[pbs-devel] [PATCH proxmox-backup 1/1] pbs-client: use proxmox-https openssl callback

[Dominik Csapak <d.csapak@proxmox.com>]

instead of implementing it here. This changes the behavior when giving a
fingerprint explicitly when the certificate chain is trusted by openssl.
Previously this would be accepted due to openssls checks, regardless if
the given fingerprint would match or not.

With this patch, a given fingerprint has higher priority than openssls
validation.

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
---
 Cargo.toml                    |   2 +-
 pbs-client/src/http_client.rs | 151 ++++++++++++++--------------------
 2 files changed, 62 insertions(+), 91 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index 6de6a6527..c6076c9a6 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -62,7 +62,7 @@ proxmox-compression = "0.2"
 proxmox-config-digest = "0.1.0"
 proxmox-daemon = "0.1.0"
 proxmox-fuse = "0.1.3"
-proxmox-http = { version = "0.9.5", features = [ "client", "http-helpers", "websocket" ] } # see below
+proxmox-http = { version = "0.9.5", features = [ "client", "http-helpers", "websocket", "tls" ] } # see below
 proxmox-human-byte = "0.1"
 proxmox-io = "1.0.1" # tools and client use "tokio" feature
 proxmox-lang = "1.1"
diff --git a/pbs-client/src/http_client.rs b/pbs-client/src/http_client.rs
index c95def07b..4356af210 100644
--- a/pbs-client/src/http_client.rs
+++ b/pbs-client/src/http_client.rs
@@ -11,10 +11,7 @@ use hyper::http::header::HeaderValue;
 use hyper::http::Uri;
 use hyper::http::{Request, Response};
 use hyper::{body::HttpBody, Body};
-use openssl::{
-    ssl::{SslConnector, SslMethod},
-    x509::X509StoreContextRef,
-};
+use openssl::ssl::{SslConnector, SslMethod};
 use percent_encoding::percent_encode;
 use serde_json::{json, Value};
 use xdg::BaseDirectories;
@@ -26,7 +23,7 @@ use proxmox_sys::linux::tty;
 use proxmox_async::broadcast_future::BroadcastFuture;
 use proxmox_http::client::HttpsConnector;
 use proxmox_http::uri::{build_authority, json_object_to_query};
-use proxmox_http::{ProxyConfig, RateLimiter};
+use proxmox_http::{openssl_verify_callback, ProxyConfig, RateLimiter, SslVerifyError};
 use proxmox_log::{error, info, warn};
 
 use pbs_api_types::percent_encoding::DEFAULT_ENCODE_SET;
@@ -403,30 +400,42 @@ impl HttpClient {
             let interactive = options.interactive;
             let fingerprint_cache = options.fingerprint_cache;
             let prefix = options.prefix.clone();
-            let trust_openssl_valid = Arc::new(Mutex::new(true));
             ssl_connector_builder.set_verify_callback(
                 openssl::ssl::SslVerifyMode::PEER,
-                move |valid, ctx| match Self::verify_callback(
+                move |valid, ctx| match openssl_verify_callback(
                     valid,
                     ctx,
-                    expected_fingerprint.as_ref(),
-                    interactive,
-                    Arc::clone(&trust_openssl_valid),
+                    expected_fingerprint.as_deref(),
                 ) {
-                    Ok(None) => true,
-                    Ok(Some(fingerprint)) => {
-                        if fingerprint_cache && prefix.is_some() {
-                            if let Err(err) =
-                                store_fingerprint(prefix.as_ref().unwrap(), &server, &fingerprint)
-                            {
-                                error!("{}", err);
+                    Ok(()) => true,
+                    Err(err) => {
+                        match err {
+                            SslVerifyError::NoCertificate => error!(
+                                "certificate validation failed - context lacks current certificate"
+                            ),
+                            SslVerifyError::InvalidFingerprint(error_stack) => {
+                                error!("certificate validation failed - failed to calculate FP - {error_stack}")
+                            },
+                            SslVerifyError::UntrustedCertificate { fingerprint } => {
+                                if interactive && std::io::stdin().is_terminal() {
+                                    match Self::interactive_fp_check(prefix.as_deref(), &server, verified_fingerprint.clone(), fingerprint_cache, fingerprint) {
+                                        Ok(()) => return true,
+                                        Err(err) => error!("certificate validation failed - {err}"),
+                                    }
+                                }
                             }
+                            SslVerifyError::FingerprintMismatch { fingerprint, expected } => {
+                                warn!("WARNING: certificate fingerprint does not match expected fingerprint!");
+                                warn!("expected:    {expected}");
+
+                                if interactive && std::io::stdin().is_terminal() {
+                                    match Self::interactive_fp_check(prefix.as_deref(), &server, verified_fingerprint.clone(), fingerprint_cache, fingerprint) {
+                                        Ok(()) => return true,
+                                        Err(err) => error!("certificate validation failed - {err}"),
+                                    }
+                                }
+                            },
                         }
-                        *verified_fingerprint.lock().unwrap() = Some(fingerprint);
-                        true
-                    }
-                    Err(err) => {
-                        error!("certificate validation failed - {}", err);
                         false
                     }
                 },
@@ -631,79 +640,41 @@ impl HttpClient {
         bail!("no password input mechanism available");
     }
 
