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update generate_credentials to embed account id the way AWS does

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This commit is contained in:
Emil Lerch 2024-03-04 13:09:58 -08:00
parent 25f92b741d
commit aa051b5220
Signed by: lobo
GPG Key ID: A7B62D657EF764F8
1 changed files with 63 additions and 38 deletions
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101
build.zig
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@ -153,34 +153,29 @@ pub fn build(b: *std.Build) !void {
}
fn generateCredentials(s: *std.build.Step, prog_node: *std.Progress.Node) error{ MakeFailed, MakeSkipped }!void {
_ = s;
// Account id:
// Documentation describes account id as a 12 digit number:
// https://docs.aws.amazon.com/accounts/latest/reference/manage-acct-identifiers.html
// This can be a random u64, but must be in a 12 digit range, which
// is:
// This can be a random number, but must be in a 12 digit range.
//
// Min: 0x05f5e100 (0d100000000)
// Max: 0x3b9ac9ff (0d999999999)
// The access key is 32 bit encoded, which leaves us with
// 8 * 5 = 40 bits of information to work with. The maximum value of
// a u40 in decimal is 1099511627775, a 13 digit number. So our maximum
// decimal is below, and fits into u40.
//
// Min: 0x0000000000 (0d000000000000)
// Max: 0xe8d4a50fff (0d999999999999)
//
// Access key:
// Access key is 20 characters and can be represented by base36
// https://en.wikipedia.org/wiki/Base36
// (it is nearly definitely base36 in AWS in practice)
// At least the first two characters are not part of the number...they
// have meaning. AK for a permanent key, AS for a session token.
// We shall use "EL" just...because. Maybe ET later for session tokens.
// This gives us 18 characters to work with, making our range like this:
// This page shows how the access key is put together:
// https://medium.com/@TalBeerySec/a-short-note-on-aws-key-id-f88cc4317489
// tl;dr
// * First 4 characters: designates type of key: We will use "ELAK" for access key
// * Next 8 characters: Account ID, base32 encoded, shifted by one bit
// * Next 8 characters: Unknown. Assume random base32, which would give us 8 * 5 = u40;
//
// Min:
// NN100000000000000000 (hex: 0xECFF3BCC40CA2000000000)
// Max:
// NNZZZZZZZZZZZZZZZZZZ (hex: 0x2153E468B91C6E0000000000)
//
// The max value therefore requires a u96 to represent, as does the
// difference between max and min (0x2066e52cecdba40000000000). However,
// Zig 0.11.0 cannot handle random numbers that large
// (https://github.com/ziglang/zig/blob/0.11.0/lib/std/rand.zig#L145),
// so for now we use a random u64 and call it good.
//
// Secret Access Key:
// In the wild, these are 40 characters and appear to be base64 encoded.
@ -194,19 +189,11 @@ fn generateCredentials(s: *std.build.Step, prog_node: *std.Progress.Node) error{
const seed = @as(u64, @truncate(@as(u128, @bitCast(std.time.nanoTimestamp()))));
var prng = std.rand.DefaultPrng.init(seed);
var rand = prng.random();
const account_number = rand.intRangeAtMost(u64, 100000000000, 999999999999);
const access_key_suffix: u128 = blk: { // workaround for u64 max on rand.intRangeAtMost
const min = 0xECFF3BCC40CA2000000000;
// const max = 0x2153E468B91C6E0000000000;
// const diff = max - min; // 0x2066e52cecdba40000000000 (is 12 bytes/96 bits)
// So we can use a full 64 bit range and just add to the min
break :blk @as(u128, rand.int(u64)) + min;
};
const access_key_suffix_encoded = encode(
u128,
s.owner.allocator,
access_key_suffix,
) catch return error.MakeFailed;
const account_number = rand.intRangeAtMost(u40, 0, 999999999999); // 100000000000, 999999999999);
const access_key_random_suffix = rand.int(u39);
const access_key_suffix: u80 = (@as(u80, account_number) << 39) + @as(u80, access_key_random_suffix);
const access_key_suffix_encoded = base32Encode(u80, access_key_suffix);
// std.debug.assert(access_key_suffix_encoded.len == 16);
var secret_key: [30]u8 = undefined;
rand.bytes(&secret_key); // The rest don't need to be cryptographically secure...does this?
