Prevent various panics when deserializing malformed SystemTime

Author: cyang1

serde/build.rs

@@ -76,12 +76,14 @@ fn main() {
         println!("cargo:rustc-cfg=serde_derive");
     }
 
-    // TryFrom, Atomic types, and non-zero signed integers stabilized in Rust 1.34:
+    // TryFrom, Atomic types, non-zero signed integers, and `SystemTime::checked_add`
+    // stabilized in Rust 1.34:
     // https://blog.rust-lang.org/2019/04/11/Rust-1.34.0.html#tryfrom-and-tryinto
     // https://blog.rust-lang.org/2019/04/11/Rust-1.34.0.html#library-stabilizations
     if minor >= 34 {
         println!("cargo:rustc-cfg=core_try_from");
         println!("cargo:rustc-cfg=num_nonzero_signed");
+        println!("cargo:rustc-cfg=systemtime_checked_add");
 
         // Whitelist of archs that support std::sync::atomic module. Ideally we
         // would use #[cfg(target_has_atomic = "...")] but it is not stable yet.

serde/src/de/impls.rs

@@ -2046,6 +2046,17 @@ impl<'de> Deserialize<'de> for SystemTime {
             }
         }
 
+        fn check_overflow<E>(secs: u64, nanos: u32) -> Result<(), E>
+        where
+            E: Error,
+        {
+            static NANOS_PER_SEC: u32 = 1_000_000_000;
+            match secs.checked_add((nanos / NANOS_PER_SEC) as u64) {
+                Some(_) => Ok(()),
+                None => Err(E::custom("overflow deserializing SystemTime epoch offset")),
+            }
+        }
+
         struct DurationVisitor;
 
         impl<'de> Visitor<'de> for DurationVisitor {
@@ -2071,6 +2082,7 @@ impl<'de> Deserialize<'de> for SystemTime {
                         return Err(Error::invalid_length(1, &self));
                     }
                 };
+                try!(check_overflow(secs, nanos));
                 Ok(Duration::new(secs, nanos))
             }
 
@@ -2108,13 +2120,20 @@ impl<'de> Deserialize<'de> for SystemTime {
                     Some(nanos) => nanos,
                     None => return Err(<A::Error as Error>::missing_field("nanos_since_epoch")),
                 };
+                try!(check_overflow(secs, nanos));
                 Ok(Duration::new(secs, nanos))
             }
         }
 
         const FIELDS: &'static [&'static str] = &["secs_since_epoch", "nanos_since_epoch"];
         let duration = try!(deserializer.deserialize_struct("SystemTime", FIELDS, DurationVisitor));
-        Ok(UNIX_EPOCH + duration)
+        #[cfg(systemtime_checked_add)]
+        let ret = UNIX_EPOCH
+            .checked_add(duration)
+            .ok_or(D::Error::custom("overflow deserializing SystemTime"));
+        #[cfg(not(systemtime_checked_add))]
+        let ret = Ok(UNIX_EPOCH + duration);
+        ret
     }
 }
 

test_suite/tests/test_de.rs

@@ -15,7 +15,7 @@ use std::sync::atomic::{
     AtomicUsize, Ordering,
 };
 use std::sync::{Arc, Weak as ArcWeak};
-use std::time::{Duration, UNIX_EPOCH};
+use std::time::{Duration, SystemTime, UNIX_EPOCH};
 
 #[cfg(target_arch = "x86_64")]
 use std::sync::atomic::{AtomicI64, AtomicU64};
@@ -199,6 +199,19 @@ macro_rules! declare_error_tests {
                 assert_de_tokens_error::<$target>($tokens, $expected);
             }
         )+
+    };
+
+    ($(
+        $(#[$cfg:meta])*
+        $name:ident<$target:ty> { $tokens:expr, $expected:expr, }
+    )+) => {
+        $(
+            $(#[$cfg])*
+            #[test]
+            fn $name() {
+                assert_de_tokens_error::<$target>($tokens, $expected);
+            }
+        )+
     }
 }
 
@@ -1614,4 +1627,35 @@ declare_error_tests! {
         ],
         "overflow deserializing Duration",
     }
+    test_systemtime_overflow_seq<SystemTime> {
+        &[
+            Token::Seq { len: Some(2) },
+                Token::U64(u64::max_value()),
+                Token::U32(1_000_000_000),
+            Token::SeqEnd,
+        ],
+        "overflow deserializing SystemTime epoch offset",
+    }
+    test_systemtime_overflow_struct<SystemTime> {
+        &[
+            Token::Struct { name: "SystemTime", len: 2 },
+                Token::Str("secs_since_epoch"),
+                Token::U64(u64::max_value()),
+
+                Token::Str("nanos_since_epoch"),
+                Token::U32(1_000_000_000),
+            Token::StructEnd,
+        ],
+        "overflow deserializing SystemTime epoch offset",
+    }
+    #[cfg(systemtime_checked_add)]
+    test_systemtime_overflow<SystemTime> {
+        &[
+            Token::Seq { len: Some(2) },
+                Token::U64(u64::max_value()),
+                Token::U32(0),
+            Token::SeqEnd,
+        ],
+        "overflow deserializing SystemTime",
+    }
 }