1 files changed, 104 insertions, 0 deletions
diff --git a/src/nxt_capability.c b/src/nxt_capability.c
new file mode 100644
index 00000000..805faff6
--- /dev/null
+++ b/src/nxt_capability.c
@@ -0,0 +1,104 @@
+/*
+ * Copyright (C) Igor Sysoev
+ * Copyright (C) NGINX, Inc.
+ */
+
+#include <nxt_main.h>
+
+#if (NXT_HAVE_LINUX_CAPABILITY)
+
+#include <linux/capability.h>
+#include <sys/syscall.h>
+
+#define nxt_capget(hdrp, datap)                                               \
+            syscall(SYS_capget, hdrp, datap)
+#define nxt_capset(hdrp, datap)                                               \
+            syscall(SYS_capset, hdrp, datap)
+
+#endif /* NXT_HAVE_LINUX_CAPABILITY */
+
+
+static nxt_int_t nxt_capability_specific_set(nxt_task_t *task,
+    nxt_capabilities_t *cap);
+
+
+nxt_int_t
+nxt_capability_set(nxt_task_t *task, nxt_capabilities_t *cap)
+{
+    nxt_assert(cap->setid == 0);
+
+    if (geteuid() == 0) {
+        cap->setid = 1;
+        return NXT_OK;
+    }
+
+    return nxt_capability_specific_set(task, cap);
+}
+
+
+#if (NXT_HAVE_LINUX_CAPABILITY)
+
+static uint32_t
+nxt_capability_linux_get_version()
+{
+    struct __user_cap_header_struct hdr;
+
+    hdr.version = _LINUX_CAPABILITY_VERSION;
+    hdr.pid     = nxt_pid;
+
+    nxt_capget(&hdr, NULL);
+    return hdr.version;
+}
+
+
+static nxt_int_t
+nxt_capability_specific_set(nxt_task_t *task, nxt_capabilities_t *cap)
+{
+    struct __user_cap_data_struct    *val, data[2];
+    struct __user_cap_header_struct  hdr;
+
+    /*
+     * Linux capability v1 fills an u32 struct.
+     * Linux capability v2 and v3 fills an u64 struct.
+     * We allocate data[2] for compatibility, we waste 4 bytes on v1.
+     *
+     * This is safe as we only need to check CAP_SETUID and CAP_SETGID
+     * that resides in the first 32-bit chunk.
+     */
+
+    val = &data[0];
+
+    /*
+     * Ask the kernel the preferred capability version
+     * instead of using _LINUX_CAPABILITY_VERSION from header.
+     * This is safer when distributing a pre-compiled Unit binary.
+     */
+    hdr.version = nxt_capability_linux_get_version();
+    hdr.pid = nxt_pid;
+
+    if (nxt_slow_path(nxt_capget(&hdr, val) == -1)) {
+        nxt_alert(task, "failed to get process capabilities: %E", nxt_errno);
+        return NXT_ERROR;
+    }
+
+    if ((val->effective & (1 << CAP_SETUID)) == 0) {
+        return NXT_OK;
+    }
+
+    if ((val->effective & (1 << CAP_SETGID)) == 0) {
+        return NXT_OK;
+    }
+
+    cap->setid = 1;
+    return NXT_OK;
+}
+
+#else
+
+static nxt_int_t
+nxt_capability_specific_set(nxt_task_t *task, nxt_capabilities_t *cap)
+{
+    return NXT_OK;
+}
+
+#endif