cert rdn: fix struct hierarchy

Cargo.toml

@@ -71,6 +71,11 @@ version = "0.4.19"
 default-features = false
 features = []
 
+[dependencies.intrusive-collections]
+version = "0.9.0"
+default-features = false
+features = []
+
 [dependencies.simple_logger]
 version = "1.11.0"
 optional = true

src/certificate.rs

@@ -24,7 +24,10 @@ use p256::ecdsa::signature::{Verifier, DigestVerifier};
 use alloc::vec::Vec;
 use heapless::{ Vec as HeaplessVec, consts::* };
 
+use byteorder::{ByteOrder, NetworkEndian};
+
 use core::convert::TryFrom;
+use core::convert::TryInto;
 
 #[derive(Debug, Clone)]
 pub struct Certificate<'a> {
@@ -64,6 +67,15 @@ pub struct Validity {
     pub not_after: DateTime<FixedOffset>,
 }
 
+impl Validity {
+    pub fn is_valid(&self, current_time: &DateTime<FixedOffset>) -> Result<(), TlsError> {
+        match (current_time >= &self.not_before) && (current_time <= &self.not_after) {
+            true => Ok(()),
+            false => Err(TlsError::TimeValidityError),
+        }
+    }
+}
+
 #[derive(Debug, Clone)]
 pub enum Time<'a> {
     UTCTime(&'a [u8]),
@@ -156,7 +168,9 @@ pub enum ExtensionValue<'a> {
     Unrecognized,
 }
 
-#[derive(Debug, Clone)]
+// Embedded value might be empty (&[])
+// This means a reject-all/accept-none condition
+#[derive(Debug, Clone, Copy, Eq, PartialEq)]
 pub enum GeneralName<'a> {
     OtherName {
         type_id: &'a [u8],
@@ -175,6 +189,131 @@ pub enum GeneralName<'a> {
     RegisteredID(&'a [u8]),
 }
 
+// Set operation for General Name (X is a subset of Y, where X, Y are the same variant)
+// Will not handle `OtherName`, `X400Address`, `EDIPartyName`, `RegisteredID`,
+// as these restrictions of these variants are not suggested
+impl<'a> GeneralName<'a> {
+    
+    pub fn is_subset_of(&self, other: &Self) -> bool {
+        match (self, other) {
+            // Special case: empty set
+            // Empty set is a subset of everything
+            (Self::URI(self_uri), Self::URI(other_uri)) => {
+                if self_uri.len() == 0 || other_uri.len() == 0 {
+                    self_uri.len() == 0
+                } else {
+                    self_uri.ends_with(other_uri)
+                }
+            },
+            (Self::RFC822Name(self_mail), Self::RFC822Name(other_mail)) => {
+                if self_mail.len() == 0 || other_mail.len() == 0 {
+                    self_mail.len() == 0
+                } else {
+                    self_mail.ends_with(other_mail)
+                }
+            },
+            (Self::DNSName(self_dns), Self::DNSName(other_dns)) => {
+                if self_dns.len() == 0 || other_dns.len() == 0 {
+                    self_dns.len() == 0
+                } else {
+                    self_dns.ends_with(other_dns)
+                }
+            },
+            (Self::IPAddress(self_ip), Self::IPAddress(other_ip)) => {
+                match (self_ip.len(), other_ip.len()) {
+                    // `self` is a NULL network block
+                    // It is always a subset of any network block
+                    (0, _) => true,
+
+                    // IPv4 Addresses
+                    (8, 8) => {
+                        let mut self_ip_prefix_len = 0;
+                        for index in 4..8 {
+                            self_ip_prefix_len += self_ip[index].count_ones();
+                        }
+                        let self_ipv4_cidr = smoltcp::wire::IpCidr::new(
+                            smoltcp::wire::IpAddress::v4(
+                                self_ip[0], self_ip[1], self_ip[2], self_ip[3]
+                            ),
+                            self_ip_prefix_len.try_into().unwrap()
+                        );
+
+                        let mut other_ip_prefix_len = 0;
