Adding upstream version 241.upstream/241upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 271 insertions, 0 deletions

diff --git a/src/core/selinux-access.c b/src/core/selinux-access.c
new file mode 100644
index 0000000..0c6d885
--- /dev/null
+++ b/src/core/selinux-access.c
@@ -0,0 +1,271 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
+#include "selinux-access.h"
+
+#if HAVE_SELINUX
+
+#include <errno.h>
+#include <selinux/avc.h>
+#include <selinux/selinux.h>
+#include <stdio.h>
+#if HAVE_AUDIT
+#include <libaudit.h>
+#endif
+
+#include "sd-bus.h"
+
+#include "alloc-util.h"
+#include "audit-fd.h"
+#include "bus-util.h"
+#include "log.h"
+#include "path-util.h"
+#include "selinux-util.h"
+#include "stdio-util.h"
+#include "strv.h"
+#include "util.h"
+
+static bool initialized = false;
+
+struct audit_info {
+        sd_bus_creds *creds;
+        const char *path;
+        const char *cmdline;
+};
+
+/*
+   Any time an access gets denied this callback will be called
+   with the audit data.  We then need to just copy the audit data into the msgbuf.
+*/
+static int audit_callback(
+                void *auditdata,
+                security_class_t cls,
+                char *msgbuf,
+                size_t msgbufsize) {
+
+        const struct audit_info *audit = auditdata;
+        uid_t uid = 0, login_uid = 0;
+        gid_t gid = 0;
+        char login_uid_buf[DECIMAL_STR_MAX(uid_t) + 1] = "n/a";
+        char uid_buf[DECIMAL_STR_MAX(uid_t) + 1] = "n/a";
+        char gid_buf[DECIMAL_STR_MAX(gid_t) + 1] = "n/a";
+
+        if (sd_bus_creds_get_audit_login_uid(audit->creds, &login_uid) >= 0)
+                xsprintf(login_uid_buf, UID_FMT, login_uid);
+        if (sd_bus_creds_get_euid(audit->creds, &uid) >= 0)
+                xsprintf(uid_buf, UID_FMT, uid);
+        if (sd_bus_creds_get_egid(audit->creds, &gid) >= 0)
+                xsprintf(gid_buf, GID_FMT, gid);
+
+        snprintf(msgbuf, msgbufsize,
+                 "auid=%s uid=%s gid=%s%s%s%s%s%s%s",
+                 login_uid_buf, uid_buf, gid_buf,
+                 audit->path ? " path=\"" : "", strempty(audit->path), audit->path ? "\"" : "",
+                 audit->cmdline ? " cmdline=\"" : "", strempty(audit->cmdline), audit->cmdline ? "\"" : "");
+
+        return 0;
+}
+
+static int callback_type_to_priority(int type) {
+        switch(type) {
+
+        case SELINUX_ERROR:
+                return LOG_ERR;
+
+        case SELINUX_WARNING:
+                return LOG_WARNING;
+
+        case SELINUX_INFO:
+                return LOG_INFO;
+
+        case SELINUX_AVC:
+        default:
+                return LOG_NOTICE;
+        }
+}
+
+/*
+   libselinux uses this callback when access gets denied or other
+   events happen. If audit is turned on, messages will be reported
+   using audit netlink, otherwise they will be logged using the usual
+   channels.
+
+   Code copied from dbus and modified.
+*/
+_printf_(2, 3) static int log_callback(int type, const char *fmt, ...) {
+        va_list ap;
+        const char *fmt2;
+
+#if HAVE_AUDIT
+        int fd;
+
+        fd = get_audit_fd();
+
+        if (fd >= 0) {
+                _cleanup_free_ char *buf = NULL;
+                int r;
+
+                va_start(ap, fmt);
+                r = vasprintf(&buf, fmt, ap);
+                va_end(ap);
+
+                if (r >= 0) {
+                        audit_log_user_avc_message(fd, AUDIT_USER_AVC, buf, NULL, NULL, NULL, 0);
+                        return 0;
+                }
+        }
+#endif
+
+        fmt2 = strjoina("selinux: ", fmt);
+
+        va_start(ap, fmt);
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wformat-nonliteral"
+        log_internalv(LOG_AUTH | callback_type_to_priority(type),
+                      0, __FILE__, __LINE__, __FUNCTION__,
+                      fmt2, ap);
+#pragma GCC diagnostic pop
+        va_end(ap);
+
+        return 0;
+}
+
+static int access_init(sd_bus_error *error) {
+
+        if (!mac_selinux_use())
+                return 0;
+
+        if (initialized)
+                return 1;
+
+        if (avc_open(NULL, 0) != 0) {
+                int enforce, saved_errno = errno;
+
+                enforce = security_getenforce();
+                log_full_errno(enforce != 0 ? LOG_ERR : LOG_WARNING, saved_errno, "Failed to open the SELinux AVC: %m");
+
+                /* If enforcement isn't on, then let's suppress this
+                 * error, and just don't do any AVC checks. The
+                 * warning we printed is hence all the admin will
+                 * see. */
+                if (enforce == 0)
+                        return 0;
+
+                /* Return an access denied error, if we couldn't load
+                 * the AVC but enforcing mode was on, or we couldn't
+                 * determine whether it is one. */
+                return sd_bus_error_setf(error, SD_BUS_ERROR_ACCESS_DENIED, "Failed to open the SELinux AVC: %s", strerror(saved_errno));
+        }
+
+        selinux_set_callback(SELINUX_CB_AUDIT, (union selinux_callback) audit_callback);
+        selinux_set_callback(SELINUX_CB_LOG, (union selinux_callback) log_callback);
+
+        initialized = true;
+        return 1;
+}
+
+/*
+   This function communicates with the kernel to check whether or not it should
+   allow the access.
