feat(crypto): add a system OpenSSL backend and dependency guardrails

.agents/skills/build-from-issue/SKILL.md

@@ -34,3 +34,5 @@ Every PR from this issue-backed workflow must have its own existing issue and us
 Do not apply acceptance or roadmap decisions on behalf of a maintainer. Do not introduce `agent:*` workflow labels.
 
 For first-party security-sensitive crypto, use `openshell-crypto` and extend its facade/backend contracts when needed. Follow the [crypto architecture](../../../crates/openshell-crypto/CRYPTO.md) for compatibility, failure handling, and explicit coverage exceptions.
+
+When changing crypto dependencies, run `mise run rust:deny:policy`, including its dependency-boundary regression fixtures. Review any `deny.toml` wrapper change against the documented exception scope; an existing allowance does not authorize new security-sensitive operations outside the facade.

.agents/skills/fix-security-issue/SKILL.md

@@ -18,3 +18,5 @@ Use this skill after an authorized `review-security-issue` review identifies an
 Begin any fix comments with `> **🔧 security-fix-agent**`. Do not change human disposition or introduce `agent:*` workflow labels.
 
 For first-party security-sensitive crypto, use `openshell-crypto` and extend its facade/backend contracts when needed. Follow the [crypto architecture](../../../crates/openshell-crypto/CRYPTO.md) for compatibility, failure handling, and explicit coverage exceptions.
+
+When changing crypto dependencies, run `mise run rust:deny:policy`, including its dependency-boundary regression fixtures. Review any `deny.toml` wrapper change against the documented exception scope; an existing allowance does not authorize new security-sensitive operations outside the facade.

.agents/skills/review-github-pr/SKILL.md

@@ -153,7 +153,7 @@ Read through the full diff (and the PR description if available). Produce a summ
     suggested change.
   - Do not fabricate concerns or claim a behavioral regression without evidence
     for both the prior and proposed behavior.
-- **Cryptographic boundaries**: For changed first-party security-sensitive crypto, verify use of `openshell-crypto`, backend dispatch, failure propagation without fallback, and protocol/storage compatibility. Missing operations belong in the facade/backend contracts. Check dependency-owned and non-security exceptions against the repository's [crypto architecture](../../../crates/openshell-crypto/CRYPTO.md); protocol/parsing types alone are not bypasses. Report undocumented bypasses or scope expansion under **Potential Concerns**.
+- **Cryptographic boundaries**: For changed first-party security-sensitive crypto, verify use of `openshell-crypto`, backend dispatch, failure propagation without fallback, and protocol/storage compatibility. Missing operations belong in the facade/backend contracts. Check dependency-owned and other explicit exceptions against the repository's [crypto architecture](../../../crates/openshell-crypto/CRYPTO.md); protocol/parsing types alone are not bypasses. Check `mise run rust:deny:policy` results and review changes to `deny.toml` wrappers; package-level allowances do not authorize new bypasses within those packages. Report undocumented bypasses or scope expansion under **Potential Concerns**.
 - **Agent infrastructure**: When the PR changes behavior, commands, or development workflows, use the `sync-agent-infra` maintenance map to check that related skills were updated. When it adds, removes, or renames skills or crates; changes workflow relationships or skill coverage; modifies issue or PR templates; or changes agent cross-references, apply the full consistency checklist. Report missing companion updates or drift under **Potential Concerns**.
 
 ## Step 5: Output

.github/workflows/branch-checks.yml

@@ -196,8 +196,15 @@ jobs:
           prepare-shell: "true"
           shell-installable: .#devShells.x86_64-linux.default
 
+      - name: Install pinned cargo-deny
+        run: mise install --locked github:EmbarkStudios/cargo-deny
+
+      # Enter mise inside the Nix shell so Nix's cargo-deny cannot shadow the pin.
+      - name: Verify crypto dependency guardrail
+        run: mise exec github:EmbarkStudios/cargo-deny -- uv run --no-project python tasks/scripts/test-crypto-dependency-policy.py
+
       - name: Check dependencies
-        run: cargo deny check licenses bans sources
+        run: mise exec github:EmbarkStudios/cargo-deny -- cargo deny check licenses bans sources
 
   rust-format:
     name: Rust format
@@ -312,14 +319,52 @@ jobs:
       - name: Verify crypto backend independence
         shell: nix develop -c bash -euo pipefail {0}
         run: |
-          cargo tree --locked -p openshell-crypto --no-default-features --edges normal,build,dev --prefix none > /tmp/openshell-crypto-dependencies.txt
+          cargo tree --locked -p openshell-crypto --no-default-features --edges normal,build,dev --target all --prefix none > /tmp/openshell-crypto-dependencies.txt
           if grep -Eq '^(ring|aws-lc-rs|aws-lc-sys|aws-lc-fips-sys) v' /tmp/openshell-crypto-dependencies.txt; then
             echo "ERROR: backend-free crypto build includes Ring or AWS-LC" >&2
             cat /tmp/openshell-crypto-dependencies.txt >&2
             exit 1
           fi
           cargo test --locked -p openshell-crypto --no-default-features --test independent_backend
 