+                        for index in 4..8 {
+                            other_ip_prefix_len += other_ip[index].count_ones();
+                        }
+                        let other_ipv4_cidr = smoltcp::wire::IpCidr::new(
+                            smoltcp::wire::IpAddress::v4(
+                                other_ip[0], other_ip[1], other_ip[2], other_ip[3]
+                            ),
+                            other_ip_prefix_len.try_into().unwrap()
+                        );
+
+                        other_ipv4_cidr.contains_subnet(&self_ipv4_cidr)
+                    },
+
+                    // Ipv6 Addresses
+                    (32, 32) => {
+                        let mut self_ip_prefix_len = 0;
+                        for index in 16..32 {
+                            self_ip_prefix_len += self_ip[index].count_ones();
+                        }
+                        let self_ipv4_cidr = smoltcp::wire::IpCidr::new(
+                            smoltcp::wire::IpAddress::v6(
+                                NetworkEndian::read_u16(&self_ip[0..2]),
+                                NetworkEndian::read_u16(&self_ip[2..4]),
+                                NetworkEndian::read_u16(&self_ip[4..6]),
+                                NetworkEndian::read_u16(&self_ip[6..8]),
+                                NetworkEndian::read_u16(&self_ip[8..10]),
+                                NetworkEndian::read_u16(&self_ip[10..12]),
+                                NetworkEndian::read_u16(&self_ip[12..14]),
+                                NetworkEndian::read_u16(&self_ip[14..16]),
+                            ),
+                            self_ip_prefix_len.try_into().unwrap()
+                        );
+
+                        let mut other_ip_prefix_len = 0;
+                        for index in 16..32 {
+                            other_ip_prefix_len += other_ip[index].count_ones();
+                        }
+                        let other_ipv4_cidr = smoltcp::wire::IpCidr::new(
+                            smoltcp::wire::IpAddress::v6(
+                                NetworkEndian::read_u16(&other_ip[0..2]),
+                                NetworkEndian::read_u16(&other_ip[2..4]),
+                                NetworkEndian::read_u16(&other_ip[4..6]),
+                                NetworkEndian::read_u16(&other_ip[6..8]),
+                                NetworkEndian::read_u16(&other_ip[8..10]),
+                                NetworkEndian::read_u16(&other_ip[10..12]),
+                                NetworkEndian::read_u16(&other_ip[12..14]),
+                                NetworkEndian::read_u16(&other_ip[14..16]),
+                            ),
+                            other_ip_prefix_len.try_into().unwrap()
+                        );
+
+                        other_ipv4_cidr.contains_subnet(&self_ipv4_cidr)
+                    },
+
+                    (_, _) => false     // Heterogeneity, in terms of IP address type
+                                        // Self IP address is not NULL
+                }
+            },
+            _ => false                  // Heterogeneity, in terms of GeneralName variant
+        }
+    }
+
+    pub fn is_same_variant(&self, other: &Self) -> bool {
+        match (self, other) {
+            (Self::URI(..), Self::URI(..))
+            | (Self::RFC822Name(..), Self::RFC822Name(..))
+            | (Self::DNSName(..), Self::DNSName(..))
+            | (Self::IPAddress(..), Self::IPAddress(..)) => {
+                true
+            },
+            _ => false
+        }
+    }
+}
+
 #[derive(Debug, Clone)]
 pub struct PolicyInformation<'a> {
     pub id: &'a [u8],
@@ -189,10 +328,28 @@ pub struct AlgorithmIdentifier<'a> {
 