+   If the machine is in permissive mode it will return ok.  Audit messages will
+   still be generated if the access would be denied in enforcing mode.
+*/
+int mac_selinux_generic_access_check(
+                sd_bus_message *message,
+                const char *path,
+                const char *permission,
+                sd_bus_error *error) {
+
+        _cleanup_(sd_bus_creds_unrefp) sd_bus_creds *creds = NULL;
+        const char *tclass = NULL, *scon = NULL;
+        struct audit_info audit_info = {};
+        _cleanup_free_ char *cl = NULL;
+        char *fcon = NULL;
+        char **cmdline = NULL;
+        int r = 0;
+
+        assert(message);
+        assert(permission);
+        assert(error);
+
+        r = access_init(error);
+        if (r <= 0)
+                return r;
+
+        r = sd_bus_query_sender_creds(
+                        message,
+                        SD_BUS_CREDS_PID|SD_BUS_CREDS_EUID|SD_BUS_CREDS_EGID|
+                        SD_BUS_CREDS_CMDLINE|SD_BUS_CREDS_AUDIT_LOGIN_UID|
+                        SD_BUS_CREDS_SELINUX_CONTEXT|
+                        SD_BUS_CREDS_AUGMENT /* get more bits from /proc */,
+                        &creds);
+        if (r < 0)
+                goto finish;
+
+        /* The SELinux context is something we really should have
+         * gotten directly from the message or sender, and not be an
+         * augmented field. If it was augmented we cannot use it for
+         * authorization, since this is racy and vulnerable. Let's add
+         * an extra check, just in case, even though this really
+         * shouldn't be possible. */
+        assert_return((sd_bus_creds_get_augmented_mask(creds) & SD_BUS_CREDS_SELINUX_CONTEXT) == 0, -EPERM);
+
+        r = sd_bus_creds_get_selinux_context(creds, &scon);
+        if (r < 0)
+                goto finish;
+
+        if (path) {
+                /* Get the file context of the unit file */
+
+                r = getfilecon_raw(path, &fcon);
+                if (r < 0) {
+                        r = sd_bus_error_setf(error, SD_BUS_ERROR_ACCESS_DENIED, "Failed to get file context on %s.", path);
+                        goto finish;
+                }
+
+                tclass = "service";
+        } else {
+                r = getcon_raw(&fcon);
+                if (r < 0) {
+                        r = sd_bus_error_setf(error, SD_BUS_ERROR_ACCESS_DENIED, "Failed to get current context.");
+                        goto finish;
+                }
+
+                tclass = "system";
+        }
+
+        sd_bus_creds_get_cmdline(creds, &cmdline);
+        cl = strv_join(cmdline, " ");
+
+        audit_info.creds = creds;
+        audit_info.path = path;
+        audit_info.cmdline = cl;
+
+        r = selinux_check_access(scon, fcon, tclass, permission, &audit_info);
+        if (r < 0)
+                r = sd_bus_error_setf(error, SD_BUS_ERROR_ACCESS_DENIED, "SELinux policy denies access.");
+
+        log_debug("SELinux access check scon=%s tcon=%s tclass=%s perm=%s path=%s cmdline=%s: %i", scon, fcon, tclass, permission, path, cl, r);
+
+finish:
+        freecon(fcon);
+
+        if (r < 0 && security_getenforce() != 1) {
+                sd_bus_error_free(error);
+                r = 0;
+        }
+
+        return r;
+}
+
+#else
+
+int mac_selinux_generic_access_check(
+                sd_bus_message *message,
+                const char *path,
+                const char *permission,
+                sd_bus_error *error) {
+
+        return 0;
+}
+
+#endif