diff --git a/crates/signer/src/utils.rs b/crates/signer/src/utils.rs
index 5ee808e8..bfc28f9f 100644
--- a/crates/signer/src/utils.rs
+++ b/crates/signer/src/utils.rs
@@ -37,16 +37,17 @@ fn get_ip_from_unique_header(headers: &HeaderMap, header_name: &str) -> Result<I
     let mut values = headers.get_all(header_name).iter();
 
     let first_value = values.next().ok_or(IpError::NotPresent(header_name.to_string()))?;
+
+    if values.next().is_some() {
+        return Err(IpError::NotUnique(header_name.to_string()));
+    }
+
     let ip = first_value
         .to_str()
         .map_err(|_| IpError::HasInvalidCharacters)?
         .parse::<IpAddr>()
         .map_err(|_| IpError::InvalidValue)?;
 
-    if values.next().is_some() {
-        return Err(IpError::NotUnique(header_name.to_string()));
-    }
-
     Ok(ip)
 }
 
@@ -55,23 +56,187 @@ fn get_ip_from_rightmost_value(
     header_name: &str,
     trusted_count: usize,
 ) -> Result<IpAddr, IpError> {
-    let last_value = headers
+    let joined_values = headers
         .get_all(header_name)
         .iter()
-        .next_back()
-        .ok_or(IpError::NotPresent(header_name.to_string()))?
-        .to_str()
-        .map_err(|_| IpError::HasInvalidCharacters)?;
+        .map(|x| x.to_str().map_err(|_| IpError::HasInvalidCharacters))
+        .collect::<Result<Vec<&str>, IpError>>()?
+        .join(",");
+
+    if joined_values.is_empty() {
+        return Err(IpError::NotPresent(header_name.to_string()))
+    }
 
