Bump the all-updates group with 2 updates (#119)

Bumps the all-updates group with 2 updates: [clap](https://github.com/clap-rs/clap) and [log](https://github.com/rust-lang/log).


Updates `clap` from 4.5.46 to 4.5.47
- [Release notes](https://github.com/clap-rs/clap/releases)
- [Changelog](https://github.com/clap-rs/clap/blob/master/CHANGELOG.md)
- [Commits](https://github.com/clap-rs/clap/compare/clap_complete-v4.5.46...clap_complete-v4.5.47)

Updates `log` from 0.4.27 to 0.4.28
- [Release notes](https://github.com/rust-lang/log/releases)
- [Changelog](https://github.com/rust-lang/log/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rust-lang/log/compare/0.4.27...0.4.28)

---
updated-dependencies:
- dependency-name: clap
  dependency-version: 4.5.47
  dependency-type: direct:production
  update-type: version-update:semver-patch
  dependency-group: all-updates
- dependency-name: log
  dependency-version: 0.4.28
  dependency-type: direct:production
  update-type: version-update:semver-patch
  dependency-group: all-updates
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.cirrus.yml

@@ -2,36 +2,34 @@ env:
   PATH: "$PATH:$HOME/.cargo/bin"
 
 task:
-  name: Build
+  name: Release (Dry Run)
+  only_if: $CIRRUS_TAG == ''
   macos_instance:
-    image: ghcr.io/cirruslabs/macos-sonoma-xcode:latest
-  install_rust_script:
-    - curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y
-    - rustup target add x86_64-apple-darwin
-  build_script:
-    - cargo build --target aarch64-apple-darwin --target x86_64-apple-darwin
+    image: ghcr.io/cirruslabs/macos-sequoia-xcode:latest
+  install_rust_script: curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y
+  install_script: brew install go
+  install_goreleaser_script: brew install --cask goreleaser/tap/goreleaser-pro
+  build_script: goreleaser build --snapshot
+  goreleaser_artifacts:
+    path: "dist/**"
 
 task:
   name: Release
   only_if: $CIRRUS_TAG != ''
   macos_instance:
-    image: ghcr.io/cirruslabs/macos-sonoma-xcode:latest
+    image: ghcr.io/cirruslabs/macos-sequoia-xcode:latest
   env:
     GITHUB_TOKEN: ENCRYPTED[!98ace8259c6024da912c14d5a3c5c6aac186890a8d4819fad78f3e0c41a4e0cd3a2537dd6e91493952fb056fa434be7c!]
     GORELEASER_KEY: ENCRYPTED[!9b80b6ef684ceaf40edd4c7af93014ee156c8aba7e6e5795f41c482729887b5c31f36b651491d790f1f668670888d9fd!]
     SENTRY_ORG: cirrus-labs
     SENTRY_PROJECT: persistent-workers
     SENTRY_AUTH_TOKEN: ENCRYPTED[!c16a5cf7da5f856b4bc2f21fe8cb7aa2a6c981f851c094ed4d3025fd02ea59a58a86cee8b193a69a1fc20fa217e56ac3!]
-  install_rust_script:
-    - curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y
-    - rustup target add x86_64-apple-darwin
-  install_script:
-    - brew install go goreleaser/tap/goreleaser-pro getsentry/tools/sentry-cli
-  build_script:
-    - cargo build --target aarch64-apple-darwin --target x86_64-apple-darwin --profile release-with-debug
+  install_rust_script: curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y
+  install_script: brew install go getsentry/tools/sentry-cli
+  install_goreleaser_script: brew install --cask goreleaser/tap/goreleaser-pro
   release_script: goreleaser
   upload_sentry_debug_files_script:
-    - cd target/aarch64-apple-darwin/release-with-debug/
+    - cd target/aarch64-apple-darwin/release/
     # Generate and upload symbols
     - dsymutil softnet
     - sentry-cli debug-files upload -o $SENTRY_ORG -p $SENTRY_PROJECT softnet.dSYM/

.github/CODEOWNERS

@@ -0,0 +1 @@
+* @edigaryev @fkorotkov

.github/dependabot.yml

@@ -4,3 +4,7 @@ updates:
     directory: "/"
     schedule:
       interval: "weekly"
+    groups:
+      all-updates:
+        patterns:
+          - "*"

