fix: audit PgValueRef::get() and usage sites for bad casts

sqlx-postgres/src/types/array.rs

@@ -242,6 +242,9 @@ where
                 // length of the array axis
                 let len = buf.get_i32();
 
+                let len = usize::try_from(len)
+                    .map_err(|_| format!("overflow converting array len ({len}) to usize"))?;
+
                 // the lower bound, we only support arrays starting from "1"
                 let lower = buf.get_i32();
 
@@ -249,14 +252,12 @@ where
                     return Err(format!("encountered an array with a lower bound of {lower} in the first dimension; only arrays starting at one are supported").into());
                 }
 
-                let mut elements = Vec::with_capacity(len as usize);
+                let mut elements = Vec::with_capacity(len);
 
                 for _ in 0..len {
-                    elements.push(T::decode(PgValueRef::get(
-                        &mut buf,
-                        format,
-                        element_type_info.clone(),
-                    ))?)
+                    let value_ref = PgValueRef::get(&mut buf, format, element_type_info.clone())?;
+
+                    elements.push(T::decode(value_ref)?);
                 }
 
                 Ok(elements)

sqlx-postgres/src/types/range.rs

@@ -350,7 +350,7 @@ where
 
                 if !flags.contains(RangeFlags::LB_INF) {
                     let value =
-                        T::decode(PgValueRef::get(&mut buf, value.format, element_ty.clone()))?;
+                        T::decode(PgValueRef::get(&mut buf, value.format, element_ty.clone())?)?;
 
                     start = if flags.contains(RangeFlags::LB_INC) {
                         Bound::Included(value)
@@ -361,7 +361,7 @@ where
 
                 if !flags.contains(RangeFlags::UB_INF) {
                     let value =
-                        T::decode(PgValueRef::get(&mut buf, value.format, element_ty.clone()))?;
+                        T::decode(PgValueRef::get(&mut buf, value.format, element_ty.clone())?)?;
 
                     end = if flags.contains(RangeFlags::UB_INC) {
                         Bound::Included(value)

sqlx-postgres/src/types/record.rs

@@ -137,7 +137,7 @@ impl<'r> PgRecordDecoder<'r> {
 
                 self.ind += 1;
 
-                T::decode(PgValueRef::get(&mut self.buf, self.fmt, element_type))
+                T::decode(PgValueRef::get(&mut self.buf, self.fmt, element_type)?)
             }
 
             PgValueFormat::Text => {

sqlx-postgres/src/value.rs

@@ -1,11 +1,10 @@
 use crate::error::{BoxDynError, UnexpectedNullError};
 use crate::{PgTypeInfo, Postgres};
 use sqlx_core::bytes::{Buf, Bytes};
+pub(crate) use sqlx_core::value::{Value, ValueRef};
 use std::borrow::Cow;
 use std::str::from_utf8;
 
-pub(crate) use sqlx_core::value::{Value, ValueRef};
-
 #[derive(Debug, Clone, Copy, Eq, PartialEq)]
 #[repr(u8)]
 pub enum PgValueFormat {
@@ -31,24 +30,31 @@ pub struct PgValue {
 }
 
 impl<'r> PgValueRef<'r> {
-    pub(crate) fn get(buf: &mut &'r [u8], format: PgValueFormat, ty: PgTypeInfo) -> Self {
-        let mut element_len = buf.get_i32();
+    pub(crate) fn get(
+        buf: &mut &'r [u8],
+        format: PgValueFormat,
+        ty: PgTypeInfo,
+    ) -> Result<Self, String> {
+        let element_len = buf.get_i32();
 
         let element_val = if element_len == -1 {
-            element_len = 0;
             None
         } else {
-            Some(&buf[..(element_len as usize)])
+            let element_len: usize = element_len
+                .try_into()
+                .map_err(|_| format!("overflow converting element_len ({element_len}) to usize"))?;
+
+            let val = &buf[..element_len];
+            buf.advance(element_len);
+            Some(val)
         };
 
-        buf.advance(element_len as usize);
-
-        PgValueRef {
+        Ok(PgValueRef {
             value: element_val,
             row: None,
             type_info: ty,
             format,
-        }
+        })
     }
 
     pub fn format(&self) -> PgValueFormat {