FIT cipher support currently allocates the output buffer inside the AES helper. SPL often needs to decrypt directly into a caller-selected buffer, for example a load buffer or a scratch buffer used before decompression.
Add a decrypt_to callback to the FIT cipher algorithm and wire it up for AES. The existing allocating decrypt path becomes a wrapper around the new helper. Validate the FIT cipher key length, IV length and unciphered-size property while preparing decryption, and build lib/aes/ by phase when FIT_CIPHER is enabled so the target-side decrypt helper is available to SPL builds. Use the DM AES provider helper when enabled, retaining the software implementation only when no provider supports the operation. For U-Boot proper, use decrypt_to for in-place decryption when the FIT payload is already in writable RAM. The encrypted data is no longer needed after hash verification, and this avoids a full-size allocation for encrypted payloads loaded into DRAM. Add sandbox coverage for out-of-place and in-place AES-256 decrypt and malformed key, IV and size inputs. Signed-off-by: James Hilliard <[email protected]> --- Changes v3 -> v4: - Validate cipher metadata before reading the key length - Preserve hard provider failures and fall back only when unsupported - Treat -EINVAL as a hard provider error - Fix disabled-feature declarations and use the public test prototype - Add in-place decrypt and malformed-input tests - Simplify the legacy allocating decrypt wrapper Changes v2 -> v3: - Flip the image_aes_decrypt_to() host-tool guard (suggested by Simon Glass) - Let image_aes_decrypt_to() be the single length-validation path (suggested by Simon Glass) - Document that AES CBC decrypt providers must support in-place decrypt (suggested by Simon Glass) Changes v1 -> v2: - Explain FIT cipher validation (suggested by Simon Glass) - Explain phase-keyed lib/aes builds (suggested by Simon Glass) - Return -ENOSYS without decrypt support (suggested by Simon Glass) - Use decrypt_to for U-Boot proper in-place decrypt --- boot/image-cipher.c | 45 ++++++++++++++++++---- boot/image-fit.c | 33 ++++++++++++++-- include/image.h | 39 +++++++++++++++++-- include/u-boot/aes.h | 27 ++++++++++---- lib/Makefile | 2 +- lib/aes/aes-decrypt.c | 91 +++++++++++++++++++++++++++++++++++++-------- test/lib/Makefile | 3 ++ test/lib/test_aes_decrypt.c | 89 ++++++++++++++++++++++++++++++++++++++++++++ 8 files changed, 290 insertions(+), 39 deletions(-) diff --git a/boot/image-cipher.c b/boot/image-cipher.c index 9d389f26cea..9470370a534 100644 --- a/boot/image-cipher.c +++ b/boot/image-cipher.c @@ -25,6 +25,7 @@ struct cipher_algo cipher_algos[] = { #endif .encrypt = image_aes_encrypt, .decrypt = image_aes_decrypt, + .decrypt_to = image_aes_decrypt_to, .add_cipher_data = image_aes_add_cipher_data }, { @@ -36,6 +37,7 @@ struct cipher_algo cipher_algos[] = { #endif .encrypt = image_aes_encrypt, .decrypt = image_aes_decrypt, + .decrypt_to = image_aes_decrypt_to, .add_cipher_data = image_aes_add_cipher_data }, { @@ -47,6 +49,7 @@ struct cipher_algo cipher_algos[] = { #endif .encrypt = image_aes_encrypt, .decrypt = image_aes_decrypt, + .decrypt_to = image_aes_decrypt_to, .add_cipher_data = image_aes_add_cipher_data } }; @@ -70,6 +73,7 @@ static int fit_image_setup_decrypt(struct image_cipher_info *info, int cipher_noffset) { const void *fdt = gd_fdt_blob(); + int key_len, iv_len; const char *node_name; char node_path[128]; int noffset; @@ -94,7 +98,7 @@ static int fit_image_setup_decrypt(struct image_cipher_info *info, return -1; } - info->iv = fdt_getprop(fit, cipher_noffset, "iv", NULL); + info->iv = fdt_getprop(fit, cipher_noffset, "iv", &iv_len); info->ivname = fdt_getprop(fit, cipher_noffset, "iv-name-hint", NULL); if (!info->iv && !info->ivname) { @@ -136,20 +140,28 @@ static int fit_image_setup_decrypt(struct image_cipher_info *info, } /* read key */ - info->key = fdt_getprop(fdt, noffset, "key", NULL); + info->key = fdt_getprop(fdt, noffset, "key", &key_len); if (!info->key) { printf("Can't get key in cipher node '%s'\n", node_path); return -1; } + if (key_len != info->cipher->key_len) { + printf("Bad key length in cipher node '%s'\n", node_path); + return -1; + } /* read iv */ if (!info->iv) { - info->iv = fdt_getprop(fdt, noffset, "iv", NULL); + info->iv = fdt_getprop(fdt, noffset, "iv", &iv_len); if (!info->iv) { printf("Can't get IV in cipher node '%s'\n", node_path); return -1; } } + if (iv_len != info->cipher->iv_len) { + printf("Bad IV length for cipher in image '%s'\n", node_name); + return -1; + } return 0; } @@ -165,11 +177,28 @@ int fit_image_decrypt_data(const void *fit, ret = fit_image_setup_decrypt(&info, fit, image_noffset, cipher_noffset); if (ret < 0) - goto out; + return ret; + + return info.cipher->decrypt(&info, data_ciphered, size_ciphered, + data_unciphered, size_unciphered); +} + +int fit_image_decrypt_data_to(const void *fit, + int image_noffset, int cipher_noffset, + const void *data_ciphered, size_t size_ciphered, + void *data_unciphered, size_t *size_unciphered) +{ + struct image_cipher_info info; + int ret; + + ret = fit_image_setup_decrypt(&info, fit, image_noffset, + cipher_noffset); + if (ret < 0) + return ret; - ret = info.cipher->decrypt(&info, data_ciphered, size_ciphered, - data_unciphered, size_unciphered); + if (!info.cipher->decrypt_to) + return -ENOSYS; - out: - return ret; + return info.cipher->decrypt_to(&info, data_ciphered, size_ciphered, + data_unciphered, size_unciphered); } diff --git a/boot/image-fit.c b/boot/image-fit.c index 9af38ed8d82..6b55316dd37 100644 --- a/boot/image-fit.c +++ b/boot/image-fit.c @@ -1028,7 +1028,7 @@ int fit_image_get_data_size(const void *fit, int noffset, int *data_size) * * @fit: pointer to the FIT image header * @noffset: component image node offset - * @data_size: holds the data-size property + * @data_size: holds the data-size-unciphered property * * returns: * 0, on success @@ -1038,10 +1038,13 @@ int fit_image_get_data_size_unciphered(const void *fit, int noffset, size_t *data_size) { const fdt32_t *val; + int len; - val = fdt_getprop(fit, noffset, "data-size-unciphered", NULL); + val = fdt_getprop(fit, noffset, "data-size-unciphered", &len); if (!val) return -ENOENT; + if (len != sizeof(*val)) + return -EINVAL; *data_size = (size_t)fdt32_to_cpu(*val); @@ -1562,15 +1565,37 @@ static int fit_image_uncipher(const void *fit, int image_noffset, if (cipher_noffset < 0) return 0; +#ifndef USE_HOSTCC + if (!tools_build()) { + ulong start = map_to_sysmem(*data); + ulong end = start + *size; + + /* + * Avoid a full-size allocation when the FIT payload is already + * in writable DRAM. The encrypted bytes are no longer needed + * after hash verification has completed. + */ + if (end >= start && start >= gd->ram_base && end <= gd->ram_top) { + ret = fit_image_decrypt_data_to(fit, image_noffset, + cipher_noffset, + *data, *size, *data, + &size_dst); + if (ret != -ENOSYS) + goto out; + } + } +#endif + ret = fit_image_decrypt_data(fit, image_noffset, cipher_noffset, *data, *size, &dst, &size_dst); if (ret) goto