ANDROID: crypto: lib/sha256 - add vendor hook for sha256() routine

Add a vendor hook that will allow the FIPS140 kernel module to override
the implementation of the sha256() library routine. The FIPS 140 version
is identical to the normal one, but its code and rodata will have been
integrity checked at module load time.

Original commits:
  android12-5.10:
    1e351b98e7c7 ("ANDROID: crypto: lib/sha256 - add vendor hook for sha256() routine")
  android14-5.15:
    0ef21e1c1ae5 ("ANDROID: vendor_hooks: Reduce pointless modversions CRC churn")
    d4966a820397 ("ANDROID: fips140: remove CONFIG_CRYPTO_FIPS140 option")

Bug: 153614920
Bug: 188620248
Change-Id: I8ccc4f0cc8206af39fa922134b438dacac2a614a
Signed-off-by: Ard Biesheuvel <ardb@google.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>

drivers/android/vendor_hooks.c

@@ -20,6 +20,7 @@
 #include <trace/hooks/epoch.h>
 #include <trace/hooks/cpufreq.h>
 #include <trace/hooks/preemptirq.h>
+#include <trace/hooks/fips140.h>
 #include <trace/hooks/ufshcd.h>
 #include <trace/hooks/cgroup.h>
 #include <trace/hooks/sys.h>
@@ -138,6 +139,7 @@ EXPORT_TRACEPOINT_SYMBOL_GPL(android_vh_ftrace_oops_exit);
 EXPORT_TRACEPOINT_SYMBOL_GPL(android_vh_ftrace_size_check);
 EXPORT_TRACEPOINT_SYMBOL_GPL(android_vh_ftrace_format_check);
 EXPORT_TRACEPOINT_SYMBOL_GPL(android_vh_ftrace_dump_buffer);
+EXPORT_TRACEPOINT_SYMBOL_GPL(android_vh_sha256);
 EXPORT_TRACEPOINT_SYMBOL_GPL(android_vh_mem_cgroup_free);
 EXPORT_TRACEPOINT_SYMBOL_GPL(android_vh_mem_cgroup_alloc);
 EXPORT_TRACEPOINT_SYMBOL_GPL(android_vh_cma_alloc_bypass);

include/trace/hooks/fips140.h

@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM fips140
+#define TRACE_INCLUDE_PATH trace/hooks
+
+#if !defined(_TRACE_HOOK_FIPS140_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_HOOK_FIPS140_H
+#include <trace/hooks/vendor_hooks.h>
+
+/*
+ * These hooks exist only for the benefit of the FIPS140 crypto module, which
+ * uses them to swap out the underlying implementation with one that is integrity
+ * checked as per FIPS 140 requirements. No other uses are allowed or supported.
+ */
+
+DECLARE_HOOK(android_vh_sha256,
+	     TP_PROTO(const u8 *data,
+		      unsigned int len,
+		      u8 *out,
+		      int *hook_inuse),
+	     TP_ARGS(data, len, out, hook_inuse));
+
+#endif /* _TRACE_HOOK_FIPS140_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>

lib/crypto/sha256.c

@@ -16,6 +16,7 @@
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/string.h>
+#include <trace/hooks/fips140.h>
 
 static const u32 SHA256_K[] = {
 	0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5,
@@ -159,6 +160,14 @@ void sha256(const u8 *data, unsigned int len, u8 *out)
 {
 	struct sha256_state sctx;
 
+#ifndef __DISABLE_EXPORTS
+	int hook_inuse = 0;
+
+	trace_android_vh_sha256(data, len, out, &hook_inuse);
+	if (hook_inuse)
+		return;
+#endif
+
 	sha256_init(&sctx);
 	sha256_update(&sctx, data, len);
 	sha256_final(&sctx, out);