use std::borrow::Cow; use std::num::NonZeroU32; use std::collections::HashSet; use anyhow::{anyhow, bail, Result}; use imap_codec::imap_types::body::{BasicFields, Body as FetchBody, BodyStructure, SpecificFields}; use imap_codec::imap_types::core::{AString, IString, NonEmptyVec}; use imap_codec::imap_types::fetch::{ Section as FetchSection, Part as FetchPart }; use eml_codec::{ header, part::AnyPart, part::composite, part::discrete, }; pub enum BodySection<'a> { Full(Cow<'a, [u8]>), Slice { body: Cow<'a, [u8]>, origin_octet: u32, }, } /// Logic for BODY[
]<> /// Works in 3 times: /// 1. Find the section (RootMime::subset) /// 2. Apply the extraction logic (SelectedMime::extract), like TEXT, HEADERS, etc. /// 3. Keep only the given subset provided by partial /// /// Example of message sections: /// /// ``` /// HEADER ([RFC-2822] header of the message) /// TEXT ([RFC-2822] text body of the message) MULTIPART/MIXED /// 1 TEXT/PLAIN /// 2 APPLICATION/OCTET-STREAM /// 3 MESSAGE/RFC822 /// 3.HEADER ([RFC-2822] header of the message) /// 3.TEXT ([RFC-2822] text body of the message) MULTIPART/MIXED /// 3.1 TEXT/PLAIN /// 3.2 APPLICATION/OCTET-STREAM /// 4 MULTIPART/MIXED /// 4.1 IMAGE/GIF /// 4.1.MIME ([MIME-IMB] header for the IMAGE/GIF) /// 4.2 MESSAGE/RFC822 /// 4.2.HEADER ([RFC-2822] header of the message) /// 4.2.TEXT ([RFC-2822] text body of the message) MULTIPART/MIXED /// 4.2.1 TEXT/PLAIN /// 4.2.2 MULTIPART/ALTERNATIVE /// 4.2.2.1 TEXT/PLAIN /// 4.2.2.2 TEXT/RICHTEXT /// ``` pub fn body_ext<'a>( part: &'a AnyPart<'a>, section: &'a Option>, partial: &'a Option<(u32, NonZeroU32)> ) -> Result> { let root_mime = NodeMime(part); let (extractor, path) = SubsettedSection::from(section); let selected_mime = root_mime.subset(path)?; let extracted_full = selected_mime.extract(&extractor)?; Ok(extracted_full.to_body_section(partial)) } /// Logic for BODY and BODYSTRUCTURE /// /// ```raw /// b fetch 29878:29879 (BODY) /// * 29878 FETCH (BODY (("text" "plain" ("charset" "utf-8") NIL NIL "quoted-printable" 3264 82)("text" "html" ("charset" "utf-8") NIL NIL "quoted-printable" 31834 643) "alternative")) /// * 29879 FETCH (BODY ("text" "html" ("charset" "us-ascii") NIL NIL "7bit" 4107 131)) /// ^^^^^^^^^^^^^^^^^^^^^^ ^^^ ^^^ ^^^^^^ ^^^^ ^^^ /// | | | | | | number of lines /// | | | | | size /// | | | | content transfer encoding /// | | | description /// | | id /// | parameter list /// b OK Fetch completed (0.001 + 0.000 secs). /// ``` pub fn bodystructure(part: &AnyPart) -> Result> { unimplemented!(); } /// NodeMime /// struct NodeMime<'a>(&'a AnyPart<'a>); impl<'a> NodeMime<'a> { /// A MIME object is a tree of elements. /// The path indicates which element must be picked. /// This function returns the picked element as the new view fn subset(self, path: Option<&'a FetchPart>) -> Result> { match path { None => Ok(SelectedMime(self.0)), Some(v) => self.rec_subset(v.0.as_ref()), } } fn rec_subset(self, path: &'a [NonZeroU32]) -> Result { if path.is_empty() { Ok(SelectedMime(self.0)) } else { match self.0 { AnyPart::Mult(x) => { let next = Self(x.children .get(path[0].get() as usize - 1) .ok_or(anyhow!("Unable to resolve subpath {:?}, current multipart has only {} elements", path, x.children.len()))?); next.rec_subset(&path[1..]) }, AnyPart::Msg(x) => { let next = Self(x.child.as_ref()); next.rec_subset(path) }, _ => bail!("You tried to access a subpart on an atomic part (text or binary). Unresolved subpath {:?