-    fn verify_callback(
-        openssl_valid: bool,
-        ctx: &mut X509StoreContextRef,
-        expected_fingerprint: Option<&String>,
-        interactive: bool,
-        trust_openssl: Arc<Mutex<bool>>,
-    ) -> Result<Option<String>, Error> {
-        let mut trust_openssl_valid = trust_openssl.lock().unwrap();
-
-        // we can only rely on openssl's prevalidation if we haven't forced it earlier
-        if openssl_valid && *trust_openssl_valid {
-            return Ok(None);
-        }
-
-        let cert = match ctx.current_cert() {
-            Some(cert) => cert,
-            None => bail!("context lacks current certificate."),
-        };
-
-        // force trust in case of a chain, but set flag to no longer trust prevalidation by openssl
-        if ctx.error_depth() > 0 {
-            *trust_openssl_valid = false;
-            return Ok(None);
-        }
-
-        // leaf certificate - if we end up here, we have to verify the fingerprint!
-        let fp = match cert.digest(openssl::hash::MessageDigest::sha256()) {
-            Ok(fp) => fp,
-            Err(err) => bail!("failed to calculate certificate FP - {}", err), // should not happen
-        };
-        let fp_string = hex::encode(fp);
-        let fp_string = fp_string
-            .as_bytes()
-            .chunks(2)
-            .map(|v| std::str::from_utf8(v).unwrap())
-            .collect::<Vec<&str>>()
-            .join(":");
-
-        if let Some(expected_fingerprint) = expected_fingerprint {
-            let expected_fingerprint = expected_fingerprint.to_lowercase();
-            if expected_fingerprint == fp_string {
-                return Ok(Some(fp_string));
-            } else {
-                warn!("WARNING: certificate fingerprint does not match expected fingerprint!");
-                warn!("expected:    {}", expected_fingerprint);
-            }
-        }
-
-        // If we're on a TTY, query the user
-        if interactive && std::io::stdin().is_terminal() {
-            info!("fingerprint: {}", fp_string);
-            loop {
-                eprint!("Are you sure you want to continue connecting? (y/n): ");
-                let _ = std::io::stdout().flush();
-                use std::io::{BufRead, BufReader};
-                let mut line = String::new();
-                match BufReader::new(std::io::stdin()).read_line(&mut line) {
-                    Ok(_) => {
-                        let trimmed = line.trim();
-                        if trimmed == "y" || trimmed == "Y" {
-                            return Ok(Some(fp_string));
-                        } else if trimmed == "n" || trimmed == "N" {
-                            bail!("Certificate fingerprint was not confirmed.");
-                        } else {
-                            continue;
+    fn interactive_fp_check(
+        prefix: Option<&str>,
+        server: &str,
+        verified_fingerprint: Arc<Mutex<Option<String>>>,
+        fingerprint_cache: bool,
+        fingerprint: String,
+    ) -> Result<(), Error> {
+        info!("fingerprint: {fingerprint}");
+        loop {
+            eprint!("Are you sure you want to continue connecting? (y/n): ");
+            let _ = std::io::stdout().flush();
+            use std::io::{BufRead, BufReader};
+            let mut line = String::new();
+            match BufReader::new(std::io::stdin()).read_line(&mut line) {
+                Ok(_) => {
+                    let trimmed = line.trim();
+                    if trimmed == "y" || trimmed == "Y" {
+                        if fingerprint_cache && prefix.is_some() {
+                            if let Err(err) =
+                                store_fingerprint(prefix.unwrap(), server, &fingerprint)
+                            {
+                                error!("{}", err);
+                            }
                         }
+                        *verified_fingerprint.lock().unwrap() = Some(fingerprint);
+                        return Ok(());
+                    } else if trimmed == "n" || trimmed == "N" {
+                        bail!("Certificate fingerprint was not confirmed.");
+                    } else {
+                        continue;
                     }
-                    Err(err) => bail!("Certificate fingerprint was not confirmed - {}.", err),
                 }
+                Err(err) => bail!("Certificate fingerprint was not confirmed - {}.", err),
             }
         }
-
-        bail!("Certificate fingerprint was not confirmed.");
     }
 
     pub async fn request(&self, mut req: Request<Body>) -> Result<Value, Error> {
-- 
2.39.5



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