openpgp: Change CertBuilder to use a relative expiration time.

  - `CertBuilder::set_expiration_time` takes an absolute time.

    - Most callers use a relative time.

    - Internally, we need a relative time (that's what the Key
      Expiration Time packet takes).

    - Converting the absolute time to a relative time is error prone:
      should it be relative to the creation time when called or when
      `CertBuilder` is finalized?

  - KISS: Change it to just take a relative time.

  - To better reflect the new semantics, also change the name to
    `CertBuilder::set_validity_period`.

1 files changed, 12 insertions, 10 deletions

diff --git a/tool/src/commands/key.rs b/tool/src/commands/key.rs
index abd95433..dc78866f 100644
--- a/tool/src/commands/key.rs
+++ b/tool/src/commands/key.rs
@@ -33,22 +33,24 @@ pub fn generate(m: &ArgMatches, force: bool) -> Result<()> {
     // Expiration.
     match (m.value_of("expires"), m.value_of("expires-in")) {
         (None, None) => // Default expiration.
-            builder = builder.set_expiration_time(
-                Some(SystemTime::now()
-                     + Duration::new(3 * SECONDS_IN_YEAR, 0))),
+            builder = builder.set_validity_period(
+                Some(Duration::new(3 * SECONDS_IN_YEAR, 0))),
         (Some(t), None) if t == "never" =>
-            builder = builder.set_expiration_time(None),
+            builder = builder.set_validity_period(None),
         (Some(t), None) => {
-            let t =
-                crate::parse_iso8601(t, chrono::NaiveTime::from_hms(0, 0, 0))?;
-            builder = builder.set_expiration_time(Some(t.into()));
+            let now = builder.creation_time()
+                .unwrap_or_else(std::time::SystemTime::now);
+            let expiration = SystemTime::from(
+                crate::parse_iso8601(t, chrono::NaiveTime::from_hms(0, 0, 0))?);
+            let validity = expiration.duration_since(now)?;
+            builder = builder.set_creation_time(now)
+                .set_validity_period(validity);
         },
         (None, Some(d)) if d == "never" =>
-            builder = builder.set_expiration_time(None),
+            builder = builder.set_validity_period(None),
         (None, Some(d)) => {
             let d = parse_duration(d)?;
-            builder = builder.set_expiration_time(
-                Some(SystemTime::now() + d));
+            builder = builder.set_validity_period(Some(d));
         },
         (Some(_), Some(_)) => unreachable!("conflicting args"),
     }