refactor(dstack-volume): read the veritysetup root hash through one grammar

dstack/crates/dstack-volume/src/bin/dstack-volume.rs

@@ -431,15 +431,7 @@ fn unescape_mountinfo(value: &[u8]) -> Vec<u8> {
 
 fn mapping_root(mapper_name: &str) -> Result<String> {
     let status = run_fun!(veritysetup status $mapper_name)?;
-    status
-        .lines()
-        .find_map(|line| {
-            let line = line.trim();
-            line.strip_prefix("root hash:")
-                .or_else(|| line.strip_prefix("Root hash:"))
-        })
-        .map(|root| root.trim().to_string())
-        .context("verity mapping status has no root hash")
+    dstack_volume::parse_verity_root_hash(&status).context("verity mapping status has no root hash")
 }
 
 #[cfg(test)]

dstack/crates/dstack-volume/src/lib.rs

@@ -23,6 +23,21 @@ pub mod volume_format;
 
 pub use volume::Compression;
 
+/// Read the root hash from `veritysetup format` (`Root hash:`) or
+/// `veritysetup status` (indented `root hash:`) output.
+pub fn parse_verity_root_hash(output: &str) -> Option<String> {
+    output
+        .lines()
+        .filter_map(|line| {
+            let line = line.trim();
+            line.strip_prefix("Root hash:")
+                .or_else(|| line.strip_prefix("root hash:"))
+        })
+        .map(str::trim)
+        .find(|root| !root.is_empty() && root.bytes().all(|byte| byte.is_ascii_hexdigit()))
+        .map(str::to_string)
+}
+
 /// A fixed dm-verity salt.
 ///
 /// The root is a function of the squashfs bytes and this salt, so keeping the
@@ -93,3 +108,21 @@ async fn verity_fs_image(fs_image: PathBuf, output: PathBuf) -> Result<VerityRes
         output,
     })
 }
+
+#[cfg(test)]
+mod root_hash_tests {
+    use super::parse_verity_root_hash;
+
+    #[test]
+    fn both_veritysetup_spellings_parse() {
+        assert_eq!(
+            parse_verity_root_hash("Salt:\t00\nRoot hash:      \tabc123\n").as_deref(),
+            Some("abc123")
+        );
+        assert_eq!(
+            parse_verity_root_hash("  type:  VERITY\n  root hash:   abc123\n").as_deref(),
+            Some("abc123")
+        );
+        assert_eq!(parse_verity_root_hash("Root hash:\n"), None);
+    }
+}

dstack/crates/dstack-volume/src/volume.rs

@@ -146,8 +146,8 @@ fn seal_data_image(
             $data_path $hash_path
     )
     .context("running veritysetup format")?;
-    let verity_root =
-        parse_root_hash(&out).context("could not find the root hash in veritysetup output")?;
+    let verity_root = crate::parse_verity_root_hash(&out)
+        .context("could not find the root hash in veritysetup output")?;
 
     // Wrap the two blobs in a deterministic GPT disk image. Partition 1 is the
     // generic volume envelope, partition 2 is data, and partition 3 is verity.
@@ -383,13 +383,6 @@ fn copy_into(src: &Path, out: &mut fs::File, offset: u64) -> Result<()> {
     Ok(())
 }
 
-fn parse_root_hash(output: &str) -> Option<String> {
-    output
-        .lines()
-        .find_map(|l| l.strip_prefix("Root hash:"))
-        .map(|v| v.trim().to_string())
-}
-
 fn require_tool(name: &str) -> Result<()> {
     let present = run_cmd!(which $name >/dev/null 2>&1).is_ok();
     if !present {
@@ -402,13 +395,6 @@ fn require_tool(name: &str) -> Result<()> {
 mod tests {
     use super::*;
 
-    #[test]
-    fn parses_veritysetup_root() {
-        let sample = "VERITY header information for x\nUUID:  \nHash type:  1\n\
-                      Data blocks:  10\nRoot hash:      abc123def\n";
-        assert_eq!(parse_root_hash(sample).as_deref(), Some("abc123def"));
-    }
-
     #[test]
     fn uuid_is_deterministic_and_content_specific() {
         use std::io::Write;