out; *data = dst; - *size = size_dst; +out: + if (!ret) + *size = size_dst; - out: return ret; } diff --git a/include/image.h b/include/image.h index 9c8a746d576..5edbf8fdc33 100644 --- a/include/image.h +++ b/include/image.h @@ -1862,11 +1862,40 @@ int fit_image_check_sig(const void *fit, int noffset, const void *data, size_t size, const void *key_blob, int required_keynode, char **err_msgp); -int fit_image_decrypt_data(const void *fit, - int image_noffset, int cipher_noffset, - const void *data, size_t size, +/** + * fit_image_decrypt_data() - Decrypt a FIT image payload + * + * @fit: FIT image + * @image_noffset: Offset of the image node to decrypt + * @cipher_noffset: Offset of the cipher node for the image + * @data: Encrypted image payload + * @size: Size of encrypted image payload + * @data_unciphered: Returns allocated decrypted payload + * @size_unciphered: Returns size of decrypted payload + * Return: 0 on success, <0 on error + */ +int fit_image_decrypt_data(const void *fit, int image_noffset, + int cipher_noffset, const void *data, size_t size, void **data_unciphered, size_t *size_unciphered); +/** + * fit_image_decrypt_data_to() - Decrypt a FIT image payload to a buffer + * + * @fit: FIT image + * @image_noffset: Offset of the image node to decrypt + * @cipher_noffset: Offset of the cipher node for the image + * @data: Encrypted image payload + * @size: Size of encrypted image payload + * @data_unciphered: Destination buffer for decrypted payload. The caller + * must provide at least @size bytes. + * @size_unciphered: Returns size of decrypted payload + * Return: 0 on success, <0 on error + */ +int fit_image_decrypt_data_to(const void *fit, + int image_noffset, int cipher_noffset, + const void *data, size_t size, + void *data_unciphered, size_t *size_unciphered); + /** * fit_region_make_list() - Make a list of regions to hash * @@ -1960,6 +1989,10 @@ struct cipher_algo { int (*decrypt)(struct image_cipher_info *info, const void *cipher, size_t cipher_len, void **data, size_t *data_len); + + int (*decrypt_to)(struct image_cipher_info *info, + const void *cipher, size_t cipher_len, + void *data, size_t *data_len); }; int fit_image_cipher_get_algo(const void *fit, int noffset, char **algo); diff --git a/include/u-boot/aes.h b/include/u-boot/aes.h index acbc50b9e6f..8fd43f02adc 100644 --- a/include/u-boot/aes.h +++ b/include/u-boot/aes.h @@ -16,15 +16,16 @@ int image_aes_encrypt(struct image_cipher_info *info, int image_aes_add_cipher_data(struct image_cipher_info *info, void *keydest, void *fit, int node_noffset); #else -int image_aes_encrypt(struct image_cipher_info *info, - const unsigned char *data, int size, - unsigned char **cipher, int *cipher_len) +static inline int image_aes_encrypt(struct image_cipher_info *info, + const unsigned char *data, int size, + unsigned char **cipher, int *cipher_len) { return -ENXIO; } -int image_aes_add_cipher_data(struct image_cipher_info *info, void *keydest, - void *fit, int node_noffset) +static inline int image_aes_add_cipher_data(struct image_cipher_info *info, + void *keydest, void *fit, + int node_noffset) { return -ENXIO; } @@ -34,10 +35,20 @@ int image_aes_add_cipher_data(struct image_cipher_info *info, void *keydest, int image_aes_decrypt(struct image_cipher_info *info, const void *cipher, size_t cipher_len, void **data, size_t *size); +int image_aes_decrypt_to(struct image_cipher_info *info, + const void *cipher, size_t cipher_len, + void *data, size_t *size); #else -int image_aes_decrypt(struct image_cipher_info *info, - const void *cipher, size_t cipher_len, - void **data, size_t *size) +static inline int image_aes_decrypt(struct image_cipher_info *info, + const void *cipher, size_t cipher_len, + void **data, size_t *size) +{ + return -ENXIO; +} + +static inline int image_aes_decrypt_to(struct image_cipher_info *info, + const void *cipher, size_t cipher_len, + void *data, size_t *size) { return -ENXIO; } diff --git a/lib/Makefile b/lib/Makefile index d0ffabc2b47..c69a928e6d8 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -19,7 +19,6 @@ obj-$(CONFIG_ARCH_AT91) += at91/ obj-$(CONFIG_OPTEE_LIB) += optee/ obj-$(CONFIG_AES) += aes.o -obj-$(CONFIG_AES) += aes/ obj-$(CONFIG_$(PHASE_)BINMAN_FDT) += binman.o obj-$(CONFIG_FW_LOADER) += fw_loader.o @@ -88,6 +87,7 @@ obj-$(CONFIG_$(PHASE_)ASN1_DECODER_LEGACY) += asn1_decoder.o obj-$(CONFIG_$(PHASE_)ZLIB) += zlib/ obj-$(CONFIG_$(PHASE_)ZSTD) += zstd/ +obj-$(CONFIG_$(PHASE_)FIT_CIPHER) += aes/ obj-$(CONFIG_$(PHASE_)GZIP) += gunzip.o obj-$(CONFIG_$(PHASE_)LZO) += lzo/ obj-$(CONFIG_$(PHASE_)LZMA) += lzma/ diff --git a/lib/aes/aes-decrypt.c b/lib/aes/aes-decrypt.c index 741102a4723..43a5f8742bb 100644 --- a/lib/aes/aes-decrypt.c +++ b/lib/aes/aes-decrypt.c @@ -4,37 +4,98 @@ */ #ifndef USE_HOSTCC +#include <dm.h> #include <malloc.h> #endif #include <image.h> #include <uboot_aes.h> +#ifndef USE_HOSTCC +static int image_aes_validate(struct image_cipher_info *info, + const void *cipher, size_t cipher_len, + void *data, size_t *size) +{ + if (!info || !info->cipher || !info->key || !info->iv || !cipher || + !data || !size) + return -EINVAL; + if (info->cipher->iv_len != AES_BLOCK_LENGTH || + (info->cipher->key_len != AES128_KEY_LENGTH && + info->cipher->key_len != AES192_KEY_LENGTH && + info->cipher->key_len != AES256_KEY_LENGTH)) + return -EINVAL; + if (!cipher_len || cipher_len % AES_BLOCK_LENGTH || + info->size_unciphered > cipher_len) + return -EINVAL; + + return 0; +} +#endif + +int image_aes_decrypt_to(struct image_cipher_info *info, + const void *cipher, size_t cipher_len, + void *data, size_t *size) +{ +#ifdef USE_HOSTCC + return -ENOSYS; +#else + unsigned int aes_blocks, key_len; + int ret; + + ret = image_aes_validate(info, cipher, cipher_len, data, size); + if (ret) + return ret; + key_len = info->cipher->key_len; + aes_blocks = cipher_len / AES_BLOCK_LENGTH; + + if (CONFIG_IS_ENABLED(DM_AES)) { + ret = dm_aes_cbc_decrypt_with_key(key_len * 8, (u8 *)info->key, + (u8 *)info->iv, (u8 *)cipher, + data, aes_blocks); + if (!ret) { + *size = info->size_unciphered; + return 0; + } + if (ret != -ENODEV && ret != -EOPNOTSUPP) + return ret; + } + + if (!IS_ENABLED(CONFIG_XPL_BUILD)) { + unsigned char key_exp[AES256_EXPAND_KEY_LENGTH]; + + /* First we expand the key. */ + aes_expand_key((u8 *)info->key, key_len, key_exp); + + aes_cbc_decrypt_blocks(key_len, key_exp, (u8 *)info->iv, + (u8 *)cipher, data, aes_blocks); + *size = info->size_unciphered; + return 0; + } + + return -ENOSYS; +#endif +} + int image_aes_decrypt(struct image_cipher_info *info, const void *cipher, size_t cipher_len, void **data, size_t *size) { -#ifndef USE_HOSTCC - unsigned char key_exp[AES256_EXPAND_KEY_LENGTH]; - unsigned int aes_blocks, key_len = info->cipher->key_len; +#ifdef USE_HOSTCC + return 0; +#else + int ret; *data = malloc(cipher_len); if (!