use email_address crate for checking formats (#763)

The email_address crate is more strict in validating user and domain
parts of email addresses. For example, it verifies the total size
of the local part, which the current method does not, and this has
caused upstream servers to fail to accept an email.

Cargo.toml

@@ -67,6 +67,9 @@ sha2 = { version = "0.10", optional = true }
 rsa = { version = "0.6.0", optional = true }
 ed25519-dalek = { version = "1.0.1", optional = true }
 
+# email formats
+email_address = { version = "0.2.1", default-features = false }
+
 [dev-dependencies]
 criterion = "0.3"
 tracing-subscriber = "0.3"

src/address/types.rs

@@ -8,6 +8,7 @@ use std::{
     str::FromStr,
 };
 
+use email_address::EmailAddress;
 use idna::domain_to_ascii;
 use once_cell::sync::Lazy;
 use regex::Regex;
@@ -55,17 +56,6 @@ pub struct Address {
     at_start: usize,
 }
 
-// Regex from the specs
-// https://html.spec.whatwg.org/multipage/forms.html#valid-e-mail-address
-// It will mark esoteric email addresses like quoted string as invalid
-static USER_RE: Lazy<Regex> =
-    Lazy::new(|| Regex::new(r"^(?i)[a-z0-9.!#$%&'*+/=?^_`{|}~-]+\z").unwrap());
-static DOMAIN_RE: Lazy<Regex> = Lazy::new(|| {
-    Regex::new(
-        r"(?i)^[a-z0-9](?:[a-z0-9-]{0,61}[a-z0-9])?(?:.[a-z0-9](?:[a-z0-9-]{0,61}[a-z0-9])?)*$",
-    )
-    .unwrap()
-});
 // literal form, ipv4 or ipv6 address (SMTP 4.1.3)
 static LITERAL_RE: Lazy<Regex> = Lazy::new(|| Regex::new(r"(?i)\[([A-f0-9:\.]+)\]\z").unwrap());
 
@@ -126,7 +116,7 @@ impl Address {
     }
 
     pub(super) fn check_user(user: &str) -> Result<(), AddressError> {
-        if USER_RE.is_match(user) {
+        if EmailAddress::is_valid_local_part(user) {
             Ok(())
         } else {
             Err(AddressError::InvalidUser)
@@ -142,7 +132,7 @@ impl Address {
     }
 
     fn check_domain_ascii(domain: &str) -> Result<(), AddressError> {
-        if DOMAIN_RE.is_match(domain) {
+        if EmailAddress::is_valid_domain(domain) {
             return Ok(());
         }
 
@@ -278,5 +268,10 @@ mod tests {
         assert_eq!(addr.domain(), "example.com");
         assert_eq!(addr2.user(), "something");
         assert_eq!(addr2.domain(), "example.com");
+
+        assert!(Address::check_user("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa").is_err());
+        assert!(
+            Address::check_domain("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa.com").is_err()
+        );
     }
 }