webadmin/pico-keys-sdk
1
0
Fork 0
mirror of https://github.com/polhenarejos/pico-keys-sdk synced 2026-05-25 15:45:11 +02:00
Code Issues Packages Projects Releases Wiki Activity

Added session key negotiation.

Browse Source 
Signed-off-by: Pol Henarejos <pol.henarejos@cttc.es>
This commit is contained in:
Pol Henarejos
2026-04-21 20:40:19 +02:00
parent 9ab9d96af5
commit a906628318
3 changed files with 95 additions and 14 deletions
Download Patch File Download Diff File Expand all files Collapse all files

76
src/usb/lwip/rest.c
View File

@@ -21,17 +21,29 @@
#include <strings.h>
#include "random.h"
#include "crypto_utils.h"
#include "serial.h"
#include "mbedtls/ecdh.h"
#include "mbedtls/ecp.h"
#include "mbedtls/hkdf.h"
#include "mbedtls/platform_util.h"
#define REST_MAX_SESSIONS 4
static rest_session_t rest_sessions[REST_MAX_SESSIONS] = {0};
static int x25519_hkdf_derive_key32(const uint8_t sk[32], const uint8_t pk[32], const uint8_t *salt, size_t salt_len, const uint8_t *info, size_t info_len, uint8_t out_key[32]);
rest_session_t *rest_session_create(const rest_session_role_t role, rest_session_status_t status) {
rest_session_t *rest_session_create(const rest_session_role_t role, rest_session_status_t status, const uint8_t public_key[32]) {
for (int i = 0; i < REST_MAX_SESSIONS; i++) {
if (rest_sessions[i].status == REST_SESSION_UNKNOWN || rest_sessions[i].status == REST_SESSION_EXPIRED || rest_sessions[i].status == REST_SESSION_TERMINATED) {
memset(&rest_sessions[i], 0, sizeof(rest_session_t));
rest_sessions[i].status = status;
rest_sessions[i].role = role;
if (public_key != NULL) {
memcpy(rest_sessions[i].public_key, public_key, sizeof(rest_sessions[i].public_key));
} else {
memset(rest_sessions[i].public_key, 0, sizeof(rest_sessions[i].public_key));
}
random_fill_buffer(rest_sessions[i].id, sizeof(rest_sessions[i].id));
rest_sessions[i].created_at = board_millis();
rest_sessions[i].last_activity_timestamp = rest_sessions[i].created_at;
@@ -268,3 +280,65 @@ __attribute__((weak)) const rest_route_t *rest_get_routes(size_t *count) {
}
return NULL;
}
static int x25519_hkdf_derive_key32(const uint8_t sk[32], const uint8_t pk[32], const uint8_t *salt, size_t salt_len, const uint8_t *info, size_t info_len, uint8_t out_key[32]) {
int ret = -1;
size_t shared_len = 0;
uint8_t shared[32] = {0};
mbedtls_ecdh_context ecdh;
mbedtls_ecp_keypair ours, theirs;
const mbedtls_md_info_t *md = mbedtls_md_info_from_type(MBEDTLS_MD_SHA256);
mbedtls_ecdh_init(&ecdh);
mbedtls_ecp_keypair_init(&ours);
mbedtls_ecp_keypair_init(&theirs);
if (md == NULL) {
ret = MBEDTLS_ERR_MD_BAD_INPUT_DATA;
goto cleanup;
}
MBEDTLS_MPI_CHK(mbedtls_ecp_group_load(&ours.grp, MBEDTLS_ECP_DP_CURVE25519));
MBEDTLS_MPI_CHK(mbedtls_ecp_group_load(&theirs.grp, MBEDTLS_ECP_DP_CURVE25519));
MBEDTLS_MPI_CHK(mbedtls_ecp_read_key(MBEDTLS_ECP_DP_CURVE25519, &ours, sk, 32));
// Carrega pública remota (32 bytes)
MBEDTLS_MPI_CHK(mbedtls_ecp_point_read_binary(&theirs.grp, &theirs.Q, pk, 32));
MBEDTLS_MPI_CHK(mbedtls_ecdh_setup(&ecdh, MBEDTLS_ECP_DP_CURVE25519));
MBEDTLS_MPI_CHK(mbedtls_ecdh_get_params(&ecdh, &ours, MBEDTLS_ECDH_OURS));
MBEDTLS_MPI_CHK(mbedtls_ecdh_get_params(&ecdh, &theirs, MBEDTLS_ECDH_THEIRS));
MBEDTLS_MPI_CHK(mbedtls_ecdh_calc_secret(&ecdh, &shared_len, shared, sizeof(shared), random_fill_iterator, NULL));
if (shared_len != 32) {
ret = MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
goto cleanup;
}
ret = mbedtls_hkdf(md, salt, salt_len, shared, shared_len, info, info_len, out_key, 32);
cleanup:
mbedtls_platform_zeroize(shared, sizeof(shared));
mbedtls_ecdh_free(&ecdh);
mbedtls_ecp_keypair_free(&ours);
mbedtls_ecp_keypair_free(&theirs);
return ret;
}
int rest_session_derive_key(const rest_session_t *session, uint8_t derived_key[32]) {
uint8_t kver[32], sk[32];
const mbedtls_md_info_t *md_info = mbedtls_md_info_from_type(MBEDTLS_MD_SHA256);
derive_kver(session->id, sizeof(session->id), kver);
mbedtls_hkdf(md_info, pico_serial_hash, sizeof(pico_serial_hash), kver, 32, (const uint8_t *)"REST/SESSION", 12, derived_key, 32);
mbedtls_platform_zeroize(kver, sizeof(kver));
int ret = x25519_hkdf_derive_key32(sk, session->public_key, session->id, sizeof(session->id), (const uint8_t *)"REST/SESSION/DERIVE", 20, derived_key);
mbedtls_platform_zeroize(sk, sizeof(sk));
if (ret != 0) {
return -1;
}
return PICOKEYS_OK;
}

