adjust spec_version to proper semver format

Signed-off-by: Luke Steensen <luke.steensen@gmail.com>

tuf/src/interchange/cjson/shims.rs

@@ -8,7 +8,15 @@ use crate::error::Error;
 use crate::metadata::{self, Metadata};
 use crate::Result;
 
-const SPEC_VERSION: &str = "1.0";
+const SPEC_VERSION: &str = "1.0.0";
+
+// Ensure the given spec version matches our spec version.
+//
+// We also need to handle the literal "1.0" here, despite that fact that it is not a valid version
+// according to the SemVer spec, because it is already baked into some of the old roots.
+fn valid_spec_version(other: &str) -> bool {
+    other == SPEC_VERSION || other == "1.0"
+}
 
 fn parse_datetime(ts: &str) -> Result<DateTime<Utc>> {
     Utc.datetime_from_str(ts, "%FT%TZ")
@@ -70,7 +78,7 @@ impl RootMetadata {
             )));
         }
 
-        if self.spec_version != SPEC_VERSION {
+        if !valid_spec_version(&self.spec_version) {
             return Err(Error::Encoding(format!(
                 "Unknown spec version {}",
                 self.spec_version
@@ -184,7 +192,7 @@ impl TimestampMetadata {
             )));
         }
 
-        if self.spec_version != SPEC_VERSION {
+        if !valid_spec_version(&self.spec_version) {
             return Err(Error::Encoding(format!(
                 "Unknown spec version {}",
                 self.spec_version
@@ -233,7 +241,7 @@ impl SnapshotMetadata {
             )));
         }
 
-        if self.spec_version != SPEC_VERSION {
+        if !valid_spec_version(&self.spec_version) {
             return Err(Error::Encoding(format!(
                 "Unknown spec version {}",
                 self.spec_version
@@ -299,7 +307,7 @@ impl TargetsMetadata {
             )));
         }
 
-        if self.spec_version != SPEC_VERSION {
+        if !valid_spec_version(&self.spec_version) {
             return Err(Error::Encoding(format!(
                 "Unknown spec version {}",
                 self.spec_version