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Merged
jviotti merged 1 commit into from
May 15, 2026
Merged

Perform JSON Schema input validation of MCP requests #907

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5 changes: 3 additions & 2 deletions src/actions/CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -23,9 +23,10 @@ target_link_libraries(sourcemeta_one_actions PRIVATE sourcemeta::core::jsonpoint
target_link_libraries(sourcemeta_one_actions PRIVATE sourcemeta::core::io)
target_link_libraries(sourcemeta_one_actions PRIVATE sourcemeta::core::time)
target_link_libraries(sourcemeta_one_actions PRIVATE sourcemeta::one::shared)
target_link_libraries(sourcemeta_one_actions PRIVATE sourcemeta::one::metapack)
target_link_libraries(sourcemeta_one_actions PUBLIC sourcemeta::one::metapack)
target_link_libraries(sourcemeta_one_actions PRIVATE sourcemeta::one::search)
target_link_libraries(sourcemeta_one_actions PRIVATE sourcemeta::blaze::evaluator)
target_link_libraries(sourcemeta_one_actions PUBLIC sourcemeta::blaze::evaluator)
target_link_libraries(sourcemeta_one_actions PUBLIC sourcemeta::blaze::compiler)
target_link_libraries(sourcemeta_one_actions PRIVATE sourcemeta::blaze::output)

if(ONE_ENTERPRISE)
Expand Down
37 changes: 11 additions & 26 deletions src/actions/action_jsonschema_evaluate_v1.h
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Expand Up @@ -38,13 +38,15 @@ class ActionJSONSchemaEvaluate_v1 : public sourcemeta::one::Action {
request_schema = std::get<std::string_view>(value);
} else if (key == "responseSchema") {
this->response_schema_ = std::get<std::string_view>(value);
} else if (key == "rpcSchema") {
this->rpc_schema_ = std::get<std::string_view>(value);
} else if (key == "errorSchema") {
this->error_schema_ = std::get<std::string_view>(value);
}
});

this->request_schema_template_ = ActionJSONSchemaEvaluate_v1::load_template(
this->base(), router.base_path(), request_schema);
this->request_schema_template_ = this->blaze_template(
request_schema, sourcemeta::blaze::Mode::FastValidation);
}

auto rest(const std::span<std::string_view> matches,
Expand All @@ -68,13 +70,16 @@ class ActionJSONSchemaEvaluate_v1 : public sourcemeta::one::Action {

const auto *params{sourcemeta::one::jsonrpc_params(envelope)};
if (params == nullptr || !params->is_object() ||
!params->defines("arguments") || !params->at("arguments").is_object()) {
!params->defines("arguments")) {
return sourcemeta::one::jsonrpc_make_error_invalid_params(request_id);
}

const auto &arguments{params->at("arguments")};
if (!arguments.defines("schema") || !arguments.at("schema").is_string() ||
!arguments.defines("instance")) {
// TODO: Cache the compiled template across invocations
const auto rpc_schema_template{this->blaze_template(
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@augmentcode augmentcode Bot May 15, 2026 •
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src/actions/action_jsonschema_evaluate_v1.h:79: this->blaze_template(this->rpc_schema_, ...) will assert/throw if rpcSchema wasn’t provided by the router (or the corresponding metapack is missing/corrupt), which would turn a request-time input-validation step into a process-terminating failure. Is that failure mode intended for runtime request handling, or should it degrade to an InvalidParams-style error?

Severity: medium

Other Locations
  • src/actions/action_jsonschema_trace_v1.h:81
  • src/actions/action_schema_search_v1.h:172
  • src/actions/action_serve_explorer_artifact_v1.h:70
  • src/actions/action_serve_schema_artifact_v1.h:74

Fix This in Augment

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this->rpc_schema_, sourcemeta::blaze::Mode::FastValidation)};
sourcemeta::blaze::Evaluator rpc_evaluator;
if (!rpc_evaluator.validate(rpc_schema_template, arguments)) {
return sourcemeta::one::jsonrpc_make_error_invalid_params(request_id);
}

