Adding upstream version 2.41.

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

lib/caputils.c

@@ -0,0 +1,156 @@
+/*
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2, or (at your option) any
+ * later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include <sys/prctl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <limits.h>
+#include <errno.h>
+
+#include "c.h"
+#include "caputils.h"
+#include "pathnames.h"
+#include "procfs.h"
+#include "nls.h"
+
+static int test_cap(unsigned int cap)
+{
+	/* prctl returns 0 or 1 for valid caps, -1 otherwise */
+	return prctl(PR_CAPBSET_READ, cap, 0, 0, 0) >= 0;
+}
+
+static int cap_last_by_bsearch(int *ret)
+{
+	/* starting with cap=INT_MAX means we always know
+	 * that cap1 is invalid after the first iteration */
+	int cap = INT_MAX;
+	unsigned int cap0 = 0, cap1 = INT_MAX;
+
+	while ((int)cap0 < cap) {
+		if (test_cap(cap))
+			cap0 = cap;
+		else
+			cap1 = cap;
+
+		cap = (cap0 + cap1) / 2U;
+	}
+
+	*ret = cap;
+	return 0;
+}
+
+static int cap_last_by_procfs(int *ret)
+{
+	FILE *f = fopen(_PATH_PROC_CAPLASTCAP, "r");
+	int rc = -EINVAL;
+
+	*ret = 0;
+
+	if (f && fd_is_procfs(fileno(f))) {
+		int cap;
+
+		/* we check if the cap after this one really isn't valid */
+		if (fscanf(f, "%d", &cap) == 1 &&
+		    cap < INT_MAX && !test_cap(cap + 1)) {
+
+			*ret = cap;
+			rc = 0;
+		}
+	}
+
+	if (f)
+		fclose(f);
+	return rc;
+}
+
+int cap_last_cap(void)
+{
+	static int cap = -1;
+
+	if (cap != -1)
+		return cap;
+	if (cap_last_by_procfs(&cap) < 0)
+		cap_last_by_bsearch(&cap);
+
+	return cap;
+}
+
+void cap_permitted_to_ambient(void)
+{
+	/* We use capabilities system calls to propagate the permitted
+	 * capabilities into the ambient set because we may have
+	 * already forked so be in async-signal-safe context. */
+	struct __user_cap_header_struct header = {
+		.version = _LINUX_CAPABILITY_VERSION_3,
+		.pid = 0,
+	};
+	struct __user_cap_data_struct payload[_LINUX_CAPABILITY_U32S_3] = {{ 0 }};
+	uint64_t effective, cap;
+
+	if (capget(&header, payload) < 0)
+		err(EXIT_FAILURE, _("capget failed"));
+
+	/* In order the make capabilities ambient, we first need to ensure
+	 * that they are all inheritable. */
+	payload[0].inheritable = payload[0].permitted;
+	payload[1].inheritable = payload[1].permitted;
+
+	if (capset(&header, payload) < 0)
+		err(EXIT_FAILURE, _("capset failed"));
+
+	effective = ((uint64_t)payload[1].effective << 32) |  (uint64_t)payload[0].effective;
+
+	for (cap = 0; cap < (sizeof(effective) * 8); cap++) {
+		/* This is the same check as cap_valid(), but using
+		 * the runtime value for the last valid cap. */
+		if (cap > (uint64_t) cap_last_cap())
+			continue;
+
+		if ((effective & (1ULL << cap))
+		    && prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_RAISE, cap, 0, 0) < 0)
+			err(EXIT_FAILURE, _("prctl(PR_CAP_AMBIENT) failed"));
+	}
+}
+
+#ifdef TEST_PROGRAM_CAPUTILS
+int main(int argc, char *argv[])
+{
+	int rc = 0, cap;
+
+	if (argc < 2) {
+		fprintf(stderr, "usage: %1$s --last-by-procfs\n"
+				"       %1$s --last-by-bsearch\n"
+				"       %1$s --last\n",
+				program_invocation_short_name);
+		return EXIT_FAILURE;
+	}
+
+	if (strcmp(argv[1], "--last-by-procfs") == 0) {
+		rc = cap_last_by_procfs(&cap);
+		if (rc == 0)
+			printf("last cap: %d\n", cap);
+
+	} else if (strcmp(argv[1], "--last-by-bsearch") == 0) {
+		rc = cap_last_by_bsearch(&cap);
+		if (rc == 0)
+			printf("last cap: %d\n", cap);
+
+	} else if (strcmp(argv[1], "--last") == 0)
+		printf("last cap: %d\n", cap_last_cap());
+
+	return rc == 0 ? EXIT_SUCCESS : EXIT_FAILURE;
+}
+#endif