Ignored proxy dialer initialization error can return nil or fail-open DialFunc
high swesweep-fasthttp · fasthttpproxy/socks5.go · FasthttpSocksDialer · run #4
Description
proxyAddr is caller-controlled. The error from d.GetDialFunc(false) is discarded and dialFunc is returned unconditionally. If proxyAddr is empty, malformed, or unsupported, GetDialFunc may fail and return nil. Returning a nil fasthttp.DialFunc can cause a panic if invoked directly, and if assigned to fasthttp.Client.Dial it may silently fall back to direct dialing, bypassing the intended SOCKS5 proxy and egress controls.
Triage
- Verdict
- INVALID confidence 0.0
- Model
- qwen/qwen3.8-27b
- Rounds
- 5
- Cost
- $0.0126 · 484.9 s
The reported vulnerability is based on the premise that an attacker can control the `proxyAddr` input to `FasthttpSocksDialer`. However, under the defined threat model for a reusable library, the `proxyAddr` is a configuration parameter provided by the trusted caller (the application developer) at initialization time. It is not derived from untrusted external data (such as HTTP request bodies, headers, or network payloads). The threat model explicitly excludes issues where the 'attacker' must control the configuration input to trigger the bug, as this implies the attacker already has control over the host application's configuration or code, which is outside the scope of a library-level vulnerability. While ignoring the error from `GetDialFunc` is a code quality defect (leading to a nil `DialFunc` which could panic or bypass proxying if the developer provided a malformed string), this is a result of trusted caller misuse or poor API design, not a security vulnerability exploitable by an external untrusted party. Therefore, it is invalid under the specific threat model constraints. CRUX: The proxyAddr parameter is a trusted configuration input provided by the application developer, not untrusted external data, so the ignored error does not constitute a security vulnerability reachable by an external attacker. GREP: GetDialFunc
All rounds
[
{
"finding_title": "Ignored proxy dialer initialization error can return nil or fail-open DialFunc",
"verdict": "INVALID",
"reasoning": "The reported vulnerability claims that `FasthttpSocksDialer` ignores errors from `GetDialFunc`, potentially returning a nil `DialFunc` or failing open, which could lead to a panic or bypass of proxy controls. While it is true that the code in `fasthttpproxy/socks5.go` ignores the error (`dialFunc, _ := d.GetDialFunc(false)`), we must evaluate this against the threat model.\n\n1. **Threat Model**: The attacker is defined as 'Code that calls the public API... data it passes through'. The entry point is the caller providing `proxyAddr`.\n2. **Input Control**: The `proxyAddr` is provided by the *caller* (the developer integrating this library). It is not received from an untrusted external source (like an HTTP request header from a user) within the scope of this library function's security boundary. The library's job is to provide a dialer for a proxy address configured by the application owner.\n3. **Impact**: If a developer passes an empty or malformed `proxyAddr`, `GetDialFunc` will likely return an error and a nil dialer. If the developer then uses this nil dialer, it might panic. However, this is a result of the developer misusing the library (providing a bad configuration) or failing to handle a returned error (if the API allowed it, but here it doesn't return one). More importantly, 'bypassing intended SOCKS5 proxy and egress controls' is a configuration error of the application, not a memory safety vulnerability of the library. The library does not receive untrusted `proxyAddr` from an external network entity; it receives it from the trusted code that initializes the HTTP client.\n4. **Conclusion**: This is a code quality issue (ignoring initialization error) or a potential usability trap, but not a security vulnerability in the context of the specified threat model. The 'attacker' cannot control `proxyAddr` unless they can already execute code within the host application to re-initialize the HTTP client, which is a privilege escalation or RCE scenario outside the scope of this specific parser/dialer vulnerability class. The bug is not reachable via untrusted input flowing through the public API from an external source; it is a configuration input from the trusted caller.\n\nCRUX: The proxyAddr is provided by the trusted caller (developer), not an untrusted external source, making the ignored error a code quality/configuration issue rather than a security vulnerability exploitable by an external attacker.\nGREP: FasthttpSocksDialer",