Expand Down Expand Up @@ -106,27 +111,6 @@ class ActionJSONSchemaEvaluate_v1 : public sourcemeta::one::Action {
}
}

static auto load_template(const std::filesystem::path &base,
const std::string_view base_path,
std::string_view request_schema)
-> sourcemeta::blaze::Template {
if (!base_path.empty() && request_schema.starts_with(base_path)) {
request_schema.remove_prefix(base_path.size());
}
if (request_schema.starts_with('/')) {
request_schema.remove_prefix(1);
}

const auto template_path{base / "schemas" / request_schema / "%" /
"blaze-fast.metapack"};
const auto template_json{
sourcemeta::one::metapack_read_json(template_path)};
assert(template_json.has_value());
auto compiled{sourcemeta::blaze::from_json(template_json.value())};
assert(compiled.has_value());
return std::move(compiled.value());
}

template <typename Perform>
static auto
serve_post(const std::span<std::string_view> matches,
Expand Down Expand Up @@ -281,6 +265,7 @@ class ActionJSONSchemaEvaluate_v1 : public sourcemeta::one::Action {
}

std::string_view response_schema_;
std::string_view rpc_schema_;
std::string_view error_schema_;
sourcemeta::blaze::Template request_schema_template_;
};
Expand Down
16 changes: 11 additions & 5 deletions src/actions/action_jsonschema_trace_v1.h
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Original file line number Diff line number Diff line change
Expand Up @@ -41,13 +41,15 @@ class ActionJSONSchemaTrace_v1 : public sourcemeta::one::Action {
request_schema = std::get<std::string_view>(value);
} else if (key == "responseSchema") {
this->response_schema_ = std::get<std::string_view>(value);
} else if (key == "rpcSchema") {
this->rpc_schema_ = std::get<std::string_view>(value);
} else if (key == "errorSchema") {
this->error_schema_ = std::get<std::string_view>(value);
}
});

this->request_schema_template_ = ActionJSONSchemaEvaluate_v1::load_template(
this->base(), router.base_path(), request_schema);
this->request_schema_template_ = this->blaze_template(
request_schema, sourcemeta::blaze::Mode::FastValidation);
}

auto rest(const std::span<std::string_view> matches,
Expand All @@ -70,13 +72,16 @@ class ActionJSONSchemaTrace_v1 : public sourcemeta::one::Action {

const auto *params{sourcemeta::one::jsonrpc_params(envelope)};
if (params == nullptr || !params->is_object() ||
!params->defines("arguments") || !params->at("arguments").is_object()) {
!params->defines("arguments")) {
return sourcemeta::one::jsonrpc_make_error_invalid_params(request_id);
}

const auto &arguments{params->at("arguments")};
if (!arguments.defines("schema") || !arguments.at("schema").is_string() ||
!arguments.defines("instance")) {
// TODO: Cache the compiled template across invocations
const auto rpc_schema_template{this->blaze_template(
this->rpc_schema_, sourcemeta::blaze::Mode::FastValidation)};
sourcemeta::blaze::Evaluator rpc_evaluator;
if (!rpc_evaluator.validate(rpc_schema_template, arguments)) {
return sourcemeta::one::jsonrpc_make_error_invalid_params(request_id);
}

Expand Down Expand Up @@ -319,6 +324,7 @@ class ActionJSONSchemaTrace_v1 : public sourcemeta::one::Action {
}

std::string_view response_schema_;
std::string_view rpc_schema_;
std::string_view error_schema_;
sourcemeta::blaze::Template request_schema_template_;
};
Expand Down
31 changes: 11 additions & 20 deletions src/actions/action_schema_search_v1.h
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@@ -1,6 +1,7 @@
#ifndef SOURCEMETA_ONE_ACTIONS_SCHEMA_SEARCH_V1_H
#define SOURCEMETA_ONE_ACTIONS_SCHEMA_SEARCH_V1_H

#include <sourcemeta/blaze/evaluator.h>
#include <sourcemeta/core/json.h>
#include <sourcemeta/core/uritemplate.h>

Expand Down Expand Up @@ -32,6 +33,8 @@ class ActionSchemaSearch_v1 : public sourcemeta::one::Action {
router.arguments(identifier, [this](const auto &key, const auto &value) {
if (key == "responseSchema") {
this->response_schema_ = std::get<std::string_view>(value);
} else if (key == "rpcSchema") {
this->rpc_schema_ = std::get<std::string_view>(value);
} else if (key == "errorSchema") {
this->error_schema_ = std::get<std::string_view>(value);
}
Expand Down Expand Up @@ -160,51 +163,38 @@ class ActionSchemaSearch_v1 : public sourcemeta::one::Action {

const auto *params{sourcemeta::one::jsonrpc_params(envelope)};
if (params == nullptr || !params->is_object() ||
!params->defines("arguments") || !params->at("arguments").is_object()) {
!params->defines("arguments")) {
return sourcemeta::one::jsonrpc_make_error_invalid_params(request_id);
}

