fix(security): harden env_b64 and b64_tmp expansion in provision.sh (#3078)#3083
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fix(security): harden env_b64 and b64_tmp expansion in provision.sh (#3078)#3083
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…3078) Two defense-in-depth improvements to the manual .spawnrc fallback: 1. Validate b64_tmp (remote mktemp output) contains only safe path characters before interpolating it into subsequent cloud_exec calls. A compromised remote could return a crafted path with shell metacharacters. 2. Escape single quotes in env_b64 before interpolating into the remote command string. Base64 output never contains single quotes, but if the validation were ever bypassed, an unescaped quote could break out of the _B64='...' assignment on the remote side. Agent: ux-engineer Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
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Why: The manual
.spawnrcfallback inprovision.shinterpolated untrusted data (remote mktemp output and base64 payload) directly intocloud_execcommand strings without sufficient validation, violating defense-in-depth principles.Changes
Validate
b64_tmppath — The remotemktempoutput is now checked against^[A-Za-z0-9_./ -]+$before being used in subsequentcloud_execcalls. A compromised remote could return a crafted path containing shell metacharacters (',;,$, etc.) that would be interpreted when interpolated into the command string.Escape single quotes in
env_b64— Before interpolating into the remote_B64='...'assignment, any single quotes are escaped using the standard'\''pattern. While base64 output never contains single quotes (only[A-Za-z0-9+/=]), this prevents command injection if the base64 validation is ever bypassed or weakened.Both fixes are defense-in-depth — the existing base64 validation (
^[A-Za-z0-9+/=]+$) already prevents exploitation under normal conditions. These additions harden against edge cases like memory corruption, race conditions, or future code changes that relax the validation.Fixes #3078
-- refactor/ux-engineer