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Fix MAILBOX_SIZE constant: 256 KB → 16 KB #3651

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Fix MAILBOX_SIZE constant: 256 KB → 16 KB #3651

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Copilot Apr 23, 2026
3b1d189
Fix MAILBOX_SIZE constant from 256KB to 16KB
Copilot Apr 23, 2026
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8 changes: 4 additions & 4 deletions api/src/mailbox.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -14,8 +14,8 @@ use zerocopy::{FromBytes, Immutable, IntoBytes, KnownLayout};

/// Maximum input data size for cryptographic mailbox commands.
pub const MAX_CMB_DATA_SIZE: usize = 4096;
/// Mailbox size in bytes (256 KB).
pub const MAILBOX_SIZE: usize = 256 * 1024;
/// Mailbox size in bytes (16 KB).
pub const MAILBOX_SIZE: usize = 16 * 1024;
/// Maximum input size for CM_SHA command (mailbox size minus header overhead).
/// The overhead consists of: MailboxReqHeader (4 bytes) + hash_algorithm (4 bytes) + input_size (4 bytes) = 12 bytes.
pub const MAX_CM_SHA_INPUT_SIZE: usize = MAILBOX_SIZE - 12;
Expand Down Expand Up @@ -5745,12 +5745,12 @@ pub fn mbox_write_fifo(
mbox: &mbox::RegisterBlock<impl MmioMut>,
buf: &[u8],
) -> core::result::Result<(), CaliptraApiError> {
const MAILBOX_SIZE: u32 = 256 * 1024;
const PASSIVE_MAILBOX_SIZE: u32 = 256 * 1024;

let Ok(input_len) = u32::try_from(buf.len()) else {
return Err(CaliptraApiError::BufferTooLargeForMailbox);
};
if input_len > MAILBOX_SIZE {
if input_len > PASSIVE_MAILBOX_SIZE {
return Err(CaliptraApiError::BufferTooLargeForMailbox);
}
mbox.dlen().write(|_| input_len);
Expand Down