ssh-key: use u64 type for certificate timestamps

Closes #174

Previously certificates only supported the `i64` range to allow for
infallible conversions to/from `SystemTime`.

Unfortunately OpenSSH defaults to using `u64::MAX` as the `valid_before`
time in order to represent certificate that's valid "forever". The
previous restriction meant that `ssh-key` was incapible of parsing such
certificates.

This commit switches to using a raw `u64` everywhere, and changing
conversions to `SystemTime` to return an `Option<SystemTime>` which is
`None` if the `u64` value overflows an `i64`.

ssh-cipher/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "ssh-cipher"
-version = "0.2.0"
+version = "0.3.0-pre"
 description = """
 Pure Rust implementation of SSH symmetric encryption including support for the
 modern [email protected]/[email protected] and
@@ -18,8 +18,8 @@ edition = "2021"
 rust-version = "1.72"
 
 [dependencies]
-cipher = "0.5.0-pre.4"
-encoding = { package = "ssh-encoding", version = "0.2", path = "../ssh-encoding" }
+cipher = "=0.5.0-pre.4"
+encoding = { package = "ssh-encoding", version = "=0.3.0-pre", path = "../ssh-encoding" }
 
 # optional dependencies
 aes = { version = "=0.9.0-pre", optional = true, default-features = false }

ssh-encoding/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "ssh-encoding"
-version = "0.2.0"
+version = "0.3.0-pre"
 description = """
 Pure Rust implementation of SSH data type decoders/encoders as described
 in RFC4251

ssh-key/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "ssh-key"
-version = "0.6.5"
+version = "0.7.0-pre"
 description = """
 Pure Rust implementation of SSH key file format decoders/encoders as described
 in RFC4251/RFC4253 and OpenSSH key formats, as well as "sshsig" signatures and
@@ -17,8 +17,8 @@ edition = "2021"
 rust-version = "1.73"
 
 [dependencies]
-cipher = { package = "ssh-cipher", version = "0.2", path = "../ssh-cipher" }
-encoding = { package = "ssh-encoding", version = "0.2", features = ["base64", "pem", "sha2"], path = "../ssh-encoding" }
+cipher = { package = "ssh-cipher", version = "=0.3.0-pre", path = "../ssh-cipher" }
+encoding = { package = "ssh-encoding", version = "=0.3.0-pre", features = ["base64", "pem", "sha2"], path = "../ssh-encoding" }
 sha2 = { version = "=0.11.0-pre.3", default-features = false }
 signature = { version = "=2.3.0-pre.3", default-features = false }
 subtle = { version = "2", default-features = false }

ssh-key/src/authorized_keys.rs

@@ -36,7 +36,7 @@ const COMMENT_DELIMITER: char = '#';
 ///   the key).
 pub struct AuthorizedKeys<'a> {
     /// Lines of the file being iterated over
-    lines: core::str::Lines<'a>,
+    lines: str::Lines<'a>,
 }
 
 impl<'a> AuthorizedKeys<'a> {

ssh-key/src/certificate.rs

@@ -8,7 +8,6 @@ mod unix_time;
 
 pub use self::{builder::Builder, cert_type::CertType, field::Field, options_map::OptionsMap};
 
-use self::unix_time::UnixTime;
 use crate::{
     public::{KeyData, SshFormat},
     Algorithm, Error, Fingerprint, HashAlg, Result, Signature,
@@ -26,7 +25,10 @@ use signature::Verifier;
 use serde::{de, ser, Deserialize, Serialize};
 
 #[cfg(feature = "std")]
-use std::{fs, path::Path, time::SystemTime};
+use {
+    self::unix_time::UnixTime,
+    std::{fs, path::Path, time::SystemTime},
+};
 
 /// OpenSSH certificate as specified in [PROTOCOL.certkeys].
 ///
@@ -137,10 +139,10 @@ pub struct Certificate {
     valid_principals: Vec<String>,
 
     /// Valid after.
-    valid_after: UnixTime,
+    valid_after: u64,
 
     /// Valid before.
-    valid_before: UnixTime,
+    valid_before: u64,
 
     /// Critical options.
     critical_options: OptionsMap,
@@ -281,26 +283,34 @@ impl Certificate {
         &self.valid_principals
     }
 
-    /// Valid after (Unix time).
+    /// Valid after (Unix time), i.e. certificate issuance time.
     pub fn valid_after(&self) -> u64 {
-        self.valid_after.into()
+        self.valid_after
     }
 
