Commit `79b41dbdbf`

Andrew Kelley <andrew@ziglang.org>

2022-12-30 04:49:56

std.crypto.tls: avoid heap allocation

The code we are borrowing from https://github.com/shiguredo/tls13-zig requires an Allocator for doing RSA certificate verification. As a stopgap measure, this commit uses a FixedBufferAllocator to avoid heap allocation for these functions. Thank you to @naoki9911 for providing this great resource which has been extremely helpful for me when working on this standard library TLS implementation. Until Zig has std.crypto.rsa officially, we will borrow this implementation of RSA. 🙏

master

1 parent 2d090f6

Changed files (2)

lib

std

crypto

tls

Client.zig

Certificate.zig

@@ -544,11 +544,14 @@ pub fn init(stream: net.Stream, ca_bundle: Certificate.Bundle, host: []const u8)
                                             const components = try rsa.PublicKey.parseDer(main_cert_pub_key);
                                             const exponent = components.exponent;
                                             const modulus = components.modulus;
+                                            var rsa_mem_buf: [512 * 32]u8 = undefined;
+                                            var fba = std.heap.FixedBufferAllocator.init(&rsa_mem_buf);
+                                            const ally = fba.allocator();
                                             switch (modulus.len) {
                                                 inline 128, 256, 512 => |modulus_len| {
-                                                    const key = try rsa.PublicKey.fromBytes(exponent, modulus, rsa.poop);
+                                                    const key = try rsa.PublicKey.fromBytes(exponent, modulus, ally);
                                                     const sig = rsa.PSSSignature.fromBytes(modulus_len, encoded_sig);
-                                                    try rsa.PSSSignature.verify(modulus_len, sig, verify_bytes, key, Hash, rsa.poop);
+                                                    try rsa.PSSSignature.verify(modulus_len, sig, verify_bytes, key, Hash, ally);
                                                 },
                                                 else => {
                                                     return error.TlsBadRsaSignatureBitCount;

@@ -511,6 +511,10 @@ fn verifyRsa(
     var msg_hashed: [Hash.digest_length]u8 = undefined;
     Hash.hash(message, &msg_hashed, .{});
 
+    var rsa_mem_buf: [512 * 32]u8 = undefined;
+    var fba = std.heap.FixedBufferAllocator.init(&rsa_mem_buf);
+    const ally = fba.allocator();
+
     switch (modulus.len) {
         inline 128, 256, 512 => |modulus_len| {
             const ps_len = modulus_len - (hash_der.len + msg_hashed.len) - 3;
@@ -521,11 +525,11 @@ fn verifyRsa(
                 hash_der ++
                 msg_hashed;
 
-            const public_key = rsa.PublicKey.fromBytes(exponent, modulus, rsa.poop) catch |err| switch (err) {
-                error.OutOfMemory => @panic("TODO don't heap allocate"),
+            const public_key = rsa.PublicKey.fromBytes(exponent, modulus, ally) catch |err| switch (err) {
+                error.OutOfMemory => unreachable, // rsa_mem_buf is big enough
             };
-            const em_dec = rsa.encrypt(modulus_len, sig[0..modulus_len].*, public_key, rsa.poop) catch |err| switch (err) {
-                error.OutOfMemory => @panic("TODO don't heap allocate"),
+            const em_dec = rsa.encrypt(modulus_len, sig[0..modulus_len].*, public_key, ally) catch |err| switch (err) {
+                error.OutOfMemory => unreachable, // rsa_mem_buf is big enough
 
                 error.MessageTooLong => unreachable,
                 error.NegativeIntoUnsigned => @panic("TODO make RSA not emit this error"),
@@ -977,7 +981,4 @@ pub const rsa = struct {
 
         return i;
     }
-
-    // TODO: flush the toilet
-    pub const poop = std.heap.page_allocator;
 };

Commit 79b41dbdbf

Commit `79b41dbdbf`