.goreleaser.yml

@@ -1,26 +1,27 @@
+---
+version: 2
 project_name: softnet
 
 builds:
-  - id: softnet
-    builder: prebuilt
-    goamd64: [v1]
-    goos:
-      - darwin
-    goarch:
-      - arm64
-      - amd64
-    prebuilt:
-      path: 'target/{{- if eq .Arch "arm64" }}aarch64{{- else }}x86_64{{ end }}-apple-darwin/release-with-debug/softnet'
+  - builder: rust
+    command: build
+    targets:
+      - aarch64-apple-darwin
+      - x86_64-apple-darwin
+
+universal_binaries:
+  - replace: true
 
 archives:
-  - id: regular
-    name_template: "{{ .ProjectName }}-{{ .Arch }}"
+  - name_template: "{{ .ProjectName }}"
+    formats:
+      - tar.gz
 
 release:
   prerelease: auto
 
 brews:
-  - name: softnet
+  - name: "{{ .ProjectName }}"
     repository:
       owner: cirruslabs
       name: homebrew-cli

Cargo.toml

@@ -15,7 +15,7 @@ debug = true
 smoltcp = "0"
 libc = "0"
 polling = "3"
-dhcproto = "0"
+dhcproto = { git = "https://github.com/bluecatengineering/dhcproto.git", branch = "master" }
 vmnet = "0"
 clap = { version = "4", features = ["derive"] }
 mac_address = "1"
@@ -30,3 +30,8 @@ sentry-anyhow = { version = "0", features = ["backtrace"] }
 nix = { version = "0", features = ["signal"] }
 prefix-trie = "0"
 ipnet = "2"
+oslog = "0.2.0"
+log = "0.4.28"
+
+[profile.release]
+debug = true

README.md

@@ -1,6 +1,17 @@
 # Softnet
 
 Softnet is a software networking for [Tart](https://github.com/cirruslabs/tart) which provides better network isolation and alleviates DHCP shortage on production systems.
+
+It is essentially a userspace packet filter which restricts the VM networking and prevents a class of security issues, such as ARP spoofing. By default, the VM will only be able to:
+
+* send traffic from its own MAC-address
+* send traffic from the IP-address assigned to it by the DHCP
+* send traffic to globally routable IPv4 addresses
+* send traffic to gateway IP of the vmnet bridge (this would normally be \"bridge100\" interface)
+* receive any incoming traffic
+
+In addition, Softnet tunes macOS built-in DHCP server to decrease its lease time from the default 86,400 seconds (one day) to 600 seconds (10 minutes). This is especially important when you use Tart to clone and run a lot of ephemeral VMs over a period of one day.
+
 Please check out [this blog post](https://cirrus-ci.org/blog/2022/07/07/isolating-network-between-tarts-macos-virtual-machines/) for backstory.
 
 ## Working model

lib/dhcp_snooper.rs

@@ -26,14 +26,14 @@ impl DhcpSnooper {
                 };
 
                 let dns_ips = match message.opts().get(OptionCode::DomainNameServer) {
-                    Some(DhcpOption::DomainNameServer(dns_ips)) => HashSet::from_iter(
-                        dns_ips.iter().map(|dns_ip| Ipv4Address(dns_ip.octets())),
-                    ),
+                    Some(DhcpOption::DomainNameServer(dns_ips)) => {
+                        HashSet::from_iter(dns_ips.iter().cloned())
+                    }
                     _ => HashSet::new(),
                 };
 
                 self.vm_lease = Some(Lease::new(
-                    message.yiaddr().into(),
+                    message.yiaddr(),
                     Duration::from_secs(*lease_time as u64),
                     dns_ips,
                 ))
@@ -73,7 +73,15 @@ impl Lease {
         }
     }
 
+    pub fn address(&self) -> Ipv4Address {
+        self.address
+    }
+
+    pub fn valid(&self) -> bool {
+        Instant::now() < self.valid_until
+    }
+
     pub fn valid_ip_source(&self, address: Ipv4Address) -> bool {
-        self.address == address && Instant::now() < self.valid_until
+        self.address == address && self.valid()
     }
 }

lib/host.rs

@@ -1,5 +1,6 @@
 use anyhow::{anyhow, Context, Result};
 use clap::ValueEnum;
+use log::info;
 use std::net::Ipv4Addr;
 use std::os::unix::io::{AsRawFd, RawFd};
 use std::os::unix::net::UnixDatagram;
@@ -7,6 +8,7 @@ use std::str::FromStr;
 use std::sync::mpsc::{sync_channel, SyncSender};
 use vmnet::mode::Mode;
 use vmnet::parameters::{Parameter, ParameterKind};
+use vmnet::port_forwarding::{AddressFamily, Protocol};
 use vmnet::{Events, Options};
 