-    /// Valid before (Unix time).
+    /// Valid before (Unix time), i.e. certificate expiration time.
     pub fn valid_before(&self) -> u64 {
-        self.valid_before.into()
+        self.valid_before
     }
 
-    /// Valid after (system time).
+    /// Valid after (system time), i.e. certificate issuance time.
+    ///
+    /// # Returns
+    /// - `Some` if the `u64` value is a valid `SystemTime`
+    /// - `None` if it is not (i.e. overflows `i64`)
     #[cfg(feature = "std")]
-    pub fn valid_after_time(&self) -> SystemTime {
-        self.valid_after.into()
+    pub fn valid_after_time(&self) -> Option<SystemTime> {
+        UnixTime::try_from(self.valid_after).ok().map(Into::into)
     }
 
-    /// Valid before (system time).
+    /// Valid before (system time), i.e. certificate expiration time.
+    ///
+    /// # Returns
+    /// - `Some` if the `u64` value is a valid `SystemTime`
+    /// - `None` if it is not (i.e. overflows `i64`, effectively never-expiring)
     #[cfg(feature = "std")]
-    pub fn valid_before_time(&self) -> SystemTime {
-        self.valid_before.into()
+    pub fn valid_before_time(&self) -> Option<SystemTime> {
+        UnixTime::try_from(self.valid_before).ok().map(Into::into)
     }
 
     /// The critical options section of the certificate specifies zero or more
@@ -391,8 +401,6 @@ impl Certificate {
             return Err(Error::CertificateValidation);
         }
 
-        let unix_timestamp = UnixTime::new(unix_timestamp)?;
-
         // From PROTOCOL.certkeys:
         //
         //  "valid after" and "valid before" specify a validity period for the
@@ -462,8 +470,8 @@ impl Decode for Certificate {
             cert_type: CertType::decode(reader)?,
             key_id: String::decode(reader)?,
             valid_principals: Vec::decode(reader)?,
-            valid_after: UnixTime::decode(reader)?,
-            valid_before: UnixTime::decode(reader)?,
+            valid_after: u64::decode(reader)?,
+            valid_before: u64::decode(reader)?,
             critical_options: OptionsMap::decode(reader)?,
             extensions: OptionsMap::decode(reader)?,
             reserved: Vec::decode(reader)?,

ssh-key/src/certificate/builder.rs

@@ -1,14 +1,14 @@
 //! OpenSSH certificate builder.
 
-use super::{unix_time::UnixTime, CertType, Certificate, Field, OptionsMap};
+use super::{CertType, Certificate, Field, OptionsMap};
 use crate::{public, Result, Signature, SigningKey};
 use alloc::{string::String, vec::Vec};
 
 #[cfg(feature = "rand_core")]
 use rand_core::CryptoRngCore;
 
 #[cfg(feature = "std")]
-use std::time::SystemTime;
+use {super::UnixTime, std::time::SystemTime};
 
 #[cfg(doc)]
 use crate::PrivateKey;
@@ -84,8 +84,8 @@ pub struct Builder {
     cert_type: Option<CertType>,
     key_id: Option<String>,
     valid_principals: Option<Vec<String>>,
-    valid_after: UnixTime,
-    valid_before: UnixTime,
+    valid_after: u64,
+    valid_before: u64,
     critical_options: OptionsMap,
     extensions: OptionsMap,
     comment: Option<String>,
@@ -105,12 +105,6 @@ impl Builder {
         valid_after: u64,
         valid_before: u64,
     ) -> Result<Self> {
-        let valid_after =
-            UnixTime::new(valid_after).map_err(|_| Field::ValidAfter.invalid_error())?;
-
-        let valid_before =
-            UnixTime::new(valid_before).map_err(|_| Field::ValidBefore.invalid_error())?;
-
         if valid_before < valid_after {
             return Err(Field::ValidBefore.invalid_error());
         }
@@ -304,7 +298,7 @@ impl Builder {
 
         #[cfg(debug_assertions)]
         cert.validate_at(
-            cert.valid_after.into(),
+            cert.valid_after,
             &[cert.signature_key.fingerprint(Default::default())],
         )?;
 

ssh-key/src/known_hosts.rs

@@ -46,7 +46,7 @@ const MAGIC_HASH_PREFIX: &str = "|1|";
 ///   the key).
 pub struct KnownHosts<'a> {
     /// Lines of the file being iterated over
-    lines: core::str::Lines<'a>,
+    lines: str::Lines<'a>,
 }
 
 impl<'a> KnownHosts<'a> {