     // Selecting the first untrusted IP from the right according to:
     // https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/X-Forwarded-For#selecting_an_ip_address
-    last_value
+    joined_values
         .rsplit(",")
         .nth(trusted_count - 1)
         .ok_or(IpError::NotEnoughValues {
-            found: last_value.split(",").count(),
+            found: joined_values.split(",").count(),
             required: trusted_count,
         })?
+        .trim()
         .parse::<IpAddr>()
         .map_err(|_| IpError::InvalidValue)
 }
+
+#[cfg(test)]
+mod tests {
+    use std::net::Ipv4Addr;
+
+    use super::*;
+
+    #[test]
+    fn test_unique_header_pass() {
+        let header_name = "X-Real-IP";
+        let real_ip = IpAddr::V4(Ipv4Addr::new(1, 1, 1, 1));
+
+        let mut headers = HeaderMap::new();
+        headers.insert(header_name, real_ip.to_string().parse().unwrap());
+
+        let ip = get_ip_from_unique_header(&headers, header_name).unwrap();
+        assert_eq!(ip, real_ip);
+    }
+
+    #[test]
+    fn test_unique_header_duplicated() {
+        let header_name = "X-Real-IP";
+        let real_ip = IpAddr::V4(Ipv4Addr::new(1, 1, 1, 1));
+        let fake_ip = IpAddr::V4(Ipv4Addr::new(2, 2, 2, 2));
+
+        let mut headers = HeaderMap::new();
+        headers.insert(header_name, real_ip.to_string().parse().unwrap());
+        headers.append(header_name, fake_ip.to_string().parse().unwrap());
+
+        let err = get_ip_from_unique_header(&headers, header_name)
+            .expect_err("Not unique header should fail");
+        assert!(matches!(err, IpError::NotUnique(_)));
+    }
+    #[test]
+    fn test_unique_header_not_present() {
+        let header_name = "X-Real-IP";
+        let headers = HeaderMap::new();
+
+        let err = get_ip_from_unique_header(&headers, header_name)
+            .expect_err("Missing header should fail");
+        assert!(matches!(err, IpError::NotPresent(_)));
+    }
+
+    #[test]
+    fn test_unique_header_invalid_value() {
+        let header_name = "X-Real-IP";
+        let mut headers = HeaderMap::new();
+        headers.insert(header_name, "invalid-ip".parse().unwrap());
+
+        let err =
+            get_ip_from_unique_header(&headers, header_name).expect_err("Invalid IP should fail");
+        assert!(matches!(err, IpError::InvalidValue));
+    }
+
+    #[test]
+    fn test_unique_header_empty_value() {
+        let header_name = "X-Real-IP";
+        let mut headers = HeaderMap::new();
+        headers.insert(header_name, "".parse().unwrap());
+
+        let err =
+            get_ip_from_unique_header(&headers, header_name).expect_err("Invalid IP should fail");
+        assert!(matches!(err, IpError::InvalidValue));
+    }
+
+    #[test]
+    fn test_rightmost_header_comma_separated() {
+        let header_name = "X-Forwarded-For";
+        let ip1 = IpAddr::V4(Ipv4Addr::new(1, 1, 1, 1));
+        let ip2 = IpAddr::V4(Ipv4Addr::new(2, 2, 2, 2));
+        let ip3 = IpAddr::V4(Ipv4Addr::new(3, 3, 3, 3));
+
+        let mut headers = HeaderMap::new();
+        headers.insert(header_name, format!("{},{},{}", ip1, ip2, ip3).parse().unwrap());
+
+        let ip = get_ip_from_rightmost_value(&headers, header_name, 1).unwrap();
+        assert_eq!(ip, ip3);
+
+        let ip = get_ip_from_rightmost_value(&headers, header_name, 2).unwrap();
+        assert_eq!(ip, ip2);
+
+        let ip = get_ip_from_rightmost_value(&headers, header_name, 3).unwrap();
+        assert_eq!(ip, ip1);
+
+        let err = get_ip_from_rightmost_value(&headers, header_name, 4)
+            .expect_err("Not enough values should fail");
+        assert!(matches!(err, IpError::NotEnoughValues { .. }));
+    }
+
+    #[test]
+    fn test_rightmost_header_comma_space_separated() {
+        let header_name = "X-Forwarded-For";
+        let ip1 = IpAddr::V4(Ipv4Addr::new(1, 1, 1, 1));
+        let ip2 = IpAddr::V4(Ipv4Addr::new(2, 2, 2, 2));
+        let ip3 = IpAddr::V4(Ipv4Addr::new(3, 3, 3, 3));
+
+        let mut headers = HeaderMap::new();
+        headers.insert(header_name, format!("{}, {}, {}", ip1, ip2, ip3).parse().unwrap());
+
+        let ip = get_ip_from_rightmost_value(&headers, header_name, 1).unwrap();
+        assert_eq!(ip, ip3);
+
+        let ip = get_ip_from_rightmost_value(&headers, header_name, 2).unwrap();
+        assert_eq!(ip, ip2);
+
+        let ip = get_ip_from_rightmost_value(&headers, header_name, 3).unwrap();
+        assert_eq!(ip, ip1);
+
+        let err = get_ip_from_rightmost_value(&headers, header_name, 4)
+            .expect_err("Not enough values should fail");
+        assert!(matches!(err, IpError::NotEnoughValues { .. }));
+    }
+
+    #[test]
+    fn test_rightmost_header_duplicated() {
+        // If the header appears multiple times, they should be joined together
+        // as if they were a single value.
+        let header_name = "X-Forwarded-For";
+        let ip1 = IpAddr::V4(Ipv4Addr::new(1, 1, 1, 1));
+        let ip2 = IpAddr::V4(Ipv4Addr::new(2, 2, 2, 2));
+        let ip3 = IpAddr::V4(Ipv4Addr::new(3, 3, 3, 3));
+        let ip4 = IpAddr::V4(Ipv4Addr::new(4, 4, 4, 4));
+        let ip5 = IpAddr::V4(Ipv4Addr::new(5, 5, 5, 5));
+
+        let mut headers = HeaderMap::new();
+        headers.insert(header_name, format!("{},{},{}", ip1, ip2, ip3).parse().unwrap());
+        headers.append(header_name, format!("{},{}", ip4, ip5).parse().unwrap());
+
+        let ip = get_ip_from_rightmost_value(&headers, header_name, 1).unwrap();
+        assert_eq!(ip, ip5);
+
+        let ip = get_ip_from_rightmost_value(&headers, header_name, 5).unwrap();
+        assert_eq!(ip, ip1);
+
+        let err = get_ip_from_rightmost_value(&headers, header_name, 6)
+            .expect_err("Not enough values should fail");
+        assert!(matches!(err, IpError::NotEnoughValues { .. }));
+    }
+
+    #[test]
+    fn test_rightmost_header_not_present() {
+        let header_name = "X-Forwarded-For";
+        let headers = HeaderMap::new();
+
+        let err = get_ip_from_rightmost_value(&headers, header_name, 1)
+            .expect_err("Missing header should fail");
+        assert!(matches!(err, IpError::NotPresent(_)));
+    }
+
+    #[test]
+    fn test_rightmost_header_invalid_value() {
+        let header_name = "X-Forwarded-For";
+        let mut headers = HeaderMap::new();
+        headers.insert(header_name, "invalid-ip".parse().unwrap());
+
+        let err = get_ip_from_rightmost_value(&headers, header_name, 1)
+            .expect_err("Invalid IP should fail");
+        assert!(matches!(err, IpError::InvalidValue));
+    }
+}