apksig 0.4.0

Decoding the APK Signing Block
Documentation 
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
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255

//! Signatures for APK Signing Block

#[cfg(feature = "serde")]
use serde::{Deserialize, Serialize};

/// Id of RSASSA-PSS with SHA2-256 digest, SHA2-256 MGF1, 32 bytes of salt
pub const SIGNATURE_RSA_PSS_256: u32 = 0x0101;
/// Id of RSASSA-PSS with SHA2-512 digest, SHA2-512 MGF1, 64 bytes of salt
pub const SIGNATURE_RSA_PSS_512: u32 = 0x0102;
/// Id of RSASSA-PKCS1-v1_5 with SHA2-256 digest
pub const SIGNATURE_RSA_PKCS1_256: u32 = 0x0103;
/// Id of RSASSA-PKCS1-v1_5 with SHA2-512 digest
pub const SIGNATURE_RSA_PKCS1_512: u32 = 0x0104;
/// Id of ECDSA with SHA2-256 digest
pub const SIGNATURE_ECDSA_256: u32 = 0x0201;
/// Id of ECDSA with SHA2-512 digest
pub const SIGNATURE_ECDSA_512: u32 = 0x0202;
/// Id of DSA with SHA2-256 digest
pub const SIGNATURE_DSA_256: u32 = 0x0301;

/// Signature algorithms
#[derive(Debug, Clone, PartialEq, Eq)]
#[allow(non_camel_case_types)]
pub enum Algorithms {
    /// RSASSA-PSS with SHA2-256 digest, SHA2-256 MGF1, 32 bytes of salt
    RSASSA_PSS_256,
    /// RSASSA-PSS with SHA2-512 digest, SHA2-512 MGF1, 64 bytes of salt
    RSASSA_PSS_512,
    /// RSASSA-PKCS1-v1_5 with SHA2-256 digest.
    RSASSA_PKCS1_v1_5_256,
    /// RSASSA-PKCS1-v1_5 with SHA2-512 digest.
    RSASSA_PKCS1_v1_5_512,
    /// ECDSA with SHA2-256 digest
    ECDSA_SHA2_256,
    /// ECDSA with SHA2-512 digest
    ECDSA_SHA2_512,
    /// DSA with SHA2-256 digest
    DSA_SHA2_256,
    /// Unknown algorithm
    Unknown(u32),
}

#[cfg(feature = "serde")]
impl Serialize for Algorithms {
    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
    where
        S: serde::ser::Serializer,
    {
        u32::from(self).serialize(serializer)
    }
}

#[cfg(feature = "serde")]
impl<'de> Deserialize<'de> for Algorithms {
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
    where
        D: serde::de::Deserializer<'de>,
    {
        let sig = u32::deserialize(deserializer)?;
        Ok(Self::from(sig))
    }
}

impl PartialEq<Algorithms> for u32 {
    fn eq(&self, sig: &Algorithms) -> bool {
        match sig {
            Algorithms::RSASSA_PSS_256 => self == &SIGNATURE_RSA_PSS_256,
            Algorithms::RSASSA_PSS_512 => self == &SIGNATURE_RSA_PSS_512,
            Algorithms::RSASSA_PKCS1_v1_5_256 => self == &SIGNATURE_RSA_PKCS1_256,
            Algorithms::RSASSA_PKCS1_v1_5_512 => self == &SIGNATURE_RSA_PKCS1_512,
            Algorithms::ECDSA_SHA2_256 => self == &SIGNATURE_ECDSA_256,
            Algorithms::ECDSA_SHA2_512 => self == &SIGNATURE_ECDSA_512,
            Algorithms::DSA_SHA2_256 => self == &SIGNATURE_DSA_256,
            Algorithms::Unknown(u) => self == u,
        }
    }
}

