Add instructions for managing CA certificates

manchoz · manchoz · commit 69dc896872b9 · 2023-08-09T11:55:54.000+02:00
diff --git a/libraries/STM32H747_System/examples/WiFiFirmwareUpdater/Readme.md b/libraries/STM32H747_System/examples/WiFiFirmwareUpdater/Readme.md
@@ -0,0 +1,35 @@
+# Managing CA Certs for TLS connections
+
+## Generating `certificates.h` from PEM file:
+
+> [!NOTE]
+> Pre-requisites: `xxd` from `vim` packages or standalone
+```
+xxd -i cacert.pem -n cacert_pem | sed 's/^unsigned/const unsigned/g' > certificates.h
+```
+
+## Getting PEM file from `certificates.h`
+
+> [!NOTE]
+> Pre-requisites: `xxd`, GNU Tools (Use g-tools on MacOS: e.g., `gtail`, `ghead`)
+```
+cat certificates.h | tail -n +2 | head -n -2 | head -c -7 | xxd -r -p > cacert.pem
+```
+## Listing certifcates in `certificates.h`
+
+> [!NOTE]
+> Pre-requisites: `openssl`
+
+```
+cat certificates.h | tail -n +2 | head -n -2 | head -c -7 | xxd -r -p > cacert.pem
+openssl crl2pkcs7 -nocrl -certfile cacert.pem | openssl pkcs7 -print_certs | grep '^subject'
+```
+
+## Adding a new root certificate to `certificates.h`
+
+> [!Note]
+> The PEM file for the root CA to add, e.g., `new_root.pem` 
+
+```
+cat certificates.h | tail -n +2 | head -n -2 | head -c -7 | xxd -r -p | cat - new_root.pem | xxd -n cacert_pem -i | sed 's/^unsigned/const unsigned/g' > certificates.h
+```
