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
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
//! Functions for decoding Base58 encoded strings.

use core::fmt;

#[cfg(feature = "alloc")]
use alloc::{vec, vec::Vec};

use crate::Check;
#[cfg(feature = "check")]
use crate::CHECKSUM_LEN;

use crate::Alphabet;

/// A builder for setting up the alphabet and output of a base58 decode.
///
/// See the documentation for [`bs58::decode`](crate::decode()) for a more
/// high level view of how to use this.
#[allow(missing_debug_implementations)]
pub struct DecodeBuilder<'a, I: AsRef<[u8]>> {
    input: I,
    alpha: &'a Alphabet,
    check: Check,
}

/// A specialized [`Result`](core::result::Result) type for [`bs58::decode`](module@crate::decode)
pub type Result<T> = core::result::Result<T, Error>;

/// Errors that could occur when decoding a Base58 encoded string.
#[derive(Copy, Clone, Debug, Eq, PartialEq)]
#[non_exhaustive]
pub enum Error {
    /// The output buffer was too small to contain the entire input.
    BufferTooSmall,

    /// The input contained a character that was not part of the current Base58
    /// alphabet.
    InvalidCharacter {
        /// The unexpected character.
        character: char,
        /// The (byte) index in the input string the character was at.
        index: usize,
    },

    /// The input contained a multi-byte (or non-utf8) character which is
    /// unsupported by this Base58 decoder.
    NonAsciiCharacter {
        /// The (byte) index in the input string the start of the character was
        /// at.
        index: usize,
    },

    #[cfg(feature = "check")]
    #[cfg_attr(docsrs, doc(cfg(feature = "check")))]
    /// The checksum did not match the payload bytes
    InvalidChecksum {
        ///The given checksum
        checksum: [u8; CHECKSUM_LEN],
        ///The checksum calculated for the payload
        expected_checksum: [u8; CHECKSUM_LEN],
    },

    #[cfg(feature = "check")]
    #[cfg_attr(docsrs, doc(cfg(feature = "check")))]
    /// The version did not match the payload bytes
    InvalidVersion {
        ///The given version
        ver: u8,
        ///The expected version
        expected_ver: u8,
    },

    #[cfg(feature = "check")]
    #[cfg_attr(docsrs, doc(cfg(feature = "check")))]
    ///Not enough bytes to have both a checksum and a payload (less than to CHECKSUM_LEN)
    NoChecksum,
}

impl<'a, I: AsRef<[u8]>> DecodeBuilder<'a, I> {
    /// Setup decoder for the given string using the given alphabet.
    /// Preferably use [`bs58::decode`](crate::decode()) instead of this directly.
    pub fn new(input: I, alpha: &'a Alphabet) -> DecodeBuilder<'a, I> {
        DecodeBuilder {
            input,
            alpha,
            check: Check::Disabled,
        }
    }

    /// Setup decoder for the given string using default prepared alphabet.
    pub(crate) fn from_input(input: I) -> DecodeBuilder<'static, I> {
        DecodeBuilder {
            input,
            alpha: Alphabet::DEFAULT,
            check: Check::Disabled,
        }
    }

    /// Change the alphabet that will be used for decoding.
    ///
    /// # Examples
    ///
    /// ```rust
    /// assert_eq!(
    ///     vec![0x60, 0x65, 0xe7, 0x9b, 0xba, 0x2f, 0x78],
    ///     bs58::decode("he11owor1d")
    ///         .with_alphabet(bs58::Alphabet::RIPPLE)
    ///         .into_vec()?);
    /// # Ok::<(), bs58::decode::Error>(())
    /// ```
    pub fn with_alphabet(self, alpha: &'a Alphabet) -> DecodeBuilder<'a, I> {
        DecodeBuilder { alpha, ..self }
    }

    /// Expect and check checksum using the [Base58Check][] algorithm when
    /// decoding.
    ///
    /// Optional parameter for version byte. If provided, the version byte will
    /// be used in verification.
    ///
    /// [Base58Check]: https://en.bitcoin.it/wiki/Base58Check_encoding
    ///
    /// # Examples
    ///
    /// ```rust
    /// assert_eq!(
    ///     vec![0x2d, 0x31],
    ///     bs58::decode("PWEu9GGN")
    ///         .with_check(None)
    ///         .into_vec()?);
    /// # Ok::<(), bs58::decode::Error>(())
    /// ```
    #[cfg(feature = "check")]
    #[cfg_attr(docsrs, doc(cfg(feature = "check")))]
    pub fn with_check(self, expected_ver: Option<u8>) -> DecodeBuilder<'a, I> {
        let check = Check::Enabled(expected_ver);
        DecodeBuilder { check, ..self }
    }

    /// Decode into a new vector of bytes.
    ///
    /// See the documentation for [`bs58::decode`](crate::decode()) for an
    /// explanation of the errors that may occur.
    ///
    /// # Examples
    ///
    /// ```rust
    /// assert_eq!(
    ///     vec![0x04, 0x30, 0x5e, 0x2b, 0x24, 0x73, 0xf0, 0x58],
    ///     bs58::decode("he11owor1d").into_vec()?);
    /// # Ok::<(), bs58::decode::Error>(())
    /// ```
    ///
    #[cfg(feature = "alloc")]
    #[cfg_attr(docsrs, doc(cfg(any(feature = "alloc", feature = "std"))))]
    pub fn into_vec(self) -> Result<Vec<u8>> {
        let mut output = vec![0; self.input.as_ref().len()];
        self.into(&mut output).map(|len| {
            output.truncate(len);
            output
        })
    }