 #[derive(Debug, Clone)]
 pub struct Name<'a> {
-    pub relative_distinguished_name: Vec<AttributeTypeAndValue<'a>>
+    pub relative_distinguished_name: Vec<RelativeDistinguishedName<'a>>
 }
 
-#[derive(Debug, Clone)]
+impl<'a> PartialEq for Name<'a> {
+    fn eq(&self, other: &Self) -> bool {
+        for self_name in self.relative_distinguished_name.iter() {
+            if other.relative_distinguished_name.iter().find(
+                |&att_type_val| att_type_val == self_name
+            ).is_none() {
+                return false;
+            }
+        }
+        true
+    }
+}
+
+#[derive(Debug, Clone, PartialEq)]
+pub struct RelativeDistinguishedName<'a> {
+    pub type_and_attributes: Vec<AttributeTypeAndValue<'a>>
+}
+
+#[derive(Debug, Clone, PartialEq)]
 pub struct AttributeTypeAndValue<'a> {
     pub attribute_type: &'a [u8],       // OID
     pub attribute_value: &'a str,
@@ -438,3 +595,606 @@ impl<'a> Certificate<'a> {
         }
     }
 }
+
+pub struct ValidPolicyNode<'a> {
+    valid_policy: &'a [u8],
+    qualifier_set: &'a [u8],
+    expected_policy_set: Vec<&'a [u8]>,
+}
+
+// Method to verify a prospective certificate chain
+// Section 6.1, RFC 5280
+pub fn verify_certificate_chain(
+    certificates: Vec<Certificate>,
+    current_time: DateTime<FixedOffset>,
+    // `user_initial_policy_set`, it is any_policy
+    trusted_issuer_name: Name,
+    // trusted_signature_algorithm: crate::tls_packet::SignatureScheme,
+    trusted_public_key: CertificatePublicKey,
+    initial_policy_mapping_inhibit: bool,
+    initial_explicit_policy: bool,
+    initial_any_policy_inhibit: bool,
+    initial_permitted_subtrees: Vec<GeneralName>,
+    initial_excluded_subtrees: Vec<GeneralName>
+) -> Result<(), TlsError> {
+    // Note that if the `user_initial_policy_set` variable is set to anyPolicy,
+    // Requirement: The existance of `valid_policy_tree`
+    // `valid_policy_tree` is not NULL iff leaves exist at depth k when k certificates are processed
+    // This leave us with a mapping of operation in the processing steps:
+    // Adding nodes below leaves -> Swap the leaves with a new set of nodes as leaves
+    // Pruning a branch due to the lack of new leaf -> no-op (old leaves are deallocated)
+    let mut valid_policy_tree: Vec<ValidPolicyNode> = Vec::new();
+    let mut initial_policy = ValidPolicyNode {
+        valid_policy: crate::oid::ANY_POLICY,
+        qualifier_set: &[],
+        expected_policy_set: Vec::new(),
+    };
+    initial_policy.expected_policy_set.push(crate::oid::ANY_POLICY);
+    valid_policy_tree.push(initial_policy);
+
+    let mut permitted_subtrees = initial_permitted_subtrees;
+    let mut excluded_subtrees = initial_excluded_subtrees;
+    let mut explicit_policy = if initial_explicit_policy {
+        0
+    } else {
+        certificates.len() + 1
+    };
+    let mut inhibit_any_policy = if initial_any_policy_inhibit {
+        0
+    } else {
+        certificates.len() + 1
+    };
+    let mut policy_mapping = if initial_policy_mapping_inhibit {
+        0
+    } else {
+        certificates.len() + 1
+    };
+    let mut working_public_key = trusted_public_key;
+    // working_public_key_parameters, except it is compeltely unnecessary
+    let mut working_issuer_name = trusted_issuer_name;
+    let mut max_path_length = certificates.len();
+
+    for cert_index in 0..certificates.len() {
+        let current_certificate = &certificates[cert_index];
+        current_certificate
+            .validate_signature_with_trusted(&working_public_key)
+            .map_err(|_| TlsError::SignatureValidationError)?;
+        current_certificate.tbs_certificate.validity
+            .is_valid(&current_time)?;
+        // Certificate Revocation List is not implemented
+        // This is a certificate-in-certificate scenario
+        if current_certificate.tbs_certificate.issuer != working_issuer_name {
+            return Err(TlsError::CertificateIssuerMismatch);
+        }
+
+        if current_certificate.tbs_certificate.issuer != current_certificate.tbs_certificate.subject
+            && (cert_index + 1) != certificates.len() {
+
+            if permitted_subtrees.len() != 0 {
+                // Find the SAN extension
+                for extension in current_certificate.tbs_certificate
+                    .extensions.extensions.iter() {
+                    if let ExtensionValue::SubjectAlternativeName {
+                        general_names
+                    } = &extension.extension_value {
+                        // For each alt. names in SAN, it is within one of the
+                        // permitted_subtrees for that name type
+                        // TODO: Do more than find exact match
+                        for general_name in general_names.iter() {
+                            permitted_subtrees.iter().find(
+                                |&permitted_name| permitted_name == general_name
+                            ).ok_or(
+                                TlsError::CertificateSubjectNotPermitted
+                            )?;
+                        }
+                    }
+                }
+            }
+
+            if excluded_subtrees.len() != 0 {
+                // Find the SAN extension
+                for extension in current_certificate.tbs_certificate
+                    .extensions.extensions.iter() {
