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Zach
112c921235
commandEnvExecer.prepare rebuilt commands into a single shell string
using `fmt.Sprintf("%q", arg)`, which produces Go string literals, not
shell-quoted tokens. Go's %q does not escape `$`, backticks, or other
metacharacters that remain active inside double quotes, so an argument
such as `$(...)` was evaluated by the shell as command substitution.
Arguments flow from devcontainer config and workspace-folder, making
this exploitable.
Pass the command to the shell as positional parameters and run `"$@"` so
the shell forwards argv verbatim without re-parsing it.
The Windows previous handling is not required because Coder doesn't
support devcontainers on Windows, so it is removed.
78 lines
2.6 KiB
Go
78 lines
2.6 KiB
Go
package agentcontainers
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import (
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"context"
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"os/exec"
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"cdr.dev/slog/v3"
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"github.com/coder/coder/v2/agent/agentexec"
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"github.com/coder/coder/v2/agent/usershell"
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"github.com/coder/coder/v2/pty"
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)
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// CommandEnv is a function that returns the shell, working directory,
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// and environment variables to use when executing a command. It takes
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// an EnvInfoer and a pre-existing environment slice as arguments.
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// This signature matches agentssh.Server.CommandEnv.
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type CommandEnv func(ei usershell.EnvInfoer, addEnv []string) (shell, dir string, env []string, err error)
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// commandEnvExecer is an agentexec.Execer that uses a CommandEnv to
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// determine the shell, working directory, and environment variables
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// for commands. It wraps another agentexec.Execer to provide the
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// necessary context.
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type commandEnvExecer struct {
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logger slog.Logger
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commandEnv CommandEnv
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execer agentexec.Execer
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}
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func newCommandEnvExecer(
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logger slog.Logger,
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commandEnv CommandEnv,
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execer agentexec.Execer,
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) *commandEnvExecer {
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return &commandEnvExecer{
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logger: logger,
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commandEnv: commandEnv,
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execer: execer,
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}
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}
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// Ensure commandEnvExecer implements agentexec.Execer.
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var _ agentexec.Execer = (*commandEnvExecer)(nil)
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func (e *commandEnvExecer) prepare(ctx context.Context, inName string, inArgs ...string) (name string, args []string, dir string, env []string) {
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shell, dir, env, err := e.commandEnv(nil, nil)
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if err != nil {
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e.logger.Error(ctx, "get command environment failed", slog.Error(err))
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return inName, inArgs, "", nil
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}
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name = shell
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// Pass the command through the shell as positional parameters and run
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// "$@" so the shell re-emits argv verbatim without re-parsing it. This
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// prevents arguments containing shell metacharacters such as $, `, and
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// quotes from being interpreted (e.g. command substitution). The token
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// before them fills $0, which "$@" never references, so it is discarded.
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// This assumes a POSIX shell; Windows is not supported here.
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cmdArgs := append([]string{inName}, inArgs...)
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args = append([]string{"-c", `"$@"`, ""}, cmdArgs...)
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return name, args, dir, env
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}
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func (e *commandEnvExecer) CommandContext(ctx context.Context, cmd string, args ...string) *exec.Cmd {
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name, args, dir, env := e.prepare(ctx, cmd, args...)
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c := e.execer.CommandContext(ctx, name, args...)
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c.Dir = dir
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c.Env = env
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return c
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}
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func (e *commandEnvExecer) PTYCommandContext(ctx context.Context, cmd string, args ...string) *pty.Cmd {
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name, args, dir, env := e.prepare(ctx, cmd, args...)
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c := e.execer.PTYCommandContext(ctx, name, args...)
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c.Dir = dir
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c.Env = env
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return c
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}
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