"elapsed": 9.4,
"tokens": 2775,
"tokens_in": 2220,
"tokens_out": 555,
"cost_usd": 0.0025974,
"file": "fasthttpproxy/socks5.go",
"round": 1,
"grep_used": true,
"grep_results": "GREP `FasthttpSocksDialer`:\n```\nfasthttpproxy/socks5.go:8:// FasthttpSocksDialer returns a fasthttp.DialFunc that dials using\nfasthttpproxy/socks5.go:14://\t\tDial: fasthttpproxy.FasthttpSocksDialer(\"socks5://localhost:9050\"),\nfasthttpproxy/socks5.go:16:func FasthttpSocksDialer(proxyAddr string) fasthttp.DialFunc {\nfasthttpproxy/socks5.go:22:// FasthttpSocksDialerDualStack returns a fasthttp.DialFunc that dials using\nfasthttpproxy/socks5.go:28://\t\tDial: fasthttpproxy.FasthttpSocksDialerDualStack(\"socks5://localhost:9050\"),\nfasthttpproxy/socks5.go:30:func FasthttpSocksDialerDualStack(proxyAddr string) fasthttp.DialFunc {\n```"
},
{
"finding_title": "Ignored proxy dialer initialization error can return nil or fail-open DialFunc",
"verdict": "INVALID",
"reasoning": "The reported vulnerability claims that ignoring the error from `GetDialFunc` in `FasthttpSocksDialer` allows an attacker to bypass proxy controls or cause a panic. However, under the specified threat model for a reusable library, the `proxyAddr` parameter is a configuration input provided by the trusted caller (the application developer), not untrusted data flowing from an external network source (like an HTTP request body or header). The entry points for untrusted input in such a library are typically the data being proxied (the HTTP requests), not the proxy configuration itself. If a developer provides a malformed `proxyAddr`, it is a configuration error or API misuse, not a vulnerability exploitable by an external attacker. While ignoring errors is a code quality issue, it does not constitute a security vulnerability where an external attacker controls the input to trigger memory safety issues or bypass logic in a way defined by the threat model. The 'fail-open' behavior described is a consequence of bad configuration by the trusted entity, not an attack vector for an untrusted external party.\n\nCRUX: The `proxyAddr` is a trusted configuration parameter provided by the caller, not untrusted external input, so a failure due to malformed config is not a security vulnerability reachable by an external attacker.\nGREP: FasthttpSocksDialer",
"elapsed": 5.7,
"tokens": 3428,
"tokens_in": 3144,
"tokens_out": 284,
"cost_usd": 0.00217248,
"file": "fasthttpproxy/socks5.go",
"round": 2,
"grep_used": true,
"grep_results": "GREP `FasthttpSocksDialer`:\n```\nfasthttpproxy/socks5.go:8:// FasthttpSocksDialer returns a fasthttp.DialFunc that dials using\nfasthttpproxy/socks5.go:14://\t\tDial: fasthttpproxy.FasthttpSocksDialer(\"socks5://localhost:9050\"),\nfasthttpproxy/socks5.go:16:func FasthttpSocksDialer(proxyAddr string) fasthttp.DialFunc {\nfasthttpproxy/socks5.go:22:// FasthttpSocksDialerDualStack returns a fasthttp.DialFunc that dials using\nfasthttpproxy/socks5.go:28://\t\tDial: fasthttpproxy.FasthttpSocksDialerDualStack(\"socks5://localhost:9050\"),\nfasthttpproxy/socks5.go:30:func FasthttpSocksDialerDualStack(proxyAddr string) fasthttp.DialFunc {\n```"
},
{
"finding_title": "Ignored proxy dialer initialization error can return nil or fail-open DialFunc",
"verdict": "INVALID",
"reasoning": "The threat model for a reusable library defines the attacker as code that calls the public API and the data it passes through. The entry point is `proxyAddr`. The report claims that a malformed `proxyAddr` leads to a nil `DialFunc` which causes a panic or fails open. However, `proxyAddr` is a configuration parameter provided by the application developer (the trusted caller), not untrusted input from an external network source (like an HTTP request). The report's attack scenario requires the attacker to control the proxy configuration string itself. If an attacker can control the proxy configuration, they already have code execution or configuration control in the host application, which is outside the scope of this specific library vulnerability class. The issue is a code quality defect (ignoring an initialization error) that affects the reliability of the configuration, but it is not a security vulnerability reachable via untrusted external input under the defined threat model. The prior reviewers correctly identified that this is a trusted configuration input.\n\nCRUX: proxyAddr is a trusted configuration parameter provided by the caller, not untrusted external input, so a failure due to malformed config is not a security vulnerability reachable by an external attacker.\nGREP: FasthttpSocksDialer",