+                    if let ExtensionValue::SubjectAlternativeName {
+                        general_names
+                    } = &extension.extension_value {
+                        // For each alt. names in SAN, it is NOT within one of the
+                        // excluded_subtrees for that name type
+                        // TODO: Do more than find exact match
+                        for general_name in general_names.iter() {
+                            excluded_subtrees.iter().find(
+                                |&excluded_name| excluded_name == general_name
+                            ).map_or(
+                                Ok(()),
+                                |_| Err(TlsError::CertificateSubjectExcluded)
+                            )?;
+                        }
+                    }
+                }
+            }
+        }
+
+        // Certificate policy, find a new set of leaves if exist
+        let mut new_valid_policy_leaves: Vec<ValidPolicyNode> = Vec::new();
+        let mut policy_info = None;
+        for extension in current_certificate.tbs_certificate.extensions.extensions.iter() {
+            if let ExtensionValue::CertificatePolicies { info } = &extension.extension_value {
+                policy_info.replace(info);
+                break;
+            }
+        }
+
+        if policy_info.is_some() {
+            let mut possible_any_policy = None;
+            // For each policy P that is not anyPolicy
+            for policy in policy_info.unwrap().iter() {
+                if policy.id == crate::oid::ANY_POLICY {
+                    possible_any_policy.replace(policy);
+                    continue;
+                }
+    
+                let mut policy_not_matched = true;
+                let mut any_policy_found = false;
+    
+                // For each node S at depth i-1, if S expects P,
+                // create a child with (P-OID, P-Q, {P-OID})
+                for policy_parent in valid_policy_tree.iter() {
+                    if policy_parent.expected_policy_set
+                        .iter()
+                        .find(|&&expected_policy| expected_policy == policy.id)
+                        .is_some() {
+                        let mut new_node = ValidPolicyNode {
+                            valid_policy: policy.id,
+                            qualifier_set: policy.qualifier,
+                            expected_policy_set: Vec::new()
+                        };
+                        new_node.expected_policy_set.push(policy.id);
+                        new_valid_policy_leaves.push(new_node);
+                        policy_not_matched = false;
+                    }
+    
+                    if policy_parent.valid_policy == crate::oid::ANY_POLICY {
+                        any_policy_found = true;
+                    }
+                }
+    
+                // If a match is not found for this policy,
+                // while an `anyPolicy' parent exists,
+                // Add policy P with (P-OID, P-Q, {P-OID})
+                // There is no need to add more than once
+                // Only `horizontal` leaf search will be performed,
+                // will only duplicate branch
+                if !policy_not_matched && any_policy_found {
+                    let mut new_node = ValidPolicyNode {
+                        valid_policy: policy.id,
+                        qualifier_set: policy.qualifier,
+                        expected_policy_set: Vec::new()
+                    };
+                    new_node.expected_policy_set.push(policy.id);
+                    new_valid_policy_leaves.push(new_node);                        
+                }
+            }
+    
+            // If cert has anyPolicy, and either (inhibit_anyPolicy > 0 OR i < n)
+            // AND certificate is self-issued, then forward all yet-to-be-copied
+            // policies in depth i-1 to leaves with qualifier as AP-Q
+            if possible_any_policy.is_some()
+                && inhibit_any_policy > 0
+                && cert_index + 1 < certificates.len()
+            {
+                for policy_parent in valid_policy_tree.iter() {
+                    for expected_policy in policy_parent.expected_policy_set.iter() {
+                        // If any expected policy cannot be found among the new leaves
+                        // it needs to be added into the valid policies
+                        if new_valid_policy_leaves.iter().find(
+                            |&leaf_policy| &leaf_policy.valid_policy == expected_policy
+                        ).is_none() {
+                            let mut new_node = ValidPolicyNode {
+                                valid_policy: expected_policy,
+                                qualifier_set: possible_any_policy.unwrap().qualifier,
+                                expected_policy_set: Vec::new()
+                            };
+                            new_node.expected_policy_set.push(expected_policy);
+                            new_valid_policy_leaves.push(new_node);     
+                        }
+                    }
+                }
+            }
+        }
+        // Otherwise, do nothing.
+        // Empty vector can represent NULL.
+        
+        // Replace old `valid_policy_tree` with new leaves
+        // This automatically does the following things:
