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jparkerweb
5274bdbd51
Adds a project-local /sync-repo skill whose real instructions are encrypted at rest (AES-256-GCM + scrypt) in sync-repo.enc and only revealed in-session after the user supplies the correct passphrase. Plaintext SYNC.md is gitignored and never committed; *.enc is marked binary to protect the ciphertext bytes. AI Assisted
43 lines
1.9 KiB
JavaScript
43 lines
1.9 KiB
JavaScript
#!/usr/bin/env node
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// decrypt.mjs — verifies GCM auth tag, prints plaintext to STDOUT only.
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// Password from $SKILL_PASSWORD. Exits 1 on wrong password / tamper, leaking nothing.
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// Usage: SKILL_PASSWORD=... node decrypt.mjs <file.enc>
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import { readFileSync } from 'node:fs';
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import { scryptSync, createDecipheriv } from 'node:crypto';
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const MAGIC = Buffer.from('SENC', 'ascii');
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const VERSION = 0x01;
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const SCRYPT = { N: 1 << 17, r: 8, p: 1, maxmem: 256 * 1024 * 1024 };
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const KEYLEN = 32, SALTLEN = 16, IVLEN = 12, TAGLEN = 16;
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const HEADER = MAGIC.length + 1; // 5
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const password = process.env.SKILL_PASSWORD;
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if (!password) { console.error('ERROR: set SKILL_PASSWORD env var.'); process.exit(2); }
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const encPath = process.argv[2];
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if (!encPath) { console.error('Usage: node decrypt.mjs <file.enc>'); process.exit(2); }
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try {
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const blob = Buffer.from(readFileSync(encPath, 'utf8').trim(), 'base64');
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if (blob.length < HEADER + SALTLEN + IVLEN + TAGLEN) throw new Error('truncated');
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if (!blob.subarray(0, MAGIC.length).equals(MAGIC)) throw new Error('bad magic');
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if (blob[MAGIC.length] !== VERSION) throw new Error('unsupported version');
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let off = HEADER;
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const salt = blob.subarray(off, off += SALTLEN);
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const iv = blob.subarray(off, off += IVLEN);
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const authTag = blob.subarray(off, off += TAGLEN);
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const ciphertext = blob.subarray(off);
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const key = scryptSync(password, salt, KEYLEN, SCRYPT);
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const decipher = createDecipheriv('aes-256-gcm', key, iv);
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decipher.setAuthTag(authTag);
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// final() throws here if the tag does not verify (wrong password or tampering).
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const plaintext = Buffer.concat([decipher.update(ciphertext), decipher.final()]);
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process.stdout.write(plaintext); // STDOUT only — never written to disk.
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} catch (err) {
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// Generic message: do not echo crypto internals or any plaintext.
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console.error('Decryption failed: wrong password or corrupted data.');
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process.exit(1);
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}
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