[add] Fetch seed from env at startup then stick with it

CHANGELOG.md

@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [0.5.0] - 2023-??-??
+
+### Added
+- Seed is fetched from the environment during the Speculos launch and stored internally for further
+  use. This avoids several Speculos instances from messing up with each other's seeds.
+
 ## [0.4.0] - 2023-12-04
 
 ### Fixed

src/CMakeLists.txt

@@ -56,6 +56,7 @@ add_library(emu
         emulate_blue_2.2.5.c
         emulate_lnsp_1.0.c
         emulate_unified_sdk.c
+        seed.c
         svc.c)
 
 add_dependencies(emu openssl)

src/bolos/os_bip32.c

@@ -2,31 +2,23 @@
 #include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <unistd.h>
 
 #include "os_bip32.h"
 
 #include "bolos/exception.h"
 #include "cx.h"
 #include "cx_utils.h"
 #include "emulate.h"
+#include "seed.h"
 
 #define BIP32_HARDEN_MASK      0x80000000
 #define BIP32_SECP_SEED_LENGTH 12
-#define MAX_SEED_SIZE          64
 
 #define cx_ecfp_generate_pair     sys_cx_ecfp_generate_pair
 #define cx_ecfp_init_private_key  sys_cx_ecfp_init_private_key
 #define cx_ecdsa_init_private_key cx_ecfp_init_private_key
 
-/* glory promote mansion idle axis finger extra february uncover one trip
- * resource lawn turtle enact monster seven myth punch hobby comfort wild raise
- * skin */
-static uint8_t default_seed[MAX_SEED_SIZE] =
-    "\xb1\x19\x97\xfa\xff\x42\x0a\x33\x1b\xb4\xa4\xff\xdc\x8b\xdc\x8b\xa7\xc0"
-    "\x17\x32\xa9\x9a\x30\xd8\x3d\xbb\xeb\xd4\x69\x66\x6c\x84\xb4\x7d\x09\xd3"
-    "\xf5\xf4\x72\xb3\xb9\x38\x4a\xc6\x34\xbe\xba\x2a\x44\x0b\xa3\x6e\xc7\x66"
-    "\x11\x44\x13\x2f\x35\xe2\x06\x87\x35\x64";
-
 static uint8_t const BIP32_SECP_SEED[] = { 'B', 'i', 't', 'c', 'o', 'i',
                                            'n', ' ', 's', 'e', 'e', 'd' };
 
@@ -166,65 +158,6 @@ static void expand_seed(cx_curve_t curve, const uint8_t *sk, size_t sk_length,
   }
 }
 
-int unhex(uint8_t *dst, size_t dst_size, const char *src, size_t src_size)
-{
-  unsigned int i;
-  uint8_t acc;
-  int8_t c;
-
-  acc = 0;
-  for (i = 0; i < src_size && (i >> 1) < dst_size; i++) {
-    c = src[i];
-    switch (c) {
-    case '0' ... '9':
-      acc = (acc << 4) + c - '0';
-      break;
-    case 'a' ... 'f':
-      acc = (acc << 4) + c - 'a' + 10;
-      break;
-    case 'A' ... 'F':
-      acc = (acc << 4) + c - 'A' + 10;
-      break;
-    default:
-      return -1;
-    }
-
-    if (i % 2 != 0) {
-      dst[i >> 1] = acc;
-      acc = 0;
-    }
-  }
-
-  if (i != src_size) {
-    return -1;
-  }
-
-  return src_size / 2;
-}
-
-size_t get_seed_from_env(const char *name, uint8_t *seed, size_t max_size)
-{
-  ssize_t seed_size;
-  char *p;
-
-  p = getenv(name);
-  if (p != NULL) {
-    seed_size = unhex(seed, max_size, p, strlen(p));
-    if (seed_size < 0) {
-      warnx("invalid seed passed through %s environment variable", name);
-      p = NULL;
-    }
-  }
-
-  if (p == NULL) {
-    warnx("using default seed");
-    memcpy(seed, default_seed, sizeof(default_seed));
-    seed_size = sizeof(default_seed);
-  }
-
-  return seed_size;
-}
-
 static int hdw_bip32_ed25519(extended_private_key *key, const uint32_t *path,
                              size_t length, uint8_t *private_key,
                              uint8_t *chain)
@@ -512,7 +445,7 @@ unsigned long sys_os_perso_derive_node_with_seed_key(
     sk_length = seed_key_length;
   }
 
-  seed_size = get_seed_from_env("SPECULOS_SEED", seed, sizeof(seed));
+  seed_size = get_seed(seed, sizeof(seed));
 
   if (mode == HDW_SLIP21) {
     ret = hdw_slip21(sk, sk_length, seed, seed_size, (const uint8_t *)path,

src/bolos/os_bip32.h

@@ -16,5 +16,3 @@ typedef struct {
 
 void expand_seed_bip32(const cx_curve_domain_t *domain, uint8_t *seed,
                        unsigned int seed_length, extended_private_key *key);
-int unhex(uint8_t *dst, size_t dst_size, const char *src, size_t src_size);
-size_t get_seed_from_env(const char *name, uint8_t *seed, size_t max_size);

src/bolos/os_eip2333.c

@@ -7,7 +7,7 @@
 #include "cx_utils.h"
 #include "emulate.h"
 #include "exception.h"
-#include "os_bip32.h"
+#include "seed.h"
 