+        // (d) prune childless branches, and
+        // (e) set the entire tree to NULL, if there are no cert policies.
+        valid_policy_tree = new_valid_policy_leaves;
+
+        // (f) Verify that either:
+        // -`explicit_policy` is greater than 0, OR
+        // -`valid_policy_tree` is not NULL
+        if explicit_policy == 0 && valid_policy_tree.len() == 0 {
+            return Err(TlsError::CertificatePolicyError);
+        }
+
+        // Prepare for the next certificate (towards end cert)
+        // Policy mapping is not handled
+        if cert_index + 1 == certificates.len() {
+            return wrap_up_verification(
+                current_certificate,
+                explicit_policy,
+                &valid_policy_tree
+            );
+        }
+
+        // (c, d, e, f) Re-assign `working_issuer_name` and `working_public_key`
+        // working_public_key already includes the algorithm of the key
+        working_issuer_name = current_certificate.tbs_certificate.subject.clone();
+        working_public_key = current_certificate.get_cert_public_key()
+            .map_err(|_| TlsError::SignatureValidationError)?;
+        // Only default pre-set signature algorithms are used.
+        // Parameter will never be relavent
+
+        // Counter updates, (l) verification for non-self-issued certs
+        // (h) If certificate is not self-issued, decrement all counters if non-zero
+        if current_certificate.tbs_certificate.issuer != current_certificate.tbs_certificate.subject {
+            explicit_policy -= 1;
+            policy_mapping -= 1;
+            inhibit_any_policy -= 1;
+
+            if max_path_length == 0 {
+                return Err(TlsError::CertificateVersionError);
+            } else {
+                max_path_length -= 1;
+            }
+        }
+
+        // Ensure that the certificate is v3
+        if current_certificate.tbs_certificate.version != Version::v3 {
+            return Err(TlsError::CertificateVersionError);
+        }
+
+        // (g) Permitted/Excluded subtrees operations
+        for extension in current_certificate.tbs_certificate.extensions.extensions.iter() {
+            if let ExtensionValue::NameConstraints {
+                permitted_subtrees: certificate_permitted_subtrees,
+                excluded_subtrees: certificate_excluded_subtrees
+            } = &extension.extension_value {
+                if certificate_permitted_subtrees.len() != 0 {
+                    get_subtree_intersection(
+                        &mut permitted_subtrees,
+                        certificate_permitted_subtrees
+                    );
+                }
+                if certificate_excluded_subtrees.len() != 0 {
+                    get_subtree_union(
+                        &mut excluded_subtrees,
+                        certificate_excluded_subtrees
+                    );
+                }
+            }
+
+            // (i) If policyConstraint extension is found, modify
+            // - explicit_policy, and/or
+            // - policy_mapping
+            if let ExtensionValue::PolicyConstraints {
+                require_explicit_policy,
+                inhibit_policy_mapping,
+            } = &extension.extension_value {
+                if require_explicit_policy.is_some() {
+                    if usize::from(require_explicit_policy.unwrap()) < explicit_policy {
+                        explicit_policy = require_explicit_policy.unwrap().into();
+                    }
+                }
+                if inhibit_policy_mapping.is_some() {
+                    if usize::from(inhibit_policy_mapping.unwrap()) < policy_mapping {
+                        policy_mapping = inhibit_policy_mapping.unwrap().into();
+                    }
+                }
+            }
+
+            // (j) Reduce inhibit_anyPolicy to that stated in the certificate
+            if let ExtensionValue::InhibitAnyPolicy {
+                skip_certs
+            } = &extension.extension_value {
+                if usize::from(*skip_certs) < inhibit_any_policy {
+                    inhibit_any_policy = (*skip_certs).into();
+                }
+            }
+
+            // (m) Verify that there is a BasicConstraint extension,
+            // with cA set to true
+            if let ExtensionValue::BasicConstraints {
+                is_ca,
+                path_len_constraint
+            } = &extension.extension_value {
+                if !is_ca {
+                    return Err(TlsError::CertificateVersionError);
+                }
+                if path_len_constraint.is_some() {
+                    if path_len_constraint.unwrap() < max_path_length as u8 {
+                        max_path_length = path_len_constraint.unwrap().into();
+                    }
+                }
+            }
+
+            // (n) If key usage extension is found, keyCertSignbit must be set
+            if let ExtensionValue::KeyUsage {
+                usage
+            } = &extension.extension_value {
+                if usage & 0x0020 == 0 {
+                    return Err(TlsError::CertificateVersionError);
+                }
+            }
+        }
+    }
+
+    Ok(())
+}
+
+fn wrap_up_verification(
+    end_cert: &Certificate,
+    mut explicit_policy: usize,
+    valid_policy_tree: &Vec<ValidPolicyNode>
+) -> Result<(), TlsError> {
+