4
src/usb/lwip/rest.h
View File

@@ -102,6 +102,7 @@ typedef enum {
} rest_session_status_t;
typedef struct {
uint8_t public_key[32];
uint8_t id[16];
uint8_t id_str[25];
time_t last_activity_timestamp;
@@ -120,7 +121,7 @@ bool rest_content_type_is_json(const char *content_type);
const rest_route_t *rest_get_routes(size_t *count);
extern rest_session_t *rest_session_create(const rest_session_role_t role, rest_session_status_t status);
extern rest_session_t *rest_session_create(const rest_session_role_t role, rest_session_status_t status, const uint8_t public_key[32]);
extern rest_session_t *rest_session_get(const uint8_t *id, size_t id_len);
extern rest_session_t *rest_session_get_by_id_str(const char *id_str);
extern int rest_session_terminate(const uint8_t *id, size_t id_len);
@@ -128,6 +129,7 @@ extern int rest_session_update_activity(const uint8_t *id, size_t id_len);
extern int rest_session_set_status(const uint8_t *id, size_t id_len, rest_session_status_t status);
extern int rest_session_set_role(const uint8_t *id, size_t id_len, rest_session_role_t role);
extern int rest_session_cleanup_expired(time_t expiration_time);
extern int rest_session_derive_key(const rest_session_t *session, uint8_t derived_key[32]);
#ifdef DEBUG_APDU
extern void rest_debug_dump_payload(const char *tag, const char *buffer, size_t len);

29
src/usb/lwip/rest_server.c
View File

@@ -597,13 +597,11 @@ static int parse_request(rest_conn_t *conn, rest_request_t *request) {
return 1;
}
static int rest_session_derive_key(const uint8_t *session_id, size_t session_id_len, uint8_t derived_key[32]) {
uint8_t kver[32];
const mbedtls_md_info_t *md_info = mbedtls_md_info_from_type(MBEDTLS_MD_SHA256);
derive_kver(session_id, session_id_len, kver);
mbedtls_hkdf(md_info, pico_serial_hash, sizeof(pico_serial_hash), kver, 32, (const uint8_t *)"REST/SESSION", 12, derived_key, 32);
mbedtls_platform_zeroize(kver, sizeof(kver));
return PICOKEYS_OK;
static uint32_t rest_request_get_seq(const rest_request_t *request) {
if (request == NULL || request->headers[REST_HEADER_X_SEQ] == NULL) {
return 0;
}
return (uint32_t)strtoul(request->headers[REST_HEADER_X_SEQ], NULL, 10);
}
static int rest_verify_request_signature(const rest_request_t *request, const rest_session_t *session) {
@@ -625,25 +623,28 @@ static int rest_verify_request_signature(const rest_request_t *request, const re
const char *body_empty = "{}";
const char *body = request->body_len > 0 ? request->body : body_empty;
const char *method_str = rest_method_to_string(request->method);
char seq[16];
size_t body_len = request->body_len > 0 ? request->body_len : strlen((const char *)body_empty);
snprintf(seq, sizeof(seq), "%s", request->headers[REST_HEADER_X_SEQ] ? request->headers[REST_HEADER_X_SEQ] : "0");
uint8_t derived_key[32];
if (rest_session_derive_key(session->id, sizeof(session->id), derived_key) != 0) {
if (rest_session_derive_key(session, derived_key) != 0) {
mbedtls_md_free(&ctx);
return PICOKEYS_EXEC_ERROR;
}
uint32_t seq = htonl(rest_request_get_seq(request));
if (mbedtls_md_hmac_starts(&ctx, (const unsigned char *)derived_key, sizeof(derived_key)) != 0 ||
mbedtls_md_hmac_starts(&ctx, (const unsigned char *)session->id, sizeof(session->id)) != 0 ||
mbedtls_md_hmac_update(&ctx, (const unsigned char *)method_str, strlen(method_str)) != 0 ||
mbedtls_md_hmac_update(&ctx, (const unsigned char *)request->path, strlen(request->path)) != 0 ||
mbedtls_md_hmac_update(&ctx, (const unsigned char *)seq, strlen(seq)) != 0 ||
mbedtls_md_hmac_update(&ctx, (const unsigned char *)body, body_len) != 0) {
mbedtls_md_hmac_update(&ctx, (const unsigned char *)&seq, sizeof(uint32_t)) != 0 ||
mbedtls_md_hmac_update(&ctx, (const unsigned char *)body, body_len) != 0)
{
mbedtls_platform_zeroize(derived_key, sizeof(derived_key));
mbedtls_md_free(&ctx);
return PICOKEYS_EXEC_ERROR;
}
mbedtls_platform_zeroize(derived_key, sizeof(derived_key));
if (mbedtls_md_hmac_finish(&ctx, hmac) != 0) {
mbedtls_platform_zeroize(derived_key, sizeof(derived_key));
mbedtls_md_free(&ctx);
return PICOKEYS_EXEC_ERROR;
}
@@ -720,6 +721,10 @@ void rest_handle_request(rest_conn_t *conn) {
send_json_error(conn, 401, "session_expired");
return;
}
if (rest_request_get_seq(request) < session->last_seq) {
send_json_error(conn, 401, "invalid_seq");
return;
}
if (rest_verify_request_signature(request, session) != PICOKEYS_OK) {
send_json_error(conn, 401, "invalid_signature");
return;