set the final bit to make these AWS-compatible

build.zig

@@ -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 +189,16 @@ 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);
+    // We need the most significant bit as a 1 to make the key compatible with
+    // AWS. Like...you can literally send these keys to public AWS `aws sts get-access-key-info --access-key-id <blah>`
+    // and get your account number (after changing ELAK to AKIA!
+    //
+    // Without this bit set, AWS' sts will complain that this is not a valid key
+    const access_key_suffix: u80 = (1 << 79) | (@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 +207,20 @@ 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:0>12}, db_encryption_key: {s}",
         .{
             access_key_suffix_encoded,
             encoded_secret,
@@ -225,7 +229,7 @@ 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:0>12},{s}\n",
         .{
             access_key_suffix_encoded,
             encoded_secret,
@@ -237,8 +241,9 @@ 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 +253,36 @@ 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;
+}

build.zig.zon

@@ -12,8 +12,8 @@
             .hash = "12208c654deea149cee27eaa45d0e6515c3d8f97d775a4156cbcce0ff424b5d26ea3",
         },
         .universal_lambda_build = .{
-            .url = "https://git.lerch.org/lobo/universal-lambda-zig/archive/e5a1099f741ddd6327e015e4c068de5c18d09393.tar.gz",
-            .hash = "122037f0b35ab67002ef039410ae4ddb6805e14c111557ab0ae2ec7837211f7a1c51",
+            .url = "https://git.lerch.org/lobo/universal-lambda-zig/archive/5f1b1a52beea841e130ea4d878437f9488da0eb7.tar.gz",
+            .hash = "12202e3f5cc4db196d9bef727e10b407413d6dd95a6e94d66f11c4c14dc5ee060b58",
         },
         .flexilib = .{
             .url = "https://git.lerch.org/lobo/flexilib/archive/3d3dab9c792651477932e2b61c9f4794ac694dcb.tar.gz",

src/Account.zig

@@ -1,3 +1,4 @@
+const builtin = @import("builtin");
 const std = @import("std");
 const encryption = @import("encryption.zig");
 const sqlite = @import("sqlite"); // TODO: If we use this across all services, Account should not have this, and we should have a localdbaccount struct
@@ -10,10 +11,10 @@ const Self = @This();
 allocator: std.mem.Allocator,
 root_account_key: *[encryption.key_length]u8,
 
-pub var root_key_mapping: ?std.StringHashMap([]const u8) = null;
+pub var root_key_mapping: ?std.AutoHashMap(u40, []const u8) = null;
 
-pub fn accountForId(allocator: std.mem.Allocator, account_id: []const u8) !Self {
-    if (std.mem.eql(u8, account_id, "1234")) {
+pub fn accountForId(allocator: std.mem.Allocator, account_id: u40) !Self {
+    if (account_id == 1234) {
         var key = try allocator.alloc(u8, encryption.key_length);
         errdefer allocator.free(key);
         try encryption.decodeKey(key[0..encryption.key_length], test_account_key.*);
@@ -37,7 +38,7 @@ pub fn accountForId(allocator: std.mem.Allocator, account_id: []const u8) !Self
     }
 
     // TODO: Check STS
-    log.err("Got account id '{s}', but could not find this ('1234' is test account). STS GetAccessKeyInfo not implemented", .{account_id});
+    log.err("Got account id '{d:0>12}', but could not find this ('1234' is test account). STS GetAccessKeyInfo not implemented", .{account_id});
     return error.NotImplemented;
 }
 
@@ -59,14 +60,13 @@ pub fn testDbDeinit() void {
 }
 /// Gets the database for this account. If under test, a memory database is used
 /// instead. Will initialize the database with appropriate metadata tables
-pub fn dbForAccount(allocator: std.mem.Allocator, account_id: []const u8) !*sqlite.Db {
-    const builtin = @import("builtin");
+pub fn dbForAccount(allocator: std.mem.Allocator, account_id: u40) !*sqlite.Db {
     if (builtin.is_test and test_retain_db)
         if (test_db) |db| return db;
     // TODO: Need to move this function somewhere central
     // TODO: Need configuration for what directory to use
     // TODO: Should this be a pool, and if so, how would we know when to close?
-    const file_without_path = try std.fmt.allocPrint(allocator, "ddb-{s}.sqlite3", .{account_id});
+    const file_without_path = try std.fmt.allocPrint(allocator, "ddb-{d:0>12}.sqlite3", .{account_id});
     defer allocator.free(file_without_path);
     const db_file_name = try std.fs.path.joinZ(allocator, &[_][]const u8{ data_dir, file_without_path });
     defer allocator.free(db_file_name);

