[hsmtool] Support sphincs+ signing domains

Prepare data according to the input format (plain-text, sha256-hash, etc) and the sphincs+ signing domain (none, pure, prehashedsha256). Signed-off-by: Chris Frantz <[email protected]>
lowRISC · Dec 4, 2024 · ccd8f9a · ccd8f9a
1 parent 7171f28
commit ccd8f9a
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Showing 4 changed files with 74 additions and 1 deletion.
diff --git a/sw/host/hsmtool/src/commands/spx/sign.rs b/sw/host/hsmtool/src/commands/spx/sign.rs
@@ -6,20 +6,30 @@ use anyhow::Result;
 use cryptoki::session::Session;
 use serde::{Deserialize, Serialize};
 use serde_annotate::Annotate;
+use sphincsplus::SpxDomain;
 use std::any::Any;
 use std::path::PathBuf;
 
 use crate::commands::{BasicResult, Dispatch};
 use crate::error::HsmError;
 use crate::module::Module;
 use crate::util::helper;
+use crate::util::signing::SignData;
 
 #[derive(clap::Args, Debug, Serialize, Deserialize)]
 pub struct Sign {
     #[arg(long)]
     id: Option<String>,
     #[arg(short, long)]
     label: Option<String>,
+    #[arg(short, long, default_value = "plain-text", help=SignData::HELP)]
+    format: SignData,
+    /// Reverse the input data (for little-endian targets).
+    #[arg(short = 'r', long)]
+    little_endian: bool,
+    /// The SPHINCS+ signing domain.
+    #[arg(short = 'd', long, default_value = "pure")]
+    domain: SpxDomain,
     #[arg(short, long)]
     output: PathBuf,
     input: PathBuf,
@@ -37,6 +47,9 @@ impl Dispatch for Sign {
         let _token = hsm.token.as_deref().ok_or(HsmError::SessionRequired)?;
 
         let data = helper::read_file(&self.input)?;
+        let data = self
+            .format
+            .spx_prepare(self.domain, &data, self.little_endian)?;
         let result = acorn.sign(self.label.as_deref(), self.id.as_deref(), &data)?;
         helper::write_file(&self.output, &result)?;
         Ok(Box::<BasicResult>::default())

diff --git a/sw/host/hsmtool/src/commands/spx/verify.rs b/sw/host/hsmtool/src/commands/spx/verify.rs
@@ -6,20 +6,30 @@ use anyhow::Result;
 use cryptoki::session::Session;
 use serde::{Deserialize, Serialize};
 use serde_annotate::Annotate;
+use sphincsplus::SpxDomain;
 use std::any::Any;
 use std::path::PathBuf;
 
 use crate::commands::{BasicResult, Dispatch};
 use crate::error::HsmError;
 use crate::module::Module;
 use crate::util::helper;
+use crate::util::signing::SignData;
 
 #[derive(clap::Args, Debug, Serialize, Deserialize)]
 pub struct Verify {
     #[arg(long)]
     id: Option<String>,
     #[arg(short, long)]
     label: Option<String>,
+    #[arg(short, long, default_value = "plain-text", help=SignData::HELP)]
+    format: SignData,
+    /// Reverse the input data (for little-endian targets).
+    #[arg(short = 'r', long)]
+    little_endian: bool,
+    /// The SPHINCS+ signing domain.
+    #[arg(short = 'd', long, default_value = "pure")]
+    domain: SpxDomain,
     input: PathBuf,
     signature: PathBuf,
 }
@@ -36,6 +46,9 @@ impl Dispatch for Verify {
         let _token = hsm.token.as_deref().ok_or(HsmError::SessionRequired)?;
 
         let data = helper::read_file(&self.input)?;
+        let data = self
+            .format
+            .spx_prepare(self.domain, &data, self.little_endian)?;
         let signature = helper::read_file(&self.signature)?;
         let result = acorn.verify(self.label.as_deref(), self.id.as_deref(), &data, &signature)?;
         Ok(Box::new(BasicResult {

diff --git a/sw/host/hsmtool/src/util/signing.rs b/sw/host/hsmtool/src/util/signing.rs
@@ -9,6 +9,7 @@ use serde::{Deserialize, Serialize};
 use sha2::digest::const_oid::AssociatedOid;
 use sha2::digest::Digest;
 use sha2::Sha256;
+use sphincsplus::SpxDomain;
 use std::str::FromStr;
 
 use crate::error::HsmError;
@@ -94,6 +95,51 @@ impl SignData {
         }
     }
 
+    pub fn spx_prepare(
+        &self,
+        domain: SpxDomain,
+        input: &[u8],
+        little_endian: bool,
+    ) -> Result<Vec<u8>> {
+        match self {
+            SignData::PlainText => {
+                match domain {
+                    // Plaintext in domain None or Pure: prepare.
+                    SpxDomain::None | SpxDomain::Pure => Ok(domain.prepare(input).into()),
+                    // Plaintext in domain PreHashed: hash first, then prepare.
+                    SpxDomain::PreHashedSha256 => {
+                        let digest = Sha256::digest(input).as_slice().to_vec();
+                        Ok(domain.prepare(&digest).into())
+                    }
+                }
+            }
+            SignData::Sha256Hash => {
+                // Sha256 input in any domain: perform the domain preparation.
+                // If the `little_endian` flag is true, we assume the pre-hashed input came
+                // from opentitantool, which writes out the hash in little endian order,
+                // and therefore, needs to be reversed before the signing operation.
+                let digest = Self::data_raw(input, little_endian)?;
+                Ok(domain.prepare(&digest).into())
+            }
+            SignData::Raw => {
+                // Raw data in any domain: perform the domain preparation.
+                Ok(domain.prepare(input).into())
+            }
+            SignData::Slice(a, b) => {
+                let input = &input[*a..*b];
+                match domain {
+                    // A slice of the input in domain None or Pure: prepare.
+                    SpxDomain::None | SpxDomain::Pure => Ok(domain.prepare(input).into()),
+                    // A slice of the input in domain PreHashed: hash first, then prepare.
+                    SpxDomain::PreHashedSha256 => {
+                        let digest = Sha256::digest(input).as_slice().to_vec();
+                        Ok(domain.prepare(&digest).into())
+                    }
+                }
+            }
+        }
+    }
+
     /// Return the `Mechanism` needed during signing or verification.
     pub fn mechanism(&self, keytype: KeyType) -> Result<Mechanism> {
         match keytype {

diff --git a/sw/host/sphincsplus/key.rs b/sw/host/sphincsplus/key.rs
@@ -4,6 +4,7 @@
 
 use crate::{DecodeKey, EncodeKey, SphincsPlus, SpxError};
 use pem_rfc7468::LineEnding;
+use serde::{Deserialize, Serialize};
 use std::borrow::Cow;
 use std::fmt;
 use std::str::FromStr;
@@ -31,7 +32,7 @@ impl fmt::Debug for SpxSecretKey {
     }
 }
 
-#[derive(Default, Debug, Clone, Copy, EnumString, Display)]
+#[derive(Default, Debug, Clone, Copy, EnumString, Display, Serialize, Deserialize)]
 #[strum(ascii_case_insensitive)]
 pub enum SpxDomain {
     None,