Add ownership validation to cargo_util.

ehuss · ehuss · commit 218946206f86 · 2022-06-09T17:05:50.000-07:00
diff --git a/crates/cargo-util/Cargo.toml b/crates/cargo-util/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "cargo-util"
-version = "0.1.3"
+version = "0.1.4"
 edition = "2021"
 license = "MIT OR Apache-2.0"
 homepage = "https://github.com/rust-lang/cargo"
@@ -25,4 +25,4 @@ core-foundation = { version = "0.9.0", features = ["mac_os_10_7_support"] }
 
 [target.'cfg(windows)'.dependencies]
 miow = "0.3.6"
-winapi = { version = "0.3.9", features = ["consoleapi", "minwindef"] }
+winapi = { version = "0.3.9", features = ["consoleapi", "minwindef", "sddl", "accctrl", "aclapi", "securitybaseapi"] }
diff --git a/crates/cargo-util/src/paths.rs b/crates/cargo-util/src/paths.rs
@@ -1,5 +1,8 @@
 //! Various utilities for working with files and paths.
 
+mod ownership;
+
+pub use self::ownership::{validate_ownership, OwnershipError};
 use anyhow::{Context, Result};
 use filetime::FileTime;
 use std::env;
diff --git a/crates/cargo-util/src/paths/ownership.rs b/crates/cargo-util/src/paths/ownership.rs
@@ -0,0 +1,318 @@
+use anyhow::Result;
+use std::collections::HashSet;
+use std::fmt;
+use std::path::{Path, PathBuf};
+
+/// Checks the ownership of the given path matches the current user.
+///
+/// The `safe_directories` is a set of paths to allow, usually loaded from config.
+pub fn validate_ownership(path: &Path, safe_directories: &HashSet<PathBuf>) -> Result<()> {
+    if safe_directories.get(Path::new("*")).is_some() {
+        return Ok(());
+    }
+    for safe_dir in safe_directories {
+        if path.starts_with(safe_dir) {
+            return Ok(());
+        }
+    }
+    _validate_ownership(path)
+}
+
+#[cfg(unix)]
+fn _validate_ownership(path: &Path) -> Result<()> {
+    use super::symlink_metadata;
+    use std::env;
+    use std::os::unix::fs::MetadataExt;
+    let meta = symlink_metadata(path)?;
+    let current_user = unsafe { libc::geteuid() };
+    fn get_username(uid: u32) -> String {
+        unsafe {
+            let amt = match libc::sysconf(libc::_SC_GETPW_R_SIZE_MAX) {
+                n if n < 0 => 512 as usize,
+                n => n as usize,
+            };
+            let mut buf = Vec::with_capacity(amt);
+            let mut passwd: libc::passwd = std::mem::zeroed();
+            let mut result = std::ptr::null_mut();
+            match libc::getpwuid_r(
+                uid,
+                &mut passwd,
+                buf.as_mut_ptr(),
+                buf.capacity(),
+                &mut result,
+            ) {
+                0 if !result.is_null() => {
+                    let ptr = passwd.pw_name as *const _;
+                    let bytes = std::ffi::CStr::from_ptr(ptr).to_bytes().to_vec();
+                    String::from_utf8_lossy(&bytes).into_owned()
+                }
+                _ => String::from("Unknown"),
+            }
+        }
+    }
+    // This is used for testing to simulate a failure.
+    let simulate = match env::var_os("__CARGO_TEST_OWNERSHIP") {
+        Some(p) if path == p => true,
+        _ => false,
+    };
+    if current_user != meta.uid() || simulate {
+        return Err(OwnershipError {
+            owner: get_username(meta.uid()),
+            current_user: get_username(current_user),
+            path: path.to_owned(),
+        }
+        .into());
+    }
+    Ok(())
+}
+
+#[cfg(windows)]
+fn _validate_ownership(path: &Path) -> Result<()> {
+    unsafe { windows::_validate_ownership(path) }
+}
+
+/// An error representing a file that is owned by a different user.
