Merge pull request #769 from jyn514/ydbrust

Add use-after-free advisory for `yottadb 1.1.0` and earlier

Author: Shnatsel

crates/yottadb/RUSTSEC-0000-0000.md

@@ -0,0 +1,41 @@
+```toml
+[advisory]
+id = "RUSTSEC-0000-0000"
+package = "yottadb"
+date = "2021-02-09"
+url = "https://gitlab.com/YottaDB/Lang/YDBRust/-/issues/40"
+categories = ["memory-corruption"]
+keywords = ["use-after-free"]
+
+[versions]
+patched = [">= 1.2.0"]
+
+[affected.functions]
+"yottadb::Key::sub_next_self_st" = ["< 1.2.0"]
+"yottadb::Key::sub_prev_self_st" = ["< 1.2.0"]
+"yottadb::KeyContext::sub_next_self_st" = ["< 1.2.0"]
+"yottadb::KeyContext::sub_prev_self_st" = ["< 1.2.0"]
+```
+
+# Use-after-free in `subscript_next` and `subscript_prev` wrappers
+
+Affected versions of this crate had an unsound implementation which could pass
+a pointer to freed memory to `ydb_subscript_next_st` and
+`ydb_subscript_prev_st` if the variable and subscripts did not have enough
+memory allocated on the first call to hold the next variable in the database.
+
+For example, the following code had undefined behavior:
+
+```rust
+let mut key = Key::variable(String::from("a"));
+Key::variable("averylongkeywithlotsofletters")
+    .set_st(YDB_NOTTP, Vec::new(), b"some val")
+    .unwrap();
+key.sub_next_self_st(YDB_NOTTP, Vec::new()).unwrap();
+```
+
+`yottadb` has no reverse-dependencies on crates.io and there are no known
+instances of this API being used incorrectly in practice. The fix is backwards
+compatible.
+
+The flaw was corrected by recalculating the pointer each time it was reallocated.