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docs(ssl): Update TLS/SSL certificate fingerprint instructions #177

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docs(ssl): Update TLS/SSL certificate fingerprint instructions #177

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docs(ssl): Update TLS/SSL certificate fingerprint instructions
tyeth Jan 16, 2026
8e0bff5
docs(ssl): improve comment format for fingerprint updates
tyeth Jan 21, 2026
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9 changes: 6 additions & 3 deletions src/AdafruitIO_Definitions.h
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Original file line number Diff line number Diff line change
Expand Up @@ -115,9 +115,12 @@ class AdafruitIOGroupCallback {
#define AIO_ERROR_TOPIC "/errors" ///< Adafruit IO Error MQTT Topic
#define AIO_THROTTLE_TOPIC "/throttle" ///< Adafruit IO Throttle MQTT Topic

// latest fingerprint can be generated with
// echo | openssl s_client -connect io.adafruit.com:443 | openssl x509
// -fingerprint -noout
/* NB: io.adafruit.com TLS/SSL certificate changes every 6months, and pinning
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@brentru brentru Jan 21, 2026

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NB -> NOTE:

certificates is no longer recommended. Migrate to a larger MCU like ESP32
which can accomodate root certificates and verify chains of trust. */
/* For older devices like ESP8266 you can generate the latest fingerprint with:
echo | openssl s_client -connect io.adafruit.com:443 | openssl x509 -fingerprint -noout
*/
#define AIO_SSL_FINGERPRINT \
"47 D2 CB 14 DF 38 97 59 C6 65 1A 1F 3E 00 1E 53 CC A5 17 E0" ///< Latest
///< Adafruit IO
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5 changes: 3 additions & 2 deletions src/wifi/AdafruitIO_ESP8266.h
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Expand Up @@ -25,12 +25,13 @@
/* NOTE - Projects that require "Secure MQTT" (TLS/SSL) also require a new
* SSL certificate every year. If adding Secure MQTT to your ESP8266 project is
* important - please switch to using the modern ESP32 (and related models)
* instead of the ESP8266 to avoid updating the SSL fingerprint every year.
* instead of the ESP8266 to avoid updating the SSL fingerprint every 6months.
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@brentru brentru Jan 21, 2026

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"6months" -> "6 months"

*
* If you've read through this and still want to use "Secure MQTT" with your
* ESP8266 project, we've left the "WiFiClientSecure" lines commented out. To
* use them, uncomment the commented out lines within `AdafruitIO_ESP8266.h` and
* `AdafruitIO_ESP8266.cpp` and recompile the library.
* `AdafruitIO_ESP8266.cpp`, update fingerprint in `AdafruitIO_Definitions.h`,
* and then recompile the library.
*/
// #include "WiFiClientSecure.h"

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