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feat(core/prodtest): Verify device certificate chain in CERTDEV WRITE.

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This commit is contained in:
Andrew Kozlik 2023-11-30 21:01:47 +01:00 committed by matejcik
parent 41c305f6cd
commit cbea765e38
7 changed files with 200 additions and 3 deletions
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2
core/SConscript.prodtest
View File

@ -57,8 +57,10 @@ SOURCE_MOD += [
'vendor/trezor-crypto/aes/aeskey.c',
'vendor/trezor-crypto/aes/aestab.c',
'vendor/trezor-crypto/bignum.c',
'vendor/trezor-crypto/buffer.c',
'vendor/trezor-crypto/chacha_drbg.c',
'vendor/trezor-crypto/chacha20poly1305/chacha_merged.c',
'vendor/trezor-crypto/der.c',
'vendor/trezor-crypto/ecdsa.c',
'vendor/trezor-crypto/hmac.c',
'vendor/trezor-crypto/hmac_drbg.c',

187
core/embed/prodtest/optiga_prodtest.c
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@ -17,12 +17,16 @@
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "optiga_prodtest.h"
#include <string.h>
#include "aes/aes.h"
#include "buffer.h"
#include "der.h"
#include "ecdsa.h"
#include "memzero.h"
#include "nist256p1.h"
#include "optiga_commands.h"
#include "optiga_prodtest.h"
#include "optiga_transport.h"
#include "prodtest_common.h"
#include "rand.h"
@ -295,7 +299,7 @@ void optigaid_read(void) {
void cert_read(uint16_t oid) {
if (!optiga_paired()) return;
static uint8_t cert[2048] = {0};
static uint8_t cert[OPTIGA_MAX_CERT_SIZE] = {0};
size_t cert_size = 0;
optiga_result ret =
optiga_get_data_object(oid, false, cert, sizeof(cert), &cert_size);
@ -337,7 +341,7 @@ void cert_write(uint16_t oid, char *data) {
metadata.change = OPTIGA_META_ACCESS_ALWAYS;
set_metadata(oid, &metadata); // Ignore result.
uint8_t data_bytes[1024];
uint8_t data_bytes[OPTIGA_MAX_CERT_SIZE];
int len = get_from_hex(data_bytes, sizeof(data_bytes), data);
if (len < 0) {
@ -351,6 +355,21 @@ void cert_write(uint16_t oid, char *data) {
return;
}
// Verify that the certificate was written correctly.
static uint8_t cert[OPTIGA_MAX_CERT_SIZE] = {0};
size_t cert_size = 0;
ret = optiga_get_data_object(oid, false, cert, sizeof(cert), &cert_size);
if (OPTIGA_SUCCESS != ret || cert_size != len ||
memcmp(data_bytes, cert, len) != 0) {
vcp_println("ERROR optiga_get_data_object error %d for 0x%04x.", ret, oid);
return;
}
if (oid == OID_CERT_DEV && !check_device_cert_chain(cert, cert_size)) {
// Error returned by check_device_cert_chain().
return;
}
vcp_println("OK");
}
@ -512,3 +531,165 @@ void sec_read(void) {
vcp_print("OK ");
vcp_println_hex(&sec, sizeof(sec));
}
// clang-format off
static const uint8_t ECDSA_WITH_SHA256[] = {
0x30, 0x0a, // a sequence of 10 bytes
0x06, 0x08, // an OID of 8 bytes
0x2a, 0x86, 0x48, 0xce, 0x3d, 0x04, 0x03, 0x02,
};
// clang-format on
static const uint8_t ROOT_PUBLIC_KEYS[][65] = {
{
// Production root public key.
0x04, 0xca, 0x97, 0x48, 0x0a, 0xc0, 0xd7, 0xb1, 0xe6, 0xef, 0xaf,
0xe5, 0x18, 0xcd, 0x43, 0x3c, 0xec, 0x2b, 0xf8, 0xab, 0x98, 0x22,
0xd7, 0x6e, 0xaf, 0xd3, 0x43, 0x63, 0xb5, 0x5d, 0x63, 0xe6, 0x03,
0x80, 0xbf, 0xf2, 0x0a, 0xcc, 0x75, 0xcd, 0xe0, 0x3c, 0xff, 0xcb,
0x50, 0xab, 0x6f, 0x8c, 0xe7, 0x0c, 0x87, 0x8e, 0x37, 0xeb, 0xc5,
0x8f, 0xf7, 0xcc, 0xa0, 0xa8, 0x3b, 0x16, 0xb1, 0x5f, 0xa5,
},
{
// Development root public key.
0x04, 0x7f, 0x77, 0x36, 0x8d, 0xea, 0x2d, 0x4d, 0x61, 0xe9, 0x89,
0xf4, 0x74, 0xa5, 0x67, 0x23, 0xc3, 0x21, 0x2d, 0xac, 0xf8, 0xa8,
0x08, 0xd8, 0x79, 0x55, 0x95, 0xef, 0x38, 0x44, 0x14, 0x27, 0xc4,
0x38, 0x9b, 0xc4, 0x54, 0xf0, 0x20, 0x89, 0xd7, 0xf0, 0x8b, 0x87,
0x30, 0x05, 0xe4, 0xc2, 0x8d, 0x43, 0x24, 0x68, 0x99, 0x78, 0x71,
0xc0, 0xbf, 0x28, 0x6f, 0xd3, 0x86, 0x1e, 0x21, 0xe9, 0x6a,
},
};
bool check_device_cert_chain(const uint8_t *chain, size_t chain_size) {
// Checks the integrity of the device certificate chain to ensure that the