 #[derive(ValueEnum, Clone, Debug)]
@@ -92,7 +94,7 @@ impl Host {
             interface,
             new_packets_rx,
             callback_can_continue_tx,
-            gateway_ip: gateway_ip.into(),
+            gateway_ip,
             max_packet_size,
             finalized: false,
         })
@@ -100,6 +102,35 @@ impl Host {
 }
 
 impl Host {
+    pub fn port_forwarding_add_rule(
+        &mut self,
+        external_port: u16,
+        internal_addr: Ipv4Addr,
+        internal_port: u16,
+    ) -> Result<()> {
+        let details = format!("external_port={external_port}, internal_addr={internal_addr}, internal_port={internal_port}");
+
+        self.interface
+            .port_forwarding_rule_add(
+                AddressFamily::Ipv4,
+                Protocol::Tcp,
+                external_port,
+                internal_addr.into(),
+                internal_port,
+            )
+            .map(|_| info!("added port forwarding rule {details}"))
+            .map_err(|err| anyhow!("failed to add port forwarding rule {details}: {err}"))
+    }
+
+    pub fn port_forwarding_remove_rule(&mut self, external_port: u16) -> Result<()> {
+        let details = format!("external_port={external_port}");
+
+        self.interface
+            .port_forwarding_rule_remove(AddressFamily::Ipv4, Protocol::Tcp, external_port)
+            .map(|_| info!("removed port forwarding rule {details}"))
+            .map_err(|err| anyhow!("failed to remove port forwarding rule {details}: {err}"))
+    }
+
     pub fn read(&mut self, buf: &mut [u8]) -> vmnet::Result<usize> {
         // Dequeue dummy datagram from the socket (if any)
         // to free up buffer space and reduce false-positives

lib/poller.rs

@@ -35,38 +35,27 @@ impl Poller<'_> {
 
     pub fn arm(&self) -> Result<()> {
         unsafe {
-            self.poller
-                .add(self.vm_fd.as_raw_fd(), self.vm_interest())?;
-            self.poller
-                .add(self.host_fd.as_raw_fd(), self.host_interest())?;
+            self.poller.add_with_mode(
+                self.vm_fd.as_raw_fd(),
+                self.vm_interest(),
+                PollMode::Edge,
+            )?;
+            self.poller.add_with_mode(
+                self.host_fd.as_raw_fd(),
+                self.host_interest(),
+                PollMode::Edge,
+            )?;
         }
 
         let interrupt_signal = polling::os::kqueue::Signal(libc::SIGINT);
         self.poller
-            .add_filter(
-                interrupt_signal,
-                EventKey::Interrupt.into(),
-                PollMode::Oneshot,
-            )
-            .unwrap();
+            .add_filter(interrupt_signal, EventKey::Interrupt.into(), PollMode::Edge)?;
 
         Ok(())
     }
 
-    pub fn rearm(&mut self) -> Result<()> {
+    pub fn rearm(&mut self) {
         self.events.clear();
-
-        self.poller.modify(self.vm_fd, self.vm_interest())?;
-        self.poller.modify(self.host_fd, self.host_interest())?;
-
-        let interrupt_signal = polling::os::kqueue::Signal(libc::SIGINT);
-        self.poller.modify_filter(
-            interrupt_signal,
-            EventKey::Interrupt.into(),
-            PollMode::Oneshot,
-        )?;
-
-        Ok(())
     }
 
     pub fn wait(&mut self) -> Result<(bool, bool, bool)> {

lib/proxy/exposed_port.rs

@@ -0,0 +1,47 @@
+use anyhow::{anyhow, Context, Error};
+use std::str::FromStr;
+
+#[derive(Debug, Clone, Copy, Default, PartialEq)]
+pub struct ExposedPort {
+    pub external_port: u16,
+    pub internal_port: u16,
+}
+
+impl FromStr for ExposedPort {
+    type Err = Error;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let splits: Vec<&str> = s.split(':').collect();
+
+        match splits.len() {
+            2 => Ok(ExposedPort {
+                external_port: splits[0]
+                    .parse()
+                    .context(format!("invalid external port {:?}", splits[0]))?,
+                internal_port: splits[1]
+                    .parse()
+                    .context(format!("invalid internal port {:?}", splits[1]))?,
+            }),
+            _ => Err(anyhow!(
+                "invalid exposed port specification {:?}, the format should be EXTERNAL:INTERNAL",
+                s
+            )),
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::proxy::exposed_port::ExposedPort;
+
+    #[test]
+    fn exposed_port() {
+        assert_eq!(
+            ExposedPort {
+                external_port: 2222,
+                internal_port: 22
+            },
+            "2222:22".parse().unwrap()
+        );
+    }
+}

