[pve-devel] [PATCH proxmox-offline-mirror 2/2] fix #4632: allow escape hatches for legacy repositories

["Fabian Grünbichler" <f.gruenbichler@proxmox.com>]

there are still repositories out there that are using things like DSA/RSA-1024
and SHA1, so let's allow POM users to opt into accepting those insecure
cryptographic parameters, but keep the default settings secure.

Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
---
 src/bin/proxmox-offline-mirror.rs             |  2 +
 src/bin/proxmox_offline_mirror_cmds/config.rs |  4 ++
 src/config.rs                                 | 42 ++++++++++++++++++-
 src/helpers/verifier.rs                       | 20 ++++++++-
 src/mirror.rs                                 | 17 +++++++-
 5 files changed, 81 insertions(+), 4 deletions(-)

diff --git a/src/bin/proxmox-offline-mirror.rs b/src/bin/proxmox-offline-mirror.rs
index 3af33bb..bec366a 100644
--- a/src/bin/proxmox-offline-mirror.rs
+++ b/src/bin/proxmox-offline-mirror.rs
@@ -423,6 +423,7 @@ fn action_add_mirror(config: &SectionConfigData) -> Result<Vec<MirrorConfig>, Er
                 use_subscription: None,
                 ignore_errors: false,
                 skip,
+                weak_crypto: None,
             });
         }
     }
@@ -438,6 +439,7 @@ fn action_add_mirror(config: &SectionConfigData) -> Result<Vec<MirrorConfig>, Er
         use_subscription,
         ignore_errors: false,
         skip,
+        weak_crypto: None,
     };
 
     configs.push(main_config);
diff --git a/src/bin/proxmox_offline_mirror_cmds/config.rs b/src/bin/proxmox_offline_mirror_cmds/config.rs
index 3ebf4ad..696da11 100644
--- a/src/bin/proxmox_offline_mirror_cmds/config.rs
+++ b/src/bin/proxmox_offline_mirror_cmds/config.rs
@@ -274,6 +274,10 @@ pub fn update_mirror(
         data.skip.skip_sections = Some(skip_sections);
     }
 
+    if let Some(weak_crypto) = update.weak_crypto {
+        data.weak_crypto = Some(weak_crypto);
+    }
+
     config.set_data(&id, "mirror", &data)?;
     proxmox_offline_mirror::config::save_config(&config_file, &config)?;
 
diff --git a/src/config.rs b/src/config.rs
index 39b1193..0e19c77 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -5,7 +5,7 @@ use lazy_static::lazy_static;
 use proxmox_subscription::{sign::ServerBlob, SubscriptionInfo};
 use serde::{Deserialize, Serialize};
 
-use proxmox_schema::{api, ApiType, Schema, Updater};
+use proxmox_schema::{api, ApiStringFormat, ApiType, Schema, Updater};
 use proxmox_section_config::{SectionConfig, SectionConfigData, SectionConfigPlugin};
 use proxmox_sys::fs::{replace_file, CreateOptions};
 
@@ -46,6 +46,38 @@ pub struct SkipConfig {
     pub skip_packages: Option<Vec<String>>,
 }
 
+#[api(
+    properties: {
+        "allow-sha1": {
+            type: bool,
+            default: false,
+            optional: true,
+        },
+        "min-dsa-key-size": {
+            type: u64,
+            optional: true,
+        },
+        "min-rsa-key-size": {
+            type: u64,
+            optional: true,
+        },
+    },
+)]
+#[derive(Default, Serialize, Deserialize, Updater, Clone, Debug)]
+#[serde(rename_all = "kebab-case")]
+/// Weak Cryptography Configuration
+pub struct WeakCryptoConfig {
+    /// Whether to allow SHA-1 based signatures
+    #[serde(default)]
+    pub allow_sha1: bool,
+    /// Whether to lower the key size cutoff for DSA-based signatures
+    #[serde(default)]
+    pub min_dsa_key_size: Option<u64>,
+    /// Whether to lower the key size cutoff for RSA-based signatures
+    #[serde(default)]
+    pub min_rsa_key_size: Option<u64>,
+}
+
 #[api(
     properties: {
         id: {
@@ -81,6 +113,11 @@ pub struct SkipConfig {
         "skip": {
             type: SkipConfig,
         },
+        "weak-crypto": {
+            type: String,
+            optional: true,
+            format: &ApiStringFormat::PropertyString(&WeakCryptoConfig::API_SCHEMA),
+        },
     }
 )]
 #[derive(Clone, Debug, Serialize, Deserialize, Updater)]
@@ -111,6 +148,9 @@ pub struct MirrorConfig {
     /// Skip package files using these criteria
     #[serde(default, flatten)]
     pub skip: SkipConfig,
+    /// Whether to allow using weak cryptography algorithms or parameters, deviating from the default policy.
+    #[serde(default)]
+    pub weak_crypto: Option<String>,
 }
 