+    // (a) Decrement explicit_policy
+    if explicit_policy != 0 {
+        explicit_policy -= 1;
+    }
+
+    for extension in end_cert.tbs_certificate.extensions.extensions.iter() {
+        // (b) If there is policy constraint extension, and
+        // require_explicit_policy is 0, set explicit_policy_state to be 0
+        if let ExtensionValue::PolicyConstraints {
+            require_explicit_policy,
+            inhibit_policy_mapping
+        } = &extension.extension_value {
+            if require_explicit_policy.is_some() {
+                if require_explicit_policy.unwrap() == 0 {
+                    explicit_policy = 0;
+                }
+            }
+        }
+    }
+
+    // (c) Instantiate cert key again, but only for returning to other procedure
+    // Getting it directly from certificate when needs to
+
+    // (d, e, f) Will not work with customized algorithm
+    // Only TLS signature algorithm will be supported
+
+    // (e) `initial_policy_set` is hardwired to any-policy
+    // The intersection is the entire valid_policy_tree (case II, section 6.1.4)
+    if explicit_policy > 0 || valid_policy_tree.len() != 0 {
+        Ok(())
+    } else {
+        Err(TlsError::CertificatePolicyError)
+    }
+
+}
+
+// Mutate state_subtree to get the intersection
+fn get_subtree_intersection<'a>(
+    state_subtree: &mut Vec<GeneralName<'a>>,
+    cert_subtree: &Vec<GeneralName<'a>>
+) {
+    // 1. Determine the variants that need to be preserved (i.e. body-count)
+    let mut has_self_uri_tree = false;
+    let mut has_other_uri_tree = false;
+    let mut has_self_rfc_822_name_tree = false;
+    let mut has_other_rfc_822_name_tree = false;
+    let mut has_self_dns_name_tree = false;
+    let mut has_other_dns_name_tree = false;
+    let mut has_self_ip_address_tree = false;
+    let mut has_other_ip_address_tree = false;
+
+    for general_name in state_subtree.iter() {
+        match general_name {
+            GeneralName::URI(..) => has_self_uri_tree = true,
+            GeneralName::RFC822Name(..) => has_self_rfc_822_name_tree = true,
+            GeneralName::DNSName(..) => has_self_dns_name_tree = true,
+            GeneralName::IPAddress(..) => has_self_ip_address_tree = true,
+            // Other general_name variants should not appear in this subtree
+            _ => {},
+        }
+    }
+
+    for general_name in cert_subtree.iter() {
+        match general_name {
+            GeneralName::URI(..) => has_other_uri_tree = true,
+            GeneralName::RFC822Name(..) => has_other_rfc_822_name_tree = true,
+            GeneralName::DNSName(..) => has_other_dns_name_tree = true,
+            GeneralName::IPAddress(..) => has_other_ip_address_tree = true,
+            // Other general_name variants should not appear in this subtree
+            _ => {},
+        }
+    }
+
+    // 2. Preserve subtrees that fit into the variants
+    let mut preserved_subtrees: Vec<GeneralName> = Vec::new();
+
+    for general_name in state_subtree.iter() {
+        match general_name {
+            GeneralName::URI(..) => {
+                if !has_other_uri_tree {
+                    preserved_subtrees.push(*general_name);
+                }
+            },
+            GeneralName::RFC822Name(..) => {
+                if !has_other_rfc_822_name_tree {
+                    preserved_subtrees.push(*general_name);
+                }
+            }
+            GeneralName::DNSName(..) => {
+                if !has_other_dns_name_tree {
+                    preserved_subtrees.push(*general_name);
+                }
+            }
+            GeneralName::IPAddress(..) => {
+                if !has_other_ip_address_tree {
+                    preserved_subtrees.push(*general_name);
+                }
+            }
+            // Other general_name variants should not appear in this subtree
+            _ => {},
+        }
+    }
+
+    for general_name in cert_subtree.iter() {
+        match general_name {
+            GeneralName::URI(..) => {
+                if !has_self_uri_tree {
+                    preserved_subtrees.push(*general_name);
+                }
+            },
+            GeneralName::RFC822Name(..) => {
+                if !has_self_rfc_822_name_tree {
+                    preserved_subtrees.push(*general_name);
+                }
+            }
+            GeneralName::DNSName(..) => {
+                if !has_self_dns_name_tree {
+                    preserved_subtrees.push(*general_name);
+                }
+            }
+            GeneralName::IPAddress(..) => {
+                if !has_self_ip_address_tree {
+                    preserved_subtrees.push(*general_name);
+                }
+            }
+            // Other general_name variants should not appear in this subtree
+            _ => {},
+        }
+    }
+
+    // 3. Perform intersection operation among 2 sets indirectly
+    //
+    // First, if the certificate does not specify any URI restrictions,
+    // leave the stored URI be.
+    //
+    // Assume all elements smong self_xxxx_tree and other_xxxx_tree are homogeneous.
+    //
+    // For each element in self_xxxx_tree, find intersection with other_xxxx_tree
+    // Take union operation at the result of each operations at the end
+    // i.e. (S1 U S2 U ... U Sk) n O = (S1 n O) U (S2 n O) U ... U (Sk n O)
+    //      as stated in distributive law
+    //