+      - name: Verify OpenSSL backend
+        shell: nix develop -c bash -euo pipefail {0}
+        env:
+          OPENSSL_NO_VENDOR: "1"
+          OPENSSL_STATIC: "0"
+        run: |
+          cargo tree --locked -p openshell-crypto --no-default-features --features openssl --edges normal,build,dev --target all --prefix none > /tmp/openshell-openssl-dependencies.txt
+          if grep -Eq '^(ring|aws-lc-rs|aws-lc-sys|aws-lc-fips-sys|openssl-src) v' /tmp/openshell-openssl-dependencies.txt; then
+            echo "ERROR: OpenSSL-only crypto build includes another backend or vendored OpenSSL" >&2
+            cat /tmp/openshell-openssl-dependencies.txt >&2
+            exit 1
+          fi
+          cargo clippy --locked -p openshell-crypto --no-default-features --features openssl --all-targets -- -D warnings
+          cargo test --locked -p openshell-crypto --no-default-features --features openssl
+          for feature in tls-tonic tls-kube tls-sqlx; do
+            cargo check --locked -p openshell-crypto --no-default-features --features "openssl,$feature"
+          done
+          cargo clippy --locked -p openshell-crypto --features openssl --all-targets -- -D warnings
+          cargo test --locked -p openshell-crypto --features openssl
+
+      - name: Verify dynamic OpenSSL linkage on Linux
+        if: runner.os == 'Linux'
+        shell: nix develop -c bash -euo pipefail {0}
+        env:
+          OPENSSL_NO_VENDOR: "1"
+          OPENSSL_STATIC: "0"
+        run: |
+          cargo test --locked -p openshell-crypto --no-default-features --features openssl --test openssl_tls --no-run --message-format=json > "$RUNNER_TEMP/openssl-artifacts.jsonl"
+          executable=$(uv run --no-project python -c 'import json, sys; artifacts = [json.loads(line) for line in sys.stdin]; paths = [a["executable"] for a in artifacts if a.get("reason") == "compiler-artifact" and a.get("target", {}).get("name") == "openssl_tls" and a.get("executable")]; assert len(paths) == 1, paths; print(paths[0])' < "$RUNNER_TEMP/openssl-artifacts.jsonl")
+          ldd "$executable" > "$RUNNER_TEMP/openssl-linkage.txt"
+          cat "$RUNNER_TEMP/openssl-linkage.txt"
+          for library in libssl libcrypto; do
+            if ! grep -Eq "^[[:space:]]*$library\\.so[^[:space:]]* => /" "$RUNNER_TEMP/openssl-linkage.txt"; then
+              echo "ERROR: $library did not resolve to a dynamic library" >&2
+              exit 1
+            fi
+          done
+
       - name: Test
         shell: nix develop -c bash -euo pipefail {0}
         env:

AGENTS.md

@@ -237,7 +237,7 @@ When behavior, commands, or development workflows change, review the related age
 
 ## Security
 
-- Route first-party security-sensitive cryptographic operations through `openshell-crypto`. If an operation is missing, extend the facade and backend implementation instead of adding a direct cryptographic implementation in an application crate. Preserve protocol compatibility and propagate backend failures without fallback. Protocol/parsing types and documented non-security or dependency-owned exceptions remain permitted; classify exceptions explicitly. Follow [Cryptography and FIPS](crates/openshell-crypto/CRYPTO.md).
+- Route first-party security-sensitive cryptographic operations through `openshell-crypto`. If an operation is missing, extend the facade and backend implementation instead of adding a direct cryptographic implementation in an application crate. Preserve protocol compatibility and propagate backend failures without fallback. Protocol/parsing types and documented exceptions remain permitted; classify exceptions explicitly. Run `mise run rust:deny:policy` when changing crypto dependencies; review `deny.toml` exceptions rather than widening them to pass CI. Follow [Cryptography and FIPS](crates/openshell-crypto/CRYPTO.md).
 - Never commit secrets, API keys, or credentials. If a file looks like it contains secrets (`.env`, `credentials.json`, etc.), do not stage it.
 - Do not run destructive operations (force push, hard reset, database drops) without explicit human confirmation.
 - Scope changes to the issue at hand. Do not make unrelated changes in the same branch.

crates/openshell-cli/src/tls.rs

@@ -205,7 +205,9 @@ pub fn build_rustls_config(materials: &TlsMaterials) -> Result<rustls::ClientCon
         .into_diagnostic()?;
     let key = load_private_key(&materials.key)?;
 
-    openshell_crypto::tls::client_builder()
+    openshell_crypto::tls::try_client_builder()
+        .into_diagnostic()
+        .wrap_err("configure gateway TLS client")?
         .with_root_certificates(roots)
         .with_client_auth_cert(cert_chain, key)
         .into_diagnostic()
@@ -252,7 +254,9 @@ impl ServerCertVerifier for InsecureServerCertVerifier {
 }
 
 pub fn build_insecure_rustls_config() -> Result<rustls::ClientConfig> {
-    let config = openshell_crypto::tls::client_builder()
+    let config = openshell_crypto::tls::try_client_builder()
+        .into_diagnostic()
+        .wrap_err("configure gateway TLS client")?
         .dangerous()
         .with_custom_certificate_verifier(std::sync::Arc::new(InsecureServerCertVerifier))
         .with_no_client_auth();