1//! Base64 encoding support.
2use crate::error::ErrorStack;
3use crate::{cvt_n, LenType};
4use libc::c_int;
5use openssl_macros::corresponds;
6
7/// Encodes a slice of bytes to a base64 string.
8///
9/// # Panics
10///
11/// Panics if the input length or computed output length overflow a signed C integer.
12#[corresponds(EVP_EncodeBlock)]
13pub fn encode_block(src: &[u8]) -> String {
14    assert!(src.len() <= c_int::max_value() as usize);
15    let src_len = src.len() as LenType;
16
17    let len = encoded_len(src_len).unwrap();
18    let mut out = Vec::with_capacity(len as usize);
19
20    // SAFETY: `encoded_len` ensures space for 4 output characters
21    // for every 3 input bytes including padding and nul terminator.
22    // `EVP_EncodeBlock` will write only single byte ASCII characters.
23    // `EVP_EncodeBlock` will only write to not read from `out`.
24    unsafe {
25        let out_len = ffi::EVP_EncodeBlock(out.as_mut_ptr(), src.as_ptr(), src_len);
26        out.set_len(out_len as usize);
27        String::from_utf8_unchecked(out)
28    }
29}
30
31/// Decodes a base64-encoded string to bytes.
32///
33/// # Panics
34///
35/// Panics if the input length or computed output length overflow a signed C integer.
36#[corresponds(EVP_DecodeBlock)]
37pub fn decode_block(src: &str) -> Result<Vec<u8>, ErrorStack> {
38    let src = src.trim();
39
40    // https://github.com/openssl/openssl/issues/12143
41    if src.is_empty() {
42        return Ok(vec![]);
43    }
44
45    assert!(src.len() <= c_int::max_value() as usize);
46    let src_len = src.len() as LenType;
47
48    let len = decoded_len(src_len).unwrap();
49    let mut out = Vec::with_capacity(len as usize);
50
51    // SAFETY: `decoded_len` ensures space for 3 output bytes
52    // for every 4 input characters including padding.
53    // `EVP_DecodeBlock` can write fewer bytes after stripping
54    // leading and trailing whitespace, but never more.
55    // `EVP_DecodeBlock` will only write to not read from `out`.
56    unsafe {
57        let out_len = cvt_n(ffi::EVP_DecodeBlock(
58            out.as_mut_ptr(),
59            src.as_ptr(),
60            src_len,
61        ))?;
62        out.set_len(out_len as usize);
63    }
64
65    if src.ends_with('=') {
66        out.pop();
67        if src.ends_with("==") {
68            out.pop();
69        }
70    }
71
72    Ok(out)
73}
74
75fn encoded_len(src_len: LenType) -> Option<LenType> {
76    let mut len = (src_len / 3).checked_mul(4)?;
77
78    if src_len % 3 != 0 {
79        len = len.checked_add(4)?;
80    }
81
82    len = len.checked_add(1)?;
83
84    Some(len)
85}
86
87fn decoded_len(src_len: LenType) -> Option<LenType> {
88    let mut len = (src_len / 4).checked_mul(3)?;
89
90    if src_len % 4 != 0 {
91        len = len.checked_add(3)?;
92    }
93
94    Some(len)
95}
96
97#[cfg(test)]
98mod tests {
99    use super::*;
100
101    #[test]
102    fn test_encode_block() {
103        assert_eq!("".to_string(), encode_block(b""));
104        assert_eq!("Zg==".to_string(), encode_block(b"f"));
105        assert_eq!("Zm8=".to_string(), encode_block(b"fo"));
106        assert_eq!("Zm9v".to_string(), encode_block(b"foo"));
107        assert_eq!("Zm9vYg==".to_string(), encode_block(b"foob"));
108        assert_eq!("Zm9vYmE=".to_string(), encode_block(b"fooba"));
109        assert_eq!("Zm9vYmFy".to_string(), encode_block(b"foobar"));
110    }
111
112    #[test]
113    fn test_decode_block() {
114        assert_eq!(b"".to_vec(), decode_block("").unwrap());
115        assert_eq!(b"f".to_vec(), decode_block("Zg==").unwrap());
116        assert_eq!(b"fo".to_vec(), decode_block("Zm8=").unwrap());
117        assert_eq!(b"foo".to_vec(), decode_block("Zm9v").unwrap());
118        assert_eq!(b"foob".to_vec(), decode_block("Zm9vYg==").unwrap());
119        assert_eq!(b"fooba".to_vec(), decode_block("Zm9vYmE=").unwrap());
120        assert_eq!(b"foobar".to_vec(), decode_block("Zm9vYmFy").unwrap());
121    }
122
123    #[test]
124    fn test_strip_whitespace() {
125        assert_eq!(b"foobar".to_vec(), decode_block(" Zm9vYmFy\n").unwrap());
126        assert_eq!(b"foob".to_vec(), decode_block(" Zm9vYg==\n").unwrap());
127    }
128}
129