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fix(protocol): Resolve desync by handling HMAC signature in reader and normalizing env vars
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Amr Gharbeia
2026-04-19 20:03:19 -04:00
parent 95fecdd64c
commit 6a5695310c
3 changed files with 17 additions and 25 deletions
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14
literate/communication.org
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@@ -59,17 +59,17 @@ The system maintains a decoupled registry of target actuators. This allows the s
#+end_src
** Message Framing (frame-message)
The ~frame-message~ function prepares an outgoing Lisp string for transmission. It calculates the byte length, converts it into a 6-character padded hex string, and prefixes it. If ~COMMUNICATION_PROTOCOL_ENFORCE_HMAC~ is enabled in the environment, it also prepends a cryptographic signature to ensure the message hasn't been tampered with.
The ~frame-message~ function prepares an outgoing Lisp string for transmission. It calculates the byte length, converts it into a 6-character padded hex string, and prefixes it. If ~PROTOCOL_ENFORCE_HMAC~ is enabled in the environment, it also prepends a cryptographic signature to ensure the message hasn't been tampered with.
#+begin_src lisp :tangle ../src/communication.lisp
(defun frame-message (msg-string)
"Prefixes MSG-STRING with a 6-character hex length.
If security is enabled, prefixes a 64-char HMAC-SHA256 signature."
(let ((len (length msg-string))
(enforce-hmac (uiop:getenv "COMMUNICATION_PROTOCOL_ENFORCE_HMAC")))
(enforce-hmac (uiop:getenv "PROTOCOL_ENFORCE_HMAC")))
(if (and enforce-hmac (string-equal enforce-hmac "true"))
(let ((secret (uiop:getenv "COMMUNICATION_PROTOCOL_HMAC_SECRET")))
(unless secret (error "COMMUNICATION_PROTOCOL_HMAC_SECRET is required when security is enabled."))
(let ((secret (uiop:getenv "PROTOCOL_HMAC_SECRET")))
(unless secret (error "PROTOCOL_HMAC_SECRET is required when security is enabled."))
(let* ((key (ironclad:ascii-string-to-byte-array secret))
(hmac (ironclad:make-mac :hmac key :sha256))
(payload-bytes (ironclad:ascii-string-to-byte-array msg-string)))
@@ -87,7 +87,7 @@ Parsing is the high-security inverse of framing. This function acts as the final
"Extracts and parses the S-expression from a framed string securely."
(when (< (length framed-string) 6)
(error "Framed string too short"))
(let* ((enforce-hmac (uiop:getenv "COMMUNICATION_PROTOCOL_ENFORCE_HMAC"))
(let* ((enforce-hmac (uiop:getenv "PROTOCOL_ENFORCE_HMAC"))
(use-hmac (and enforce-hmac (string-equal enforce-hmac "true")))
(prefix-len (if use-hmac 70 6)))
(when (< (length framed-string) prefix-len)
@@ -103,8 +103,8 @@ Parsing is the high-security inverse of framing. This function acts as the final
(error "Message length mismatch. Expected ~a, got ~a" expected-len (length actual-msg)))
(when use-hmac
(let ((secret (uiop:getenv "COMMUNICATION_PROTOCOL_HMAC_SECRET")))
(unless secret (error "COMMUNICATION_PROTOCOL_HMAC_SECRET is required when security is enabled."))
(let ((secret (uiop:getenv "PROTOCOL_HMAC_SECRET")))
(unless secret (error "PROTOCOL_HMAC_SECRET is required when security is enabled."))
(let* ((key (ironclad:ascii-string-to-byte-array secret))
(hmac (ironclad:make-mac :hmac key :sha256))
(payload-bytes (ironclad:ascii-string-to-byte-array actual-msg)))