.

software/ors-amarisoft/ru/xexec.c → software/ors-amarisoft/ru/capdo.c

@@ -16,27 +16,72 @@
 // See COPYING file for full licensing terms.
 // See https://www.nexedi.com/licensing for rationale and options.
 
-// Program xexec does what exec in shell does but as standalone program.
-// It is used as trampoline to run a script under setcap environment.
+// `capdo prog ...` executes prog with inherited capabilities.
+// It is used as trampoline to run script under setcap environment.
 
 #include <errno.h>
+#include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
 
+#include <sys/capability.h>
+#include <sys/prctl.h>
+
+static int die(const char *fmt, ...);
+static int die_err(const char *msg);
 
 int main(int argc, const char *argv[]) {
-    if (argc < 2) {
-        fprintf(stderr, "E: usage: xexec prog arguments...\n");
-        exit(128);
+    cap_t caps;
+    cap_value_t cap;
+    cap_flag_value_t flag;
+    uint64_t capbits = 0;
+
+    if (argc < 2)
+        die("usage: capdo prog arguments...");
+
+    // permitted -> inheritable  (so that we can raise ambient)
+    caps = cap_get_proc();
+    if (!caps)
+        die("cap_get_proc failed");
+    for (cap = 0; cap < CAP_LAST_CAP; cap++) {
+        cap_get_flag(caps, cap, CAP_PERMITTED, &flag)       && die_err("cap_get_flag");
+        if (flag) {
+            cap_set_flag(caps, CAP_INHERITABLE, 1, &cap, flag)  && die_err("cap_set_flag");
+            capbits |= (1ULL << cap);
+        }
     }
+    cap_set_proc(caps) && die_err("cap_set_proc");
 
-    argv++;
+    // raise ambient capabities to what is permitted/inheritable
+    for (cap = 0; cap <= CAP_LAST_CAP; cap++) {
+        if (capbits & (1ULL << cap))
+            prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_RAISE, cap, 0, 0)  && die_err("prctl ambient raise");
+    }
 
+    // tail to exec target
+    argv++;
     execv(argv[0], argv);
 
-    // the only chance we are here is due to error
-    fprintf(stderr, "xexec: %s: %s\n", argv[0], strerror(errno));
+    // the only chance we are here is due to exec error
+    die_err(argv[0]);
+}
+
+static int die(const char* fmt, ...) {
+    va_list ap;
+
+    fprintf(stderr, "E: capdo: ");
+
+    va_start(ap, fmt);
+    vfprintf(stderr, fmt, ap);
+    va_end(ap);
+
+    fprintf(stderr, "\n");
     exit(128);
+    return 0;
+}
+
+static int die_err(const char* msg) {
+    return die("%s: %s", msg, strerror(errno));
 }