}", path), } } } } //---------------------------------------------------------- /// A FetchSection must be handled in 2 times: /// - First we must extract the MIME part /// - Then we must process it as desired /// The given struct mixes both work, so /// we separate this work here. enum SubsettedSection<'a> { Part, Header, HeaderFields(&'a NonEmptyVec>), HeaderFieldsNot(&'a NonEmptyVec>), Text, Mime, } impl<'a> SubsettedSection<'a> { fn from(section: &'a Option) -> (Self, Option<&'a FetchPart>) { match section { Some(FetchSection::Text(maybe_part)) => (Self::Text, maybe_part.as_ref()), Some(FetchSection::Header(maybe_part)) => (Self::Header, maybe_part.as_ref()), Some(FetchSection::HeaderFields(maybe_part, fields)) => (Self::HeaderFields(fields), maybe_part.as_ref()), Some(FetchSection::HeaderFieldsNot(maybe_part, fields)) => (Self::HeaderFieldsNot(fields), maybe_part.as_ref()), Some(FetchSection::Mime(part)) => (Self::Mime, Some(part)), Some(FetchSection::Part(part)) => (Self::Part, Some(part)), None => (Self::Part, None), } } } struct SelectedMime<'a>(&'a AnyPart<'a>); impl<'a> SelectedMime<'a> { /// The subsetted fetch section basically tells us the /// extraction logic to apply on our selected MIME. /// This function acts as a router for these logic. fn extract(&self, extractor: &SubsettedSection<'a>) -> Result> { match extractor { SubsettedSection::Text => self.text(), SubsettedSection::Header => self.header(), SubsettedSection::HeaderFields(fields) => self.header_fields(fields, false), SubsettedSection::HeaderFieldsNot(fields) => self.header_fields(fields, true), SubsettedSection::Part => self.part(), SubsettedSection::Mime => self.mime(), } } fn mime(&self) -> Result> { let bytes = match &self.0 { AnyPart::Txt(p) => p.mime.fields.raw, AnyPart::Bin(p) => p.mime.fields.raw, AnyPart::Msg(p) => p.child.mime().raw, AnyPart::Mult(p) => p.mime.fields.raw, }; Ok(ExtractedFull(bytes.into())) } fn part(&self) -> Result> { let bytes = match &self.0 { AnyPart::Txt(p) => p.body, AnyPart::Bin(p) => p.body, AnyPart::Msg(p) => p.raw_part, AnyPart::Mult(_) => bail!("Multipart part has no body"), }; Ok(ExtractedFull(bytes.to_vec().into())) } /// The [...] HEADER.FIELDS, and HEADER.FIELDS.NOT part /// specifiers refer to the [RFC-2822] header of the message or of /// an encapsulated [MIME-IMT] MESSAGE/RFC822 message. /// HEADER.FIELDS and HEADER.FIELDS.NOT are followed by a list of /// field-name (as defined in [RFC-2822]) names, and return a /// subset of the header. The subset returned by HEADER.FIELDS /// contains only those header fields with a field-name that /// matches one of the names in the list; similarly, the subset /// returned by HEADER.FIELDS.NOT contains only the header fields /// with a non-matching field-name. The field-matching is /// case-insensitive but otherwise exact. fn header_fields(&self, fields: &'a NonEmptyVec>, invert: bool) -> Result> { // Build a lowercase ascii hashset with the fields to fetch let index = fields .as_ref() .iter() .map(|x| match x { AString::Atom(a) => a.inner().as_bytes(), AString::String(IString::Literal(l)) => l.as_ref(), AString::String(IString::Quoted(q)) => q.inner().as_bytes(), }.to_ascii_lowercase()) .collect::>(); // Extract MIME headers let mime = match &self.0 { AnyPart::Msg(msg) => msg.child.mime(), other => other.mime(), }; // Filter our MIME headers based on the field index // 1. Keep only the correctly formatted headers // 2. Keep only based on the index presence or absence // 3. Reduce as a byte vector let buffer = mime.kv.iter() .filter_map(|field| match