.36])
 PKG_CHECK_MODULES([glib],    [glib-2.0 >= 2.50 gio-2.0 gio-unix-2.0])
 PKG_CHECK_MODULES([jansson], [jansson >= 2.0.0])
 PKG_CHECK_MODULES([libite],  [libite >= 2.5.0])
@@ -104,6 +114,7 @@ cat <<EOF
 Optional features:
   Container support ....: $enable_containers
   Login shell ..........: $login_shell
+  Default crypt algo ...: $crypt
 
 ------------- Compiler version --------------
 $($CC --version || true)

src/confd/src/Makefile.am

@@ -6,6 +6,7 @@ plugin_LTLIBRARIES      = confd-plugin.la
 confd_plugin_la_LDFLAGS = -module -avoid-version -shared
 
 confd_plugin_la_CFLAGS  =			\
+	$(crypt_CFLAGS)				\
 	$(glib_CFLAGS)				\
 	$(jansson_CFLAGS)			\
 	$(libite_CFLAGS)			\
@@ -14,6 +15,7 @@ confd_plugin_la_CFLAGS  =			\
 	$(CFLAGS)
 
 confd_plugin_la_LIBADD  =			\
+	$(crypt_LIBS)				\
 	$(glib_LIBS)				\
 	$(jansson_LIBS)				\
 	$(libite_LIBS)				\

src/confd/src/ietf-system.c

@@ -1,6 +1,7 @@
 /* SPDX-License-Identifier: BSD-3-Clause */
 
 #include <assert.h>
+#include <crypt.h>
 #include <ctype.h>
 #include <paths.h>
 #include <pwd.h>
@@ -1219,6 +1220,87 @@ static sr_error_t generate_auth_keys(sr_session_ctx_t *session, const char *xpat
 	return err;
 }
 
+static const char *ctp_crypt(void)
+{
+	struct {
+		const char *crypt;
+		const char *prefix;
+	} list[] = {
+		{ "md5crypt",    "$1$" },
+		{ "sha256crypt", "$5$" },
+		{ "sha512crypt", "$6$" },
+		{ "yescrypt",    "$y$" },
+	};
+	size_t i;
+
+	for (i = 0; i < NELEMS(list); i++) {
+		if (strcmp(list[i].crypt, DEFAULT_CRYPT))
+			continue;
+
+		return list[i].prefix;
+	}
+
+	return "$y$";		/* fallback */
+}
+
+static int ctp_hash_is_cleartext(const char *hash)
+{
+    if (strlen(hash) < 3)
+        return 0;
+
+    if (hash[0] == '$' && hash[1] == '0' && hash[2] == '$')
+        return 1;
+
+    return 0;
+}
+
+static sr_error_t check_user_ctp(sr_session_ctx_t *session, struct confd *_, struct sr_change *change)
+{
+	const char *prefix = ctp_crypt();
+	char *hash, *salt;
+	sr_val_t *val;
+
+	val = change->new;
+	if (!val)
+		return SR_ERR_OK;
+
+	hash = val->data.string_val;
+	if (!ctp_hash_is_cleartext(hash))
+		return SR_ERR_OK;
+
+	if (strlen(hash) < 4) {
+		sr_session_set_error(session, NULL, SR_ERR_VALIDATION_FAILED, "Too short password.");
+		return SR_ERR_VALIDATION_FAILED;
+	}
+
+	salt = crypt_gensalt(prefix, 0, NULL, 0);
+	if (!salt) {
+		sr_session_set_error(session, NULL, SR_ERR_INTERNAL, "error %d generating salt, "
+				     "prefix '%s'.", errno, prefix);
+		return SR_ERR_INTERNAL;
+	}
+
+	hash = crypt(hash + 3, salt);
+	if (!hash) {
+		sr_session_set_error(session, NULL, SR_ERR_INTERNAL, "failed hashing password, "
+				     "error %d.", errno);
+		return SR_ERR_INTERNAL;
+	}
+
+	return sr_set_item_str(session, val->xpath, hash, NULL, 0);
+}
+
+static sr_error_t change_auth_ctp(struct confd *confd, sr_session_ctx_t *session)
+{
+	sr_error_t err;
+
+	err = _sr_change_iter(session, confd, XPATH_AUTH_"/user[*]/password", check_user_ctp);
+	if (err)
+		return err;
+
+	return SR_ERR_OK;
+}
+
 static sr_error_t change_auth_check(struct confd *confd, sr_session_ctx_t *session)
 {
 	sr_error_t err;
@@ -1262,10 +1344,16 @@ static int change_auth(sr_session_ctx_t *session, uint32_t sub_id, const char *m
 {
 	struct confd *confd = (struct confd *)priv;
 
