1 files changed, 38 insertions, 0 deletions
diff --git a/src/shared/keyring-util.c b/src/shared/keyring-util.c
new file mode 100644
index 0000000..655cf52
--- /dev/null
+++ b/src/shared/keyring-util.c
@@ -0,0 +1,38 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include "keyring-util.h"
+#include "memory-util.h"
+#include "missing_syscall.h"
+
+int keyring_read(key_serial_t serial, void **ret, size_t *ret_size) {
+        size_t m = 100;
+
+        for (;;) {
+                _cleanup_(erase_and_freep) uint8_t *p = NULL;
+                long n;
+
+                p = new(uint8_t, m+1);
+                if (!p)
+                        return -ENOMEM;
+
+                n = keyctl(KEYCTL_READ, (unsigned long) serial, (unsigned long) p, (unsigned long) m, 0);
+                if (n < 0)
+                        return -errno;
+
+                if ((size_t) n <= m) {
+                        p[n] = 0; /* NUL terminate, just in case */
+
+                        if (ret)
+                                *ret = TAKE_PTR(p);
+                        if (ret_size)
+                                *ret_size = n;
+
+                        return 0;
+                }
+
+                if (m > (SIZE_MAX-1) / 2) /* overflow check */
+                        return -ENOMEM;
+
+                m *= 2;
+        }
+}