// certificate data was not corrupted in transport and that the device
// certificate belongs to this device. THIS IS NOT A FULL VERIFICATION OF THE
// CERTIFICATE CHAIN.
// Generate a P-256 signature using the device private key.
uint8_t digest[SHA256_DIGEST_LENGTH] = {1};
uint8_t der_sig[72] = {DER_SEQUENCE};
size_t der_sig_size = 0;
if (optiga_calc_sign(OID_KEY_DEV, digest, sizeof(digest), &der_sig[2],
sizeof(der_sig) - 2, &der_sig_size) != OPTIGA_SUCCESS) {
vcp_println("ERROR check_device_cert_chain, optiga_calc_sign.");
return false;
}
der_sig[1] = der_sig_size;
uint8_t sig[64] = {0};
if (ecdsa_sig_from_der(der_sig, der_sig_size + 2, sig) != 0) {
vcp_println("ERROR check_device_cert_chain, ecdsa_sig_from_der.");
return false;
}
BUFFER_READER chain_reader = {0};
buffer_reader_init(&chain_reader, chain, chain_size);
int cert_count = 0;
while (buffer_remaining(&chain_reader) > 0) {
// Read the next certificate in the chain.
cert_count += 1;
DER_ITEM cert = {0};
if (!der_read_item(&chain_reader, &cert) || cert.id != DER_SEQUENCE) {
vcp_println("ERROR check_device_cert_chain, der_read_item 1, cert %d.",
cert_count);
return false;
}
// Read the tbsCertificate.
DER_ITEM tbs_cert = {0};
if (!der_read_item(&cert.buf, &tbs_cert)) {
vcp_println("ERROR check_device_cert_chain, der_read_item 2, cert %d.",
cert_count);
return false;
}
// Read the Subject Public Key Info.
DER_ITEM pub_key_info = {0};
for (int i = 0; i < 7; ++i) {
if (!der_read_item(&tbs_cert.buf, &pub_key_info)) {
vcp_println("ERROR check_device_cert_chain, der_read_item 3, cert %d.",
cert_count);
return false;
}
}
// Read the public key.
DER_ITEM pub_key = {0};
uint8_t unused_bits = 0;
const uint8_t *pub_key_bytes = NULL;
for (int i = 0; i < 2; ++i) {
if (!der_read_item(&pub_key_info.buf, &pub_key)) {
vcp_println("ERROR check_device_cert_chain, der_read_item 4, cert %d.",
cert_count);
return false;
}
}
if (!buffer_get(&pub_key.buf, &unused_bits) ||
buffer_remaining(&pub_key.buf) != 65 ||
!buffer_ptr(&pub_key.buf, &pub_key_bytes)) {
vcp_println("ERROR check_device_cert_chain, reading public key, cert %d.",
cert_count);
return false;
}
// Verify the previous signature.
if (ecdsa_verify_digest(&nist256p1, pub_key_bytes, sig, digest) != 0) {
vcp_println(
"ERROR check_device_cert_chain, ecdsa_verify_digest, cert %d.",
cert_count);
return false;
}
// Prepare the hash of tbsCertificate for the next signature verification.
sha256_Raw(tbs_cert.buf.data, tbs_cert.buf.size, digest);
// Read the signatureAlgorithm and ensure it matches ECDSA_WITH_SHA256.
DER_ITEM sig_alg = {0};
if (!der_read_item(&cert.buf, &sig_alg) ||
sig_alg.buf.size != sizeof(ECDSA_WITH_SHA256) ||
memcmp(ECDSA_WITH_SHA256, sig_alg.buf.data,
sizeof(ECDSA_WITH_SHA256)) != 0) {
vcp_println(
"ERROR check_device_cert_chain, checking signatureAlgorithm, cert "
"%d.",
cert_count);
return false;
}
// Read the signatureValue.
DER_ITEM sig_val = {0};
if (!der_read_item(&cert.buf, &sig_val) || sig_val.id != DER_BIT_STRING ||
!buffer_get(&sig_val.buf, &unused_bits) || unused_bits != 0) {
vcp_println(
"ERROR check_device_cert_chain, reading signatureValue, cert %d.",
cert_count);
return false;
}
// Extract the signature for the next signature verification.
const uint8_t *sig_bytes = NULL;
if (!buffer_ptr(&sig_val.buf, &sig_bytes) ||
ecdsa_sig_from_der(sig_bytes, buffer_remaining(&sig_val.buf), sig) !=
0) {
vcp_println("ERROR check_device_cert_chain, ecdsa_sig_from_der, cert %d.",
cert_count);
return false;
}
}
// Verify that the last certificate in the chain is valid for one of the known
// root public keys.
for (int i = 0; i < sizeof(ROOT_PUBLIC_KEYS) / sizeof(ROOT_PUBLIC_KEYS[0]);
++i) {
if (ecdsa_verify_digest(&nist256p1, ROOT_PUBLIC_KEYS[i], sig, digest) ==
0) {
return true;
}
}
vcp_println("ERROR check_device_cert_chain, ecdsa_verify_digest root.");
return false;
}

