1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158

/*
 * 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/>.
 */

/*! Verification of OpenPGP signatures */
use crate::email::{
    attachment_types::{ContentType, MultipartType},
    attachments::Attachment,
};
use crate::{MeliError, Result};

/// Convert raw attachment to the form needed for signature verification ([rfc3156](https://tools.ietf.org/html/rfc3156))
///
/// ## rfc3156
/// ```text
/// 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>, &Attachment)> {
    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
                        && p.content_type != ContentType::CMSSignature
                })
                .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
                    || s.content_type == ContentType::CMSSignature
            }) {
                sig
            } else {
                return Err(MeliError::new(
                    "multipart/signed attachment without a signature part".to_string(),
                ));
            };
            Ok((signed_part, signature))
        }
        _ => Err(MeliError::new(
            "Should not give non-signed attachments to this function",
        )),
    }
}

#[derive(Debug, Clone, Default)]
pub struct DecryptionMetadata {
    pub recipients: Vec<Recipient>,
    pub file_name: Option<String>,
    pub session_key: Option<String>,
    pub is_mime: bool,
}

#[derive(Debug, Clone)]
pub struct Recipient {
    pub keyid: Option<String>,
    pub status: Result<()>,
}

#[derive(Debug, Clone, Default)]
pub struct SignatureMetadata {
    pub signatures: Vec<Recipient>,
    pub file_name: Option<String>,
    pub is_mime: bool,
}