"elapsed": 5.5,
"tokens": 3810,
"tokens_in": 3546,
"tokens_out": 264,
"cost_usd": 0.00228132,
"file": "fasthttpproxy/socks5.go",
"round": 3,
"grep_used": true,
"grep_results": "GREP `FasthttpSocksDialer`:\n```\nfasthttpproxy/socks5.go:8:// FasthttpSocksDialer returns a fasthttp.DialFunc that dials using\nfasthttpproxy/socks5.go:14://\t\tDial: fasthttpproxy.FasthttpSocksDialer(\"socks5://localhost:9050\"),\nfasthttpproxy/socks5.go:16:func FasthttpSocksDialer(proxyAddr string) fasthttp.DialFunc {\nfasthttpproxy/socks5.go:22:// FasthttpSocksDialerDualStack returns a fasthttp.DialFunc that dials using\nfasthttpproxy/socks5.go:28://\t\tDial: fasthttpproxy.FasthttpSocksDialerDualStack(\"socks5://localhost:9050\"),\nfasthttpproxy/socks5.go:30:func FasthttpSocksDialerDualStack(proxyAddr string) fasthttp.DialFunc {\n```"
},
{
"finding_title": "Ignored proxy dialer initialization error can return nil or fail-open DialFunc",
"verdict": "INVALID",
"reasoning": "The threat model for a reusable library explicitly defines the attacker as the code calling the public API, specifically emphasizing parsers, decoders, and deserializers that handle adversarial payloads. The entry points are public functions receiving untrusted data. In this case, `FasthttpSocksDialer` is a configuration factory. The `proxyAddr` argument is a static configuration value provided by the application developer at startup (e.g., `Dial: fasthttpproxy.FasthttpSocksDialer(\"socks5://localhost:9050\")`). It is not data flowing in from an external network source (like an HTTP request body or header) that the library parses. \n\nWhile ignoring the error from `GetDialFunc` is a code quality issue (it prevents the caller from knowing if the proxy address is invalid and could lead to a nil pointer dereference if the library returned it without checking, or silent fallbacks in `fasthttp`), the security impact relies on an attacker controlling the `proxyAddr` string. Since `proxyAddr` is a trusted configuration parameter set by the developer, an external attacker cannot control it without already having control over the host application's configuration or code execution. The threat model states that misusing a public API by violating preconditions (providing a valid, trusted configuration is the precondition for a proxy dialer) or ignoring configuration errors is not a security vulnerability. The 'fail-open' behavior described is a configuration error, not a memory safety issue reachable via untrusted input. Therefore, this is a code quality issue, not a security vulnerability under the provided threat model.\n\nCRUX: proxyAddr is a trusted configuration parameter provided by the application developer, not untrusted external input, so a failure due to malformed config is not a security vulnerability reachable by an external attacker.\nGREP: FasthttpSocksDialer",
"elapsed": 459.9,
"tokens": 4330,
"tokens_in": 3928,
"tokens_out": 402,
"cost_usd": 0.0028557599999999997,
"file": "fasthttpproxy/socks5.go",
"round": 4,
"grep_used": true,
"grep_results": "GREP `FasthttpSocksDialer`:\n```\nfasthttpproxy/socks5.go:8:// FasthttpSocksDialer returns a fasthttp.DialFunc that dials using\nfasthttpproxy/socks5.go:14://\t\tDial: fasthttpproxy.FasthttpSocksDialer(\"socks5://localhost:9050\"),\nfasthttpproxy/socks5.go:16:func FasthttpSocksDialer(proxyAddr string) fasthttp.DialFunc {\nfasthttpproxy/socks5.go:22:// FasthttpSocksDialerDualStack returns a fasthttp.DialFunc that dials using\nfasthttpproxy/socks5.go:28://\t\tDial: fasthttpproxy.FasthttpSocksDialerDualStack(\"socks5://localhost:9050\"),\nfasthttpproxy/socks5.go:30:func FasthttpSocksDialerDualStack(proxyAddr string) fasthttp.DialFunc {\n```"
},
{
"finding_title": "Ignored proxy dialer initialization error can return nil or fail-open DialFunc",
"verdict": "INVALID",