src/AuthenticatedRequest.zig

@@ -5,7 +5,7 @@ event_data: []const u8,
 headers: std.http.Headers,
 status: std.http.Status,
 reason: ?[]const u8,
-account_id: []const u8,
+account_id: u40,
 output_format: OutputFormat,
 
 pub const OutputFormat = enum {

src/createtable.zig

@@ -33,6 +33,13 @@ pub fn handler(request: *AuthenticatedRequest, writer: anytype) ![]const u8 {
     var parsed = try std.json.parseFromSlice(std.json.Value, allocator, request.event_data, .{});
     defer parsed.deinit();
     const request_params = try parseRequest(request, parsed, writer);
+    defer {
+        for (request_params.table_info.attribute_definitions) |d| {
+            allocator.free(d.*.name);
+            allocator.destroy(d);
+        }
+        allocator.free(request_params.table_info.attribute_definitions);
+    }
     // Parsing does most validation for us, but we also need to make sure that
     // the attributes specified in the key schema actually exist
     var found_keys: u2 = if (request_params.table_info.range_key_attribute_name == null) 0b01 else 0b00;
@@ -54,13 +61,6 @@ pub fn handler(request: *AuthenticatedRequest, writer: anytype) ![]const u8 {
             writer,
             "Attribute names in KeySchema must also exist in AttributeDefinitions",
         );
-    defer {
-        for (request_params.table_info.attribute_definitions) |d| {
-            allocator.free(d.*.name);
-            allocator.destroy(d);
-        }
-        allocator.free(request_params.table_info.attribute_definitions);
-    }
     var db = try Account.dbForAccount(allocator, account_id);
     defer allocator.destroy(db);
     defer db.deinit();
@@ -144,7 +144,7 @@ pub fn handler(request: *AuthenticatedRequest, writer: anytype) ![]const u8 {
 
     var al = std.ArrayList(u8).init(allocator);
     var response_writer = al.writer();
-    try response_writer.print("table created for account {s}\n", .{account_id});
+    try response_writer.print("table created for account {d:0>12}\n", .{account_id});
     return al.toOwnedSlice();
 }
 

src/ddb.zig

@@ -482,7 +482,7 @@ pub const Table = struct {
 /// are stored in here, realistically, this will be the first function called
 /// every time anything interacts with the database, so this function opens
 /// the database for you
-pub fn tablesForAccount(allocator: std.mem.Allocator, account_id: []const u8) !AccountTables {
+pub fn tablesForAccount(allocator: std.mem.Allocator, account_id: u40) !AccountTables {
 
     // TODO: This function should take a list of table names, which can then be used
     // to filter the query below rather than just grabbing everything
@@ -676,7 +676,7 @@ fn insertIntoDm(
     });
 }
 
-fn testCreateTable(allocator: std.mem.Allocator, account_id: []const u8) !*sqlite.Db {
+fn testCreateTable(allocator: std.mem.Allocator, account_id: u40) !*sqlite.Db {
     var db = try Account.dbForAccount(allocator, account_id);
     const account = try Account.accountForId(allocator, account_id); // This will get us the encryption key needed
     defer account.deinit();
@@ -707,7 +707,7 @@ fn testCreateTable(allocator: std.mem.Allocator, account_id: []const u8) !*sqlit
 }
 test "can create a table" {
     const allocator = std.testing.allocator;
-    const account_id = "1234";
+    const account_id = 1234;
     var db = try testCreateTable(allocator, account_id);
     defer allocator.destroy(db);
     defer db.deinit();
@@ -715,7 +715,7 @@ test "can create a table" {
 test "can list tables in an account" {
     Account.test_retain_db = true;
     const allocator = std.testing.allocator;
-    const account_id = "1234";
+    const account_id = 1234;
     var db = try testCreateTable(allocator, account_id);
     defer allocator.destroy(db);
     defer Account.testDbDeinit();
@@ -729,7 +729,7 @@ test "can list tables in an account" {
 test "can put an item in a table in an account" {
     Account.test_retain_db = true;
     const allocator = std.testing.allocator;
-    const account_id = "1234";
+    const account_id = 1234;
     var db = try testCreateTable(allocator, account_id);
     defer allocator.destroy(db);
     defer Account.testDbDeinit();

src/main.zig

@@ -1,3 +1,4 @@
+const builtin = @import("builtin");
 const std = @import("std");
 const universal_lambda = @import("universal_lambda_handler");
 const universal_lambda_interface = @import("universal_lambda_interface");
@@ -24,24 +25,6 @@ pub fn main() !u8 {
 }
 
