src/common/dto-validation.spec.ts

@@ -1,6 +1,6 @@
 import { BadRequestException, ValidationPipe } from '@nestjs/common';
 
-import { CredentialsDto } from '../modules/auth/presentation/auth.dto';
+import { LoginDto, RegisterDto } from '../modules/auth/presentation/auth.dto';
 import {
   CreateBankCardDto,
   UpdateBankCardDto,
@@ -11,7 +11,7 @@ describe('DTO validation', () => {
     forbidUnknownValues: true, transform: true, whitelist: true });
 
   it('requires credentials and normalizes a valid email', async () => {
-    const metadata = { type: 'body' as const, metatype: CredentialsDto };
+    const metadata = { type: 'body' as const, metatype: RegisterDto };
     await expect(pipe.transform({}, metadata)).rejects.toBeInstanceOf(
       BadRequestException,
     );
@@ -29,6 +29,59 @@ describe('DTO validation', () => {
     });
   });
 
+  // Test intent: register accepts 8..72 printable ASCII characters only (bcrypt
+  // reads 72 bytes, so non-ASCII could be silently truncated); login only caps
+  // bytes so accounts created under the older policy can still sign in.
+  describe('password policy', () => {
+    const register = { type: 'body' as const, metatype: RegisterDto };
+    const login = { type: 'body' as const, metatype: LoginDto };
+    const body = (password: string) => ({ email: 'user@example.com', password });
+    const accepts = (value: unknown, metadata: typeof login | typeof register) =>
+      pipe.transform(value, metadata).then(
+        () => true,
+        (error: unknown) => {
+          if (!(error instanceof BadRequestException)) throw error;
+          return false;
+        },
+      );
+
+    it.each([
+      ['7 chars', 'a'.repeat(7), false],
+      ['8 chars', 'a'.repeat(8), true],
+      ['72 chars', 'a'.repeat(72), true],
+      ['73 chars', 'a'.repeat(73), false],
+      ['all printable symbols and space', 'Aa1 !~"#$%&\'()*+,-./:;<=>?@[\\]^_`{|}', true],
+      ['Cyrillic, 8+ chars', 'пароль-пароль', false],
+      ['emoji', 'passw😀rd', false],
+      ['tab', 'pass\tword1', false],
+      ['newline', 'password1\n', false],
+      ['DEL', 'password\x7f1', false],
+      ['non-string', 12345678, false],
+    ])('register: %s', async (_, password, accepted) => {
+      await expect(accepts(body(password as string), register)).resolves.toBe(accepted);
+    });
+
+    it('register keeps raw whitespace untouched', async () => {
+      const password = '  spaced pass  ';
+      await expect(pipe.transform(body(password), register)).resolves.toEqual(
+        body(password),
+      );
+    });
+
+    it.each([
+      ['legacy Cyrillic password', 'пароль-пароль', true],
+      ['short legacy password', 'short', true],
+      ['72 bytes', 'a'.repeat(72), true],
+      ['73 bytes', 'a'.repeat(73), false],
+      ['36 Cyrillic letters = 72 bytes', 'я'.repeat(36), true],
+      ['37 Cyrillic letters = 74 bytes', 'я'.repeat(37), false],
+      ['empty', '', false],
+      ['non-string', 12345678, false],
+    ])('login: %s', async (_, password, accepted) => {
+      await expect(accepts(body(password as string), login)).resolves.toBe(accepted);
+    });
+  });
+
   it('requires and validates nested money in a new card', async () => {
     const metadata = { type: 'body' as const, metatype: CreateBankCardDto };
     const card = {

src/modules/auth/presentation/auth.controller.ts

@@ -24,7 +24,7 @@ import { ApiProblemResponses } from '../../../common/decorators/api-safe-error-r
 import { HttpErrorCode } from '../../../common/error-code';
 import { AuthService } from '../application/auth.service';
 import { AccessPayload, AuthenticationResult } from '../application/auth.types';
-import { CredentialsDto } from './auth.dto';
+import { LoginDto, RegisterDto } from './auth.dto';
 import { JwtAuthGuard } from './jwt-auth.guard';
 
 const REFRESH_COOKIE = 'refresh_token';
@@ -56,7 +56,7 @@ export class AuthController {
   @HttpCode(HttpStatus.OK)
   @ApiOkResponse({ type: AuthenticationDto })
   async register(
-    @Body() credentials: CredentialsDto,
+    @Body() credentials: RegisterDto,
     @Res({ passthrough: true }) response: Response,
   ) {
     return this.respond(
@@ -69,7 +69,7 @@ export class AuthController {
   @HttpCode(HttpStatus.OK)
   @ApiOkResponse({ type: AuthenticationDto })
   async login(
-    @Body() credentials: CredentialsDto,
+    @Body() credentials: LoginDto,
     @Res({ passthrough: true }) response: Response,
   ) {
     return this.respond(

src/modules/auth/presentation/auth.dto.ts

@@ -1,8 +1,9 @@
 import { ApiProperty } from '@nestjs/swagger';
 import { Transform } from 'class-transformer';
 import {
+  IsNotEmpty,
   IsString,
-  MinLength,
+  Matches,
   Validate,
   ValidatorConstraint,
 } from 'class-validator';
@@ -13,8 +14,10 @@ const FIRST_CHARACTER_INDEX = 0;
 const MAX_EMAIL_LENGTH = 254;
 const ASCII_SPACE = 32;
 const ASCII_DELETE = 127;
-const MIN_PASSWORD_LENGTH = 12;
+// bcrypt reads at most 72 bytes; printable ASCII keeps characters == bytes.
+const MIN_PASSWORD_LENGTH = 8;
 const MAX_PASSWORD_BYTES = 72;
+const PASSWORD_PATTERN = `^[\\x20-\\x7E]{${MIN_PASSWORD_LENGTH},${MAX_PASSWORD_BYTES}}$`;
 