impl std::fmt::Display for Algorithms {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        let str = match *self {
            Self::RSASSA_PSS_256 => {
                "RSASSA-PSS with SHA2-256 digest, SHA2-256 MGF1, 32 bytes of salt, trailer: 0xbc"
            }
            Self::RSASSA_PSS_512 => {
                "RSASSA-PSS with SHA2-512 digest, SHA2-512 MGF1, 64 bytes of salt, trailer: 0xbc"
            }
            Self::RSASSA_PKCS1_v1_5_256 => {
                "RSASSA-PKCS1-v1_5 with SHA2-256 digest. This is for build systems which require deterministic signatures."
            }
            Self::RSASSA_PKCS1_v1_5_512 => {
                "RSASSA-PKCS1-v1_5 with SHA2-512 digest. This is for build systems which require deterministic signatures."
            }
            Self::ECDSA_SHA2_256 => "ECDSA with SHA2-256 digest",
            Self::ECDSA_SHA2_512 => "ECDSA with SHA2-512 digest",
            Self::DSA_SHA2_256 => "DSA with SHA2-256 digest",
            Self::Unknown(u) => &format!("Unknown algorithm: 0x{:04x}", u),
        };
        write!(f, "{:#x} - {}", u32::from(self), str)
    }
}

impl From<u32> for Algorithms {
    fn from(sig: u32) -> Self {
        match sig {
            SIGNATURE_RSA_PSS_256 => Self::RSASSA_PSS_256,
            SIGNATURE_RSA_PSS_512 => Self::RSASSA_PSS_512,
            SIGNATURE_RSA_PKCS1_256 => Self::RSASSA_PKCS1_v1_5_256,
            SIGNATURE_RSA_PKCS1_512 => Self::RSASSA_PKCS1_v1_5_512,
            SIGNATURE_ECDSA_256 => Self::ECDSA_SHA2_256,
            SIGNATURE_ECDSA_512 => Self::ECDSA_SHA2_512,
            SIGNATURE_DSA_256 => Self::DSA_SHA2_256,
            _ => Self::Unknown(sig),
        }
    }
}

impl From<&Algorithms> for u32 {
    fn from(sig: &Algorithms) -> Self {
        match *sig {
            Algorithms::RSASSA_PSS_256 => SIGNATURE_RSA_PSS_256,
            Algorithms::RSASSA_PSS_512 => SIGNATURE_RSA_PSS_512,
            Algorithms::RSASSA_PKCS1_v1_5_256 => SIGNATURE_RSA_PKCS1_256,
            Algorithms::RSASSA_PKCS1_v1_5_512 => SIGNATURE_RSA_PKCS1_512,
            Algorithms::ECDSA_SHA2_256 => SIGNATURE_ECDSA_256,
            Algorithms::ECDSA_SHA2_512 => SIGNATURE_ECDSA_512,
            Algorithms::DSA_SHA2_256 => SIGNATURE_DSA_256,
            Algorithms::Unknown(u) => u,
        }
    }
}

/// Hashing functions
#[cfg(feature = "hash")]
fn sha256(data: &[u8]) -> Vec<u8> {
    use sha2::{Digest, Sha256};
    let mut hasher = Sha256::new();
    hasher.update(data);
    hasher.finalize().to_vec()
}

/// Hashing functions
#[cfg(feature = "hash")]
fn sha512(data: &[u8]) -> Vec<u8> {
    use sha2::{Digest, Sha512};
    let mut hasher = Sha512::new();
    hasher.update(data);
    hasher.finalize().to_vec()
}

impl Algorithms {
    /// Hash data
    #[cfg(feature = "hash")]
    pub fn hash(&self, data: &[u8]) -> Vec<u8> {
        match &self {
            Self::RSASSA_PSS_256
            | Self::RSASSA_PKCS1_v1_5_256
            | Self::ECDSA_SHA2_256
            | Self::DSA_SHA2_256 => sha256(data),
            Self::RSASSA_PSS_512 | Self::RSASSA_PKCS1_v1_5_512 | Self::ECDSA_SHA2_512 => {
                sha512(data)
            }
            Self::Unknown(_) => Vec::new(),
        }
    }