 pub fn handler(allocator: std.mem.Allocator, event_data: []const u8, context: universal_lambda_interface.Context) ![]const u8 {
-    const builtin = @import("builtin");
-    var rss: if (builtin.os.tag == .linux) std.os.rusage else usize = undefined;
-    if (builtin.os.tag == .linux and builtin.mode == .Debug)
-        rss = std.os.getrusage(std.os.rusage.SELF);
-    defer if (builtin.os.tag == .linux and builtin.mode == .Debug) { // and  debug mode) {
-        const rusage = std.os.getrusage(std.os.rusage.SELF);
-        log.debug(
-            "Request complete, max RSS of process: {d}M. Incremental: {d}K, User: {d}μs, System: {d}μs",
-            .{
-                @divTrunc(rusage.maxrss, 1024),
-                rusage.maxrss - rss.maxrss,
-                (rusage.utime.tv_sec - rss.utime.tv_sec) * std.time.us_per_s +
-                    rusage.utime.tv_usec - rss.utime.tv_usec,
-                (rusage.stime.tv_sec - rss.stime.tv_sec) * std.time.us_per_s +
-                    rusage.stime.tv_usec - rss.stime.tv_usec,
-            },
-        );
-    };
     const access_key = try allocator.dupe(u8, "ACCESS");
     const secret_key = try allocator.dupe(u8, "SECRET");
     test_credential = signing.Credentials.init(allocator, access_key, secret_key, null);
@@ -146,7 +129,7 @@ fn authenticateUser(allocator: std.mem.Allocator, context: universal_lambda_inte
 
 var test_credential: signing.Credentials = undefined;
 var root_creds: std.StringHashMap(signing.Credentials) = undefined;
-var root_account_mapping: std.StringHashMap([]const u8) = undefined;
+// var root_account_mapping: std.StringHashMap([]const u8) = undefined;
 var creds_buf: [8192]u8 = undefined;
 fn getCreds(access: []const u8) ?signing.Credentials {
     // We have 3 levels of access here
@@ -163,8 +146,8 @@ fn getCreds(access: []const u8) ?signing.Credentials {
 
 fn fillRootCreds(allocator: std.mem.Allocator) !void {
     root_creds = std.StringHashMap(signing.Credentials).init(allocator);
-    root_account_mapping = std.StringHashMap([]const u8).init(allocator);
-    Account.root_key_mapping = std.StringHashMap([]const u8).init(allocator);
+    // root_account_mapping = std.StringHashMap([]const u8).init(allocator);
+    Account.root_key_mapping = std.AutoHashMap(u40, []const u8).init(allocator);
     var file = std.fs.cwd().openFile("access_keys.csv", .{}) catch |e| {
         log.err("Could not open access_keys.csv to access root creds: {}", .{e});
         return e;
@@ -219,8 +202,9 @@ fn fillRootCreds(allocator: std.mem.Allocator) !void {
             .session_token = null,
             .allocator = NullAllocator.init(),
         });
-        const global_account_id = try allocator.dupe(u8, account_id);
-        try root_account_mapping.put(global_access_key, global_account_id);
+        const global_account_id = try std.fmt.parseInt(u40, account_id, 10);
+        // unnecessary. Account ids are embedded in access keys!
+        // try root_account_mapping.put(global_access_key, global_account_id);
         try Account.root_key_mapping.?.put(global_account_id, try allocator.dupe(u8, existing_key));
         // TODO: key rotation will need another hash map, can be triggered on val_num == 5
 
@@ -270,19 +254,21 @@ const NullAllocator = struct {
     }
 };
 
