fix(esp_rom): Patch ets_ecdsa_verify() to include signature bounds check

components/esp_rom/CMakeLists.txt

@@ -59,6 +59,10 @@ if(CONFIG_ESP_ROM_HAS_CACHE_WRITEBACK_BUG)
     list(APPEND sources "patches/esp_rom_cache_writeback_esp32s3.S")
 endif()
 
+if(CONFIG_ESP_ROM_ECDSA_VERIFY_PATCH)
+    list(APPEND sources "patches/esp_rom_ecdsa.c")
+endif()
+
 idf_component_register(SRCS ${sources}
                        INCLUDE_DIRS ${include_dirs}
                        PRIV_REQUIRES ${private_required_comp}

components/esp_rom/esp32h2/Kconfig.soc_caps.in

@@ -78,3 +78,7 @@ config ESP_ROM_HAS_SW_FLOAT
 config ESP_ROM_SUPPORT_SECURE_BOOT_FAST_WAKEUP
     bool
     default y
+
+config ESP_ROM_ECDSA_VERIFY_PATCH
+    bool
+    default y

components/esp_rom/esp32h2/esp_rom_caps.h

@@ -25,3 +25,4 @@
 #define ESP_ROM_RAM_APP_NEEDS_MMU_INIT      (1) // ROM doesn't init cache MMU when it's a RAM APP, needs MMU hal to init
 #define ESP_ROM_HAS_SW_FLOAT                (1) // ROM has libgcc software floating point emulation functions
 #define ESP_ROM_SUPPORT_SECURE_BOOT_FAST_WAKEUP (1) // ROM supports the secure boot fast wakeup feature
+#define ESP_ROM_ECDSA_VERIFY_PATCH (1) // ROM ets_ecdsa_verify API requires a software patch

components/esp_rom/esp32h2/ld/esp32h2.rom.ld

@@ -361,7 +361,7 @@ ets_efuse_secure_boot_fast_wake_enabled = 0x40000830;
 /* Functions */
 ets_emsa_pss_verify = 0x40000834;
 ets_rsa_pss_verify = 0x40000838;
-ets_ecdsa_verify = 0x4000083c;
+_rom_ets_ecdsa_verify = 0x4000083c;
 ets_secure_boot_verify_bootloader_with_keys = 0x40000840;
 ets_secure_boot_verify_signature = 0x40000844;
 ets_secure_boot_read_key_digests = 0x40000848;

components/esp_rom/patches/esp_rom_ecdsa.c

@@ -0,0 +1,128 @@
+/*
+ * SPDX-FileCopyrightText: 2026 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <stdint.h>
+#include <stdbool.h>
+#include <string.h>
+
+#include "esp_rom_caps.h"
+#if ESP_ROM_ECDSA_VERIFY_PATCH
+#include "soc/soc_caps.h"
+#include "esp_fault.h"
+#include "rom/ecdsa.h"
+
+#define VALID_MAGIC_OK   0x6A6A6A6AU
+#define VALID_MAGIC_FAIL 0x95959595U
+
+static const uint32_t ecdsa_n_p192[6] = {
+    0xb4d22831U, 0x146bc9b1U, 0x99def836U, 0xffffffffU, 0xffffffffU, 0xffffffffU,
+};
+
+static const uint32_t ecdsa_n_p256[8] = {
+    0xfc632551U, 0xf3b9cac2U, 0xa7179e84U, 0xbce6faadU, 0xffffffffU, 0xffffffffU, 0x00000000U, 0xffffffffU,
+};
+
+#if SOC_ECDSA_SUPPORT_CURVE_P384
+static const uint32_t ecdsa_n_p384[12] = {
+    0xccc52973U, 0xecec196aU, 0x48b0a77aU, 0x581a0db2U, 0xf4372ddfU, 0xc7634d81U,
+    0xffffffffU, 0xffffffffU, 0xffffffffU, 0xffffffffU, 0xffffffffU, 0xffffffffU,
+};
+#endif
+
+static uint32_t ecdsa_mpi_isZero(const uint32_t *mpi, int num_words)
+{
+    uint32_t bits = 0;
+    for (int i = 0; i < num_words; ++i) {
+        bits |= mpi[i];
+    }
+    return (bits == 0);
+}
+
+static int ecdsa_mpi_cmp_unsafe(const uint32_t *left, const uint32_t *right, int num_words)
+{
+    for (int i = num_words - 1; i >= 0; --i) {
+        if (left[i] > right[i]) {
+            return 1;
+        } else if (left[i] < right[i]) {
+            return -1;
+        }
+    }
+    return 0;
+}
+
+static bool ecdsa_scalars_in_range(const uint32_t *r, const uint32_t *s, const uint32_t *n, int num_words, uint32_t *result)
+{
+    volatile uint32_t verdict = VALID_MAGIC_FAIL;
+    if (ecdsa_mpi_isZero(r, num_words) == 0 && ecdsa_mpi_cmp_unsafe(n, r, num_words) == 1 && ecdsa_mpi_isZero(s, num_words) == 0
+        && ecdsa_mpi_cmp_unsafe(n, s, num_words) == 1) {
+        verdict = VALID_MAGIC_OK;
+    }
+    if (verdict != VALID_MAGIC_OK) {
+        return false;
+    }
+    ESP_FAULT_ASSERT(verdict == VALID_MAGIC_OK);
+
+    *result = VALID_MAGIC_OK;
+    return true;
+}
+
+extern int _rom_ets_ecdsa_verify(const uint8_t *key, const uint8_t *sig,
+                                 ECDSA_CURVE curve_id, const uint8_t *image_digest,
+                                 uint8_t *verified_digest);
+
+int ets_ecdsa_verify(const uint8_t *key, const uint8_t *sig,
+                     ECDSA_CURVE curve_id, const uint8_t *image_digest,
+                     uint8_t *verified_digest)
+{
+    int words;
+    int bytes;
+    const uint32_t *n;
+
+    if (curve_id == ECDSA_CURVE_P256) {
+        words = 8;
+        bytes = 32;
+        n = ecdsa_n_p256;
+    }
+#if SOC_ECDSA_SUPPORT_CURVE_P384
+    else if (curve_id == ECDSA_CURVE_P384) {
+        words = 12;
+        bytes = 48;
+        n = ecdsa_n_p384;
+    }
+#endif
+    else {
+        // curve_id == ECDSA_CURVE_P192
+        words = 6;
+        bytes = 24;
+        n = ecdsa_n_p192;
+    }
+
+    uint32_t r[12] = { 0 };
+    uint32_t s[12] = { 0 };
+    memcpy(r, &sig[0], bytes);
+    memcpy(s, &sig[bytes], bytes);
+
+    uint32_t ret_status = VALID_MAGIC_FAIL;
+    bool ok = ecdsa_scalars_in_range(r, s, n, words, &ret_status);
+    if (!ok || ret_status != VALID_MAGIC_OK) {
+        return 0;
+    }
+
+    ESP_FAULT_ASSERT(ok && ret_status == VALID_MAGIC_OK);
+
+    int ret = _rom_ets_ecdsa_verify(key, sig, curve_id, image_digest, verified_digest);
+
+    if (ret == 1) {
+        ESP_FAULT_ASSERT(ret_status == VALID_MAGIC_OK);
+        int sig_diff = (memcmp(r, &sig[0], bytes) | memcmp(s, &sig[bytes], bytes));
+        ESP_FAULT_ASSERT(sig_diff == 0);
+        ESP_FAULT_ASSERT(ret == 1);
+        return ret;
+    }
+
+    return 0;
+}
+#endif /* ESP_ROM_ECDSA_VERIFY_PATCH */