ssh-key: add file I/O methods to PublicKey

.github/workflows/ssh-key.yml

@@ -39,7 +39,7 @@ jobs:
           target: ${{ matrix.target }}
           override: true
       - uses: RustCrypto/actions/cargo-hack-install@master
-      - run: cargo hack build --target ${{ matrix.target }} --feature-powerset --exclude-features std
+      - run: cargo hack build --target ${{ matrix.target }} --feature-powerset --exclude-features default,std
 
   minimal-versions:
     uses: RustCrypto/actions/.github/workflows/minimal-versions.yml@master

ssh-key/Cargo.toml

@@ -29,7 +29,7 @@ hex-literal = "0.3"
 tempfile = "3"
 
 [features]
-default = ["alloc", "ecdsa"]
+default = ["ecdsa", "std"]
 alloc = ["zeroize/alloc"]
 ecdsa = ["sec1"]
 std = ["alloc", "base64ct/std"]

ssh-key/README.md

@@ -27,9 +27,10 @@ and `authorized_keys` files.
 - [x] Parsing `autorized_keys` files
 - [x] Built-in zeroize support for private keys
 
-#### TODO:
+#### TODO
 
 - [ ] Encrypted private key support
+- [ ] SSH certificate support
 - [ ] Legacy SSH key (pre-OpenSSH) format support
 - [ ] Integrations with other RustCrypto crates (e.g. `ecdsa`, `ed25519`, `rsa`)
 - [ ] FIDO2 key support

ssh-key/src/public.rs

@@ -29,6 +29,9 @@ use alloc::{
     string::{String, ToString},
 };
 
+#[cfg(feature = "std")]
+use std::{fs, path::Path};
+
 /// SSH public key.
 #[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord)]
 pub struct PublicKey {
@@ -104,6 +107,23 @@ impl PublicKey {
         Ok(String::from_utf8(buf)?)
     }
 
+    /// Read public key from an OpenSSH-formatted PEM file.
+    #[cfg(feature = "std")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "std")))]
+    pub fn read_openssh_file(path: &Path) -> Result<Self> {
+        let input = fs::read_to_string(path)?;
+        Self::from_openssh(&*input)
+    }
+
+    /// Write public key as an OpenSSH-formatted PEM file.
+    #[cfg(feature = "std")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "std")))]
+    pub fn write_openssh_file(&self, path: &Path) -> Result<()> {
+        let encoded = self.to_openssh()?;
+        fs::write(path, encoded.as_bytes())?;
+        Ok(())
+    }
+
     /// Get the digital signature [`Algorithm`] used by this key.
     pub fn algorithm(&self) -> Algorithm {
         self.key_data.algorithm()