feat(core/prodtest): introduce CRC checks for CLI commands

diff --git a/core/SConscript.prodtest b/core/SConscript.prodtest
index c889cd812..0c0973daf 100644
--- a/core/SConscript.prodtest
+++ b/core/SConscript.prodtest
@@ -197,6 +197,7 @@ SOURCE_PRODTEST = [
     'embed/projects/prodtest/cmd/prodtest_ble.c',
     'embed/projects/prodtest/cmd/prodtest_bootloader.c',
     'embed/projects/prodtest/cmd/prodtest_button.c',
+    'embed/projects/prodtest/cmd/prodtest_crc.c',
     'embed/projects/prodtest/cmd/prodtest_display.c',
     'embed/projects/prodtest/cmd/prodtest_prodtest.c',
     'embed/projects/prodtest/cmd/prodtest_backup_ram.c',
diff --git a/core/SConscript.prodtest_emu b/core/SConscript.prodtest_emu
index dca61f1b3..8f9af6ccc 100644
--- a/core/SConscript.prodtest_emu
+++ b/core/SConscript.prodtest_emu
@@ -170,6 +170,7 @@ SOURCE_PRODTEST = [
     'embed/projects/prodtest/cmd/prodtest_ble.c',
     'embed/projects/prodtest/cmd/prodtest_bootloader.c',
     'embed/projects/prodtest/cmd/prodtest_button.c',
+    'embed/projects/prodtest/cmd/prodtest_crc.c',
     'embed/projects/prodtest/cmd/prodtest_display.c',
     'embed/projects/prodtest/cmd/prodtest_prodtest.c',
     'embed/projects/prodtest/cmd/prodtest_backup_ram.c',
diff --git a/core/embed/projects/prodtest/.changelog.d/6038.added b/core/embed/projects/prodtest/.changelog.d/6038.added
new file mode 100644
index 000000000..8ca52db75
--- /dev/null
+++ b/core/embed/projects/prodtest/.changelog.d/6038.added
@@ -0,0 +1 @@
+Added support for CRC checksums in prodtest commands.
diff --git a/core/embed/projects/prodtest/README.md b/core/embed/projects/prodtest/README.md
index fa9e533f2..7abbc8904 100644
--- a/core/embed/projects/prodtest/README.md
+++ b/core/embed/projects/prodtest/README.md
@@ -79,6 +79,28 @@ rgbled-set 0 255 0
 OK
 ```
 
+### CRC Checksum
+
+The CLI supports an optional CRC checksum for commands and responses to ensure data integrity over the communication link.
+
+When CRC is enabled, every command MUST include a CRC-32 checksum at the end of the line, preceded by a space.
+
+Command Format:
+`<command> [<args>] <CRC32>`
+
+The checksum is calculated using the standard CRC-32 algorithm (polynomial `0xEDB88320`, initial value `0xFFFFFFFF`, and final XOR `0xFFFFFFFF`) over the command string excluding the ` <CRC32>` suffix.
+
+The device also appends the checksum to every response line (including `OK`, `ERROR`, `PROGRESS`, and `#` traces).
+
+Response Format:
+`<response> <CRC32>`
+
+Example with CRC enabled:
+```
+ping ABC 70417631
+OK ABC E7193F16
+```
+
 ## List of commands
 
 ### help
@@ -272,6 +294,24 @@ display-text hello_world
 OK
 ```
 
+### crc-enable
+Enables CRC check for CLI commands. Once enabled, the device expects all subsequent commands to include a CRC-32 checksum. The response to `crc-enable` itself already includes the CRC checksum.
+
+Example:
+```
+crc-enable
+OK @C09F27E9
+```
+
+### crc-disable
+Disables CRC check for CLI commands. The command itself must still include the CRC checksum if CRC was previously enabled.
+
+Example:
+```
+crc-disable @939BC008
+OK
+```
+
 ### display-bars
 Draws vertical color bars on the screen according to a specified string of color codes.
 
