Fix panic due to incorrect ANSI escape handling, add fuzzer (#137)

* Fix subtraction with overflow with malformed ANSI escape

* Add fuzzing target

* Add assertion to avoid silent overflow

* Rename fuzzer

fuzz/.gitignore

@@ -0,0 +1,3 @@
+target
+corpus
+artifacts

fuzz/Cargo.toml

@@ -0,0 +1,25 @@
+[package]
+name = "prettytable-rs-fuzz"
+version = "0.0.0"
+authors = ["Automatically generated"]
+publish = false
+edition = "2018"
+
+[package.metadata]
+cargo-fuzz = true
+
+[dependencies]
+libfuzzer-sys = "0.4"
+
+[dependencies.prettytable-rs]
+path = ".."
+
+# Prevent this from interfering with workspaces
+[workspace]
+members = ["."]
+
+[[bin]]
+name = "render"
+path = "fuzz_targets/render.rs"
+test = false
+doc = false

fuzz/fuzz_targets/render.rs

@@ -0,0 +1,23 @@
+#![no_main]
+use libfuzzer_sys::fuzz_target;
+
+use prettytable::{Table, Row, Cell};
+
+use prettytable::format::Alignment::{self, *};
+
+fuzz_target!(|data: Vec<Vec<(String, u8)>>| {
+    fn align_from_u8(x: u8) -> Alignment {
+        match x {
+            0 => LEFT,
+            1 => CENTER,
+            _ => RIGHT,
+        }
+    }
+    let mut pt = prettytable::Table::new();
+    for row in data {
+        let cells = row.into_iter().map(|x| Cell::new_align(&x.0, align_from_u8(x.1))).collect();
+        pt.add_row(Row::new(cells));
+    }
+
+    let _ = pt.print(&mut std::io::sink());
+});

src/lib.rs

@@ -1072,4 +1072,19 @@ mod tests {
         assert!(table.print_html(&mut writer).is_ok());
         assert_eq!(writer.as_string().replace("\r\n", "\n"), out);
     }
+
+    #[test]
+    fn test_panic() {
+        let mut table = Table::new();
+
+        table.add_row(Row::new(vec![Cell::new("\u{1b}[\u{1b}\u{0}\u{0}")]));
+
+        let out = "+--+
+| \u{1b}[\u{1b}\u{0}\u{0} |
++--+
+";
+
+        assert_eq!(table.to_string().replace("\r\n", "\n"), out);
+        assert_eq!(3, table.print(&mut StringWriter::new()).unwrap());
+    }
 }