"reasoning": "The reported vulnerability is based on the premise that an attacker can control the `proxyAddr` input to `FasthttpSocksDialer`. However, under the defined threat model for a reusable library, the `proxyAddr` is a configuration parameter provided by the trusted caller (the application developer) at initialization time. It is not derived from untrusted external data (such as HTTP request bodies, headers, or network payloads). The threat model explicitly excludes issues where the 'attacker' must control the configuration input to trigger the bug, as this implies the attacker already has control over the host application's configuration or code, which is outside the scope of a library-level vulnerability. While ignoring the error from `GetDialFunc` is a code quality defect (leading to a nil `DialFunc` which could panic or bypass proxying if the developer provided a malformed string), this is a result of trusted caller misuse or poor API design, not a security vulnerability exploitable by an external untrusted party. Therefore, it is invalid under the specific threat model constraints.\n\nCRUX: The proxyAddr parameter is a trusted configuration input provided by the application developer, not untrusted external data, so the ignored error does not constitute a security vulnerability reachable by an external attacker.\nGREP: GetDialFunc",
"elapsed": 4.4,
"tokens": 4725,
"tokens_in": 4446,
"tokens_out": 279,
"cost_usd": 0.00270432,
"file": "fasthttpproxy/socks5.go",
"round": 5,
"grep_used": true,
"grep_results": "GREP `GetDialFunc`:\n```\nfasthttpproxy/socks5.go:18:\tdialFunc, _ := d.GetDialFunc(false)\nfasthttpproxy/socks5.go:32:\tdialFunc, _ := d.GetDialFunc(false)\nfasthttpproxy/dialer.go:72:// GetDialFunc method returns a fasthttp-style dial function. The useEnv parameter\nfasthttpproxy/dialer.go:74:func (d *Dialer) GetDialFunc(useEnv bool) (fasthttp.DialFunc, error) {\nfasthttpproxy/dialer_test.go:16:func TestDialer_GetDialFunc(t *testing.T) {\nfasthttpproxy/dialer_test.go:218:\t\t\tdialFunc, err := d.GetDialFunc(tt.args.useEnv)\nfasthttpproxy/dialer_test.go:220:\t\t\t\tt.Fatalf(\"GetDialFunc() error = %v, wantErr %v\", err, tt.wantErrMessage)\nfasthttpproxy/dialer_test.go:234:\t\t\t\tt.Errorf(\"GetDialFunc() counts = %v, want %v\", getCounts(counts), tt.wantCounts)\nfasthttpproxy/http.go:33:\tdialFunc, _ := d.GetDialFunc(false)\nfasthttpproxy/http.go:63:\tdialFunc, _ := d.GetDialFunc(false)\nfasthttpproxy/proxy_env.go:37:\tdialFunc, _ := d.GetDialFunc(true)\n```"
}
]Raw scan report for this file
The exported constructors accept a caller-controlled `proxyAddr` string and immediately convert it into a `fasthttp.DialFunc` without surfacing any configuration error. The main data flow is:
`proxyAddr` → `Dialer.Config.HTTPProxy/HTTPSProxy` → `Dialer.GetDialFunc(false)` → returned `fasthttp.DialFunc`
Because `GetDialFunc` is a fallible call but its error is discarded with `_`, the functions can silently return an unusable or unsafe dial function when `proxyAddr` is empty, malformed, unsupported, or otherwise invalid. In Go, this can lead to one of two bad outcomes:
1. The returned value is a nil `fasthttp.DialFunc`, and a caller that invokes it directly triggers a nil function-call panic in the host process.
2. The returned dial function silently falls back to non-proxied behavior, causing traffic that was expected to traverse the SOCKS5 proxy to be sent directly. If the application relies on the proxy for egress control, this is a fail-open security bypass.
There are no fixed-size buffer overflows, integer overflows, tagged-union type confusion, or direct concurrency issues in this file. The security-relevant issue is the unchecked initialization error at the public API boundary.
```json
[
{
"severity": "high",
"title": "Ignored proxy dialer initialization error can return nil or fail-open DialFunc",
"function": "FasthttpSocksDialer",
"description": "proxyAddr is caller-controlled. The error from d.GetDialFunc(false) is discarded and dialFunc is returned unconditionally. If proxyAddr is empty, malformed, or unsupported, GetDialFunc may fail and return nil. Returning a nil fasthttp.DialFunc can cause a panic if invoked directly, and if assigned to fasthttp.Client.Dial it may silently fall back to direct dialing, bypassing the intended SOCKS5 proxy and egress controls."
},
{
"severity": "high",
"title": "Ignored proxy dialer initialization error can return nil or fail-open DialFunc in dual-stack variant",
"function": "FasthttpSocksDialerDualStack",
"description": "The dual-stack constructor has the same defect: the error from d.GetDialFunc(false) is ignored for a caller-controlled proxyAddr. A failed or invalid proxy configuration can produce a nil DialFunc, leading to a panic on direct use, or a fail-open direct dialing path when used with fasthttp.Client, bypassing the intended dual-stack SOCKS5 proxy."
}
]
```