From 2fcf2d0d20f7e67a80c2cb5b2d0a437faed6efb7 Mon Sep 17 00:00:00 2001
From: Griffin Smith <grfn@gws.fyi>
Date: Thu, 23 Jul 2020 17:18:00 -0400
Subject: refactor(3p/nix): Remove custom base64 implementation
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Replace the custom, rather questionable base64 implementation with
absl::Base64{Une,E}scape. To make sure that the custom implementation
was doing the same thing I've also added a test covering
nix::Hash::to_string, which was one function that used it - the test
passed prior to the replacement, and continued to pass afterwards.

The previous base64Decode function threw an exception on failure - to
avoid going too far down the rabbit hole I've replicated that
functionality at all call sites, but this should be replaced with more
sensible error handling such as StatusOr eventually.

Also, before this change:

    ❯ nix eval -f . users.tazjin.emacs.outPath
    "/nix/store/g6ri2q8nra96ix20bcsc734r1yyaylb1-tazjins-emacs"

And after:

    ❯ ./result/bin/nix eval -f . users.tazjin.emacs.outPath
    "/nix/store/g6ri2q8nra96ix20bcsc734r1yyaylb1-tazjins-emacs"

Change-Id: Id292ffbb82fe808f3f1b34670afbe7b8c13ad615
Reviewed-on: https://cl.tvl.fyi/c/depot/+/1385
Reviewed-by: tazjin <mail@tazj.in>
Tested-by: BuildkiteCI
---
 third_party/nix/src/libutil/hash.cc | 11 ++++--
 third_party/nix/src/libutil/util.cc | 67 -------------------------------------
 third_party/nix/src/libutil/util.hh |  4 ---
 3 files changed, 9 insertions(+), 73 deletions(-)

(limited to 'third_party/nix/src/libutil')

diff --git a/third_party/nix/src/libutil/hash.cc b/third_party/nix/src/libutil/hash.cc
index 5c2ddc4bda8e..0d80972cceda 100644
--- a/third_party/nix/src/libutil/hash.cc
+++ b/third_party/nix/src/libutil/hash.cc
@@ -3,6 +3,7 @@
 #include <cstring>
 #include <iostream>
 
+#include <absl/strings/escaping.h>
 #include <fcntl.h>
 #include <openssl/md5.h>
 #include <openssl/sha.h>
@@ -117,7 +118,9 @@ std::string Hash::to_string(Base base, bool includeType) const {
       break;
     case Base64:
     case SRI:
-      s += base64Encode(std::string((const char*)hash, hashSize));
+      std::string b64;
+      absl::Base64Escape(std::string((const char*)hash, hashSize), &b64);
+      s += b64;
       break;
   }
   return s;
@@ -201,7 +204,11 @@ Hash::Hash(const std::string& s, HashType type) : type(type) {
   }
 
   else if (isSRI || size == base64Len()) {
-    auto d = base64Decode(std::string(s, pos));
+    std::string d;
+    if (!absl::Base64Unescape(std::string(s, pos), &d)) {
+      // TODO(grfn): replace this with StatusOr
+      throw Error("Invalid Base64");
+    }
     if (d.size() != hashSize) {
       throw BadHash("invalid %s hash '%s'", isSRI ? "SRI" : "base-64", s);
     }
diff --git a/third_party/nix/src/libutil/util.cc b/third_party/nix/src/libutil/util.cc
index b97624e58dbb..f69c341c2c59 100644
--- a/third_party/nix/src/libutil/util.cc
+++ b/third_party/nix/src/libutil/util.cc
@@ -1321,73 +1321,6 @@ std::string filterANSIEscapes(const std::string& s, bool filterAll,
   return t;
 }
 
-static char base64Chars[] =
-    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
-
-std::string base64Encode(const std::string& s) {
-  std::string res;
-  int data = 0;
-  int nbits = 0;
-
-  for (char c : s) {
-    data = data << 8 | (unsigned char)c;
-    nbits += 8;
-    while (nbits >= 6) {
-      nbits -= 6;
-      res.push_back(base64Chars[data >> nbits & 0x3f]);
-    }
-  }
-
-  if (nbits != 0) {
-    res.push_back(base64Chars[data << (6 - nbits) & 0x3f]);
-  }
-  while ((res.size() % 4) != 0u) {
-    res.push_back('=');
-  }
-
-  return res;
-}
-
-std::string base64Decode(const std::string& s) {
-  bool init = false;
-  char decode[256];
-  if (!init) {
-    // FIXME: not thread-safe.
-    memset(decode, -1, sizeof(decode));
-    for (int i = 0; i < 64; i++) {
-      decode[(int)base64Chars[i]] = i;
-    }
-    init = true;
-  }
-
-  std::string res;
-  unsigned int d = 0;
-  unsigned int bits = 0;
-
-  for (char c : s) {
-    if (c == '=') {
-      break;
-    }
-    if (c == '\n') {
-      continue;
-    }
-
-    char digit = decode[(unsigned char)c];
-    if (digit == -1) {
-      throw Error("invalid character in Base64 string");
-    }
-
-    bits += 6;
-    d = d << 6 | digit;
-    if (bits >= 8) {
-      res.push_back(d >> (bits - 8) & 0xff);
-      bits -= 8;
-    }
-  }
-
-  return res;
-}
-
 void callFailure(const std::function<void(std::exception_ptr exc)>& failure,
                  const std::exception_ptr& exc) {
   try {
diff --git a/third_party/nix/src/libutil/util.hh b/third_party/nix/src/libutil/util.hh
index 0fa15f745c86..d9fc1a27b134 100644
--- a/third_party/nix/src/libutil/util.hh
+++ b/third_party/nix/src/libutil/util.hh
@@ -358,10 +358,6 @@ std::string filterANSIEscapes(
     const std::string& s, bool filterAll = false,
     unsigned int width = std::numeric_limits<unsigned int>::max());
 
-/* Base64 encoding/decoding. */
-std::string base64Encode(const std::string& s);
-std::string base64Decode(const std::string& s);
-
 /* Get a value for the specified key from an associate container, or a
    default value if the key doesn't exist. */
 template <class T>
-- 
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