-fn accountForAccessKey(allocator: std.mem.Allocator, access_key: []const u8) ![]const u8 {
+fn accountForAccessKey(allocator: std.mem.Allocator, access_key: []const u8) !u40 {
     _ = allocator;
     log.debug("Finding account for access key: '{s}'", .{access_key});
+    if (access_key.len != 20) return error.InvalidAccessKey;
+    return try accountIdForAccessKey(@as(*[20]u8, @ptrCast(@constCast(access_key))).*);
     // Since this happens after authentication, we can assume our root creds store
     // is populated
-    if (root_account_mapping.get(access_key)) |account| return account;
-    log.err("Creds not found in store. STS GetAccessKeyInfo call is not yet implemented", .{});
-    return error.NotImplemented;
+    // if (root_account_mapping.get(access_key)) |account| return account;
+    // log.err("Creds not found in store. STS GetAccessKeyInfo call is not yet implemented", .{});
+    // return error.NotImplemented;
 }
 /// Function assumes an authenticated request, so signing.verify must be called
 /// and returned true before calling this function. If authentication header
 /// is not found, environment variable will be used
-fn accountId(allocator: std.mem.Allocator, headers: std.http.Headers) ![]const u8 {
+fn accountId(allocator: std.mem.Allocator, headers: std.http.Headers) !u40 {
     const auth_header = headers.getFirstValue("Authorization");
     if (auth_header) |h| {
         // AWS4-HMAC-SHA256 Credential=ACCESS/20230908/us-west-2/s3/aws4_request, SignedHeaders=accept;content-length;content-type;host;x-amz-content-sha256;x-amz-date;x-amz-storage-class, Signature=fcc43ce73a34c9bd1ddf17e8a435f46a859812822f944f9eeb2aabcd64b03523
@@ -326,8 +312,8 @@ fn iamCredentials(allocator: std.mem.Allocator) ![]const u8 {
     iam_credential = signing.Credentials.init(allocator, try iamAccessKey(allocator), try iamSecretKey(allocator), null);
     return iam_credential.?;
 }
-fn iamAccountId(allocator: std.mem.Allocator) ![]const u8 {
-    return try getVariable(allocator, &iam_account_id, "IAM_ACCOUNT_ID");
+fn iamAccountId(allocator: std.mem.Allocator) !u40 {
+    return std.fmt.parseInt(u40, try getVariable(allocator, &iam_account_id, "IAM_ACCOUNT_ID"), 10);
 }
 fn iamAccessKey(allocator: std.mem.Allocator) ![]const u8 {
     return try getVariable(allocator, &iam_access_key, "IAM_ACCESS_KEY");
@@ -346,3 +332,58 @@ test {
     std.testing.refAllDecls(@import("batchwriteitem.zig"));
     std.testing.refAllDecls(@import("batchgetitem.zig"));
 }
+
+test "can get account id from access key" {
+    // ELAKM5YGIGQQAD2B54IZ, Account 888534479904
+    // Also, https://medium.com/@TalBeerySec/a-short-note-on-aws-key-id-f88cc4317489
+    // aws_access_key_id: ASIAY34FZKBOKMUTVV7A yields the expected account id "609629065308"
+    try std.testing.expectEqual(@as(u40, 609629065308), try accountIdForAccessKey(@as(*[20]u8, @ptrCast(@constCast("ASIAY34FZKBOKMUTVV7A"))).*));
+    try std.testing.expectEqual(@as(u40, 888534479904), try accountIdForAccessKey(@as(*[20]u8, @ptrCast(@constCast("ELAKM5YGIGQQAD2B54IZ"))).*));
+}
+
+fn accountIdForAccessKey(access_key: [20]u8) !u40 {
+    const ak_integer_part = access_key[4..];
+    const ak_integer = try base32Decode(u80, @as(*[16]u8, @ptrCast(@constCast(ak_integer_part.ptr))).*);
+    const account_id = ak_integer >> 39;
+    return @as(u40, @truncate(account_id));
+    // Do we want an array like this? Probably so
+    // import base64
+    // import binascii
+    //
+    // def AWSAccount_from_AWSKeyID(AWSKeyID):
+    //
+    //     trimmed_AWSKeyID = AWSKeyID[4:] #remove KeyID prefix
+    //     x = base64.b32decode(trimmed_AWSKeyID) #base32 decode
+    //     y = x[0:6]
+    //
+    //     z = int.from_bytes(y, byteorder='big', signed=False)
+    //     mask = int.from_bytes(binascii.unhexlify(b'7fffffffff80'), byteorder='big', signed=False)
+    //
+    //     e = (z & mask)>>7
+    //     return (e)
+}
+
+fn base32Decode(comptime T: type, data: [@typeInfo(T).Int.bits / 5]u8) !T {
+    // const alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
+    const ti = @typeInfo(T);
+    if (ti != .Int or ti.Int.signedness != .unsigned)
+        @compileError("decode only works with unsigned integers");
+    if (ti.Int.bits % 5 != 0)
+        @compileError("unsigned integer bit length must be a multiple of 5 to use this function");
+    const Shift_type = @Type(.{ .Int = .{
+        .signedness = .unsigned,
+        .bits = @ceil(@log2(@as(f128, @floatFromInt(ti.Int.bits)))),
+    } });
+    var rc: T = 0;
+    for (data, 0..) |b, i| {
+        var curr: T = 0;
+        if (b >= 'A' and b <= 'Z') {
+            curr = b - 'A';
+        } else if (b >= '2' and b <= '7') {
+            curr = b - '2' + 26;
+        } else return error.InvalidCharacter;
+        curr <<= @as(Shift_type, @intCast((data.len - 1 - i) * 5));
+        rc |= curr;
+    }
+    return rc;
+}