field { header::Field::Good(header::Kv2(k, v)) => Some((k, v)), _ => None, }) .filter(|(k, _)| index.contains(&k.to_ascii_lowercase()) ^ invert) .fold(vec![], |mut acc, (k, v)| { acc.extend(*k); acc.extend(b": "); acc.extend(*v); acc.extend(b"\r\n"); acc }); Ok(ExtractedFull(buffer.into())) } /// The HEADER [...] part specifiers refer to the [RFC-2822] header of the message or of /// an encapsulated [MIME-IMT] MESSAGE/RFC822 message. /// ```raw /// HEADER ([RFC-2822] header of the message) /// ``` fn header(&self) -> Result> { let msg = self.0.as_message().ok_or(anyhow!("Selected part must be a message/rfc822"))?; Ok(ExtractedFull(msg.raw_headers.into())) } /// The TEXT part specifier refers to the text body of the message, omitting the [RFC-2822] header. fn text(&self) -> Result> { let msg = self.0.as_message().ok_or(anyhow!("Selected part must be a message/rfc822"))?; Ok(ExtractedFull(msg.raw_body.into())) } // ------------ /// Returns the structure of the message fn structure(&self) -> Result> { unimplemented!(); } } // --------------------------- struct SelectedMsg<'a>(&'a SelectedMime<'a>, &'a composite::Message<'a>); struct SelectedMult<'a>(&'a SelectedMime<'a>, &'a composite::Multipart<'a>); struct SelectedTxt<'a>(&'a SelectedMime<'a>, &'a discrete::Text<'a>); struct SelectedBin<'a>(&'a SelectedMime<'a>, &'a discrete::Binary<'a>); // --------------------------- struct ExtractedFull<'a>(Cow<'a, [u8]>); impl<'a> ExtractedFull<'a> { /// It is possible to fetch a substring of the designated text. /// This is done by appending an open angle bracket ("<"), the /// octet position of the first desired octet, a period, the /// maximum number of octets desired, and a close angle bracket /// (">") to the part specifier. If the starting octet is beyond /// the end of the text, an empty string is returned. /// /// Any partial fetch that attempts to read beyond the end of the /// text is truncated as appropriate. A partial fetch that starts /// at octet 0 is returned as a partial fetch, even if this /// truncation happened. /// /// Note: This means that BODY[]<0.2048> of a 1500-octet message /// will return BODY[]<0> with a literal of size 1500, not /// BODY[]. /// /// Note: A substring fetch of a HEADER.FIELDS or /// HEADER.FIELDS.NOT part specifier is calculated after /// subsetting the header. fn to_body_section(self, partial: &'_ Option<(u32, NonZeroU32)>) -> BodySection<'a> { match partial { Some((begin, len)) => self.partialize(*begin, *len), None => BodySection::Full(self.0), } } fn partialize(self, begin: u32, len: NonZeroU32) -> BodySection<'a> { // Asked range is starting after the end of the content, // returning an empty buffer if begin as usize > self.0.len() { return BodySection::Slice { body: Cow::Borrowed(&[][..]), origin_octet: begin, } } // Asked range is ending after the end of the content, // slice only the beginning of the buffer if (begin + len.get()) as usize >= self.0.len() { return BodySection::Slice { body: match self.0 { Cow::Borrowed(body) => Cow::Borrowed(&body[begin as usize..]), Cow::Owned(body) => Cow::Owned(body[begin as usize..].to_vec()), }, origin_octet: begin, } } // Range is included inside the considered content, // this is the "happy case" BodySection::Slice { body: match self.0 { Cow::Borrowed(body) => Cow::Borrowed(&body[begin as usize..(begin + len.get()) as usize]), Cow::Owned(body) => Cow::Owned(body[begin as usize..(begin + len.get()) as usize].to_vec()), }, origin_octet: begin, } } }