[Skiboot] [PATCH 08/15] libstb: Add secure boot header structures
Stewart Smith
stewart at linux.vnet.ibm.com
Wed Sep 14 19:25:58 AEST 2016
Claudio Carvalho <cclaudio at linux.vnet.ibm.com> writes:
> This adds the secure boot header structures required by the secure and
> trusted boot implementation in skiboot, and also implements some helper
> routines related to containers.
>
> Signed-off-by: Claudio Carvalho <cclaudio at linux.vnet.ibm.com>
> ---
> Makefile.main | 3 +-
> libstb/Makefile.inc | 11 +++++
> libstb/container.c | 75 ++++++++++++++++++++++++++++
> libstb/container.h | 139 ++++++++++++++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 227 insertions(+), 1 deletion(-)
> create mode 100644 libstb/Makefile.inc
> create mode 100644 libstb/container.c
> create mode 100644 libstb/container.h
This looks like a good candidate for a small unit test with some input
data, preferably something that can be fuzzed (feel free to add test
cases produced by afl-fuzz)
> diff --git a/Makefile.main b/Makefile.main
> index 159ce26..cc6cfdf 100644
> --- a/Makefile.main
> +++ b/Makefile.main
> @@ -145,6 +145,7 @@ include $(SRC)/libpore/Makefile.inc
> include $(SRC)/libc/Makefile.inc
> include $(SRC)/ccan/Makefile.inc
> include $(SRC)/$(DEVSRC)/Makefile.inc
> +include $(SRC)/libstb/Makefile.inc
>
> # hack for travis-ci and coverity
> gard:
> @@ -158,7 +159,7 @@ pflash-coverity:
>
> all: $(SUBDIRS) $(TARGET).lid $(TARGET).lid.xz $(TARGET).map extract-gcov
>
> -OBJS := $(ASM) $(CORE) $(HW) $(PLATFORMS) $(LIBFDT) $(LIBFLASH)
> +OBJS := $(ASM) $(CORE) $(HW) $(PLATFORMS) $(LIBFDT) $(LIBFLASH) $(LIBSTB)
> ifeq ($(PORE),1)
> OBJS += $(LIBPORE)
> endif
> diff --git a/libstb/Makefile.inc b/libstb/Makefile.inc
> new file mode 100644
> index 0000000..15cdfbe
> --- /dev/null
> +++ b/libstb/Makefile.inc
> @@ -0,0 +1,11 @@
> +# -*-Makefile-*-
> +
> +LIBSTB_DIR = libstb
> +
> +SUBDIRS += $(LIBSTB_DIR)
> +
> +LIBSTB_SRCS = container.c
> +LIBSTB_OBJS = $(LIBSTB_SRCS:%.c=%.o)
> +LIBSTB = $(LIBSTB_DIR)/built-in.o
> +
> +$(LIBSTB): $(LIBSTB_OBJS:%=$(LIBSTB_DIR)/%)
> diff --git a/libstb/container.c b/libstb/container.c
> new file mode 100644
> index 0000000..efa8511
> --- /dev/null
> +++ b/libstb/container.c
> @@ -0,0 +1,75 @@
> +/* Copyright 2013-2016 IBM Corp.
> + *
> + * Licensed under the Apache License, Version 2.0 (the "License");
> + * you may not use this file except in compliance with the License.
> + * You may obtain a copy of the License at
> + *
> + * http://www.apache.org/licenses/LICENSE-2.0
> + *
> + * Unless required by applicable law or agreed to in writing, software
> + * distributed under the License is distributed on an "AS IS" BASIS,
> + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
> + * implied.
> + * See the License for the specific language governing permissions and
> + * limitations under the License.
