program: Add const asserts

program/src/processor/initialize.rs

@@ -1,3 +1,5 @@
+use core::mem::{align_of, size_of};
+
 use pinocchio::{
     cpi::{Seed, Signer},
     error::ProgramError,
@@ -215,8 +217,13 @@ struct Initialize {
     pub data_source: u8,
 }
 
+// Enforces 1-byte alignment for the struct.
+const _: () = {
+    assert!(align_of::<Initialize>() == 1);
+};
+
 impl Initialize {
-    const LEN: usize = core::mem::size_of::<Self>();
+    const LEN: usize = size_of::<Self>();
 
     /// # Safety
     ///

program/src/processor/set_data.rs

@@ -1,3 +1,5 @@
+use core::mem::{align_of, size_of};
+
 use pinocchio::{account::AccountView, error::ProgramError, ProgramResult, Resize};
 
 use crate::state::{
@@ -164,8 +166,13 @@ struct SetData {
     // - `&[u8]`: remaining data
 }
 
+// Enforces 1-byte alignment for the struct.
+const _: () = {
+    assert!(align_of::<SetData>() == 1);
+};
+
 impl SetData {
-    const LEN: usize = core::mem::size_of::<Self>();
+    const LEN: usize = size_of::<Self>();
 
     /// # Safety
     ///

program/src/processor/write.rs

@@ -122,7 +122,6 @@ pub fn write(accounts: &mut [AccountView], instruction_data: &[u8]) -> ProgramRe
 }
 
 /// Instruction data expected by the `Write` instruction.
-#[repr(C)]
 struct Write<'a> {
     /// Offset to write to.
     offset: &'a [u8; 4],

program/src/state/buffer.rs

@@ -1,3 +1,5 @@
+use core::mem::align_of;
+
 use pinocchio::{
     account::{AccountView, Ref},
     error::ProgramError,
@@ -41,6 +43,11 @@ pub struct Buffer {
     _padding: [u8; 14],
 }
 
+// Enforces 1-byte alignment for the struct.
+const _: () = {
+    assert!(align_of::<Buffer>() == 1);
+};
+
 impl Buffer {
     /// The minimum size of a `Buffer` (`96` bytes).
     pub const LEN: usize = core::mem::size_of::<Buffer>();

program/src/state/data.rs

@@ -1,3 +1,5 @@
+use core::{mem::align_of, str::from_utf8};
+
 use pinocchio::{error::ProgramError, Address};
 
 use super::{DataSource, ZeroableOption};
@@ -23,12 +25,15 @@ impl<'a> Data<'a> {
         Ok(match data_source {
             DataSource::Direct => Data::Direct(DirectData(bytes)),
             DataSource::Url => Data::Url(UrlData(
-                core::str::from_utf8(bytes).map_err(|_| ProgramError::InvalidArgument)?,
+                from_utf8(bytes).map_err(|_| ProgramError::InvalidArgument)?,
             )),
             DataSource::External => {
                 if bytes.len() < ExternalData::LEN {
                     return Err(ProgramError::InvalidArgument);
                 }
+                if !(bytes.as_ptr() as usize).is_multiple_of(align_of::<ExternalData>()) {
+                    return Err(ProgramError::InvalidArgument);
+                }
                 // SAFETY: `bytes` was validated to have the expected length
                 // to hold a `Data::External` reference.
                 Data::External(unsafe { &*(bytes.as_ptr() as *const ExternalData) })
@@ -67,6 +72,11 @@ pub struct ExternalData {
     pub length: ZeroableOption<u32>,
 }
 
+// Enforces 4-byte alignment for the `ExternalData` struct.
+const _: () = {
+    assert!(align_of::<ExternalData>() == 4);
+};
+
 impl ExternalData {
     pub const LEN: usize = core::mem::size_of::<ExternalData>();
 }

program/src/state/header.rs

@@ -1,3 +1,5 @@
+use core::mem::align_of;
+
 use pinocchio::{
     account::{AccountView, Ref},
     error::ProgramError,
@@ -56,6 +58,11 @@ pub struct Header {
     _padding: [u8; 5],
 }
 
+// Enforces 1-byte alignment for the struct.
+const _: () = {
+    assert!(align_of::<Header>() == 1);
+};
+
 impl Header {
     /// Length of the header (96 bytes).
     pub const LEN: usize = core::mem::size_of::<Header>();

program/src/state/mod.rs

@@ -2,12 +2,26 @@ pub mod buffer;
 pub mod data;
 pub mod header;
 
-use pinocchio::{address::ADDRESS_BYTES, error::ProgramError, Address, ProgramResult};
+use core::mem::size_of;
 
-use data::{Data, ExternalData};
-use header::Header;
+use pinocchio::{address::ADDRESS_BYTES, error::ProgramError, Address, ProgramResult};
 
-use crate::error::ProgramMetadataError;
+use crate::{
+    error::ProgramMetadataError,
+    state::{
+        buffer::Buffer,
+        data::{Data, ExternalData},
+        header::Header,
+    },
+};
+
+// Make sure both `Header` and `Buffer` structs have the same size.
+const _: () = {
+    assert!(
+        size_of::<Header>() == size_of::<Buffer>(),
+        "Header and Buffer should be the same size"
+    );
+};
 
 /// The length of the seed used to derive the metadata account address.
 pub const SEED_LEN: usize = 16;