Thing for extracting DER from PEM files

Cargo.lock

@@ -4,6 +4,7 @@ version = "0.1.0"
 dependencies = [
  "mio 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "ring 0.1.0 (git+https://github.com/briansmith/ring)",
+ "rustc-serialize 0.3.19 (registry+https://github.com/rust-lang/crates.io-index)",
  "time 0.1.35 (registry+https://github.com/rust-lang/crates.io-index)",
  "webpki 0.1.0 (git+file:///home/jbp/webpki/)",
 ]

Cargo.toml

@@ -9,3 +9,4 @@ webpki = { version = "0.1.0", git = "file:///home/jbp/webpki/" }
 
 mio = "0.5.1"
 time = "0.1.35"
+rustc-serialize = "0.3"

src/pemfile.rs

@@ -0,0 +1,41 @@
+use std::io;
+use rustc_serialize::base64::FromBase64;
+
+static START_MARKER: &'static str = "-----BEGIN CERTIFICATE-----";
+static END_MARKER: &'static str = "-----END CERTIFICATE-----";
+
+/// Extract all the certificates from rd, and return a vec of bytevecs
+/// containing the der-format contents.
+pub fn certs(rd: &mut io::BufRead) -> Result<Vec<Vec<u8>>, ()> {
+  let mut ders = Vec::new();
+  let mut b64buf = String::new();
+  let mut take_base64 = false;
+
+  loop {
+    let mut line = String::new();
+    let len = try!(rd.read_line(&mut line)
+                   .map_err(|_| ()));
+
+    if len == 0 {
+      return Ok(ders);
+    }
+
+    if line.starts_with(START_MARKER) {
+      take_base64 = true;
+      continue;
+    }
+
+    if line.starts_with(END_MARKER) {
+      take_base64 = false;
+      let der = try!(b64buf.from_base64()
+                     .map_err(|_| ()));
+      ders.push(der);
+      b64buf = String::new();
+      continue;
+    }
+
+    if take_base64 {
+      b64buf.push_str(&line.trim());
+    }
+  }
+}