> + */
> +
> +#include <skiboot.h>
> +
> +#include "container.h"
> +
> +const uint32_t* stb_payload_magic(const void *buf)
> +{
> + if (!stb_is_container(buf))
> + return NULL;
> +
> + return (const uint32_t*) ((uint8_t*)buf + SECURE_BOOT_HEADERS_SIZE);
> +}
> +
> +bool stb_is_container(const void *buf)
> +{
> + if (!buf)
> + return false;
> +
> + if ( *((uint32_t*) buf) != ROM_MAGIC_NUMBER )
> + return false;
> +
> + return true;
> +}
> +
> +const sha2_hash_t* stb_sw_payload_hash(const void *buf)
> +{
> + const ROM_prefix_header_raw* prefix;
> + const ROM_prefix_data_raw* hw_data;
> + const ROM_sw_header_raw* header;
> +
> + if (!stb_is_container(buf))
> + return NULL;
> +
> + prefix = (ROM_prefix_header_raw*) &((ROM_container_raw*)buf)->prefix;
> + hw_data = (ROM_prefix_data_raw*) (prefix->ecid +
> + prefix->ecid_count*ECID_SIZE);
> + header = (ROM_sw_header_raw*) (hw_data->sw_pkey_p +
> + prefix->sw_key_count*sizeof(ecc_key_t));
> +
> + return &header->payload_hash;
> +}
> +
> +void stb_print_data(const void* data, size_t len)
> +{
> + int i, j;
> + unsigned char *p;
> + unsigned char hash[30];
> +
> + p = (unsigned char*) data;
> + j = 0;
> + for (i = 0; i < len; i++) {
> + if (!(i%10) && i) {
> + prlog(PR_NOTICE, "%s\n", hash);
> + j=0;
> + }
> + snprintf(&hash[j], 30-j, "%02x ", p[i]);
> + j+=3;
> + }
> + prlog(PR_NOTICE, "%s\n", hash);
> +}
> diff --git a/libstb/container.h b/libstb/container.h
> new file mode 100644
> index 0000000..8062ae1
> --- /dev/null
> +++ b/libstb/container.h
> @@ -0,0 +1,139 @@
> +/* Copyright 2013-2016 IBM Corp.
> + *
> + * Licensed under the Apache License, Version 2.0 (the "License");
> + * you may not use this file except in compliance with the License.
> + * You may obtain a copy of the License at
> + *
> + * http://www.apache.org/licenses/LICENSE-2.0
> + *
> + * Unless required by applicable law or agreed to in writing, software
> + * distributed under the License is distributed on an "AS IS" BASIS,
> + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
> + * implied.
> + * See the License for the specific language governing permissions and
> + * limitations under the License.
> + */
> +
> +#ifndef __STB_CONTAINER_H
> +#define __STB_CONTAINER_H
> +
> +#include <stdint.h>
> +
> +#define SECURE_BOOT_HEADERS_SIZE 4096
> +
> +#define SHA256_DIGEST_LENGTH 32
> +
> +/**
> + * The defines and structures below come from the secure ROM source code
> + * (trusted_boot_rom). Here you will find only the ones required by the
> + * secure and trusted boot implementation in skiboot.