const auto &arguments{params->at("arguments")};
if (!arguments.defines("q") || !arguments.at("q").is_string()) {
// TODO: Cache the compiled template across invocations
const auto rpc_schema_template{this->blaze_template(
this->rpc_schema_, sourcemeta::blaze::Mode::FastValidation)};
sourcemeta::blaze::Evaluator evaluator;
if (!evaluator.validate(rpc_schema_template, arguments)) {
return sourcemeta::one::jsonrpc_make_error_invalid_params(request_id);
}

constexpr std::size_t DEFAULT_LIMIT{10};
constexpr std::size_t MAXIMUM_LIMIT{100};
std::size_t limit{DEFAULT_LIMIT};
if (arguments.defines("limit")) {
if (!arguments.at("limit").is_integer()) {
return sourcemeta::one::jsonrpc_make_error_invalid_params(request_id);
}
const auto raw_limit{arguments.at("limit").to_integer()};
if (std::cmp_less(raw_limit, 1) ||
std::cmp_greater(raw_limit, MAXIMUM_LIMIT)) {
return sourcemeta::one::jsonrpc_make_error_invalid_params(request_id);
}
limit = static_cast<std::size_t>(raw_limit);
limit = static_cast<std::size_t>(arguments.at("limit").to_integer());
}

std::uint8_t scope{sourcemeta::one::SearchScopePath |
sourcemeta::one::SearchScopeTitle |
sourcemeta::one::SearchScopeDescription};
if (arguments.defines("scope")) {
if (!arguments.at("scope").is_array()) {
return sourcemeta::one::jsonrpc_make_error_invalid_params(request_id);
}
scope = 0;
for (const auto &item : arguments.at("scope").as_array()) {
if (!item.is_string()) {
return sourcemeta::one::jsonrpc_make_error_invalid_params(request_id);
}
const auto &token{item.to_string()};
if (token == "path") {
scope |= sourcemeta::one::SearchScopePath;
} else if (token == "title") {
scope |= sourcemeta::one::SearchScopeTitle;
} else if (token == "description") {
scope |= sourcemeta::one::SearchScopeDescription;
} else {
return sourcemeta::one::jsonrpc_make_error_invalid_params(request_id);
}
}
}
Expand All @@ -218,6 +208,7 @@ class ActionSchemaSearch_v1 : public sourcemeta::one::Action {
private:
sourcemeta::one::SearchView search_view_;
std::string_view response_schema_;
std::string_view rpc_schema_;
std::string_view error_schema_;
};

Expand Down
22 changes: 15 additions & 7 deletions src/actions/action_serve_explorer_artifact_v1.h
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Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
#ifndef SOURCEMETA_ONE_ACTIONS_SERVE_EXPLORER_ARTIFACT_V1_H
#define SOURCEMETA_ONE_ACTIONS_SERVE_EXPLORER_ARTIFACT_V1_H

#include <sourcemeta/blaze/evaluator.h>
#include <sourcemeta/core/json.h>
#include <sourcemeta/core/uritemplate.h>

Expand Down Expand Up @@ -30,6 +31,8 @@ class ActionServeExplorerArtifact_v1 : public sourcemeta::one::Action {
this->artifact_ = std::get<std::string_view>(value);
} else if (key == "responseSchema") {
this->response_schema_ = std::get<std::string_view>(value);
} else if (key == "rpcSchema") {
this->rpc_schema_ = std::get<std::string_view>(value);
} else if (key == "errorSchema") {
this->error_schema_ = std::get<std::string_view>(value);
}
Expand Down Expand Up @@ -58,20 +61,27 @@ class ActionServeExplorerArtifact_v1 : public sourcemeta::one::Action {

const auto *params{sourcemeta::one::jsonrpc_params(envelope)};
if (params == nullptr || !params->is_object() ||
!params->defines("arguments") || !params->at("arguments").is_object()) {
!params->defines("arguments")) {
return sourcemeta::one::jsonrpc_make_error_invalid_params(request_id);
}

const auto &arguments{params->at("arguments")};
// TODO: Cache the compiled template across invocations
const auto rpc_schema_template{this->blaze_template(
this->rpc_schema_, sourcemeta::blaze::Mode::FastValidation)};
sourcemeta::blaze::Evaluator evaluator;
if (!evaluator.validate(rpc_schema_template, arguments)) {
return sourcemeta::one::jsonrpc_make_error_invalid_params(request_id);
}

auto absolute_path{this->base() / "explorer"};

