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Correct Element and Tag in crypto.codecs.asn1 (#31511)

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Previously, `std.crypto.codecs.asn1.der.decode` failed to compile because of `std.Io.Reader` usage in `Element.decode` and `Tag.decode` and `DecodeError` not being compatible with `std.Io.Reader.Error`.

Reviewed-on: https://codeberg.org/ziglang/zig/pulls/31511
Reviewed-by: Andrew Kelley <andrew@ziglang.org>
Co-authored-by: nekogirl <nekogirl@noreply.codeberg.org>
Co-committed-by: nekogirl <nekogirl@noreply.codeberg.org>
This commit is contained in:
nekogirl
2026-04-09 17:59:16 +02:00
committed by Andrew Kelley
parent 36e2eaf2bd
commit ac6fb0b59a
1 changed files with 33 additions and 18 deletions
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lib/std/crypto/codecs/asn1.zig
+33 -18
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@@ -73,13 +73,13 @@ pub const Tag = struct {
const tag1: FirstTag = @bitCast(try reader.takeByte());
var number: u14 = tag1.number;
if (tag1.number == 15) {
if (tag1.number == 31) {
const tag2: NextTag = @bitCast(try reader.takeByte());
number = tag2.number;
if (tag2.continues) {
const tag3: NextTag = @bitCast(try reader.takeByte());
number = (number << 7) + tag3.number;
if (tag3.continues) return error.InvalidLength;
if (tag3.continues) return error.EndOfStream;
}
}
@@ -183,7 +183,7 @@ pub const Element = struct {
}
};
pub const DecodeError = error{ InvalidLength, EndOfStream };
pub const DecodeError = error{EndOfStream};
/// Safely decode a DER/BER/CER element at `index`:
/// - Ensures length uses shortest form
@@ -192,26 +192,35 @@ pub const Element = struct {
pub fn decode(bytes: []const u8, index: Index) DecodeError!Element {
var reader: std.Io.Reader = .fixed(bytes[index..]);
const tag = try Tag.decode(&reader);
const size_or_len_size = try reader.takeByte();
const tag = Tag.decode(&reader) catch |err| switch (err) {
error.ReadFailed => unreachable, // it's all fixed buffers
else => |e| return e,
};
const size_or_len_size = reader.takeByte() catch |err| switch (err) {
error.ReadFailed => unreachable, // it's all fixed buffers
else => |e| return e,
};
var start = index + 2;
var end = start + size_or_len_size;
// short form between 0-127
if (size_or_len_size < 128) {
if (end > bytes.len) return error.InvalidLength;
} else {
const len = if (size_or_len_size < 128)
// short form between 0-127
size_or_len_size
else blk: {
// long form between 0 and std.math.maxInt(u1024)
const len_size: u7 = @truncate(size_or_len_size);
start += len_size;
if (len_size > @sizeOf(Index)) return error.InvalidLength;
if (len_size > @sizeOf(Index)) return error.EndOfStream;
const len = try reader.takeVarInt(Index, .big, len_size);
if (len < 128) return error.InvalidLength; // should have used short form
const len = reader.takeVarInt(Index, .big, len_size) catch |err| switch (err) {
error.ReadFailed => unreachable, // it's all fixed buffers
else => |e| return e,
};
if (len < 128) return error.EndOfStream; // should have used short form
end = std.math.add(Index, start, len) catch return error.InvalidLength;
if (end > bytes.len) return error.InvalidLength;
}
break :blk len;
};
const start = index + @as(Index, @intCast(reader.seek));
const end = std.math.add(Index, start, len) catch return error.EndOfStream;
if (end > bytes.len) return error.EndOfStream;
return Element{ .tag = tag, .slice = Slice{ .start = start, .end = end } };
}
@@ -229,6 +238,12 @@ test Element {
.tag = Tag.universal(.sequence, true),
.slice = Element.Slice{ .start = 3, .end = long_form.len },
}, Element.decode(&long_form, 0));
const multi_byte_tag = [_]u8{ 0x1F, 0x20, 0x08, 0x30, 0x36, 0x3A, 0x32, 0x37, 0x3A, 0x31, 0x35 };
try std.testing.expectEqual(Element{
.tag = Tag.universal(.time_of_day, false),
.slice = Element.Slice{ .start = 3, .end = multi_byte_tag.len },
}, Element.decode(&multi_byte_tag, 0));
}
/// For decoding.