[PATCH v2 5/5] test: boot: add regression tests for the FIT cipher bounds checks

[Pranav Rajendran <pranavkasthuri@gmail.com>]

Add a fit_cipher unit test suite, gated on CONFIG_FIT_CIPHER like the
code it exercises, covering the three defects fixed in this series:

 - image_aes_decrypt() rejects a cipher_len that is not a whole number
   of AES blocks
 - image_aes_decrypt() rejects an unciphered size larger than the
   ciphertext, and accepts the boundary case where they are equal
 - fit_image_get_data_size_unciphered() rejects a 'data-size-unciphered'
   property that is not exactly one fdt32_t long, built via a minimal
   FIT constructed with libfdt, and accepts a correctly sized one

Signed-off-by: Pranav Rajendran <pranavkasthuri@gmail.com>
---
v2:
- New in v2, per Simon's request for regression tests on this series.

 test/boot/Makefile     |   1 +
 test/boot/fit_cipher.c | 113 +++++++++++++++++++++++++++++++++++++++++
 test/cmd_ut.c          |   2 +
 3 files changed, 116 insertions(+)
 create mode 100644 test/boot/fit_cipher.c

diff --git a/test/boot/Makefile b/test/boot/Makefile
index 59a87028704..cef2a236d9b 100644
--- a/test/boot/Makefile
+++ b/test/boot/Makefile
@@ -18,6 +18,7 @@ ifdef CONFIG_UT_DM
 obj-$(CONFIG_$(PHASE_)OF_LIBFDT) += image_fdt.o
 endif
 endif
+obj-$(CONFIG_$(PHASE_)FIT_CIPHER) += fit_cipher.o
 obj-$(CONFIG_$(PHASE_)FIT_VERITY) += fit_verity.o
 obj-$(CONFIG_MEASURED_BOOT) += measurement.o
 
