From b47c07b9cd35a096dcef2efb37a4d660845c03a5 Mon Sep 17 00:00:00 2001
From: Nils Tonnaett <ntonnatt@ccrma.stanford.edu>
Date: Tue, 12 May 2026 23:34:44 -0700
Subject: [PATCH] module-avb: add UTF-8 validation function

---
 .../aecp-aem-cmds-resps/cmd-get-set-name.c    |  1 +
 src/modules/module-avb/strings.c              | 78 +++++++++++++++++++
 src/modules/module-avb/strings.h              | 12 +++
 3 files changed, 91 insertions(+)
 create mode 100644 src/modules/module-avb/strings.c
 create mode 100644 src/modules/module-avb/strings.h

diff --git a/src/modules/module-avb/aecp-aem-cmds-resps/cmd-get-set-name.c b/src/modules/module-avb/aecp-aem-cmds-resps/cmd-get-set-name.c
index f1482996c..b7a5560af 100644
--- a/src/modules/module-avb/aecp-aem-cmds-resps/cmd-get-set-name.c
+++ b/src/modules/module-avb/aecp-aem-cmds-resps/cmd-get-set-name.c
@@ -12,6 +12,7 @@
 #include "../aecp-aem.h"
 #include "../aecp-aem-state.h"
 #include "../aecp-aem-descriptors.h"
+#include "../strings.h"
 
 
 #include "cmd-get-set-name.h"
diff --git a/src/modules/module-avb/strings.c b/src/modules/module-avb/strings.c
new file mode 100644
index 000000000..2f680715d
--- /dev/null
+++ b/src/modules/module-avb/strings.c
@@ -0,0 +1,78 @@
+/* SPDX-FileCopyrightText: Copyright © 2026 Nils Tonnaett
+ * Nils Tonnaett <ntonnatt@ccrma.stanford.edu> */
+/* SPDX-License-Identifier: MIT */
+
+#include "strings.h"
+
+typedef enum {
+  ST_START,
+  ST_A,
+  ST_B,
+  ST_C,
+  ST_D,
+  ST_E,
+  ST_F,
+  ST_G,
+  ST_ERROR,
+} UTF8_STATE;
+
+int validate_utf8(uint8_t *str, size_t len) {
+  UTF8_STATE state = ST_START;
+
+  for (int i = 0; i < len; ++i) {
+    switch (state) {
+    case ST_START:
+      if (str[i] <= 0x7F) {
+        continue;
+      } else if (str[i] >= 0xC2 && str[i] <= 0xDF) {
+        state = ST_A;
+      } else if (str[i] >= 0xE1 && str[i] <= 0xEC) {
+        state = ST_B;
+      } else if (str[i] >= 0xEE && str[i] <= 0xEF) {
+        state = ST_B;
+      } else if (str[i] == 0xE0) {
+        state = ST_C;
+      } else if (str[i] == 0xED) {
+        state = ST_D;
+      } else if (str[i] >= 0xF1 && str[i] <= 0xF3) {
+        state = ST_E;
+      } else if (str[i] == 0xF0) {
+        state = ST_F;
+      } else if (str[i] >= 0xF4) {
+        state = ST_G;
+      } else {
+        state = ST_ERROR;
+      }
+      break;
+    case ST_A:
+      state = (str[i] >= 0x80 && str[i] <= 0xBF) ? ST_START : ST_ERROR;
+      break;
+    case ST_B:
+      state = (str[i] >= 0x80 && str[i] <= 0xBF) ? ST_A : ST_ERROR;
+      break;
+    case ST_C:
+      state = (str[i] >= 0xA0 && str[i] <= 0xBF) ? ST_A : ST_ERROR;
+      break;
+    case ST_D:
+      state = (str[i] >= 0x80 && str[i] <= 0x9F) ? ST_A : ST_ERROR;
+      break;
+    case ST_E:
+      state = (str[i] >= 0x80 && str[i] <= 0xBF) ? ST_B : ST_ERROR;
+      break;
+    case ST_F:
+      state = (str[i] >= 0x90 && str[i] <= 0xBF) ? ST_B : ST_ERROR;
+      break;
+    case ST_G:
+      state = (str[i] >= 0x80 && str[i] <= 0x8F) ? ST_B : ST_ERROR;
+      break;
+    }
+    if (state == ST_ERROR) {
+      return -1;
+    }
+  }
+  if (state != ST_START) {
+    return -1;
+  } else {
+    return 0;
+  }
+}
diff --git a/src/modules/module-avb/strings.h b/src/modules/module-avb/strings.h
new file mode 100644
index 000000000..3cdafc303
--- /dev/null
+++ b/src/modules/module-avb/strings.h
@@ -0,0 +1,12 @@
+/* SPDX-FileCopyrightText: Copyright © 2026 Nils Tonnaett*/
+/* SPDX-License-Identifier: MIT */
+
+#ifndef AVB_STRINGS_H
+#define AVB_STRINGS_H
+
+#include <stddef.h>
+#include <stdint.h>
+
+int validate_utf8(uint8_t *str, size_t len);
+
+#endif /* AVB_STRINGS_H */