+    // The with the same argument, but reversing the self_tree and other_tree,
+    // For each element in other_xxx_tree, find intersection with that elemenet from self
+    // Take union operation of the result of each operations at the end
+    // i.e. Sx n (O1 U O2 U ... Oj) = (Sx n O1) U (Sx n O2) U ... U (Sx n Oj)
+    //      as stated in distributive law
+    //
+    // To further simplify, recognize that the brackets of (Sx n O) in the first statement
+    // encapsulates a series of union operators, while the bracks perform union operations
+    // among themselves as well.
+    // Therefore, the order of operations does not matter, stated in the associative law.
+    // i.e. S n O = U_(x, y) {Sx n Oy}
+    //
+    // Now consider all the variants, the processed subtree shall be a union of all variants
+    // where the variants are computed as a union of homogeneous intersections.
+    // By Identity law, if all heterogeneous intersections returns NULL,
+    // union of homogeneous intersections are equivalent to that of heterogeneous intersections.
+    //
+    // However, an empty set is not what always the correct solution. Here are exceptions:
+    //
+    // 1. If other_tree does not contain a variant that exists in self_tree,
+    //    that variant in self_tree shall be left untouched.
+    //
+    // 2. Reverse of (1), self_tree does not have definitions on some variant,
+    //    while other_tree has.
+    // Consider this method is for permitted_subtree operation, no definition means no restriction
+    // other_tree would like to impose tighter restriction, so every items of such variant
+    // from `other_tree` should be preserved.
+    //
+    // Both can be fixed by saving all `guaranteed` permitted subtrees before this process
+    for self_name in state_subtree.iter() {
+        for other_name in cert_subtree.iter() {
+
+            // Make use of subset method, note that all general names are hierarchical
+            if self_name.is_subset_of(other_name) {
+                preserved_subtrees.push(*self_name)
+            } else if other_name.is_subset_of(self_name) {
+                preserved_subtrees.push(*other_name)
+            }
+
+            // If neither are subset of the other, the intersection shall be none
+            // Should both names be homogeneous, it should imply an all-blocking name
+            match (self_name, other_name) {
+                (GeneralName::URI(self_uri), GeneralName::URI(other_uri)) => {
+                    preserved_subtrees.push(
+                        GeneralName::URI(&[])
+                    )
+                },
+                (GeneralName::RFC822Name(self_mail), GeneralName::RFC822Name(other_mail)) => {
+                    preserved_subtrees.push(
+                        GeneralName::RFC822Name(&[])
+                    )
+                },
+                (GeneralName::DNSName(self_dns), GeneralName::DNSName(other_dns)) => {
+                    preserved_subtrees.push(
+                        GeneralName::DNSName(&[])
+                    )
+                },
+                (GeneralName::IPAddress(self_ip), GeneralName::IPAddress(other_ip)) => {
+                    preserved_subtrees.push(
+                        GeneralName::IPAddress(&[])
+                    )
+                },
+
+                // Heterogeneous general name variants
+                _ => {}
+            }
+        }
+    }
+
+    // 4. Perform union operation
+    // Again recall that general names are hierarchical
+    // If two general names are not disjoint, one must be other's subset
+    // Therefore, pruning subsets is sufficient to determine the union.
+    // Put the result into state_subtree, as this shall be the output
+    //
+    // Note: Technically union operation can be a simple no-op
+    // But this is performed for the sake of memory space
+
+    state_subtree.clear();
+    prune_subset(state_subtree, &mut preserved_subtrees);
+}
+
+
+fn prune_subset<'a>(subtree_out: &mut Vec<GeneralName<'a>>, subtree_in: &mut Vec<GeneralName<'a>>) {
+    'outer: for i in 0..subtree_in.len() {
+        for j in 0..subtree_in.len() {
+            // A few cases to consider:
+            // If subtree_i is a strict_subset of subtree_j,
+            // then obviously i needs to be ejected
+            // However, if Si and Sj are equivalent, then only 1 needs to be ejected
+            // the following implementation will eject the one with lower index
+            if i != j {
+                if subtree_in[i] == subtree_in[j] {
+                    if i < j {
+                        continue 'outer;
+                    }
+                } else if subtree_in[i].is_subset_of(&subtree_in[j]) {
+                    continue 'outer;
+                }
+            }
+        }
+        subtree_out.push(subtree_in[i])
+    }
+}
+
+// Union operation among 2 subtrees sets, output through state_subtree
+pub fn get_subtree_union<'a>(
+    state_subtree: &mut Vec<GeneralName<'a>>,
+    other_subtree: &Vec<GeneralName<'a>>
+) {
+    // Join the 2 lists together, and then prune all subsets
+    let mut merged_subtrees: Vec<GeneralName> = Vec::new();
+    merged_subtrees.extend_from_slice(state_subtree);
+    merged_subtrees.extend_from_slice(other_subtree);
+    state_subtree.clear();
+
+    prune_subset(state_subtree, &mut merged_subtrees);
+}