diff --git a/test/boot/fit_cipher.c b/test/boot/fit_cipher.c
new file mode 100644
index 00000000000..b98c69fcb0b
--- /dev/null
+++ b/test/boot/fit_cipher.c
@@ -0,0 +1,113 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Regression tests for the FIT cipher bounds checks in
+ * image_aes_decrypt() and fit_image_get_data_size_unciphered().
+ *
+ * Copyright 2026 Pranav Rajendran <pranavkasthuri@gmail.com>
+ */
+
+#include <errno.h>
+#include <image.h>
+#include <uboot_aes.h>
+#include <u-boot/aes.h>
+#include <linux/libfdt.h>
+#include <test/test.h>
+#include <test/ut.h>
+
+#define FIT_CIPHER_TEST(_name, _flags)	UNIT_TEST(_name, _flags, fit_cipher)
+
+/* A cipher_len that is not a whole number of AES blocks must be rejected */
+static int fit_cipher_test_unaligned_len(struct unit_test_state *uts)
+{
+	struct image_cipher_info info;
+	unsigned char key[AES128_KEY_LENGTH] = { 0 };
+	unsigned char iv[AES_BLOCK_LENGTH] = { 0 };
+	unsigned char cipher[AES_BLOCK_LENGTH + 1] = { 0 };
+	void *data = NULL;
+	size_t size = 0;
+	int ret;
+
+	memset(&info, 0, sizeof(info));
+	info.cipher = image_get_cipher_algo("aes128");
+	ut_assertnonnull(info.cipher);
+	info.key = key;
+	info.iv = iv;
+
+	ret = image_aes_decrypt(&info, cipher, sizeof(cipher), &data, &size);
+	ut_asserteq(-EINVAL, ret);
+	ut_assertnull(data);
+
+	return 0;
+}
+FIT_CIPHER_TEST(fit_cipher_test_unaligned_len, 0);
+
+/*
+ * An unciphered size larger than the ciphertext must be rejected; a size
+ * exactly equal to the ciphertext length is the valid boundary case.
+ */
+static int fit_cipher_test_oversized_unciphered_size(struct unit_test_state *uts)
+{
+	struct image_cipher_info info;
+	unsigned char key[AES128_KEY_LENGTH] = { 0 };
+	unsigned char iv[AES_BLOCK_LENGTH] = { 0 };
+	unsigned char cipher[AES_BLOCK_LENGTH * 2] = { 0 };
+	void *data = NULL;
+	size_t size = 0;
+	int ret;
+
+	memset(&info, 0, sizeof(info));
+	info.cipher = image_get_cipher_algo("aes128");
+	ut_assertnonnull(info.cipher);
+	info.key = key;
+	info.iv = iv;
+
+	info.size_unciphered = sizeof(cipher) + 1;
+	ret = image_aes_decrypt(&info, cipher, sizeof(cipher), &data, &size);
+	ut_asserteq(-EINVAL, ret);
+	ut_assertnull(data);
+
+	/* the boundary itself, size_unciphered == cipher_len, is valid */
+	info.size_unciphered = sizeof(cipher);
+	ut_assertok(image_aes_decrypt(&info, cipher, sizeof(cipher), &data,
+				      &size));
+	ut_assertnonnull(data);
+	ut_asserteq(sizeof(cipher), size);
+	free(data);
+
+	return 0;
+}
+FIT_CIPHER_TEST(fit_cipher_test_oversized_unciphered_size, 0);
+
+/*
+ * A 'data-size-unciphered' property that is not exactly one fdt32_t long
+ * must be rejected rather than read out of bounds.
+ */
+static int fit_cipher_test_data_size_unciphered_len(struct unit_test_state *uts)
+{
+	char fit[512];
+	int images, img, ret;
+	u16 truncated = 0x1234;
+	fdt32_t valid = cpu_to_fdt32(0x100);
+	size_t data_size = 0;
+
+	ut_assertok(fdt_create_empty_tree(fit, sizeof(fit)));
+	images = fdt_add_subnode(fit, 0, "images");
+	ut_assert(images >= 0);
+
+	img = fdt_add_subnode(fit, images, "kernel");
+	ut_assert(img >= 0);
+	ut_assertok(fdt_setprop(fit, img, "data-size-unciphered",
+				&truncated, sizeof(truncated)));
+
+	ret = fit_image_get_data_size_unciphered(fit, img, &data_size);
+	ut_asserteq(-EINVAL, ret);
+
+	/* a correctly sized property still works */
+	ut_assertok(fdt_setprop(fit, img, "data-size-unciphered",
+				&valid, sizeof(valid)));
+	ut_assertok(fit_image_get_data_size_unciphered(fit, img, &data_size));
+	ut_asserteq(0x100, data_size);
+
+	return 0;
+}
+FIT_CIPHER_TEST(fit_cipher_test_data_size_unciphered_len, 0);
diff --git a/test/cmd_ut.c b/test/cmd_ut.c
index 4328670d0d6..95e86f7dcf6 100644
--- a/test/cmd_ut.c
+++ b/test/cmd_ut.c
@@ -59,6 +59,7 @@ SUITE_DECL(env);
 SUITE_DECL(exit);
 SUITE_DECL(fdt);
 SUITE_DECL(fdt_overlay);
+SUITE_DECL(fit_cipher);
 SUITE_DECL(fit_verity);
 SUITE_DECL(font);
 SUITE_DECL(hush);
@@ -88,6 +89,7 @@ static struct suite suites[] = {
 	SUITE(exit, "shell exit and variables"),
 	SUITE(fdt, "fdt command"),
 	SUITE(fdt_overlay, "device tree overlays"),
+	SUITE(fit_cipher, "FIT cipher bounds checks"),
 	SUITE(fit_verity, "FIT dm-verity cmdline generation"),
 	SUITE(font, "font command"),
 	SUITE(hush, "hush behaviour"),
-- 
2.50.1 (Apple Git-155)