Use ssh2 config IdentityFile as fallback for key based authentication

src/system/sshkey_storage.rs

@@ -5,12 +5,16 @@
 // Locals
 use super::config_client::ConfigClient;
 // Ext
-use remotefs_ssh::SshKeyStorage as SshKeyStorageT;
+use remotefs_ssh::SshKeyStorage as SshKeyStorageTrait;
+use ssh2_config::SshConfig;
 use std::collections::HashMap;
 use std::path::{Path, PathBuf};
 
 pub struct SshKeyStorage {
-    hosts: HashMap<String, PathBuf>, // Association between {user}@{host} and RSA key path
+    /// Association between {user}@{host} and RSA key path
+    hosts: HashMap<String, PathBuf>,
+    /// Ssh2 configuration
+    ssh_config: Option<SshConfig>,
 }
 
 impl SshKeyStorage {
@@ -19,6 +23,7 @@ impl SshKeyStorage {
     pub fn empty() -> Self {
         SshKeyStorage {
             hosts: HashMap::new(),
+            ssh_config: None,
         }
     }
 
@@ -34,21 +39,67 @@ impl SshKeyStorage {
         let key: String = Self::make_mapkey(host, username);
         self.hosts.insert(key, p);
     }
-}
 
-impl SshKeyStorageT for SshKeyStorage {
-    fn resolve(&self, host: &str, username: &str) -> Option<&Path> {
+    /// Parse ssh2 config
+    fn parse_ssh2_config(path: &str) -> Result<SshConfig, String> {
+        use std::fs::File;
+        use std::io::BufReader;
+
+        let mut reader = File::open(path)
+            .map_err(|e| format!("failed to open {}: {}", path, e))
+            .map(BufReader::new)?;
+        SshConfig::default()
+            .parse(&mut reader)
+            .map_err(|e| format!("Failed to parse ssh2 config: {}", e))
+    }
+
+    /// Resolve host via termscp ssh keys storage
+    fn resolve_host_in_termscp_storage(&self, host: &str, username: &str) -> Option<&Path> {
         let key: String = Self::make_mapkey(host, username);
         self.hosts.get(&key).map(|x| x.as_path())
     }
+
+    /// Resolve host via ssh2 configuration
+    fn resolve_host_in_ssh2_configuration(&self, host: &str) -> Option<PathBuf> {
+        if let Some(config) = self.ssh_config.as_ref() {
+            let params = config.query(host);
+            params
+                .identity_file
+                .as_ref()
+                .and_then(|x| x.get(0).cloned())
+        } else {
+            debug!("ssh2 config is not available; no key has been found");
+            None
+        }
+    }
+}
+
+impl SshKeyStorageTrait for SshKeyStorage {
+    fn resolve(&self, host: &str, username: &str) -> Option<PathBuf> {
+        // search in termscp keys
+        if let Some(path) = self.resolve_host_in_termscp_storage(host, username) {
+            return Some(path.to_path_buf());
+        }
+        debug!(
+            "couldn't find any ssh key associated to {} at {}. Trying with ssh2 config",
+            username, host
+        );
+        // otherwise search in configuration
+        self.resolve_host_in_ssh2_configuration(host)
+    }
 }
 
 impl From<&ConfigClient> for SshKeyStorage {
     fn from(cfg_client: &ConfigClient) -> Self {
+        // read ssh2 config
+        let ssh_config = cfg_client.get_ssh_config().and_then(|x| {
+            debug!("reading ssh config at {}", x);
+            Self::parse_ssh2_config(x).ok()
+        });
         let mut hosts: HashMap<String, PathBuf> =
             HashMap::with_capacity(cfg_client.iter_ssh_keys().count());
         debug!("Setting up SSH key storage");
-        // Iterate over keys
+        // Iterate over keys in storage
         for key in cfg_client.iter_ssh_keys() {
             match cfg_client.get_ssh_key(key) {
                 Ok(host) => match host {
@@ -66,7 +117,7 @@ impl From<&ConfigClient> for SshKeyStorage {
             info!("Got SSH key for {}", key);
         }
         // Return storage
-        SshKeyStorage { hosts }
+        SshKeyStorage { hosts, ssh_config }
     }
 }
 
@@ -75,6 +126,7 @@ mod tests {
 
     use super::*;
     use crate::system::config_client::ConfigClient;
+    use crate::utils::test_helpers;
 
     use pretty_assertions::assert_eq;
     use std::path::Path;
@@ -103,6 +155,35 @@ mod tests {
         assert!(storage.resolve("deskichup", "veeso").is_none());
     }
 
+    #[test]
+    fn sould_resolve_key_from_ssh2_config() {
+        let rsa_key = test_helpers::create_sample_file_with_content("ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDErJhQxEI0+VvhlXVUyh+vMCm7aXfCA/g633AG8ezD/5EylwchtAr2JCoBWnxn4zV8nI9dMqOgm0jO4IsXpKOjQojv+0VOH7I+cDlBg0tk4hFlvyyS6YviDAfDDln3jYUM+5QNDfQLaZlH2WvcJ3mkDxLVlI9MBX1BAeSmChLxwAvxALp2ncImNQLzDO9eHcig3dtMrEKkzXQowRW5Y7eUzg2+vvVq4H2DOjWwUndvB5sJkhEfTUVE7ID8ZdGJo60kUb/02dZYj+IbkAnMCsqktk0cg/4XFX82hEfRYFeb1arkysFisPU1DOb6QielL/axeTebVplaouYcXY0pFdJt root@8c50fd4c345a");
+        let ssh_config_file = test_helpers::create_sample_file_with_content(format!(
+            r#"
+Host test
+        HostName 127.0.0.1
+        Port 2222
+        User test
+        IdentityFile {}
+        StrictHostKeyChecking no
+        UserKnownHostsFile /dev/null
+"#,
+            rsa_key.path().display()
+        ));
+        // make storage
+        let tmp_dir: tempfile::TempDir = tempfile::TempDir::new().ok().unwrap();
+        let (cfg_path, key_path): (PathBuf, PathBuf) = get_paths(tmp_dir.path());
+        let mut client: ConfigClient = ConfigClient::new(cfg_path.as_path(), key_path.as_path())
+            .ok()
+            .unwrap();
+        client.set_ssh_config(Some(ssh_config_file.path().to_string_lossy().to_string()));
+        let storage: SshKeyStorage = SshKeyStorage::from(&client);
+        assert_eq!(
+            storage.resolve("test", "pi").unwrap().as_path(),
+            rsa_key.path()
+        );
+    }
+
     #[test]
     fn test_system_sshkey_storage_empty() {
         let storage: SshKeyStorage = SshKeyStorage::empty();