boring/
base64.rs

1//! Base64 encoding support.
2use crate::cvt_n;
3use crate::error::ErrorStack;
4use crate::ffi;
5use libc::c_int;
6use openssl_macros::corresponds;
7
8/// Encodes a slice of bytes to a base64 string.
9///
10/// # Panics
11///
12/// Panics if the input length or computed output length overflow a signed C integer.
13#[corresponds(EVP_EncodeBlock)]
14#[must_use]
15pub fn encode_block(src: &[u8]) -> String {
16    assert!(src.len() <= c_int::MAX as usize);
17    let src_len = src.len();
18
19    let len = encoded_len(src_len).unwrap();
20    let mut out = Vec::with_capacity(len);
21
22    // SAFETY: `encoded_len` ensures space for 4 output characters
23    // for every 3 input bytes including padding and nul terminator.
24    // `EVP_EncodeBlock` will write only single byte ASCII characters.
25    // `EVP_EncodeBlock` will only write to not read from `out`.
26    unsafe {
27        let out_len = ffi::EVP_EncodeBlock(out.as_mut_ptr(), src.as_ptr(), src_len);
28        out.set_len(out_len);
29        String::from_utf8_unchecked(out)
30    }
31}
32
33/// Decodes a base64-encoded string to bytes.
34///
35/// # Panics
36///
37/// Panics if the input length or computed output length overflow a signed C integer.
38#[corresponds(EVP_DecodeBlock)]
39pub fn decode_block(src: &str) -> Result<Vec<u8>, ErrorStack> {
40    let src = src.trim();
41
42    // https://github.com/openssl/openssl/issues/12143
43    if src.is_empty() {
44        return Ok(vec![]);
45    }
46
47    assert!(src.len() <= c_int::MAX as usize);
48    let src_len = src.len();
49
50    let len = decoded_len(src_len).unwrap();
51    let mut out = Vec::with_capacity(len);
52
53    // SAFETY: `decoded_len` ensures space for 3 output bytes
54    // for every 4 input characters including padding.
55    // `EVP_DecodeBlock` can write fewer bytes after stripping
56    // leading and trailing whitespace, but never more.
57    // `EVP_DecodeBlock` will only write to not read from `out`.
58    unsafe {
59        let out_len = cvt_n(ffi::EVP_DecodeBlock(
60            out.as_mut_ptr(),
61            src.as_ptr(),
62            src_len,
63        ))?;
64        out.set_len(out_len as usize);
65    }
66
67    if src.ends_with('=') {
68        out.pop();
69        if src.ends_with("==") {
70            out.pop();
71        }
72    }
73
74    Ok(out)
75}
76
77fn encoded_len(src_len: usize) -> Option<usize> {
78    let mut len = (src_len / 3).checked_mul(4)?;
79
80    if src_len % 3 != 0 {
81        len = len.checked_add(4)?;
82    }
83
84    len = len.checked_add(1)?;
85
86    Some(len)
87}
88
89fn decoded_len(src_len: usize) -> Option<usize> {
90    let mut len = (src_len / 4).checked_mul(3)?;
91
92    if src_len % 4 != 0 {
93        len = len.checked_add(3)?;
94    }
95
96    Some(len)
97}
98
99#[cfg(test)]
100mod tests {
101    use super::*;
102
103    #[test]
104    fn test_encode_block() {
105        assert_eq!(String::new(), encode_block(b""));
106        assert_eq!("Zg==".to_string(), encode_block(b"f"));
107        assert_eq!("Zm8=".to_string(), encode_block(b"fo"));
108        assert_eq!("Zm9v".to_string(), encode_block(b"foo"));
109        assert_eq!("Zm9vYg==".to_string(), encode_block(b"foob"));
110        assert_eq!("Zm9vYmE=".to_string(), encode_block(b"fooba"));
111        assert_eq!("Zm9vYmFy".to_string(), encode_block(b"foobar"));
112    }
113
114    #[test]
115    fn test_decode_block() {
116        assert_eq!(b"".to_vec(), decode_block("").unwrap());
117        assert_eq!(b"f".to_vec(), decode_block("Zg==").unwrap());
118        assert_eq!(b"fo".to_vec(), decode_block("Zm8=").unwrap());
119        assert_eq!(b"foo".to_vec(), decode_block("Zm9v").unwrap());
120        assert_eq!(b"foob".to_vec(), decode_block("Zm9vYg==").unwrap());
121        assert_eq!(b"fooba".to_vec(), decode_block("Zm9vYmE=").unwrap());
122        assert_eq!(b"foobar".to_vec(), decode_block("Zm9vYmFy").unwrap());
123    }
124
125    #[test]
126    fn test_strip_whitespace() {
127        assert_eq!(b"foobar".to_vec(), decode_block(" Zm9vYmFy\n").unwrap());
128        assert_eq!(b"foob".to_vec(), decode_block(" Zm9vYg==\n").unwrap());
129    }
130}
boring/base64.rs

boring/
base64.rs
