1 files changed, 129 insertions, 0 deletions
diff --git a/melib/src/email/signatures.rs b/melib/src/email/signatures.rs
new file mode 100644
index 00000000..cf6ce4ac
--- /dev/null
+++ b/melib/src/email/signatures.rs
@@ -0,0 +1,129 @@
+/*
+ * meli - email module.
+ *
+ * Copyright 2019 Manos Pitsidianakis
+ *
+ * This file is part of meli.
+ *
+ * meli is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * meli is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with meli. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+use crate::email::attachments::{Attachment, ContentType, MultipartType};
+use crate::email::parser::BytesExt;
+use crate::{MeliError, Result};
+
+/// rfc3156
+/// Upon receipt of a signed message, an application MUST:
+///
+///   (1)   Convert line endings to the canonical <CR><LF> sequence before
+///         the signature can be verified.  This is necessary since the
+///         local MTA may have converted to a local end of line convention.
+///   (2)   Pass both the signed data and its associated content headers
+///         along with the OpenPGP signature to the signature verification
+///         service.
+///
+pub fn convert_attachment_to_rfc_spec(input: &[u8]) -> Vec<u8> {
+    if input.is_empty() {
+        return Vec::new();
+    }
+    let mut ret = Vec::with_capacity(input.len());
+
+    if input[0] == b'\n' {
+        /* This is an RFC violation but test for it anyway */
+        ret.push(b'\r');
+        ret.push(b'\n');
+    } else {
+        ret.push(input[0]);
+    }
+
+    let mut ctr = 1;
+
+    while ctr < input.len() {
+        if input[ctr] == b'\r' && ctr + 1 < input.len() && input[ctr + 1] == b'\n' {
+            ret.push(b'\r');
+            ret.push(b'\n');
+            ctr += 2;
+        } else if input[ctr] == b'\n' {
+            ret.push(b'\r');
+            ret.push(b'\n');
+            ctr += 1;
+        } else {
+            ret.push(input[ctr]);
+            ctr += 1;
+        }
+    }
+    loop {
+        match ret.iter().last() {
+            None => {
+                break;
+            }
+            Some(b'\n') | Some(b'\r') => {
+                ret.pop();
+            }
+            _ => {
+                break;
+            }
+        }
+    }
+    ret.push(0x0d);
+    ret.push(0x0a);
+    ret
+}
+
+pub fn verify_signature(a: &Attachment) -> Result<(Vec<u8>, &[u8])> {
+    match a.content_type {
+        ContentType::Multipart {
+            kind: MultipartType::Signed,
+            ref parts,
+            boundary: _,
+        } => {
+            if parts.len() != 2 {
+                return Err(MeliError::new(format!(
+                    "Illegal number of parts in multipart/signed. Expected 2 got {}",
+                    parts.len()
+                )));
+            }
+
+            let part_boundaries = a.part_boundaries();
+
+            let signed_part: Vec<u8> = if let Some(v) = parts
+                .iter()
+                .zip(part_boundaries.iter())
+                .find(|(p, _)| p.content_type != ContentType::PGPSignature)
+                .map(|(_, s)| convert_attachment_to_rfc_spec(s.display_bytes(a.body())))
+            {
+                v
+            } else {
+                return Err(MeliError::new(
+                    "multipart/signed attachment without a signed part".to_string(),
+                ));
+            };
+            let signature = if let Some(sig) = parts
+                .iter()
+                .find(|s| s.content_type == ContentType::PGPSignature)
+                .map(|a| a.body())
+            {
+                sig.trim()
+            } else {
+                return Err(MeliError::new(
+                    "multipart/signed attachment without a signature part".to_string(),
+                ));
+            };
+            Ok((signed_part, signature))
+        }
+        _ => {
+            unreachable!("Should not give non-signed attachments to this function");
+        }
+    }
+}