first commit

x2t-sandbox-rulegen/Cargo.toml

@@ -0,0 +1,16 @@
+[package]
+name = "x2t-sandbox-rulegen"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[lib]
+proc-macro = true
+
+[dependencies]
+proc-macro2 = "1"
+quote = "1"
+nix = "0.27.1"
+regex = "1.10.2"
+

x2t-sandbox-rulegen/src/lib.rs

@@ -0,0 +1,63 @@
+use std::{collections::HashSet, str::FromStr};
+
+use proc_macro::*;
+use quote::{quote, format_ident, TokenStreamExt};
+
+#[proc_macro]
+pub fn generate(input: TokenStream) -> TokenStream {
+    let wd = std::path::PathBuf::from_str(&std::env::var("CARGO_MANIFEST_DIR").unwrap()).unwrap();
+
+    let syscall_filepath =
+        wd.join(std::env::var("X2T_SYSCALLS_FILE").unwrap_or("x2t-syscalls.txt".to_string()));
+
+    if let Some(syscalls) = option_env!("X2T_SYSCALLS") {
+        generate_from(input.clone(), syscalls.to_lowercase(), ":").into()
+    } else if let Ok(syscalls) = std::fs::read_to_string(&syscall_filepath) {
+        generate_from(input.clone(), syscalls, "\n").into()
+    } else {
+        panic!("either specify a X2T_SYSCALLS environment variable with values seperated by colon or write the allowed syscalls line by line into {}", syscall_filepath.to_string_lossy());
+    }
+}
+
+fn generate_from(input: proc_macro::TokenStream, buf: String, sep: &str) -> proc_macro2::TokenStream {
+    // TODO: improve generate rules to restrict arguments
+    let mut tokens = Vec::new();
+    let mut syscalls = HashSet::new();
+
+    let raw_syscall_pattern = regex::Regex::new("^\\s*([a-z_][a-z0-9_]*)").unwrap();
+    let strace_pattern = regex::Regex::new("^\\d+ ([a-z_][a-z0-9_]*)").unwrap();
+    for s in buf.split(sep) {
+        // s can be a
+        // - a name matched by [[:space:]]*(?P<syscall>[a-z_][a-z0-9_]*)
+        // - strace line matched by [[:digit:]] (?P<syscall>[a-z_][a-z0-9_]*)
+        for pattern in [&raw_syscall_pattern, &strace_pattern] {
+            if let Some(capture) = pattern.captures(s) {
+                let (_, [syscall_name]) = capture.extract();
+                syscalls.insert(syscall_name.to_string());
+                break;
+            }
+        }
+    }
+    let mut syscalls: Vec<String> = syscalls.iter().map(|s| s.to_owned()).collect();
+    syscalls.sort();
+
+    let hook: proc_macro2::TokenStream = input.into();
+
+    for syscall_name in syscalls {
+        let libc_name = format_ident!("SYS_{}", syscall_name);
+        tokens.push(
+            quote! {
+                {
+                    let syscall_nr = nix::libc::#libc_name;
+                    let syscall_name = #syscall_name;
+                    filter.add_rule_conditional(ScmpAction::Allow, syscall_nr as i32, &[])?;
+                    #hook
+                }
+            }
+        );
+    }
+
+    quote! {
+        #(#tokens);*
+    }
+}