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fix: add maximum size validation for JWT secrets to prevent DoS attacks #301

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fix: add maximum size validation for JWT secrets to prevent DoS attacks #301

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b67cf3e
Update auth.rs
crStiv Aug 15, 2025
12dab07
Update auth.rs
crStiv Aug 18, 2025
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17 changes: 14 additions & 3 deletions eth1_api/src/auth.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,7 @@ use zeroize::Zeroizing;
#[cfg(test)]
use derive_more::Debug;

const JWT_SECRET_SIZE_MIN_BYTES: usize = 32;
const JWT_SECRET_SIZE_BYTES: usize = 32; // Exactly 256 bits as per Ethereum execution API specification

#[derive(Debug)]
#[cfg_attr(test, derive(Default))]
Expand Down Expand Up @@ -160,7 +160,7 @@ impl Secret {
.context(JwtSecretError::InvalidSecret)?;

ensure!(
bytes.len() >= JWT_SECRET_SIZE_MIN_BYTES,
bytes.len() == JWT_SECRET_SIZE_BYTES,
JwtSecretError::IncorrectSize,
);

Expand All @@ -173,7 +173,7 @@ impl Secret {
#[derive(Debug, Error)]
#[cfg_attr(test, derive(PartialEq, Eq))]
enum JwtSecretError {
#[error("JWT secret must be at least {JWT_SECRET_SIZE_MIN_BYTES} bytes")]
#[error("JWT secret must be exactly {JWT_SECRET_SIZE_BYTES} bytes (256 bits)")]
IncorrectSize,
#[error("failed to parse JWT secret")]
InvalidSecret,
Expand Down Expand Up @@ -208,6 +208,17 @@ mod tests {
assert_eq!(error, JwtSecretError::IncorrectSize);
}

#[test]
fn test_large_jwt_secret_decoding() {
// Create a hex string that would decode to more than JWT_SECRET_SIZE_BYTES
let large_hex: String = "a".repeat(JWT_SECRET_SIZE_BYTES * 2 + 2); // Each byte is 2 hex chars
let error = Secret::from_hex(large_hex.as_bytes())
.expect_err("Secret::from_hex should fail")
.downcast::<JwtSecretError>()
.expect("large JWT secret must cause JwtSecretError");
assert_eq!(error, JwtSecretError::IncorrectSize);
}

#[test]
fn test_auth_with_unset_secrets_path() -> Result<()> {
let auth = Auth::new(Options::default())?;
Expand Down