From 84e21aad4e96729408937f9fdde20cfd4f087d1a Mon Sep 17 00:00:00 2001
From: Eric Huss <eric@huss.org>
Date: Fri, 9 Dec 2022 20:56:04 -0800
Subject: [PATCH] Add ability to get the SSH host key and its type.

---
 libgit2-sys/lib.rs |  4 +++
 src/cert.rs        | 81 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 85 insertions(+)

diff --git a/libgit2-sys/lib.rs b/libgit2-sys/lib.rs
index a113a29526..51e8d7968c 100644
--- a/libgit2-sys/lib.rs
+++ b/libgit2-sys/lib.rs
@@ -489,6 +489,10 @@ git_enum! {
         GIT_CERT_SSH_RAW_TYPE_UNKNOWN = 0,
         GIT_CERT_SSH_RAW_TYPE_RSA = 1,
         GIT_CERT_SSH_RAW_TYPE_DSS = 2,
+        GIT_CERT_SSH_RAW_TYPE_KEY_ECDSA_256 = 3,
+        GIT_CERT_SSH_RAW_TYPE_KEY_ECDSA_384 = 4,
+        GIT_CERT_SSH_RAW_TYPE_KEY_ECDSA_521 = 5,
+        GIT_CERT_SSH_RAW_TYPE_KEY_ED25519 = 6,
     }
 }
 
diff --git a/src/cert.rs b/src/cert.rs
index d62b8304ce..b232cc3ce8 100644
--- a/src/cert.rs
+++ b/src/cert.rs
@@ -27,6 +27,54 @@ pub struct CertX509<'a> {
     _marker: marker::PhantomData<&'a raw::git_cert>,
 }
 
+/// The SSH host key type.
+#[derive(Copy, Clone, Debug)]
+#[non_exhaustive]
+pub enum SshHostKeyType {
+    /// Unknown key type
+    Unknown = raw::GIT_CERT_SSH_RAW_TYPE_UNKNOWN as isize,
+    /// RSA key type
+    Rsa = raw::GIT_CERT_SSH_RAW_TYPE_RSA as isize,
+    /// DSS key type
+    Dss = raw::GIT_CERT_SSH_RAW_TYPE_DSS as isize,
+    /// ECDSA 256 key type
+    Ecdsa256 = raw::GIT_CERT_SSH_RAW_TYPE_KEY_ECDSA_256 as isize,
+    /// ECDSA 384 key type
+    Ecdsa384 = raw::GIT_CERT_SSH_RAW_TYPE_KEY_ECDSA_384 as isize,
+    /// ECDSA 521 key type
+    Ecdsa521 = raw::GIT_CERT_SSH_RAW_TYPE_KEY_ECDSA_521 as isize,
+    /// ED25519 key type
+    Ed255219 = raw::GIT_CERT_SSH_RAW_TYPE_KEY_ED25519 as isize,
+}
+
+impl SshHostKeyType {
+    /// The name of the key type as encoded in the known_hosts file.
+    pub fn name(&self) -> &'static str {
+        match self {
+            SshHostKeyType::Unknown => "unknown",
+            SshHostKeyType::Rsa => "ssh-rsa",
+            SshHostKeyType::Dss => "ssh-dss",
+            SshHostKeyType::Ecdsa256 => "ecdsa-sha2-nistp256",
+            SshHostKeyType::Ecdsa384 => "ecdsa-sha2-nistp384",
+            SshHostKeyType::Ecdsa521 => "ecdsa-sha2-nistp521",
+            SshHostKeyType::Ed255219 => "ssh-ed25519",
+        }
+    }
+
+    /// A short name of the key type, the colloquial form used as a human-readable description.
+    pub fn short_name(&self) -> &'static str {
+        match self {
+            SshHostKeyType::Unknown => "Unknown",
+            SshHostKeyType::Rsa => "RSA",
+            SshHostKeyType::Dss => "DSA",
+            SshHostKeyType::Ecdsa256 => "ECDSA",
+            SshHostKeyType::Ecdsa384 => "ECDSA",
+            SshHostKeyType::Ecdsa521 => "ECDSA",
+            SshHostKeyType::Ed255219 => "ED25519",
+        }
+    }
+}
+
 impl<'a> Cert<'a> {
     /// Attempt to view this certificate as an SSH hostkey.
     ///
@@ -87,6 +135,39 @@ impl<'a> CertHostkey<'a> {
             }
         }
     }
+
+    /// Returns the raw host key.
+    pub fn hostkey(&self) -> Option<&[u8]> {
+        unsafe {
+            if (*self.raw).kind & raw::GIT_CERT_SSH_RAW == 0 {
+                return None;
+            }
+            Some(slice::from_raw_parts(
+                (*self.raw).hostkey as *const u8,
+                (*self.raw).hostkey_len as usize,
+            ))
+        }
+    }
+
+    /// Returns the type of the host key.
+    pub fn hostkey_type(&self) -> Option<SshHostKeyType> {
+        unsafe {
+            if (*self.raw).kind & raw::GIT_CERT_SSH_RAW == 0 {
+                return None;
+            }
+            let t = match (*self.raw).raw_type {
+                raw::GIT_CERT_SSH_RAW_TYPE_UNKNOWN => SshHostKeyType::Unknown,
+                raw::GIT_CERT_SSH_RAW_TYPE_RSA => SshHostKeyType::Rsa,
+                raw::GIT_CERT_SSH_RAW_TYPE_DSS => SshHostKeyType::Dss,
+                raw::GIT_CERT_SSH_RAW_TYPE_KEY_ECDSA_256 => SshHostKeyType::Ecdsa256,
+                raw::GIT_CERT_SSH_RAW_TYPE_KEY_ECDSA_384 => SshHostKeyType::Ecdsa384,
+                raw::GIT_CERT_SSH_RAW_TYPE_KEY_ECDSA_521 => SshHostKeyType::Ecdsa521,
+                raw::GIT_CERT_SSH_RAW_TYPE_KEY_ED25519 => SshHostKeyType::Ed255219,
+                t => panic!("unexpected host key type {:?}", t),
+            };
+            Some(t)
+        }
+    }
 }
 
 impl<'a> CertX509<'a> {