[pve-devel] [PATCH v2 20/22] auto-installer: fetch: add http post utility module

[Aaron Lauterer]

It sends a http(s) POST request with the sysinfo as payload and expects
an answer file in return.

In order to handle non FQDN URLs (e.g. IP addresses) and self signed
certificates, it can optionally take an SHA256 fingerprint of the
certificate. This can of course also be used to pin a certificate
explicitly, even if it would be in the trust chain.

A custom cert verifier for ureq / rustl was necessary to get cert
fingerprint matching to work.

If no fingerprint is proviced, we switch rustls to native-certs and
native-tls.

Signed-off-by: Aaron Lauterer <a.lauterer at proxmox.com>
---
 proxmox-auto-installer/Cargo.toml             |  6 ++
 .../src/fetch_plugins/utils/mod.rs            |  1 +
 .../src/fetch_plugins/utils/post.rs           | 93 +++++++++++++++++++
 3 files changed, 100 insertions(+)
 create mode 100644 proxmox-auto-installer/src/fetch_plugins/utils/post.rs

diff --git a/proxmox-auto-installer/Cargo.toml b/proxmox-auto-installer/Cargo.toml
index 52bf004..8afa2ec 100644
--- a/proxmox-auto-installer/Cargo.toml
+++ b/proxmox-auto-installer/Cargo.toml
@@ -17,3 +17,9 @@ serde_json = "1.0"
 toml = "0.7"
 log = "0.4.20"
 regex = "1.7"
+ureq = { version = "2.6", features = [ "native-certs", "native-tls" ] }
+rustls = { version = "0.20", features = [ "dangerous_configuration" ] }
+rustls-native-certs = "0.6"
+native-tls = "0.2"
+sha2 = "0.10"
+hex = "0.4"
diff --git a/proxmox-auto-installer/src/fetch_plugins/utils/mod.rs b/proxmox-auto-installer/src/fetch_plugins/utils/mod.rs
index 37341ee..e4921bf 100644
--- a/proxmox-auto-installer/src/fetch_plugins/utils/mod.rs
+++ b/proxmox-auto-installer/src/fetch_plugins/utils/mod.rs
@@ -12,6 +12,7 @@ static ANSWER_MP: &str = "/mnt/answer";
 static PARTLABEL: &str = "proxmoxinst";
 static SEARCH_PATH: &str = "/dev/disk/by-label";
 
+pub mod post;
 pub mod sysinfo;
 
 /// Searches for upper and lower case existence of the partlabel in the search_path
diff --git a/proxmox-auto-installer/src/fetch_plugins/utils/post.rs b/proxmox-auto-installer/src/fetch_plugins/utils/post.rs
new file mode 100644
index 0000000..c9f6ddb
--- /dev/null
+++ b/proxmox-auto-installer/src/fetch_plugins/utils/post.rs
@@ -0,0 +1,93 @@
+use anyhow::Result;
+use rustls::ClientConfig;
+use sha2::{Digest, Sha256};
+use std::sync::Arc;
+use ureq::{Agent, AgentBuilder};
+
+/// Issues a POST request with the payload (JSON). Optionally a SHA256 fingerprint can be used to
+/// check the cert against it, instead of the regular cert validation.
+/// To gather the sha256 fingerprint you can use the following command:
+/// ```no_compile
+/// openssl s_client -connect <host>:443 < /dev/null 2>/dev/null | openssl x509 -fingerprint -sha256  -noout -in /dev/stdin
+/// ```
+///
+/// # Arguemnts
+/// * `url` - URL to call
+/// * `fingerprint` - SHA256 cert fingerprint if certificate pinning should be used. Optional.
+/// * `payload` - The payload to send to the server. Expected to be a JSON formatted string.
+pub fn call(url: String, fingerprint: Option<&str>, payload: String) -> Result<String> {
+    let answer      ;
+
+    if let Some(fingerprint) = fingerprint {
+        let tls_config = ClientConfig::builder()
+            .with_safe_defaults()
+            .with_custom_certificate_verifier(VerifyCertFingerprint::new(fingerprint)?)
+            .with_no_client_auth();
+
+        let agent: Agent = AgentBuilder::new().tls_config(Arc::new(tls_config)).build();
+
+        answer = agent
+            .post(&url)
+            .set("Content-type", "application/json; charset=utf-")
+            .send_string(&payload)?
+            .into_string()?;
+    } else {
+        let mut roots = rustls::RootCertStore::empty();
+        for cert in rustls_native_certs::load_native_certs()? {
+            roots.add(&rustls::Certificate(cert.0)).unwrap();
+        }
+
+        let tls_config = rustls::ClientConfig::builder()
+            .with_safe_defaults()
+            .with_root_certificates(roots)
+            .with_no_client_auth();
+
+        let agent = AgentBuilder::new()
+            .tls_connector(Arc::new(native_tls::TlsConnector::new()?))
+            .tls_config(Arc::new(tls_config))
+            .build();
+        answer = agent
+            .post(&url)
+            .set("Content-type", "application/json; charset=utf-")
+            .send_string(&payload)?
+            .into_string()?;
+    }
+    Ok(answer)
+}
+
+struct VerifyCertFingerprint {
+    cert_fingerprint: Vec<u8>,
+}
+
+impl VerifyCertFingerprint {
+    fn new<S: AsRef<str>>(cert_fingerprint: S) -> Result<std::sync::Arc<Self>> {
+        let cert_fingerprint = cert_fingerprint.as_ref();
+        let sanitized = cert_fingerprint.replace(':', "");
+        let decoded = hex::decode(sanitized)?;
+        Ok(std::sync::Arc::new(Self {
+            cert_fingerprint: decoded,
+        }))
+    }
+}
+
+impl rustls::client::ServerCertVerifier for VerifyCertFingerprint {
+    fn verify_server_cert(
+        &self,
+        end_entity: &rustls::Certificate,
+        _intermediates: &[rustls::Certificate],
+        _server_name: &rustls::ServerName,
+        _scts: &mut dyn Iterator<Item = &[u8]>,
+        _ocsp_response: &[u8],
+        _now: std::time::SystemTime,
+    ) -> Result<rustls::client::ServerCertVerified, rustls::Error> {
+        let mut hasher = Sha256::new();
+        hasher.update(end_entity);
+        let result = hasher.finalize();
+
+        if result.as_slice() == self.cert_fingerprint {
+            Ok(rustls::client::ServerCertVerified::assertion())
+        } else {
+            Err(rustls::Error::General("Fingerprint did not match!".into()))
+        }
+    }
+}
-- 
2.39.2