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🛡️ Sentinel: [HIGH] Fix Ed25519 signature malleability #7

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🛡️ Sentinel: [HIGH] Fix Ed25519 signature malleability #7

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4 changes: 4 additions & 0 deletions .jules/sentinel.md
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@@ -0,0 +1,4 @@
## 2024-08-11 - Use `verify_strict` for Ed25519 signature verification
**Vulnerability:** Signature malleability in Ed25519 signatures due to `verify` instead of `verify_strict`.
**Learning:** `ed25519-dalek` provides a standard `verify` method that doesn't strictly adhere to RFC 8032 requirements for non-malleability, leading to multiple valid signatures for the same message.
**Prevention:** Use `verify_strict` when verifying Ed25519 signatures using `ed25519-dalek` to ensure RFC 8032 compliance.
Comment on lines +1 to +4

@coderabbitai coderabbitai Bot Aug 11, 2026

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🔒 Security & Privacy | 🟡 Minor | ⚡ Quick win

🧩 Analysis chain

🏁 Script executed:

#!/bin/bash
set -eu

printf '%s\n' '--- cited files ---'
for file in .jules/sentinel.md crates/gitlawb-attest/src/attestation.rs crates/gitlawb-core/src/identity.rs; do
  if [ -f "$file" ]; then
    echo "--- $file ---"
    wc -l "$file"
    case "$file" in
      .jules/sentinel.md) sed -n '1,12p' "$file" ;;
      *) sed -n '70,125p' "$file" ;;
    esac
  else
    echo "MISSING: $file"
  fi
done

printf '%s\n' '--- ed25519-dalek declarations ---'
rg -n --glob 'Cargo.toml' --glob 'Cargo.lock' 'ed25519-dalek|verify_strict|verify\(' .

Repository: euxaristia/node

Length of output: 5598

🌐 Web query:

ed25519-dalek verify_strict documentation RFC 8032 ZIP-215 non-RFC 8032 compliant

💡 Result:

In the ed25519-dalek library, the verify_strict method is a specialized verification function designed to mitigate specific vulnerabilities, such as weak-key forgery [1][2][3]. It is explicitly documented as being "technically non-RFC 8032 compliant" because it enforces additional checks not mandated by the RFC [4][3]. The primary reasons for this non-compliance and the divergence from RFC 8032 are as follows: RFC 8032 Compliance: RFC 8032 mandates that signature verification must fail if the scalar s is not properly reduced modulo the group order L [4][3]. While ed25519-dalek's verification functions (including verify_strict) perform this check, the RFC also specifies optional malleability checks [4][3]. Strict Verification vs. RFC 8032: The verify_strict method performs extra checks—specifically, it verifies that neither the public key A nor the signature point R are small-order (weak) points [3][5]. These checks are not strictly required by the base RFC 8032 specification but are necessary to prevent "weak-key forgery" attacks, where an attacker crafts a signature that is valid for almost any message [1][2][5]. Relationship to ZIP-215: ZIP-215 was introduced to resolve ambiguities and consensus-critical differences in how various Ed25519 implementations interpret RFC 8032 [6][7]. ZIP-215 mandates the use of a "cofactor-multiplied" verification equation ([8][S]B = [8]R + [8][k]A), whereas RFC 8032 allows an unmultiplied version ([S]B = R + [k]A) [9][6]. Current State in ed25519-dalek: As of the latest documentation, the verify_strict implementation in ed25519-dalek does not fully conform to the ZIP-215 validation criteria [4][3]. Specifically, it historically used the unmultiplied verification equation (without the cofactor) and performed different point encoding checks than those defined in ZIP-215 [9][8]. While there have been ongoing discussions and efforts to implement ZIP-215-compliant verification within the broader curve25519-dalek ecosystem, verify_strict is primarily intended for its original purpose of weak-key resistance rather than serving as a ZIP-215 implementation [9][3][8]. In summary, verify_strict is non-compliant with RFC 8032 because it adds defensive checks against weak-key forgery that the RFC does not enforce, and it currently does not align with the specific cofactor-multiplied verification rules required by ZIP-215 [4][9][3].

Citations:

Describe verify_strict as stricter than RFC 8032.

ed25519-dalek documents verify_strict as technically non-RFC 8032 compliant because it applies additional validation. Update .jules/sentinel.md and both Sentinel comments to describe the repository’s intentional stricter policy for rejecting malleable and weak-key encodings. Keep verify_strict.

📍 Affects 3 files
  • .jules/sentinel.md#L1-L4 (this comment)
  • crates/gitlawb-attest/src/attestation.rs#L114-L115
  • crates/gitlawb-core/src/identity.rs#L82-L84
🤖 Prompt for AI Agents 
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In @.jules/sentinel.md around lines 1 - 4, Update the Ed25519 verification
documentation to state that verify_strict intentionally applies validation
stricter than RFC 8032, rejecting malleable signatures and weak-key encodings;
keep verify_strict unchanged. Revise the corresponding Sentinel comments in
.jules/sentinel.md, crates/gitlawb-attest/src/attestation.rs (114-115), and
crates/gitlawb-core/src/identity.rs (82-84) consistently.

Source: MCP tools

5 changes: 3 additions & 2 deletions crates/gitlawb-attest/src/attestation.rs
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Expand Up @@ -16,7 +16,7 @@
//! by exact match.

use base64::{engine::general_purpose::URL_SAFE_NO_PAD as B64U, Engine};
use ed25519_dalek::{Signature, Signer, SigningKey, Verifier, VerifyingKey};
use ed25519_dalek::{Signature, Signer, SigningKey, VerifyingKey};
use serde::{de::DeserializeOwned, Deserialize, Serialize};

use crate::error::{Error, Result};
Expand Down Expand Up @@ -111,7 +111,8 @@ impl Attestation {
.try_into()
.map_err(|_| Error::Signature("signature must be 64 bytes".to_string()))?;
let sig = Signature::from_bytes(&sig_bytes);
vk.verify(&bytes, &sig)
// Sentinel: Use verify_strict to prevent signature malleability (RFC 8032 compliance)
vk.verify_strict(&bytes, &sig)
.map_err(|e| Error::Signature(format!("ed25519: {e}")))?;

Ok(vk)
Expand Down
4 changes: 2 additions & 2 deletions crates/gitlawb-core/src/identity.rs
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Expand Up @@ -78,10 +78,10 @@ impl Keypair {

/// Verify an Ed25519 signature.
pub fn verify(verifying_key: &VerifyingKey, msg: &[u8], sig_bytes: &[u8; 64]) -> Result<()> {
use ed25519_dalek::Verifier;
let sig = Signature::from_bytes(sig_bytes);
// Sentinel: Use verify_strict to prevent signature malleability (RFC 8032 compliance)
verifying_key
.verify(msg, &sig)
.verify_strict(msg, &sig)
.map_err(|_| Error::SignatureInvalid)
}

Expand Down
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