    /// Verify signature
    /// # Arguments
    /// * `pubkey` - Public key from the signing block
    /// * `raw_data` - Raw data from the signed_data (without the 4 bytes of size) of the signing block
    /// * `signature` - Signature from the signing block
    /// # Errors
    /// Returns an error if the signature is invalid
    #[cfg(feature = "signing")]
    pub fn verify(&self, pubkey: &[u8], raw_data: &[u8], signature: &[u8]) -> Result<(), String> {
        use rsa::pkcs8::DecodePublicKey;
        use rsa::sha2::{Sha256, Sha512};
        use rsa::{Pkcs1v15Sign, RsaPublicKey};
        let key = match RsaPublicKey::from_public_key_der(pubkey) {
            Ok(key) => key,
            Err(_) => return Err("Invalid public key".to_string()),
        };
        let data = self.hash(raw_data);
        match &self {
            Self::RSASSA_PKCS1_v1_5_256 => {
                let pkcs = Pkcs1v15Sign::new::<Sha256>();
                match key.verify(pkcs, &data, signature) {
                    Ok(_) => Ok(()),
                    Err(_) => Err("Invalid signature".to_string()),
                }
            }
            Self::RSASSA_PKCS1_v1_5_512 => {
                let pkcs = Pkcs1v15Sign::new::<Sha512>();
                match key.verify(pkcs, &data, signature) {
                    Ok(_) => Ok(()),
                    Err(_) => Err("Invalid signature".to_string()),
                }
            }
            Self::RSASSA_PSS_256 => {
                let pkcs = rsa::pss::Pss::new::<Sha256>();
                match key.verify(pkcs, &data, signature) {
                    Ok(_) => Ok(()),
                    Err(_) => Err("Invalid signature".to_string()),
                }
            }
            Self::RSASSA_PSS_512 => {
                let pkcs = rsa::pss::Pss::new::<Sha512>();
                match key.verify(pkcs, &data, signature) {
                    Ok(_) => Ok(()),
                    Err(_) => Err("Invalid signature".to_string()),
                }
            }
            _ => Err("Not implemented".to_string()),
        }
    }

    /// Sign data
    /// # Errors
    /// Returns a string if the signing fails.
    #[cfg(feature = "signing")]
    pub fn sign(
        &self,
        private_key: rsa::RsaPrivateKey,
        raw_data: &[u8],
    ) -> Result<Vec<u8>, String> {
        let hashed = &self.hash(raw_data);
        match &self {
            Self::RSASSA_PKCS1_v1_5_256 => {
                use rsa::Pkcs1v15Sign;
                use rsa::sha2::Sha256;
                let pkcs = Pkcs1v15Sign::new::<Sha256>();
                private_key.sign(pkcs, hashed).map_err(|e| e.to_string())
            }
            Self::RSASSA_PKCS1_v1_5_512 => {
                use rsa::Pkcs1v15Sign;
                use rsa::sha2::Sha512;
                let pkcs = Pkcs1v15Sign::new::<Sha512>();
                private_key.sign(pkcs, hashed).map_err(|e| e.to_string())
            }
            Self::RSASSA_PSS_256 => {
                use rsa::pss::Pss;
                use rsa::sha2::Sha256;
                let pkcs = Pss::new::<Sha256>();
                private_key.sign(pkcs, hashed).map_err(|e| e.to_string())
            }
            Self::RSASSA_PSS_512 => {
                use rsa::pss::Pss;
                use rsa::sha2::Sha512;
                let pkcs = Pss::new::<Sha512>();
                private_key.sign(pkcs, hashed).map_err(|e| e.to_string())
            }
            _ => Err("Not implemented".to_string()),
        }
    }
}