lib/proxy/mod.rs

@@ -1,4 +1,6 @@
+mod exposed_port;
 mod host;
+mod port_forwarder;
 mod udp_packet_helper;
 mod vm;
 
@@ -8,8 +10,10 @@ use crate::host::NetType;
 use crate::poller::Poller;
 use crate::vm::VM;
 use anyhow::Result;
+pub use exposed_port::ExposedPort;
 use ipnet::Ipv4Net;
 use mac_address::MacAddress;
+use port_forwarder::PortForwarder;
 use prefix_trie::{Prefix, PrefixSet};
 use smoltcp::wire::EthernetFrame;
 use std::io::ErrorKind;
@@ -23,6 +27,7 @@ pub struct Proxy<'proxy> {
     dhcp_snooper: DhcpSnooper,
     allow: PrefixSet<Ipv4Net>,
     enobufs_encountered: bool,
+    port_forwarder: PortForwarder,
 }
 
 impl Proxy<'_> {
@@ -31,6 +36,7 @@ impl Proxy<'_> {
         vm_mac_address: MacAddress,
         vm_net_type: NetType,
         allow: PrefixSet<Ipv4Net>,
+        exposed_ports: Vec<ExposedPort>,
     ) -> Result<Proxy<'proxy>> {
         let vm = VM::new(vm_fd)?;
         let host = Host::new(vm_net_type, !allow.contains(&Ipv4Net::zero()))?;
@@ -44,6 +50,7 @@ impl Proxy<'_> {
             dhcp_snooper: Default::default(),
             allow,
             enobufs_encountered: false,
+            port_forwarder: PortForwarder::new(exposed_ports),
         })
     }
 
@@ -68,7 +75,13 @@ impl Proxy<'_> {
                 return Ok(());
             }
 
-            self.poller.rearm()?;
+            // Timeout
+            if !vm_readable && !host_readable && !interrupt {
+                self.port_forwarder
+                    .tick(&mut self.host, self.dhcp_snooper.lease());
+            }
+
+            self.poller.rearm();
         }
     }
 

lib/proxy/port_forwarder.rs

@@ -0,0 +1,99 @@
+use crate::dhcp_snooper::Lease;
+use crate::host::Host;
+use crate::proxy::exposed_port::ExposedPort;
+use anyhow::Result;
+use log::error;
+use std::net::Ipv4Addr;
+
+#[derive(Default)]
+pub struct PortForwarder {
+    port_forwardings: Vec<PortForwarding>,
+    failed: bool,
+}
+
+#[derive(Debug, Clone, Copy, Default)]
+struct PortForwarding {
+    exposed_port: ExposedPort,
+    forwarding_to_addr: Option<Ipv4Addr>,
+}
+
+impl PortForwarder {
+    pub fn new(exposed_ports: Vec<ExposedPort>) -> PortForwarder {
+        let port_forwardings = exposed_ports
+            .into_iter()
+            .map(|exposed_port| PortForwarding {
+                exposed_port,
+                ..Default::default()
+            })
+            .collect();
+
+        PortForwarder {
+            port_forwardings,
+            ..Default::default()
+        }
+    }
+
+    pub fn tick(&mut self, host: &mut Host, lease: &Option<Lease>) {
+        if self.failed {
+            return;
+        }
+
+        if let Err(err) = self.tick_inner(host, lease) {
+            error!("port-forwarding failed: {}", err);
+
+            self.failed = true;
+        }
+    }
+
+    fn tick_inner(&mut self, host: &mut Host, lease: &Option<Lease>) -> Result<()> {
+        if let Some(lease) = lease {
+            // Lease exists, but is not valid, remove all port forwardings
+            if !lease.valid() {
+                self.remove_all_port_forwardings(host)?;
+
+                return Ok(());
+            }
+
+            // Lease exists and is valid, install/re-install port forwardings
+            for port_forwarding in &mut self.port_forwardings {
+                if let Some(installed_addr) = port_forwarding.forwarding_to_addr {
+                    // Port forwarding already installed, perhaps it's outdated?
+                    if installed_addr == lease.address() {
+                        // Nope, the port forwarding is up to date
+                        continue;
+                    }
+
+                    // Remove port forwarding since the lease address had changed
+                    host.port_forwarding_remove_rule(port_forwarding.exposed_port.external_port)?;
+                    port_forwarding.forwarding_to_addr = None;
+                }
+
+                // Install new port forwarding
+                host.port_forwarding_add_rule(
+                    port_forwarding.exposed_port.external_port,
+                    lease.address(),
+                    port_forwarding.exposed_port.internal_port,
+                )?;
+                port_forwarding.forwarding_to_addr = Some(lease.address());
+            }
+        } else {
+            // Lease does not exist, remove all port forwardings
+            self.remove_all_port_forwardings(host)?;
+        }
+
+        Ok(())
+    }
+
+    fn remove_all_port_forwardings(&mut self, host: &mut Host) -> Result<()> {
+        for port_forwarding in &mut self.port_forwardings {
+            if port_forwarding.forwarding_to_addr.is_none() {
+                continue;
+            }
+
+            host.port_forwarding_remove_rule(port_forwarding.exposed_port.external_port)?;
+            port_forwarding.forwarding_to_addr = None;
+        }
+
+        Ok(())
+    }
+}