src/lib.rs

@@ -22,4 +22,10 @@ pub enum Error {
     DecryptionError,
     CapacityError,
     SignatureValidationError,
+    TimeValidityError,
+    CertificateIssuerMismatch,
+    CertificateSubjectNotPermitted,
+    CertificateSubjectExcluded,
+    CertificatePolicyError,
+    CertificateVersionError,
 }

src/main.rs

@@ -120,7 +120,7 @@ const CA_SIGNED_CERT: [u8; 0x0356] =
         "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"
     );
 
-const SELF_SIGNED_WITH_SAN: [u8; 0x046C] =
+const SELF_SIGNED_WITH_SAN: [u8; 0x048A] =
     hex_literal::hex!(
-        "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"
+        "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"
     );

src/oid.rs

@@ -83,3 +83,6 @@ pub const ID_KP_CODE_SIGNING:           &'static [u8] = &[43, 6, 1, 5, 5, 7, 3,
 pub const ID_KP_EMAIL_PROTECTION:       &'static [u8] = &[43, 6, 1, 5, 5, 7, 3, 4];         // 1.3.6.1.5.5.7.3.4
 pub const ID_KP_TIME_STAMPING:          &'static [u8] = &[43, 6, 1, 5, 5, 7, 3, 8];         // 1.3.6.1.5.5.7.3.8
 pub const ID_KP_OCSP_SIGNING:           &'static [u8] = &[43, 6, 1, 5, 5, 7, 3, 9];
+
+// anyPolicy OID
+pub const ANY_POLICY:                   &'static [u8] = &[85, 29, 32, 0];

src/parse.rs

@@ -32,6 +32,7 @@ use crate::certificate::{
     Name                        as Asn1DerName,
     AttributeTypeAndValue       as Asn1DerAttribute,
     GeneralName                 as Asn1DerGeneralName,
+    RelativeDistinguishedName   as Asn1DerRDN,
 };
 
 use crate::oid;
@@ -812,10 +813,10 @@ pub fn parse_asn1_der_oid(bytes: &[u8]) -> IResult<&[u8], &[u8]> {
 // Parser for Name, applicable to issuer and subject field of TBS cert.
 pub fn parse_asn1_der_name(bytes: &[u8]) -> IResult<&[u8], Asn1DerName> {
     let (rest, mut rdn_sequence) = parse_asn1_der_sequence(bytes)?;
-    let mut attributes_vec: Vec<Asn1DerAttribute> = Vec::new();
+    let mut attributes_vec: Vec<Asn1DerRDN> = Vec::new();
 
     while rdn_sequence.len() != 0 {
-        let (rem, attribute) = parse_asn1_der_attribute_type_and_value(
+        let (rem, attribute) = parse_asn1_der_relative_distinguished_name(
             rdn_sequence
         )?;
         rdn_sequence = rem;
@@ -830,19 +831,37 @@ pub fn parse_asn1_der_name(bytes: &[u8]) -> IResult<&[u8], Asn1DerName> {
     ))
 }
 
+// Parser for Relative Distinguished Name (RDN)
+pub fn parse_asn1_der_relative_distinguished_name(bytes: &[u8]) -> IResult<&[u8], Asn1DerRDN> {
+    let (rest, mut attribute_set) = parse_asn1_der_set(bytes)?;
+    let mut attributes_vec: Vec<Asn1DerAttribute> = Vec::new();
+
+    while attribute_set.len() != 0 {
+        let (rem, attribute) = parse_asn1_der_attribute_type_and_value(
+            attribute_set
+        )?;
+        attribute_set = rem;
+        attributes_vec.push(attribute);
+    }
+
+    Ok((
+        rest,
+        Asn1DerRDN {
+            type_and_attributes: attributes_vec
+        }
+    ))
+}
+
 // Parser for AttributeTypeAndValue struct, typically wrapped inside Name struct
 pub fn parse_asn1_der_attribute_type_and_value(bytes: &[u8]) -> IResult<&[u8], Asn1DerAttribute> {
-    let (rest, set) = parse_asn1_der_set(bytes)?;
-    let (_, attribute) = complete(
-        parse_asn1_der_sequence
-    )(set)?;
+    let (rest, set) = parse_asn1_der_sequence(bytes)?;
 
     let (_, (oid, (tag_val, _, value))) = complete(
         tuple((
             parse_asn1_der_oid,
             parse_asn1_der_object
         ))
-    )(attribute)?;
+    )(set)?;
 
     // Verify that tag_val is either "PrintableString or UTF8String"
     if tag_val != 0x13 && tag_val != 0x0C {
@@ -1419,12 +1438,7 @@ pub fn parse_asn1_der_policy_information(bytes: &[u8]) -> IResult<&[u8], Asn1Der
         return Err(nom::Err::Failure((&[], ErrorKind::Verify)));
     }
 
-    let (_, (oid, (_, _, qualifier))) = complete(
-        tuple((
-            parse_asn1_der_oid,
-            parse_asn1_der_object
-        ))
-    )(value)?;
+    let (qualifier, oid) = parse_asn1_der_oid(value)?;
 
     Ok((
         rest,

src/tls_packet.rs

@@ -595,7 +595,7 @@ pub(crate) struct Cookie {
 #[allow(non_camel_case_types)]
 #[derive(Debug, PartialEq, Eq, Clone, Copy, IntoPrimitive, TryFromPrimitive)]
 #[repr(u16)]
-pub(crate) enum SignatureScheme {
+pub enum SignatureScheme {
     /* RSASSA-PKCS1-v1_5 algorithms */
     rsa_pkcs1_sha256 = 0x0401,
     rsa_pkcs1_sha384 = 0x0501,