jdx/mise · error · eyre::Report

invalid blob digest (expected 64 lowercase hex chars): {dige

Error message

invalid blob digest (expected 64 lowercase hex chars): {digest}

What it means

The second half of validate_sha256_digest: after stripping 'sha256:', the remainder must be exactly 64 characters of lowercase hex ([0-9a-f]). Wrong length, uppercase hex, or non-hex characters (including '../' traversal payloads) all fail here. The strict charset is what makes the digest safe to use as a single filesystem path component.

Source

Thrown at src/oci/layout.rs:147

        let bytes = serde_json::to_vec(manifest)?;
        self.write_blob(&bytes)
    }
}

/// Validate that `digest` is a well-formed `sha256:<64 lowercase hex>` string.
/// Guards against path traversal from a malicious registry returning something
/// like `sha256:../../etc/passwd` as a layer digest — without this check, that
/// would be used directly as a filesystem path component.
pub(crate) fn validate_sha256_digest(digest: &str) -> Result<()> {
    let Some(hex) = digest.strip_prefix("sha256:") else {
        eyre::bail!("invalid blob digest (expected sha256: prefix): {digest}");
    };
    if hex.len() != 64
        || !hex
            .chars()
            .all(|c| c.is_ascii_digit() || ('a'..='f').contains(&c))
    {
        eyre::bail!("invalid blob digest (expected 64 lowercase hex chars): {digest}");
    }
    Ok(())
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn rejects_path_traversal() {
        assert!(validate_sha256_digest("sha256:../../etc/passwd").is_err());
        assert!(validate_sha256_digest("sha256:../foo").is_err());
        assert!(validate_sha256_digest("../bad").is_err());
        assert!(validate_sha256_digest("sha256:DEADBEEF").is_err());
    }

    #[test]
    fn accepts_valid_digest() {

View on GitHub (pinned to 9dcfcaa0dc)

Solutions

1. Use the digest verbatim from the OCI descriptor produced by a conformant registry/tool.
2. If generating digests yourself, lowercase the hex and ensure 64 chars: format!("sha256:{:x}", Sha256::digest(bytes)).
3. Treat any digest failing this check in untrusted input as tampering and reject the whole manifest rather than retrying.

Example fix

// before
let d = format!("sha256:{:X}", hash); // uppercase hex

// after
let d = format!("sha256:{:x}", hash); // 64 lowercase hex chars

fn is_sha256_digest(s: &str) -> bool {
    let Some(hex) = s.strip_prefix("sha256:") else { return false };
    hex.len() == 64 && hex.bytes().all(|b| matches!(b, b'0'..=b'9' | b'a'..=b'f'))
}   // rejects 'sha256:../foo', uppercase, short/long hex

When it happens

Trigger: Digests like 'sha256:ABCDEF...' (uppercase), 'sha256:abc' (short), 'sha256:../../etc/passwd' or 'sha256:../foo' (traversal — covered by the unit test rejects_path_traversal), or digests with whitespace/newlines from sloppy string handling.

Common situations: A malicious or broken registry returning crafted digest strings; uppercase digests copied from docs or generated by tools that uppercase hex; truncated digests from manual copying.

Related errors

• invalid blob digest (expected sha256: prefix): {digest}
• [dotfiles]."{}": target is not a safe OCI path
• unsupported remote cache digest algorithm
• invalid remote cache digest
• oci mount_point must not be empty

AI-assisted analysis of jdx/mise@9dcfcaa0dc (2026-08-17). Data as JSON: /api/errors/f5a611ae96208be0. Report an issue: GitHub.