 #define MAX_SEED_SIZE          64
 #define CX_SHA256_SIZE         32
@@ -142,7 +142,7 @@ unsigned long sys_os_perso_derive_eip2333(cx_curve_t curve,
     THROW(EXCEPTION);
   }
 
-  seed_size = get_seed_from_env("SPECULOS_SEED", seed, sizeof(seed));
+  seed_size = get_seed(seed, sizeof(seed));
 
   cx_derive_master_sk(seed, seed_size, sk);
   if (privateKey != NULL) {

src/launcher.c

@@ -15,6 +15,7 @@
 #include "emulate.h"
 #include "fonts.h"
 #include "svc.h"
+#include "seed.h"
 
 #define LOAD_ADDR     ((void *)0x40000000)
 #define LINK_RAM_ADDR (0xda7a0000)
@@ -722,6 +723,7 @@ int main(int argc, char *argv[])
   extra_rampage_size = 0;
 
   fprintf(stderr, "[*] speculos launcher revision: " GIT_REVISION "\n");
+  init_seed();
 
   while ((opt = getopt(argc, argv, "c:tr:s:m:k:a:f:")) != -1) {
     switch (opt) {

src/seed.c

@@ -0,0 +1,94 @@
+#include <err.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "seed.h"
+
+
+/* glory promote mansion idle axis finger extra february uncover one trip
+ * resource lawn turtle enact monster seven myth punch hobby comfort wild raise
+ * skin */
+static uint8_t default_seed[MAX_SEED_SIZE] =
+    "\xb1\x19\x97\xfa\xff\x42\x0a\x33\x1b\xb4\xa4\xff\xdc\x8b\xdc\x8b\xa7\xc0"
+    "\x17\x32\xa9\x9a\x30\xd8\x3d\xbb\xeb\xd4\x69\x66\x6c\x84\xb4\x7d\x09\xd3"
+    "\xf5\xf4\x72\xb3\xb9\x38\x4a\xc6\x34\xbe\xba\x2a\x44\x0b\xa3\x6e\xc7\x66"
+    "\x11\x44\x13\x2f\x35\xe2\x06\x87\x35\x64";
+
+const char *SEED_ENV_NAME = "SPECULOS_SEED";
+typedef struct {
+    size_t size;
+    uint8_t seed[MAX_SEED_SIZE];
+} seed_t;
+static seed_t actual_seed = {0};
+
+
+static int unhex(uint8_t *dst, size_t dst_size, const char *src, size_t src_size)
+{
+  unsigned int i;
+  uint8_t acc;
+  int8_t c;
+
+  acc = 0;
+  for (i = 0; i < src_size && (i >> 1) < dst_size; i++) {
+    c = src[i];
+    switch (c) {
+    case '0' ... '9':
+      acc = (acc << 4) + c - '0';
+      break;
+    case 'a' ... 'f':
+      acc = (acc << 4) + c - 'a' + 10;
+      break;
+    case 'A' ... 'F':
+      acc = (acc << 4) + c - 'A' + 10;
+      break;
+    default:
+      return -1;
+    }
+
+    if (i % 2 != 0) {
+      dst[i >> 1] = acc;
+      acc = 0;
+    }
+  }
+
+  if (i != src_size) {
+    return -1;
+  }
+
+  return src_size / 2;
+}
+
+
+void init_seed()
+{
+  ssize_t size;
+  char *p;
+
+  p = getenv(SEED_ENV_NAME);
+  if (p != NULL) {
+      size = unhex(actual_seed.seed, sizeof(actual_seed.seed), p, strlen(p));
+    if (size < 0) {
+      warnx("invalid seed passed through %s environment variable", SEED_ENV_NAME);
+      p = NULL;
+    } else {
+        fprintf(stderr, "[*] Seed initialized from environment: '%s'\n", p);
+    }
+  }
+
+  if (p == NULL) {
+    warnx("using default seed");
+    memcpy(actual_seed.seed, default_seed, sizeof(default_seed));
+    size = sizeof(default_seed);
+    fprintf(stderr, "[*] Seed initialized from default value: '%s'\n", default_seed);
+  }
+  actual_seed.size = size;
+}
+
+
+size_t get_seed(uint8_t *seed, size_t max_size)
+{
+  memcpy(seed, actual_seed.seed, max_size);
+  return (actual_seed.size < max_size) ? actual_seed.size : max_size;
+}

src/seed.h

@@ -0,0 +1,9 @@
+#pragma once
+
+#include <stdint.h>
+
+#define MAX_SEED_SIZE 64
+
+
+size_t get_seed(uint8_t *seed, size_t max_size);
+void init_seed();