-	if (event == SR_EV_CHANGE)
+	switch (event) {
+	case SR_EV_UPDATE:
+		return change_auth_ctp(confd, session);
+	case SR_EV_CHANGE:
 		return change_auth_check(confd, session);
-	if (event == SR_EV_DONE)
+	case SR_EV_DONE:
 		return change_auth_done(confd, session);
+	default:
+		break;
+	}
 
 	return SR_ERR_OK;
 }
@@ -1670,7 +1758,7 @@ int ietf_system_init(struct confd *confd)
 
 	os_init();
 
-	REGISTER_CHANGE(confd->session, "ietf-system", XPATH_AUTH_, 0, change_auth, confd, &confd->sub);
+	REGISTER_CHANGE(confd->session, "ietf-system", XPATH_AUTH_, SR_SUBSCR_UPDATE, change_auth, confd, &confd->sub);
 	REGISTER_OPER(confd->session, "ietf-system", PASSWORD_PATH, auth_cb, confd, 0, &confd->sub);
 	REGISTER_MONITOR(confd->session, "ietf-netconf-acm", "/ietf-netconf-acm:nacm//.",
 			 0, change_nacm, confd, &confd->sub);

src/confd/yang/infix-system@2024-06-15.yang

@@ -125,48 +125,45 @@ module infix-system {
       + '|$factory$.*';
     }
     description
-        "The crypt-hash type is used to store passwords using a hash
-         function. This type extends the existing crypt-hash type to
-         support yescrypt as well as the reserved string $factory$,
-         which is used for device-specific factory default hash.  It
-         is up to the underlying system to define this further, but
-         one example is to use Vital Product Data (VPD) information,
-         e.g., an onboard EEPROM where a device hash is stored for
-         the initial 'admin' user.
+        "This type is used to store passwords using a hash function.  It
+         extends the IANA crypt-hash type to support yescrypt as well as
+         a reserved string '$factory$', used for device-specific factory
+         default hash.  It is up to the underlying system to define this
+         further, one example is to use Vital Product Data (VPD), e.g.,
+         an onboard EEPROM where a device hash is stored for the initial
+         'admin' user.
 
          A value of this type matches one of the forms:
 
            $0$<clear text password>
            $<id>$<salt>$<password hash>
            $<id>$<parameter>$<salt>$<password hash>
 
-         The '$0$' prefix signals that the value is clear text. When
-         such a value is received by the server, a hash value is
-         calculated, and the string '$<id>$<salt>$' or
-         $<id>$<parameter>$<salt>$ is prepended to the result. This
-         value is stored in the configuration data store.
-         If a value starting with '$<id>$', where <id> is not '0', is
-         received, the server knows that the value already represents a
-         hashed value and stores it 'as is' in the data store.
+         The '$0$' prefix signals that the value is clear text, and even
+         though it is supported, it is *not* recommended!  When such a
+         value is received it passes through multiple subsystems before
+         a hash value is calculated and the string '$<id>$<salt>$' or
+         $<id>$<parameter>$<salt>$ is prepended and the result is stored
+         in the configuration data store.  The hash function used depend
+         on end system requirements.
+
+         When any other '$<id>$' prefix is received, the system store it
+         'as is' in the configuration data store.
 
          When a server needs to verify a password given by a user, it
          finds the stored password hash string for that user, extracts
          the salt, and calculates the hash with the salt and given
-         password as input. If the calculated hash value is the same
-         as the stored value, the password given by the client is
-         accepted.
+         password as input.  If the calculated hash value is the same as
+         the stored value, the password given by the client is accepted.
 
-         This type defines the following hash functions:
+         This type defines the following supported hash functions:
 
            id | hash function | feature
            ---+---------------+-------------------
             1 | MD5           | crypt-hash-md5
             5 | SHA-256       | crypt-hash-sha-256
             6 | SHA-512       | crypt-hash-sha-512
-            y | yescrypt      | crypt-hash-yescrypt
-
-         The server indicates support for the different hash functions
-         by advertising the corresponding feature.";
+            y | yescrypt      | crypt-hash-yescrypt";
     reference
         "IEEE Std 1003.1-2008 - crypt() function
          RFC 1321: The MD5 Message-Digest Algorithm