fc-proxy

Sits between Postman and Flexcube. Testers swap the base URL and send plain JSON — the proxy handles encryption, the bearer token, and the unique ids, and logs every call to a local SQLite file it can export as CSV.

Build for Windows

On any machine with Go 1.24+:

make windows

Produces build/fc-proxy.exe (~10 MB) plus build/fc-proxy.env.example. Pure Go, no cgo — the exe is self-contained, nothing to install on the target.

Without make:

CGO_ENABLED=0 GOOS=windows GOARCH=amd64 go build -ldflags="-s -w" -o fc-proxy.exe ./cmd/fc-proxy

make build for a native binary, make test for the tests.

Layout

cmd/fc-proxy/        the CLI: command dispatch, serve, export
internal/config/     env + flag resolution
internal/proxy/      the interception handler, session context, token cache
internal/ledger/     SQLite log and CSV export
internal/encryption/ the AES-CBC scheme, pinned by test vectors

Setup on the jump server

1. Copy fc-proxy.exe and fc-proxy.env.example into a folder.
2. Rename the example to fc-proxy.env and fill in the Flexcube base URL, API_SECRET, the SANGAM client id/secret, and the session defaults.
3. Run it:

fc-proxy.exe serve

The env file is read from the binary's folder automatically. The ledger is created next to it. Flags: -port, -base-url, -db, -env, -insecure, -quiet.

Usage

Point Postman at the proxy instead of Flexcube — the path stays identical:

Before:  POST https://flexcube.internal.example/prov/v1/query/fcdepositdetails
After:   POST http://localhost:9090/prov/v1/query/fcdepositdetails

Send plain JSON:

{ "ServiceCode": "S001", "AccountNumber": "1234567890" }

The proxy wraps it in Data with a generated SessionContext, encrypts it, attaches the token and fresh x-session-id / x-message-id, and returns the response decrypted. A 401 refreshes the token and retries once.

Overrides

Everything has a default in the env file. ServiceCode can be set from the payload (as above); everything else is an X-Proxy-* header, consumed by the proxy and never forwarded:

Header	Effect
X-Proxy-Service-Code	SessionContext.ServiceCode
X-Proxy-Bank-Code / -Branch	BankCode / TransactionBranch
X-Proxy-User-Id / -User-No	UserId / UserNo
X-Proxy-Session-Channel	SessionContext.Channel
X-Proxy-External-Ref	pin ExternalReferenceNo instead of generating one
X-Proxy-Channel	drives x-user-id: <PREFIX>_<CHANNEL>
X-Proxy-Encrypt-Body / -Encrypt-Query	false to send in the clear
X-Proxy-Decrypt-Response	false to get raw ciphertext back
X-Proxy-Session-Context	false to skip the wrap + injection

Hand-written SessionContext beats payload ServiceCode, beats header, beats default. Other Postman headers pass through untouched.

Each response carries X-Proxy-Ledger-Id, -Duration-Ms, -Session-Id, -Message-Id, -External-Ref, -Target-Url, -Decrypted, -Retried.

Exporting the log

Every call is recorded with timestamps, the URL, the payload at all three stages (as typed / after injection / encrypted), both header sets, status, duration and any error.

fc-proxy.exe export                                    # today
fc-proxy.exe export -date 2026-08-21
fc-proxy.exe export -from 2026-08-01 -to 2026-08-21 -out august.csv

Dates are local, both ends inclusive.

Defaults

Every value committed here - bank code, branch, test user, service code, x-user-id prefix, x-channel-id - is a placeholder. The real ones go in fc-proxy.env on the machine that runs the proxy; that file is gitignored and must stay out of the repo.

Gotchas

• Response stays ciphertext (decrypt_ok = 0) — wrong API_SECRET, or it isn't hex-encoded. FC_PROXY_SECRET_RAW takes it as literal text instead.
• Everything 401s — outside APP_ENV=production/uat the proxy sends a static dev token and never calls OAuth. On uat/prod, check the client creds.
• Cert errors — self-signed internal host; run with -insecure.
• Debugging a failed call — take X-Proxy-Ledger-Id from the response and read that row out of the ledger.