var encoded_secret: [40]u8 = undefined;
@ -215,8 +202,20 @@ fn generateCredentials(s: *std.build.Step, prog_node: *std.Progress.Node) error{
const stdout_raw = std.io.getStdOut().writer();
var stdout_writer = std.io.bufferedWriter(stdout_raw);
const stdout = stdout_writer.writer();
// stdout.print(
// \\# account_number: {b:0>80}
// \\# random_suffix : {b:0>80}
// \\# access_key_suffix: {b:0>80}
// \\
// ,
// .{
// @as(u80, account_number) << 39,
// @as(u80, access_key_random_suffix),
// access_key_suffix,
// },
// ) catch return error.MakeFailed;
stdout.print(
"# access_key: EL{s}, secret_key: {s}, account_number: {d}, db_encryption_key: {s}",
"# access_key: ELAK{s}, secret_key: {s}, account_number: {d}, db_encryption_key: {s}",
.{
access_key_suffix_encoded,
encoded_secret,
@ -225,7 +224,7 @@ fn generateCredentials(s: *std.build.Step, prog_node: *std.Progress.Node) error{
},
) catch return error.MakeFailed;
stdout.print(
"\n#\n# You can copy/paste the following line into access_keys.csv:\nEL{s},{s}{d}{s}\n",
"\n#\n# You can copy/paste the following line into access_keys.csv:\nELAK{s},{s},{d},{s}\n",
.{
access_key_suffix_encoded,
encoded_secret,
@ -237,8 +236,9 @@ fn generateCredentials(s: *std.build.Step, prog_node: *std.Progress.Node) error{
}
/// encodes an unsigned integer into base36
pub fn encode(comptime T: type, allocator: std.mem.Allocator, data: T) ![]const u8 {
pub fn base36encode(comptime T: type, allocator: std.mem.Allocator, data: T) ![]const u8 {
const alphabet = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
std.debug.assert(alphabet.len == 36);
const ti = @typeInfo(T);
if (ti != .Int or ti.Int.signedness != .unsigned)
@compileError("encode only works with unsigned integers");
@ -248,11 +248,36 @@ pub fn encode(comptime T: type, allocator: std.mem.Allocator, data: T) ![]const
defer al.deinit();
var remaining = data;
while (remaining > 0) : (remaining /= 36) {
al.appendAssumeCapacity(alphabet[@as(usize, @intCast(remaining % 36))]);
while (remaining > 0) : (remaining /= @as(T, @intCast(alphabet.len))) {
al.appendAssumeCapacity(alphabet[@as(usize, @intCast(remaining % alphabet.len))]);
}
// This is not exact, but 6 bits
var rc = try al.toOwnedSlice();
std.mem.reverse(u8, rc);
return rc;
}
/// Because Base32 is a power of 2, we can directly return an array and avoid
/// allocations entirely
/// To trim leading 0s, simply std.mem.trimLeft(u8, encoded_data, "A");
pub fn base32Encode(comptime T: type, data: T) [@typeInfo(T).Int.bits / 5]u8 {
const alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
std.debug.assert(alphabet.len == 32);
const ti = @typeInfo(T);
if (ti != .Int or ti.Int.signedness != .unsigned)
@compileError("encode only works with unsigned integers");
const bits = ti.Int.bits;
// We will have exactly 5 bits (2^5 = 32) represented per byte in our final output
var rc: [bits / 5]u8 = undefined;
var inx: usize = 0;
const Shift_type = @Type(.{ .Int = .{
.signedness = .unsigned,
.bits = @ceil(@log2(@as(f128, @floatFromInt(bits)))),
} });
// TODO: I think we need a table here to determine the size below
while (inx < rc.len) : (inx += 1) {
const char_bits: u5 = @as(u5, @truncate(data >> (@as(Shift_type, @intCast(inx * 5)))));
rc[rc.len - @as(usize, @intCast(inx)) - 1] = alphabet[@as(usize, @intCast(char_bits))]; // 5 bits from inx
}
return rc;
}