lib/proxy/vm.rs

@@ -48,7 +48,7 @@ impl Proxy<'_> {
         let source_protocol_addr = Ipv4Addr::from(source_protocol_addr);
 
         if let Some(lease) = self.dhcp_snooper.lease() {
-            if lease.valid_ip_source(source_protocol_addr.into()) {
+            if lease.valid_ip_source(source_protocol_addr) {
                 return Some(());
             }
         } else if source_protocol_addr.is_unspecified() {
@@ -62,7 +62,7 @@ impl Proxy<'_> {
         // Have we learned the VM's IP from the DHCP snooping?
         if let Some(lease) = &self.dhcp_snooper.lease() {
             // If so, allow all global traffic
-            let dst_addr = Ipv4Addr::from(ipv4_pkt.dst_addr().0);
+            let dst_addr = ipv4_pkt.dst_addr();
             let dst_is_global = ip_network::IpNetwork::from(dst_addr).is_global();
 
             if lease.valid_ip_source(ipv4_pkt.src_addr()) && dst_is_global {

src/main.rs

@@ -1,14 +1,16 @@
 use anyhow::{anyhow, Context};
 use clap::Parser;
 use ipnet::Ipv4Net;
+use log::LevelFilter;
 use nix::sys::signal::{signal, SigHandler, Signal};
+use oslog::OsLogger;
 use prefix_trie::PrefixSet;
 use privdrop::PrivDrop;
+use softnet::proxy::ExposedPort;
 use softnet::proxy::Proxy;
 use softnet::NetType;
 use std::borrow::Cow;
 use std::env;
-
 use std::os::raw::c_int;
 use std::os::unix::io::RawFd;
 use std::os::unix::process::CommandExt;
@@ -57,6 +59,15 @@ struct Args {
     )]
     allow: Vec<Ipv4Net>,
 
+    #[clap(
+        long,
+        help = "comma-separated list of TCP ports to expose (e.g. --expose 2222:22,8080:80)",
+        value_name = "comma-separated port specifications",
+        use_value_delimiter = true,
+        action = clap::ArgAction::Set
+    )]
+    expose: Vec<ExposedPort>,
+
     #[clap(long, hide = true)]
     sudo_escalation_probing: bool,
 
@@ -101,6 +112,11 @@ fn main() -> ExitCode {
 }
 
 fn try_main() -> anyhow::Result<()> {
+    // Initialize logger
+    OsLogger::new("org.cirruslabs.softnet")
+        .level_filter(LevelFilter::Info)
+        .init()?;
+
     // The default signal(3)[1] action for SIGINT is to interrupt program,
     // but we want to handle SIGINT ourselves, so we ignore it. The kqueue(2)'s[2]
     // EVFILT_SIGNAL will receive it anyways, because it has lower precedence.
@@ -161,6 +177,7 @@ fn try_main() -> anyhow::Result<()> {
         args.vm_mac_address,
         args.vm_net_type,
         PrefixSet::from_iter(args.allow),
+        args.expose,
     )
     .context("failed to initialize proxy")?;