 #[api(
diff --git a/src/helpers/verifier.rs b/src/helpers/verifier.rs
index 131bccd..e38ef40 100644
--- a/src/helpers/verifier.rs
+++ b/src/helpers/verifier.rs
@@ -9,10 +9,13 @@ use sequoia_openpgp::{
         Parse,
     },
     policy::StandardPolicy,
+    types::HashAlgorithm,
     Cert, KeyHandle,
 };
 use std::io;
 
+use crate::config::WeakCryptoConfig;
+
 struct Helper<'a> {
     cert: &'a Cert,
 }
@@ -91,10 +94,25 @@ pub(crate) fn verify_signature<'msg>(
     msg: &'msg [u8],
     key: &[u8],
     detached_sig: Option<&[u8]>,
+    weak_crypto: &WeakCryptoConfig,
 ) -> Result<Vec<u8>, Error> {
     let cert = Cert::from_bytes(key)?;
 
-    let policy = StandardPolicy::new();
+    let mut policy = StandardPolicy::new();
+    if weak_crypto.allow_sha1 {
+        policy.accept_hash(HashAlgorithm::SHA1);
+    }
+    if let Some(min_dsa) = weak_crypto.min_dsa_key_size {
+        if min_dsa <= 1024 {
+            policy.accept_asymmetric_algo(sequoia_openpgp::policy::AsymmetricAlgorithm::DSA1024);
+        }
+    }
+    if let Some(min_rsa) = weak_crypto.min_dsa_key_size {
+        if min_rsa <= 1024 {
+            policy.accept_asymmetric_algo(sequoia_openpgp::policy::AsymmetricAlgorithm::RSA1024);
+        }
+    }
+
     let helper = Helper { cert: &cert };
 
     let verified = if let Some(sig) = detached_sig {
diff --git a/src/mirror.rs b/src/mirror.rs
index 0dc0751..3766f23 100644
--- a/src/mirror.rs
+++ b/src/mirror.rs
@@ -10,10 +10,11 @@ use flate2::bufread::GzDecoder;
 use globset::{Glob, GlobSet, GlobSetBuilder};
 use nix::libc;
 use proxmox_http::{client::sync::Client, HttpClient, HttpOptions, ProxyConfig};
+use proxmox_schema::{ApiType, Schema};
 use proxmox_sys::fs::file_get_contents;
 
 use crate::{
-    config::{MirrorConfig, SkipConfig, SubscriptionKey},
+    config::{MirrorConfig, SkipConfig, SubscriptionKey, WeakCryptoConfig},
     convert_repo_line,
     pool::Pool,
     types::{Diff, Snapshot, SNAPSHOT_REGEX},
@@ -50,6 +51,7 @@ struct ParsedMirrorConfig {
     pub client: Client,
     pub ignore_errors: bool,
     pub skip: SkipConfig,
+    pub weak_crypto: WeakCryptoConfig,
 }
 
 impl TryInto<ParsedMirrorConfig> for MirrorConfig {
@@ -72,6 +74,15 @@ impl TryInto<ParsedMirrorConfig> for MirrorConfig {
 
         let client = Client::new(options);
 
+        let weak_crypto = match self.weak_crypto {
+            Some(property_string) => {
+                let value = (WeakCryptoConfig::API_SCHEMA as Schema)
+                    .parse_property_string(&property_string)?;
+                serde_json::from_value(value)?
+            }
+            None => WeakCryptoConfig::default(),
+        };
+
         Ok(ParsedMirrorConfig {
             repository,
             architectures: self.architectures,
@@ -83,6 +94,7 @@ impl TryInto<ParsedMirrorConfig> for MirrorConfig {
             client,
             ignore_errors: self.ignore_errors,
             skip: self.skip,
+            weak_crypto,
         })
     }
 }
@@ -208,7 +220,8 @@ fn fetch_release(
 
     println!("Verifying '{name}' signature using provided repository key..");
     let content = fetched.data_ref();
-    let verified = helpers::verify_signature(content, &config.key, sig.as_deref())?;
+    let verified =
+        helpers::verify_signature(content, &config.key, sig.as_deref(), &config.weak_crypto)?;
     println!("Success");
 
     let sha512 = Some(openssl::sha::sha512(content));
-- 
2.30.2