    /// Decode into the given buffer.
    ///
    /// Returns the length written into the buffer, the rest of the bytes in
    /// the buffer will be untouched.
    ///
    /// See the documentation for [`bs58::decode`](crate::decode()) for an
    /// explanation of the errors that may occur.
    ///
    /// # Examples
    ///
    /// ```rust
    /// let mut output = [0xFF; 10];
    /// assert_eq!(8, bs58::decode("he11owor1d").into(&mut output)?);
    /// assert_eq!(
    ///     [0x04, 0x30, 0x5e, 0x2b, 0x24, 0x73, 0xf0, 0x58, 0xFF, 0xFF],
    ///     output);
    /// # Ok::<(), bs58::decode::Error>(())
    /// ```
    pub fn into<O: AsMut<[u8]>>(self, mut output: O) -> Result<usize> {
        match self.check {
            Check::Disabled => decode_into(self.input.as_ref(), output.as_mut(), &self.alpha),
            #[cfg(feature = "check")]
            Check::Enabled(expected_ver) => decode_check_into(
                self.input.as_ref(),
                output.as_mut(),
                &self.alpha,
                expected_ver,
            ),
        }
    }
}

fn decode_into(input: &[u8], output: &mut [u8], alpha: &Alphabet) -> Result<usize> {
    let mut index = 0;
    let zero = alpha.encode[0];

    for (i, c) in input.iter().enumerate() {
        if *c > 127 {
            return Err(Error::NonAsciiCharacter { index: i });
        }

        let mut val = alpha.decode[*c as usize] as usize;
        if val == 0xFF {
            return Err(Error::InvalidCharacter {
                character: *c as char,
                index: i,
            });
        }

        for byte in &mut output[..index] {
            val += (*byte as usize) * 58;
            *byte = (val & 0xFF) as u8;
            val >>= 8;
        }

        while val > 0 {
            let byte = output.get_mut(index).ok_or(Error::BufferTooSmall)?;
            *byte = (val & 0xFF) as u8;
            index += 1;
            val >>= 8
        }
    }

    for _ in input.iter().take_while(|c| **c == zero) {
        let byte = output.get_mut(index).ok_or(Error::BufferTooSmall)?;
        *byte = 0;
        index += 1;
    }

    output[..index].reverse();
    Ok(index)
}

#[cfg(feature = "check")]
fn decode_check_into(
    input: &[u8],
    output: &mut [u8],
    alpha: &Alphabet,
    expected_ver: Option<u8>,
) -> Result<usize> {
    use sha2::{Digest, Sha256};

    let decoded_len = decode_into(input, output, alpha)?;
    if decoded_len < CHECKSUM_LEN {
        return Err(Error::NoChecksum);
    }
    let checksum_index = decoded_len - CHECKSUM_LEN;

    let expected_checksum = &output[checksum_index..decoded_len];

    let first_hash = Sha256::digest(&output[0..checksum_index]);
    let second_hash = Sha256::digest(&first_hash);
    let (checksum, _) = second_hash.split_at(CHECKSUM_LEN);

    if checksum == expected_checksum {
        if let Some(ver) = expected_ver {
            if output[0] == ver {
                Ok(checksum_index)
            } else {
                Err(Error::InvalidVersion {
                    ver: output[0],
                    expected_ver: ver,
                })
            }
        } else {
            Ok(checksum_index)
        }
    } else {
        let mut a: [u8; CHECKSUM_LEN] = Default::default();
        a.copy_from_slice(&checksum[..]);
        let mut b: [u8; CHECKSUM_LEN] = Default::default();
        b.copy_from_slice(&expected_checksum[..]);
        Err(Error::InvalidChecksum {
            checksum: a,
            expected_checksum: b,
        })
    }
}

#[cfg(feature = "std")]
#[cfg_attr(docsrs, doc(cfg(feature = "std")))]
impl std::error::Error for Error {}

impl fmt::Display for Error {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match *self {
            Error::BufferTooSmall => write!(
                f,
                "buffer provided to decode base58 encoded string into was too small"
            ),
            Error::InvalidCharacter { character, index } => write!(
                f,
                "provided string contained invalid character {:?} at byte {}",
                character, index
            ),
            Error::NonAsciiCharacter { index } => write!(
                f,
                "provided string contained non-ascii character starting at byte {}",
                index
            ),
            #[cfg(feature = "check")]
            Error::InvalidChecksum {
                checksum,
                expected_checksum,
            } => write!(
                f,
                "invalid checksum, calculated checksum: '{:?}', expected checksum: {:?}",
                checksum, expected_checksum
            ),
            #[cfg(feature = "check")]
            Error::InvalidVersion { ver, expected_ver } => write!(
                f,
                "invalid version, payload version: '{:?}', expected version: {:?}",
                ver, expected_ver
            ),
            #[cfg(feature = "check")]
            Error::NoChecksum => write!(f, "provided string is too small to contain a checksum"),
        }
    }
}