> + */
> +
> +/* From trusted_boot_rom/src/sha512.h */
> +#define SHA512_DIGEST_LENGTH 64
> +typedef uint8_t __attribute__((aligned(8))) sha2_hash_t[ SHA512_DIGEST_LENGTH / sizeof(uint8_t) ];
> +typedef uint8_t sha2_byte; // Exactly 1 byte
> +
> +/* From trusted_boot_rom/src/hw_utils.h */
> +#define ECID_SIZE 16
> +
> +/* From trusted_boot_rom/src/ecverify.h */
> +#define EC_COORDBYTES 66 /* P-521 */
> +typedef uint8_t ecc_key_t[2*EC_COORDBYTES];
> +typedef uint8_t ecc_signature_t[2*EC_COORDBYTES];
> +
> +/* From trusted_boot_rom/src/ROM.h */
> +#define ROM_MAGIC_NUMBER 0x17082011
> +
> +typedef struct {
> + uint16_t version; /* (1: see versions above) */
> + uint8_t hash_alg; /* (1: SHA-512) */
> + uint8_t sig_alg; /* (1: SHA-512/ECDSA-521) */
> +}__attribute__((packed)) ROM_version_raw;
> +
> +typedef struct {
> + uint32_t magic_number; /* (17082011) */
> + uint16_t version; /* (1: see versions above) */
> + uint64_t container_size;/* filled by caller */
> + uint64_t target_hrmor; /* filled by caller */
> + uint64_t stack_pointer; /* filled by caller */
> + /* bottom of stack -> 128k added by rom code to get real stack pointer */
> + ecc_key_t hw_pkey_a;
> + ecc_key_t hw_pkey_b;
> + ecc_key_t hw_pkey_c;
> + uint64_t prefix; /* prefix header place holder */
> + /* followed by sw header (if not special prefix) */
> + /* followed by optional unprotected payload data */
> +}__attribute__((packed)) ROM_container_raw;
> +
> +typedef struct {
> + ROM_version_raw ver_alg;
> + uint64_t code_start_offset;
> + uint64_t reserved;
> + uint32_t flags;
> + uint8_t sw_key_count;
> + uint64_t payload_size;
> + sha2_hash_t payload_hash;
> + uint8_t ecid_count;
> + uint8_t ecid[ECID_SIZE]; /* optional ecid place
> + holder ecid_count * ecid_size(128 bits) */
> + /* followed by prefix data (sig,keys) key raw */
> +}__attribute__((packed)) ROM_prefix_header_raw;
> +
> +typedef struct {
> + ecc_signature_t hw_sig_a;
> + ecc_signature_t hw_sig_b;
> + ecc_signature_t hw_sig_c;
> + ecc_key_t sw_pkey_p;
> + ecc_key_t sw_pkey_q;
> + ecc_key_t sw_pkey_r;
> +}__attribute__((packed)) ROM_prefix_data_raw;
> +
> +typedef struct {
> + ROM_version_raw ver_alg;
> + uint64_t code_start_offset;
> + uint64_t reserved;
> + uint32_t flags;
> + uint8_t reserved_0;
> + uint64_t payload_size;
> + sha2_hash_t payload_hash;
> + uint8_t ecid_count;
> + uint8_t ecid[ECID_SIZE]; /* optional ecid place
> + holder ecid_count * ecid_size(128 bits) */
> + /* followed by sw sig raw */
> +}__attribute__((packed)) ROM_sw_header_raw;
> +
> +typedef struct {
> + ecc_signature_t sw_sig_p;
> + ecc_signature_t sw_sig_q;
> + ecc_signature_t sw_sig_r;
> + /* followed by zero's padding to 4K */
> + /* followed by protected sw payload_data */
> + /* followed by unprotected sw payload_text */
> +}__attribute__((packed)) ROM_sw_sig_raw;
> +
> +typedef enum { ROM_DONE, ROM_FAILED, PHYP_PARTIAL } ROM_response;
> +
> +typedef struct {
> + sha2_hash_t hw_key_hash;
> + uint8_t my_ecid[ECID_SIZE];
> + uint64_t entry_point;
> + uint64_t log;
> +}__attribute__((packed)) ROM_hw_params;
> +
> +/**
> + * Helper functions
> + */
> +
> +/* Get the pointer for the container payload eyecatcher */
> +const uint32_t* stb_payload_magic(const void *buf);
> +
> +/* Check if buf is a secure boot container */
> +bool stb_is_container(const void* buf);
> +
> +/* Get the pointer for the sw-payload-hash field of the container header */
> +const sha2_hash_t* stb_sw_payload_hash(const void* buf);
I generally like a size_t parameter to go along with any void* buf, at
least as a sanity check.
Later on, in tb_measure(), if buf was, say len=1, then you'd access
beyond the end of the buffer (and hope that what's after the buffer
wasn't magically something that was kind of valid or could be
manipulated to do something bad), when instead you should error out.
--
Stewart Smith
OPAL Architect, IBM.
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