diff --git a/core/embed/projects/prodtest/cmd/prodtest_crc.c b/core/embed/projects/prodtest/cmd/prodtest_crc.c
new file mode 100644
index 000000000..efa7238c1
--- /dev/null
+++ b/core/embed/projects/prodtest/cmd/prodtest_crc.c
@@ -0,0 +1,54 @@
+/*
+ * This file is part of the Trezor project, https://trezor.io/
+ *
+ * Copyright (c) SatoshiLabs
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <rtl/cli.h>
+
+static void prodtest_crc_enable(cli_t* cli) {
+  if (cli_arg_count(cli) > 0) {
+    cli_error_arg_count(cli);
+    return;
+  }
+
+  cli_enable_crc(cli);
+  cli_ok(cli, "");
+}
+
+static void prodtest_crc_disable(cli_t* cli) {
+  if (cli_arg_count(cli) > 0) {
+    cli_error_arg_count(cli);
+    return;
+  }
+
+  cli_disable_crc(cli);
+  cli_ok(cli, "");
+}
+
+// clang-format off
+
+PRODTEST_CLI_CMD(
+  .name = "crc-enable",
+  .func = prodtest_crc_enable,
+  .info = "Enables CRC check",
+  .args = "");
+
+PRODTEST_CLI_CMD(
+  .name = "crc-disable",
+  .func = prodtest_crc_disable,
+  .info = "Disables CRC check",
+  .args = "");
diff --git a/core/embed/rtl/cli.c b/core/embed/rtl/cli.c
index 84dd994ba..1ba647623 100644
--- a/core/embed/rtl/cli.c
+++ b/core/embed/rtl/cli.c
@@ -11,12 +11,27 @@
 #define ESC_COLOR_GRAY "\e[37m"
 #define ESC_COLOR_RESET "\e[39m"
 
+#define CRC32_INITIAL 0xFFFFFFFF
+#define CRC32_POLYNOMIAL 0xEDB88320
+
+static uint32_t cli_crc32(uint32_t crc, const void* data, size_t size) {
+  const uint8_t* p = (const uint8_t*)data;
+  while (size--) {
+    crc ^= *p++;
+    for (int i = 0; i < 8; i++) {
+      crc = (crc >> 1) ^ (CRC32_POLYNOMIAL & (-(crc & 1)));
+    }
+  }
+  return crc;
+}
+
 bool cli_init(cli_t* cli, cli_read_cb_t read, cli_write_cb_t write,
               void* callback_context) {
   memset(cli, 0, sizeof(cli_t));
   cli->read = read;
   cli->write = write;
   cli->callback_context = callback_context;
+  cli->response_crc = CRC32_INITIAL;
 
   return true;
 }
@@ -29,8 +44,19 @@ void cli_set_commands(cli_t* cli, const cli_command_t* cmd_array,
 
 static void cli_vprintf(cli_t* cli, const char* format, va_list args) {
   char buffer[CLI_LINE_BUFFER_SIZE];
-  vsnprintf_(buffer, sizeof(buffer), format, args);
-  cli->write(cli->callback_context, buffer, strlen(buffer));
+  int len = vsnprintf_(buffer, sizeof(buffer), format, args);
+  if (len < 0) return;
+
+  size_t write_len = (size_t)len;
+  if (write_len >= sizeof(buffer)) {
+    write_len = sizeof(buffer) - 1;
+  }
+
+  if (cli->crc_req) {
+    cli->response_crc = cli_crc32(cli->response_crc, buffer, write_len);
+  }
+
+  cli->write(cli->callback_context, buffer, write_len);
 }
 
 static void cli_printf(cli_t* cli, const char* format, ...) {
@@ -40,6 +66,20 @@ static void cli_printf(cli_t* cli, const char* format, ...) {
   va_end(args);
 }
 
+static void cli_printf_newline(cli_t* cli) {
+  if (cli->crc_req) {
+    uint32_t final_crc = ~cli->response_crc;
+    cli->crc_req = false;
+    cli_printf(cli, " %08X", final_crc);
+    cli->crc_req = true;
+  }
+  bool old_crc_req = cli->crc_req;
+  cli->crc_req = false;
+  cli_printf(cli, "\r\n");
+  cli->crc_req = old_crc_req;
+  cli->response_crc = CRC32_INITIAL;
+}
+
 void cli_vtrace(cli_t* cli, const char* format, va_list args) {
   if (cli->interactive) {
     cli_printf(cli, ESC_COLOR_GRAY);
@@ -57,7 +97,7 @@ void cli_vtrace(cli_t* cli, const char* format, va_list args) {
     cli_vprintf(cli, format, args);
   }
 
-  cli_printf(cli, "\r\n");
+  cli_printf_newline(cli);
 }
 
 void cli_trace(cli_t* cli, const char* format, ...) {
@@ -87,7 +127,7 @@ void cli_ok(cli_t* cli, const char* format, ...) {
     cli_vprintf(cli, format, args);
     va_end(args);
   }
-  cli_printf(cli, "\r\n");
+  cli_printf_newline(cli);
 
   cli->final_status = true;
 }
@@ -110,7 +150,7 @@ void cli_ok_hexdata(cli_t* cli, const void* data, size_t size) {
       cli_printf(cli, "%02X", ((uint8_t*)data)[i]);
     }
   }
-  cli_printf(cli, "\r\n");
+  cli_printf_newline(cli);
 
   cli->final_status = true;
 }
@@ -136,7 +176,7 @@ static void cli_verror(cli_t* cli, const char* code, const char* format,
     cli_printf(cli, "\"");
   }
 
