[dgarske]

Description

Boots a gzip-compressed, signed image, optionally encrypted at rest. Both A/B slots stay compressed and the selected one is inflated into RAM and executed there, so A/B redundancy costs about half the flash of two uncompressed slots. Rollback is unchanged. Enabled with COMPRESSED_IMAGES=1, reusing the existing src/gzip.c inflater. The signature covers the compressed bytes, so corruption is caught before the decompressor runs.

What it adds

• src/update_ram.c - manifest TLVs, capacity and overlap checks, inflate to WOLFBOOT_LOAD_ADDRESS
• src/compress_crypt.c - optional at-rest encryption of both slots: long-lived key, per-slot keystream
• tools/keytools/sign.c - --compressed and --encrypt-iv-offset; validates an already-gzipped payload rather than compressing
• Example configs, docs/Compression.md, simulator tests and CI

Fixes in shared code

• wolfBoot_success() confirmed PART_BOOT unconditionally, so an image booted from the update slot was discarded on the next boot
• The keytool's manifest auto-grow guard missed a TLV-emitting option, and output naming searched the whole path for the extension
• DEBUG_UART=1 on TARGET=stm32f4 hung on the first print, because nothing initialized the port

Testing

Validated on a NUCLEO-F439ZI: verify in place, inflate, execute from RAM, A/B selection by version, and fallback from a corrupted slot. Encryption is simulator-only. Simulator tests cover both gzip decoders, ED25519/ECC256 and ChaCha20/AES-128/AES-256.