*data) { printf("Can't allocate memory to decrypt\n"); return -ENOMEM; } - *size = info->size_unciphered; - - memcpy(&key_exp[0], info->key, key_len); - - /* First we expand the key. */ - aes_expand_key((u8 *)info->key, key_len, key_exp); - /* Calculate the number of AES blocks to encrypt. */ - aes_blocks = DIV_ROUND_UP(cipher_len, AES_BLOCK_LENGTH); + ret = image_aes_decrypt_to(info, cipher, cipher_len, *data, size); + if (ret) { + free(*data); + *data = NULL; + } - aes_cbc_decrypt_blocks(key_len, key_exp, (u8 *)info->iv, - (u8 *)cipher, *data, aes_blocks); + return ret; #endif - - return 0; } diff --git a/test/lib/Makefile b/test/lib/Makefile index f25383a40e5..721d1470185 100644 --- a/test/lib/Makefile +++ b/test/lib/Makefile @@ -29,6 +29,9 @@ obj-$(CONFIG_ERRNO_STR) += test_errno_str.o obj-$(CONFIG_UT_LIB_ASN1) += asn1.o obj-$(CONFIG_UT_LIB_RSA) += rsa.o obj-$(CONFIG_AES) += test_aes.o +ifeq ($(CONFIG_FIT_CIPHER)$(CONFIG_DM_AES),yy) +obj-y += test_aes_decrypt.o +endif obj-$(CONFIG_SHA256) += test_sha256_hmac.o obj-$(CONFIG_HKDF_MBEDTLS) += test_sha256_hkdf.o obj-$(CONFIG_GETOPT) += getopt.o diff --git a/test/lib/test_aes_decrypt.c b/test/lib/test_aes_decrypt.c new file mode 100644 index 00000000000..3b498e23e4b --- /dev/null +++ b/test/lib/test_aes_decrypt.c @@ -0,0 +1,89 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * Tests for target-side FIT AES decryption + * + * Copyright (C) 2026 James Hilliard + */ + +#include <image.h> +#include <u-boot/aes.h> +#include <uboot_aes.h> +#include <test/lib.h> +#include <test/test.h> +#include <test/ut.h> + +static int lib_test_image_aes_decrypt(struct unit_test_state *uts) +{ + u8 key[AES256_KEY_LENGTH] = { }; + u8 key_exp[AES256_EXPAND_KEY_LENGTH]; + u8 iv[AES_BLOCK_LENGTH] = { }; + u8 plain[2 * AES_BLOCK_LENGTH]; + u8 cipher[sizeof(plain)]; + u8 output[sizeof(plain)]; + struct cipher_algo algo = { + .name = "aes256", + .key_len = sizeof(key), + .iv_len = sizeof(iv), + }; + struct image_cipher_info info = { + .cipher = &algo, + .key = key, + .iv = iv, + .size_unciphered = sizeof(plain), + }; + size_t size; + int i, ret; + + for (i = 0; i < sizeof(key); i++) + key[i] = i; + for (i = 0; i < sizeof(iv); i++) + iv[i] = 0x80 + i; + for (i = 0; i < sizeof(plain); i++) + plain[i] = 0x40 + i; + + aes_expand_key(key, sizeof(key), key_exp); + aes_cbc_encrypt_blocks(sizeof(key), key_exp, iv, plain, cipher, + ARRAY_SIZE(cipher) / AES_BLOCK_LENGTH); + + size = 0; + ut_assertok(image_aes_decrypt_to(&info, cipher, sizeof(cipher), output, + &size)); + ut_asserteq(sizeof(plain), size); + ut_asserteq_mem(plain, output, sizeof(plain)); + + memcpy(output, cipher, sizeof(cipher)); + size = 0; + ut_assertok(image_aes_decrypt_to(&info, output, sizeof(output), output, + &size)); + ut_asserteq(sizeof(plain), size); + ut_asserteq_mem(plain, output, sizeof(plain)); + + size = 0x55; + ret = image_aes_decrypt_to(&info, cipher, sizeof(cipher) - 1, output, + &size); + ut_asserteq(-EINVAL, ret); + ut_asserteq(0x55, size); + + info.size_unciphered = sizeof(cipher) + 1; + ret = image_aes_decrypt_to(&info, cipher, sizeof(cipher), output, &size); + ut_asserteq(-EINVAL, ret); + info.size_unciphered = sizeof(plain); + + info.key = NULL; + ret = image_aes_decrypt_to(&info, cipher, sizeof(cipher), output, &size); + ut_asserteq(-EINVAL, ret); + info.key = key; + info.iv = NULL; + ret = image_aes_decrypt_to(&info, cipher, sizeof(cipher), output, &size); + ut_asserteq(-EINVAL, ret); + info.iv = iv; + info.cipher = NULL; + ret = image_aes_decrypt_to(&info, cipher, sizeof(cipher), output, &size); + ut_asserteq(-EINVAL, ret); + ret = image_aes_decrypt_to(NULL, cipher, sizeof(cipher), output, &size); + ut_asserteq(-EINVAL, ret); + + return 0; +} + +LIB_TEST(lib_test_image_aes_decrypt, 0); -- 2.53.0