+#[allow(dead_code)] // Debug is required by std Error
+#[derive(Debug)]
+pub struct OwnershipError {
+    pub owner: String,
+    pub current_user: String,
+    pub path: PathBuf,
+}
+
+impl std::error::Error for OwnershipError {}
+
+impl fmt::Display for OwnershipError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{self:?}")
+    }
+}
+
+#[cfg(windows)]
+mod windows {
+    use anyhow::{bail, Error, Result};
+    use std::env;
+    use std::ffi::OsString;
+    use std::io;
+    use std::os::windows::ffi::{OsStrExt, OsStringExt};
+    use std::path::Path;
+    use std::ptr::null_mut;
+    use winapi::shared::minwindef::{DWORD, FALSE, HLOCAL, TRUE};
+    use winapi::shared::sddl::ConvertSidToStringSidW;
+    use winapi::shared::winerror::ERROR_INSUFFICIENT_BUFFER;
+    use winapi::um::accctrl::SE_FILE_OBJECT;
+    use winapi::um::aclapi::GetNamedSecurityInfoW;
+    use winapi::um::errhandlingapi::GetLastError;
+    use winapi::um::handleapi::CloseHandle;
+    use winapi::um::processthreadsapi::{GetCurrentProcess, OpenProcessToken};
+    use winapi::um::securitybaseapi::{
+        CheckTokenMembership, EqualSid, GetTokenInformation, IsValidSid, IsWellKnownSid,
+    };
+    use winapi::um::winbase::{LocalFree, LookupAccountSidW};
+    use winapi::um::winnt::{
+        TokenUser, WinBuiltinAdministratorsSid, DACL_SECURITY_INFORMATION, HANDLE,
+        OWNER_SECURITY_INFORMATION, PSID, TOKEN_QUERY, TOKEN_USER,
+    };
+
+    pub(super) unsafe fn _validate_ownership(path: &Path) -> Result<()> {
+        let me = GetCurrentProcess();
+        let mut token = null_mut();
+        if OpenProcessToken(me, TOKEN_QUERY, &mut token) == 0 {
+            return Err(
+                Error::new(io::Error::last_os_error()).context("failed to get process token")
+            );
+        }
+        let token = Handle { inner: token };
+        let mut len: DWORD = 0;
+        // Get the size of the token buffer.
+        if GetTokenInformation(token.inner, TokenUser, null_mut(), 0, &mut len) != 0
+            || GetLastError() != ERROR_INSUFFICIENT_BUFFER
+        {
+            return Err(Error::new(io::Error::last_os_error())
+                .context("failed to get token information size"));
+        }
+        // Get the SID of the current user.
+        let mut token_info = Vec::<u8>::with_capacity(len as usize);
+        if GetTokenInformation(
+            token.inner,
+            TokenUser,
+            token_info.as_mut_ptr() as *mut _,
+            len,
+            &mut len,
+        ) == 0
+        {
+            return Err(
+                Error::new(io::Error::last_os_error()).context("failed to get token information")
+            );
+        }
+        let token_user = token_info.as_ptr() as *const TOKEN_USER;
+        let user_sid = (*token_user).User.Sid;
+
+        // Get the SID of the owner of the path.
+        let path_w = wide_path(path);
+        let mut owner_sid = null_mut();
+        let mut descriptor = LocalFreeWrapper { inner: null_mut() };
+        let result = GetNamedSecurityInfoW(
+            path_w.as_ptr(),
+            SE_FILE_OBJECT,
+            OWNER_SECURITY_INFORMATION | DACL_SECURITY_INFORMATION,
+            &mut owner_sid,
+            null_mut(),
+            null_mut(),
+            null_mut(),
+            &mut descriptor.inner,
+        );
+        if result != 0 {
+            let io_err = io::Error::from_raw_os_error(result as i32);
+            return Err(Error::new(io_err).context(format!(
+                "failed to get security descriptor for path {}",
+                path.display()
+            )));
+        }
+        if IsValidSid(owner_sid) == 0 {
+            bail!(
+                "unexpected invalid file owner sid for path {}",
+                path.display()
+            );
+        }
+        let simulate = match env::var_os("__CARGO_TEST_OWNERSHIP") {
+            Some(p) if path == p => true,
+            _ => false,
+        };
+        if !simulate && EqualSid(user_sid, owner_sid) != 0 {
+            return Ok(());
+        }
+        // Allow paths that are owned by the Administrators Group if the user is
+        // also a member of the group. This is added for convenience. Files
+        // created when run with "Run as Administrator" are owned by the group.