 @ValidatorConstraint({ name: 'email' })
 class EmailConstraint {
@@ -40,8 +43,9 @@ class EmailConstraint {
   }
 }
 
-@ValidatorConstraint({ name: 'passwordBytes' })
-class PasswordBytesConstraint {
+// Login stays lenient: accounts created under an older policy must still sign in.
+@ValidatorConstraint({ name: 'passwordMaxBytes' })
+class PasswordMaxBytesConstraint {
   validate(value: unknown): boolean {
     return (
       typeof value === 'string' &&
@@ -50,11 +54,11 @@ class PasswordBytesConstraint {
   }
 
   defaultMessage(): string {
-    return 'must not exceed 72 UTF-8 bytes';
+    return `must not exceed ${MAX_PASSWORD_BYTES} UTF-8 bytes`;
   }
 }
 
-export class CredentialsDto {
+class EmailDto {
   @ApiProperty({ example: 'user@example.com' })
   @IsString()
   @Transform(({ value }: { value: unknown }) =>
@@ -62,14 +66,28 @@ export class CredentialsDto {
   )
   @Validate(EmailConstraint)
   declare email: string;
+}
 
+export class RegisterDto extends EmailDto {
   @ApiProperty({
-    minLength: MIN_PASSWORD_LENGTH,
-    maxLength: MAX_PASSWORD_BYTES,
+    description: `Raw password: ${MIN_PASSWORD_LENGTH}-${MAX_PASSWORD_BYTES} printable ASCII characters (letters, digits, symbols, space). Not trimmed or normalized.`,
+    pattern: PASSWORD_PATTERN,
     example: 'a secure password',
   })
   @IsString()
-  @MinLength(MIN_PASSWORD_LENGTH)
-  @Validate(PasswordBytesConstraint)
+  @Matches(new RegExp(PASSWORD_PATTERN), {
+    message: `must be ${MIN_PASSWORD_LENGTH}-${MAX_PASSWORD_BYTES} printable ASCII characters`,
+  })
+  declare password: string;
+}
+
+export class LoginDto extends EmailDto {
+  @ApiProperty({
+    description: `Raw password, at most ${MAX_PASSWORD_BYTES} UTF-8 bytes. Not trimmed or normalized.`,
+    example: 'a secure password',
+  })
+  @IsString()
+  @IsNotEmpty()
+  @Validate(PasswordMaxBytesConstraint)
   declare password: string;
 }

test/app.e2e-spec.ts

@@ -2,7 +2,9 @@ import { INestApplication } from '@nestjs/common';
 import { ConfigService } from '@nestjs/config';
 import { JwtService } from '@nestjs/jwt';
 import { Test, TestingModule } from '@nestjs/testing';
+import * as bcrypt from 'bcrypt';
 import { PARAMS_PROVIDER_TOKEN } from 'nestjs-pino';
+import { randomUUID } from 'node:crypto';
 import request from 'supertest';
 import { App } from 'supertest/types';
 
@@ -265,6 +267,45 @@ describe('Authentication (e2e)', () => {
     expect(await app.get(PrismaService).user.count()).toBe(0);
   });
 
+  it('applies the ASCII 8..72 password policy on register and keeps login lenient', async () => {
+    const validation = (detail: string) => ({
+      status: 400,
+      code: 'VALIDATION_ERROR',
+      errors: [{ pointer: '#/password', detail }],
+    });
+    for (const [index, password] of ['a'.repeat(8), ' '.repeat(2) + 'b'.repeat(70)].entries()) {
+      const credentials = { email: `user${index}@example.com`, password };
+      await request(app.getHttpServer()).post('/api/v1/auth/register').send(credentials).expect(200);
+      await request(app.getHttpServer()).post('/api/v1/auth/login').send(credentials).expect(200);
+    }
+    for (const password of ['a'.repeat(7), 'a'.repeat(73), 'пароль-пароль', 'passw😀rd', 'pass\tword1']) {
+      await request(app.getHttpServer())
+        .post('/api/v1/auth/register')
+        .send({ email: 'rejected@example.com', password })
+        .expect(400)
+        .expect('Content-Type', /application\/problem\+json/)
+        .expect(({ body }: { body: unknown }) =>
+          expect(body).toEqual(validation('must be 8-72 printable ASCII characters')),
+        );
+    }
+    expect(await app.get(PrismaService).user.count()).toBe(2);
+
+    // An account created under the previous policy (Cyrillic, 12+ chars) must still log in.
+    const legacy = { email: 'legacy@example.com', password: 'пароль-пароль' };
+    const prisma = app.get(PrismaService);
+    await prisma.user.create({
+      data: { id: randomUUID(), email: legacy.email, passwordHash: await bcrypt.hash(legacy.password, 4) },
+    });
+    await request(app.getHttpServer()).post('/api/v1/auth/login').send(legacy).expect(200);
+    await request(app.getHttpServer())
+      .post('/api/v1/auth/login')
+      .send({ email: legacy.email, password: 'a'.repeat(73) })
+      .expect(400)
+      .expect(({ body }: { body: unknown }) =>
+        expect(body).toEqual(validation('must not exceed 72 UTF-8 bytes')),
+      );
+  });
+
   it('guards T-Bank connection and never returns a token', async () => {
     const registration = await request(app.getHttpServer())
       .post('/api/v1/auth/register')