fix(security): pipe base64 via stdin in daytona uploadFile

[la14-1]

Why: Eliminates shell interpolation of base64 content in uploadFile's remote command, providing defense-in-depth against injection even if base64 validation were ever bypassed.

Changes

• Replace printf '%s' '${b64}' | base64 -d > '${remotePath}' with base64 -d > '${remotePath}'
• Pipe b64 content via stdin instead of embedding in command string
• Remove now-unnecessary b64 character validation (content no longer interpolated)
• Existing remotePath validation (/^[a-zA-Z0-9/_.~-]+$/) is kept (still needed for path safety)

Security Impact

• Before: b64 content interpolated into remote shell command (validated but still a pattern to avoid)
• After: b64 content sent via stdin, not visible in command string at all

Fixes #2130

-- refactor/security-auditor

[louisgv]

Security Review

Verdict: APPROVED
Commit: e6ea66e

Summary

This PR correctly fixes a command injection vulnerability (issue #2130) by changing from embedding base64 data in shell command strings to piping via stdin.

Findings

NONE - All security concerns resolved.

Analysis

FIXED: Command injection - The original code embedded base64-encoded file content directly into the SSH command string:

`printf '%s' '${b64}' | base64 -d > '${remotePath}'`

This was vulnerable despite the regex validation, because base64 encoding from arbitrary binary files could theoretically produce edge cases. The fix correctly pipes data via stdin instead:

`base64 -d > '${remotePath}'`
stdin.write(b64 + "\n");

remotePath safety: Still interpolated into the command string but protected by:

• Single-quote wrapping (prevents expansion)
• Strict allowlist validation: /^[a-zA-Z0-9/_.~-]+$/
• Path traversal prevention: blocks ".."
• Flag injection prevention: blocks "-" prefix on any path component

This is the correct security approach for this use case.

Tests

• bun test: PASS (1372 pass, 0 fail)
• biome lint: PASS (0 errors)
• Version bump: PASS (0.12.7 → 0.12.8, appropriate for patch)

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-- security/pr-reviewer