smb 0.2.0

A Pure Rust SMB Client implementation
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
159
160
161
162
163
164
165
166
167

//! Session state

use std::sync::Arc;

use crate::sync_helpers::*;
use maybe_async::*;

use crate::connection::negotiation_state::NegotiateState;
use crate::connection::preauth_hash::PreauthHashValue;
use crate::crypto::{
    kbkdf_hmacsha256, make_encrypting_algo, make_signing_algo, CryptoError, DerivedKey, KeyToDerive,
};
use crate::packets::smb2::{EncryptionCipher, SessionFlags, SigningAlgorithmId};

use super::{MessageDecryptor, MessageEncryptor, MessageSigner};

/// Holds the state of a session, to be used for actions requiring data from session,
/// without accessing the entire session object.
/// This struct should be single-per-session, and wrapped in a shared pointer.
#[derive(Debug)]
pub struct SessionState {
    pub session_id: u64,

    flags: SessionFlags,

    signer: Option<MessageSigner>,
    decryptor: Option<MessageDecryptor>,
    encryptor: Option<MessageEncryptor>,
}

impl SessionState {
    const SIGNING_KEY_LABEL: &[u8] = b"SMBSigningKey\x00";
    const S2C_DECRYPTION_KEY_LABEL: &[u8] = b"SMBS2CCipherKey\x00";
    const C2S_ENCRYPTION_KEY_LABEL: &[u8] = b"SMBC2SCipherKey\x00";

    #[maybe_async]
    pub async fn set(
        state: &mut Arc<Mutex<Self>>,
        session_key: &KeyToDerive,
        preauth_hash: &PreauthHashValue,
        negotation_state: &NegotiateState,
    ) -> crate::Result<()> {
        let deriver = KeyDeriver::new(session_key, preauth_hash);
        let signer = Self::make_signer(&deriver, negotation_state.signing_algo())?;
        let decryptor = Self::make_decryptor(&deriver, negotation_state.cipher())?;
        let encryptor = Self::make_encryptor(&deriver, negotation_state.cipher())?;

        let mut state = state.lock().await?;
        state.signer = Some(signer);
        state.decryptor = Some(decryptor);
        state.encryptor = Some(encryptor);

        Ok(())
    }

    fn make_signer(
        deriver: &KeyDeriver,
        signing_algo: SigningAlgorithmId,
    ) -> Result<MessageSigner, CryptoError> {
        let signing_key = deriver.derive(Self::SIGNING_KEY_LABEL)?;
        Ok(MessageSigner::new(make_signing_algo(
            signing_algo,
            &signing_key,
        )?))
    }

    fn make_encryptor(
        deriver: &KeyDeriver,
        cipher: EncryptionCipher,
    ) -> Result<MessageEncryptor, CryptoError> {
        let c2s_encryption_key = deriver.derive(Self::C2S_ENCRYPTION_KEY_LABEL)?;
        Ok(MessageEncryptor::new(make_encrypting_algo(
            cipher,
            &c2s_encryption_key,
        )?))
    }

    fn make_decryptor(
        deriver: &KeyDeriver,
        cipher: EncryptionCipher,
    ) -> Result<MessageDecryptor, CryptoError> {
        let s2c_decryption_key = deriver.derive(Self::S2C_DECRYPTION_KEY_LABEL)?;

        Ok(MessageDecryptor::new(make_encrypting_algo(
            cipher,
            &s2c_decryption_key,
        )?))
    }

    #[maybe_async]
    pub async fn set_flags(state: &mut Arc<Mutex<Self>>, flags: SessionFlags) -> crate::Result<()> {
        state.lock().await?.flags = flags;
        Ok(())
    }

    #[maybe_async]
    pub async fn invalidate(state: &Arc<Mutex<Self>>) -> crate::Result<()> {
        let mut state = state.lock().await?;
        state.signer = None;
        state.decryptor = None;
        state.encryptor = None;
        Ok(())
    }

    #[maybe_async]
    pub async fn signing_enabled(state: &Arc<Mutex<Self>>) -> crate::Result<bool> {
        Ok(state.lock().await?.signer.is_some())
    }

    #[maybe_async]
    pub async fn encryption_enabled(state: &Arc<Mutex<Self>>) -> crate::Result<bool> {
        let state = state.lock().await?;
        return Ok(state.flags.encrypt_data()
            && state.encryptor.is_some()
            && state.decryptor.is_some());
    }

    #[maybe_async]
    pub async fn is_set_up(state: &Arc<Mutex<Self>>) -> crate::Result<bool> {
        Ok(Self::encryption_enabled(state).await? || Self::signing_enabled(state).await?)
    }

    pub fn decryptor(&mut self) -> Option<&mut MessageDecryptor> {
        self.decryptor.as_mut()
    }

    pub fn encryptor(&mut self) -> Option<&mut MessageEncryptor> {
        self.encryptor.as_mut()
    }

    pub fn signer(&mut self) -> Option<&mut MessageSigner> {
        self.signer.as_mut()
    }
}

/// A helper struct for deriving SMB2 keys from a session key and preauth hash.
struct KeyDeriver<'a> {
    session_key: &'a KeyToDerive,
    preauth_hash: &'a PreauthHashValue,
}

impl<'a> KeyDeriver<'a> {
    #[inline]
    pub fn new(session_key: &'a KeyToDerive, preauth_hash: &'a PreauthHashValue) -> Self {
        Self {
            session_key,
            preauth_hash,
        }
    }

    #[inline]
    pub fn derive(&self, label: &[u8]) -> Result<DerivedKey, CryptoError> {
        kbkdf_hmacsha256::<16>(self.session_key, label, self.preauth_hash)
    }
}

impl Default for SessionState {
    fn default() -> Self {
        Self {
            session_id: Default::default(),
            flags: SessionFlags::new(),
            signer: Default::default(),
            decryptor: Default::default(),
            encryptor: Default::default(),
        }
    }
}