+        if !simulate && IsWellKnownSid(owner_sid, WinBuiltinAdministratorsSid) == TRUE {
+            let mut is_member = FALSE;
+            if CheckTokenMembership(null_mut(), user_sid, &mut is_member) == 0 {
+                log::info!(
+                    "failed to check if member of administrators: {}",
+                    io::Error::last_os_error()
+                );
+                // Fall through
+            } else {
+                if is_member == TRUE {
+                    return Ok(());
+                }
+            }
+        }
+
+        let owner = sid_to_name(owner_sid).unwrap_or_else(|| sid_to_string(owner_sid));
+        let current_user = sid_to_name(user_sid).unwrap_or_else(|| sid_to_string(user_sid));
+        return Err(super::OwnershipError {
+            owner,
+            current_user,
+            path: path.to_owned(),
+        }
+        .into());
+    }
+
+    unsafe fn sid_to_string(sid: PSID) -> String {
+        let mut s_ptr = null_mut();
+        if ConvertSidToStringSidW(sid, &mut s_ptr) == 0 {
+            log::info!(
+                "failed to convert sid to string: {}",
+                io::Error::last_os_error()
+            );
+            return "Unknown".to_string();
+        }
+        let len = (0..).take_while(|&i| *s_ptr.offset(i) != 0).count();
+        let slice: &[u16] = std::slice::from_raw_parts(s_ptr, len);
+        let s = OsString::from_wide(slice);
+        LocalFree(s_ptr as *mut _);
+        s.into_string().unwrap_or_else(|_| "Unknown".to_string())
+    }
+
+    unsafe fn sid_to_name(sid: PSID) -> Option<String> {
+        // Note: This operation may be very expensive and slow.
+        let mut name_size = 0;
+        let mut domain_size = 0;
+        let mut pe_use = 0;
+        // Get the length of the name.
+        if LookupAccountSidW(
+            null_mut(), // lpSystemName (where to search)
+            sid,
+            null_mut(), // Name
+            &mut name_size,
+            null_mut(), // ReferencedDomainName
+            &mut domain_size,
+            &mut pe_use,
+        ) != 0
+            || GetLastError() != ERROR_INSUFFICIENT_BUFFER
+        {
+            log::debug!(
+                "failed to determine sid name length: {}",
+                io::Error::last_os_error()
+            );
+            return None;
+        }
+        let mut name: Vec<u16> = vec![0; name_size as usize];
+        let mut domain: Vec<u16> = vec![0; domain_size as usize];
+        if LookupAccountSidW(
+            null_mut(),
+            sid,
+            name.as_mut_ptr(),
+            &mut name_size,
+            domain.as_mut_ptr(),
+            &mut domain_size,
+            &mut pe_use,
+        ) == 0
+        {
+            log::debug!(
+                "failed to fetch name ({}): {}",
+                name_size,
+                io::Error::last_os_error()
+            );
+            return None;
+        }
+        let name = str_from_wide(&name);
+        let domain = str_from_wide(&domain);
+
+        return Some(format!("{domain}\\{name}"));
+    }
+
+    struct Handle {
+        inner: HANDLE,
+    }
+    impl Drop for Handle {
+        fn drop(&mut self) {
+            unsafe {
+                CloseHandle(self.inner);
+            }
+        }
+    }
+
+    struct LocalFreeWrapper {
+        inner: HLOCAL,
+    }
+    impl Drop for LocalFreeWrapper {
+        fn drop(&mut self) {
+            unsafe {
+                if !self.inner.is_null() {
+                    LocalFree(self.inner);
+                    self.inner = null_mut();
+                }
+            }
+        }
+    }
+
+    fn str_from_wide(wide: &[u16]) -> String {
+        let len = wide.iter().position(|i| *i == 0).unwrap_or(wide.len());
+        let os_str = OsString::from_wide(&wide[..len]);
+        os_str
+            .into_string()
+            .unwrap_or_else(|_| "Invalid UTF-8".to_string())
+    }
+
+    fn wide_path(path: &Path) -> Vec<u16> {
+        let mut wide: Vec<u16> = path.as_os_str().encode_wide().collect();
+        if wide.iter().any(|b| *b == 0) {
+            panic!("nul byte in wide string");
+        }
+        wide.push(0);
+        wide
+    }
+}
