1 files changed, 67 insertions, 0 deletions
diff --git a/usr/src/lib/libc/port/gen/ssp.c b/usr/src/lib/libc/port/gen/ssp.c
new file mode 100644
index 0000000000..81d93829ea
--- /dev/null
+++ b/usr/src/lib/libc/port/gen/ssp.c
@@ -0,0 +1,67 @@
+/*
+ * This file and its contents are supplied under the terms of the
+ * Common Development and Distribution License ("CDDL"), version 1.0.
+ * You may only use this file in accordance with the terms of version
+ * 1.0 of the CDDL.
+ *
+ * A full copy of the text of the CDDL should have accompanied this
+ * source.  A copy of the CDDL is also available via the Internet at
+ * http://www.illumos.org/license/CDDL.
+ */
+
+/*
+ * Copyright 2020 Oxide Computer Company
+ */
+
+#include <upanic.h>
+#include <sys/random.h>
+
+/*
+ * This provides an implementation of the stack protector functions that are
+ * expected by gcc's ssp implementation.
+ *
+ * We attempt to initialize the stack guard with random data, which is our best
+ * protection. If that fails, we'd like to have a guard that is still meaningful
+ * and not totally predictable. The original StackGuard paper suggests using a
+ * terminator canary. To make this a little more difficult, we also use a
+ * portion of the data from gethrtime().
+ *
+ * In a 32-bit environment, we only have four bytes worth of data. We use the
+ * lower two bytes of the gethrtime() value and then use pieces of the
+ * terminator canary, '\n\0'. In a 64-bit environment we use the full four byte
+ * terminator canary and then four bytes of gethrtime.
+ */
+
+/*
+ * Use an array here so it's easier to get the length at compile time.
+ */
+static const char ssp_msg[] = "*** stack smashing detected";
+
+uintptr_t __stack_chk_guard;
+
+void
+ssp_init(void)
+{
+	if (getrandom(&__stack_chk_guard, sizeof (__stack_chk_guard), 0) !=
+	    sizeof (__stack_chk_guard)) {
+		/*
+		 * This failed, attempt to get some data that might let us get
+		 * off the ground.
+		 */
+		hrtime_t t = gethrtime();
+#ifdef	_LP32
+		const uint16_t guard = '\n' << 8 | '\0';
+		__stack_chk_guard = guard  << 16 | (uint16_t)t;
+#else
+		const uint32_t guard = '\r' << 24 | '\n' << 16 | '\0' << 8 |
+		    '\xff';
+		__stack_chk_guard = (uint64_t)guard << 32 | (uint32_t)t;
+#endif
+	}
+}
+
+void
+__stack_chk_fail(void)
+{
+	upanic(ssp_msg, sizeof (ssp_msg));
+}