1
core/embed/prodtest/optiga_prodtest.h
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@ -48,5 +48,6 @@ void optiga_lock(void);
optiga_locked_status get_optiga_locked_status(void);
void check_locked(void);
void sec_read(void);
bool check_device_cert_chain(const uint8_t *chain, size_t chain_size);
#endif

1
core/embed/trezorhal/optiga_commands.h
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@ -130,6 +130,7 @@ typedef struct {
#define OPTIGA_MAX_METADATA_SIZE 44
#define OPTIGA_RANDOM_MIN_SIZE 8
#define OPTIGA_RANDOM_MAX_SIZE 256
#define OPTIGA_MAX_CERT_SIZE 1728
#define OPTIGA_ACCESS_CONDITION(ac_id, oid) \
{ (const uint8_t[]){ac_id, oid >> 8, oid & 0xff}, 3 }

10
crypto/buffer.c
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@ -46,6 +46,16 @@ size_t buffer_remaining(BUFFER_READER *buf) {
return buf->size - buf->pos;
}
bool buffer_ptr(BUFFER_READER *buf, const uint8_t **ptr) {
if ((buf->data == NULL) || (buf->pos > buf->size)) {
return false;
}
*ptr = &buf->data[buf->pos];
return true;
}
bool buffer_peek(const BUFFER_READER *buf, uint8_t *byte) {
if ((buf->data == NULL) || (buf->pos >= buf->size)) {
return false;

1
crypto/buffer.h
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@ -46,6 +46,7 @@ typedef struct {
void buffer_reader_init(BUFFER_READER *buf, const uint8_t *data, size_t size);
void buffer_writer_init(BUFFER_WRITER *buf, uint8_t *data, size_t size);
size_t __wur buffer_remaining(BUFFER_READER *buf);
bool __wur buffer_ptr(BUFFER_READER *buf, const uint8_t **ptr);
bool __wur buffer_peek(const BUFFER_READER *buf, uint8_t *byte);
bool __wur buffer_get(BUFFER_READER *buf, uint8_t *byte);
bool __wur buffer_seek(BUFFER_READER *buf, size_t pos);

1
crypto/der.h
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@ -32,6 +32,7 @@
#define DER_SEQUENCE 0x30
#define DER_INTEGER 0x02
#define DER_BIT_STRING 0x03
// Struct representing a DER-encoded ASN.1 data value.
typedef struct {