-  cli_printf(cli, "\r\n");
+  cli_printf_newline(cli);
 
   cli->final_status = true;
 }
@@ -180,7 +220,7 @@ void cli_progress(cli_t* cli, const char* format, ...) {
     cli_vprintf(cli, format, args);
   }
 
-  cli_printf(cli, "\r\n");
+  cli_printf_newline(cli);
 
   va_end(args);
 }
@@ -189,6 +229,10 @@ void cli_abort(cli_t* cli) { cli->aborted = true; }
 
 bool cli_aborted(cli_t* cli) { return cli->aborted; }
 
+void cli_enable_crc(cli_t* cli) { cli->crc_req = true; }
+
+void cli_disable_crc(cli_t* cli) { cli->crc_req = false; }
+
 // Finds a command record by name
 //
 // Returns NULL if the command is not found
@@ -496,6 +540,7 @@ static void cli_clear_line(cli_t* cli) {
   cli->line_cursor = 0;
   cli->hist_idx = 0;
   cli->hist_prefix = 0;
+  cli->response_crc = CRC32_INITIAL;
   memset(cli->line_buffer, 0, sizeof(cli->line_buffer));
 }
 
@@ -539,6 +584,7 @@ void cli_process_command(cli_t* cli, const cli_command_t* cmd) {
   cli->current_cmd = cmd;
   cli->final_status = false;
   cli->aborted = false;
+  cli->response_crc = CRC32_INITIAL;
 
   // Call the command handler
   cmd->func(cli);
@@ -577,6 +623,37 @@ const cli_command_t* cli_process_io(cli_t* cli) {
     goto cleanup;
   }
 
+  // Handle optional CRC check
+  if (cli->crc_req) {
+    size_t len = strlen(cli->line_buffer);
+    if (len >= 9) {
+      char* space = &cli->line_buffer[len - 9];
+      if (*space == ' ') {
+        uint32_t received_crc;
+        if (cstr_parse_uint32(space + 1, 16, &received_crc)) {
+          uint32_t calculated_crc =
+              ~cli_crc32(CRC32_INITIAL, cli->line_buffer, len - 9);
+          if (calculated_crc == received_crc) {
+            *space = '\0';
+          } else {
+            cli_error(cli, CLI_ERROR_INVALID_CRC, "Expected %08X, got %08X",
+                      calculated_crc, received_crc);
+            goto cleanup;
+          }
+        } else {
+          cli_error(cli, CLI_ERROR_INVALID_CRC, "Invalid CRC format");
+          goto cleanup;
+        }
+      } else {
+        cli_error(cli, CLI_ERROR_INVALID_CRC, "CRC suffix missing");
+        goto cleanup;
+      }
+    } else {
+      cli_error(cli, CLI_ERROR_INVALID_CRC, "Line too short for CRC");
+      goto cleanup;
+    }
+  }
+
   cli_history_add(cli, cli->line_buffer);
 
   // Split command line into arguments
diff --git a/core/embed/rtl/inc/rtl/cli.h b/core/embed/rtl/inc/rtl/cli.h
index b8d6e400f..87bc96666 100644
--- a/core/embed/rtl/inc/rtl/cli.h
+++ b/core/embed/rtl/inc/rtl/cli.h
@@ -140,6 +140,11 @@ struct cli {
    * finish as soon as possible with an CLI_ERROR_ABORT
    */
   volatile bool aborted;
+
+  /** CRC of the current response line */
+  uint32_t response_crc;
+  /** CRC was requested for the current command */
+  bool crc_req;
 };
 
 /** Initializes the command line structure */
@@ -248,3 +253,17 @@ void cli_abort(cli_t* cli);
 
 /** Returns true if `cli_abort()` was called */
 bool cli_aborted(cli_t* cli);
+
+/**
+ * Enables CRC check for the CLI.
+ *
+ * When enabled, every line received from the host must be suffixed with
+ * " <CRC32>" and every line sent to the host will be suffixed with
+ * " <CRC32>".
+ */
+void cli_enable_crc(cli_t* cli);
+
+/**
+ * Disables CRC check for the CLI.
+ */
+void cli_disable_crc(cli_t* cli);