From e8b0248eef31e2960a895613f3a9102675a7baf8 Mon Sep 17 00:00:00 2001 From: Tyler Hicks Date: Wed, 12 Feb 2014 17:28:13 -0600 Subject: [PATCH 06/14] Store AppArmor label of bus during initialization During dbus-daemon initialization, the AppArmor confinement context should be stored for later use when checks are to be done on messages to/from the bus itself. AppArmor confinement contexts are documented in aa_getcon(2). They contain a confinement string and a mode string. The confinement string is typically the name of the AppArmor profile confining a given process. The mode string gives the current enforcement mode of the process confinement. For example, it may indicate that the confinement should be enforced or it may indicate that the confinement should allow all actions with the caveat that actions which would be denied should be audited. It is important to note that libapparmor mallocs a single buffer to store the con and mode strings and separates them with a NUL terminator. Because of this, only con should be freed. Bug: https://bugs.freedesktop.org/show_bug.cgi?id=75113 Signed-off-by: Tyler Hicks [smcv: use BUS_SET_OOM] [smcv: dbus_set_error doesn't need extra newlines] Reviewed-by: Simon McVittie Reviewed-by: Tyler Hicks --- bus/apparmor.c | 87 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 86 insertions(+), 1 deletion(-) diff --git a/bus/apparmor.c b/bus/apparmor.c index 645bb84..3b2be35 100644 --- a/bus/apparmor.c +++ b/bus/apparmor.c @@ -64,6 +64,67 @@ static AppArmorConfigMode apparmor_config_mode = APPARMOR_ENABLED; static int audit_fd = -1; #endif +struct BusAppArmorConfinement +{ + int refcount; /* Reference count */ + + char *context; /* AppArmor confinement context (label) */ + const char *mode; /* AppArmor confinement mode (freed by freeing *context) */ +}; + +typedef struct BusAppArmorConfinement BusAppArmorConfinement; + +static BusAppArmorConfinement *bus_con = NULL; + +/** + * Callers of this function give up ownership of the *context and *mode + * pointers. + * + * Additionally, the responsibility of freeing *context and *mode becomes the + * responsibility of the bus_apparmor_confinement_unref() function. However, it + * does not free *mode because libapparmor's aa_getcon(), and libapparmor's + * other related functions, allocate a single buffer for *context and *mode and + * then separate the two char arrays with a NUL char. See the aa_getcon(2) man + * page for more details. + */ +static BusAppArmorConfinement* +bus_apparmor_confinement_new (char *context, const char *mode) +{ + BusAppArmorConfinement *confinement; + + confinement = dbus_new0 (BusAppArmorConfinement, 1); + if (confinement != NULL) + { + confinement->refcount = 1; + confinement->context = context; + confinement->mode = mode; + } + + return confinement; +} + +static void +bus_apparmor_confinement_unref (BusAppArmorConfinement *confinement) +{ + if (!apparmor_enabled) + return; + + _dbus_assert (confinement != NULL); + _dbus_assert (confinement->refcount > 0); + + confinement->refcount -= 1; + + if (confinement->refcount == 0) + { + /** + * Do not free confinement->mode, as libapparmor does a single malloc for + * both confinement->context and confinement->mode. + */ + free (confinement->context); + dbus_free (confinement); + } +} + void bus_apparmor_audit_init (void) { @@ -203,6 +264,8 @@ dbus_bool_t bus_apparmor_full_init (DBusError *error) { #ifdef HAVE_APPARMOR + char *context, *mode; + if (apparmor_enabled) { if (apparmor_config_mode == APPARMOR_DISABLED) @@ -210,13 +273,32 @@ bus_apparmor_full_init (DBusError *error) apparmor_enabled = FALSE; return TRUE; } + + if (bus_con == NULL) + { + if (aa_getcon (&context, &mode) == -1) + { + dbus_set_error (error, DBUS_ERROR_FAILED, + "Error getting AppArmor context of bus: %s", + _dbus_strerror (errno)); + return FALSE; + } + + bus_con = bus_apparmor_confinement_new (context, mode); + if (bus_con == NULL) + { + BUS_SET_OOM (error); + free (context); + return FALSE; + } + } } else { if (apparmor_config_mode == APPARMOR_REQUIRED) { dbus_set_error (error, DBUS_ERROR_FAILED, - "AppArmor mediation required but not present\n"); + "AppArmor mediation required but not present"); return FALSE; } else if (apparmor_config_mode == APPARMOR_ENABLED) @@ -238,6 +320,9 @@ bus_apparmor_shutdown (void) _dbus_verbose ("AppArmor shutdown\n"); + bus_apparmor_confinement_unref (bus_con); + bus_con = NULL; + #ifdef HAVE_LIBAUDIT audit_close (audit_fd); #endif /* HAVE_LIBAUDIT */ -- 2.1.4