if (this->artifact_ == "list") {
if (arguments.defines("path")) {
if (!arguments.at("path").is_string()) {
return sourcemeta::one::jsonrpc_make_error_invalid_params(request_id);
}
const auto &path{arguments.at("path").to_string()};
if (!path.empty()) {
// Defense in depth: rpc.json's `path` is just `type: string`,
// so still reject filesystem-traversal attempts before joining.
const std::filesystem::path relative_path{path};
if (relative_path.is_absolute()) {
return sourcemeta::one::jsonrpc_make_error_invalid_params(
Expand All @@ -87,9 +97,6 @@ class ActionServeExplorerArtifact_v1 : public sourcemeta::one::Action {
}
}
} else {
if (!arguments.defines("schema") || !arguments.at("schema").is_string()) {
return sourcemeta::one::jsonrpc_make_error_invalid_params(request_id);
}
const auto schema_path{
this->uri_to_relative_path(arguments.at("schema").to_string())};
if (!schema_path.has_value()) {
Expand All @@ -116,6 +123,7 @@ class ActionServeExplorerArtifact_v1 : public sourcemeta::one::Action {
private:
std::string_view artifact_;
std::string_view response_schema_;
std::string_view rpc_schema_;
std::string_view error_schema_;
};

Expand Down
12 changes: 10 additions & 2 deletions src/actions/action_serve_schema_artifact_v1.h
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Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
#ifndef SOURCEMETA_ONE_ACTIONS_SERVE_SCHEMA_ARTIFACT_V1_H
#define SOURCEMETA_ONE_ACTIONS_SERVE_SCHEMA_ARTIFACT_V1_H

#include <sourcemeta/blaze/evaluator.h>
#include <sourcemeta/core/json.h>
#include <sourcemeta/core/uritemplate.h>

Expand Down Expand Up @@ -30,6 +31,8 @@ class ActionServeSchemaArtifact_v1 : public sourcemeta::one::Action {
this->artifact_ = std::get<std::string_view>(value);
} else if (key == "responseSchema") {
this->response_schema_ = std::get<std::string_view>(value);
} else if (key == "rpcSchema") {
this->rpc_schema_ = std::get<std::string_view>(value);
} else if (key == "errorSchema") {
this->error_schema_ = std::get<std::string_view>(value);
}
Expand Down Expand Up @@ -62,12 +65,16 @@ class ActionServeSchemaArtifact_v1 : public sourcemeta::one::Action {

const auto *params{sourcemeta::one::jsonrpc_params(envelope)};
if (params == nullptr || !params->is_object() ||
!params->defines("arguments") || !params->at("arguments").is_object()) {
!params->defines("arguments")) {
return sourcemeta::one::jsonrpc_make_error_invalid_params(request_id);
}

const auto &arguments{params->at("arguments")};
if (!arguments.defines("schema") || !arguments.at("schema").is_string()) {
// TODO: Cache the compiled template across invocations
const auto rpc_schema_template{this->blaze_template(
this->rpc_schema_, sourcemeta::blaze::Mode::FastValidation)};
sourcemeta::blaze::Evaluator evaluator;
if (!evaluator.validate(rpc_schema_template, arguments)) {
return sourcemeta::one::jsonrpc_make_error_invalid_params(request_id);
}

Expand All @@ -92,6 +99,7 @@ class ActionServeSchemaArtifact_v1 : public sourcemeta::one::Action {
private:
std::string_view artifact_;
std::string_view response_schema_;
std::string_view rpc_schema_;
std::string_view error_schema_;
};

Expand Down
24 changes: 24 additions & 0 deletions src/actions/base.cc
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Original file line number Diff line number Diff line change
@@ -1,7 +1,9 @@
#include <sourcemeta/core/uri.h>

#include <sourcemeta/one/actions.h>
#include <sourcemeta/one/metapack.h>

#include <cassert> // assert
#include <exception> // std::exception
#include <optional> // std::optional
#include <string_view> // std::string_view
Expand Down Expand Up @@ -43,4 +45,26 @@ auto Action::schema_directory(const std::string_view uri) const
return this->base_ / "schemas" / std::move(path).value() / "%";
}

auto Action::blaze_template(std::string_view schema_uri,
const sourcemeta::blaze::Mode mode) const
-> sourcemeta::blaze::Template {
if (!this->base_path_.empty() && schema_uri.starts_with(this->base_path_)) {
schema_uri.remove_prefix(this->base_path_.size());
}
if (schema_uri.starts_with('/')) {
schema_uri.remove_prefix(1);
}

const auto *filename{mode == sourcemeta::blaze::Mode::FastValidation
? "blaze-fast.metapack"
: "blaze-exhaustive.metapack"};
const auto template_path{this->base_ / "schemas" / schema_uri / "%" /
filename};
const auto template_json{sourcemeta::one::metapack_read_json(template_path)};
assert(template_json.has_value());
auto compiled{sourcemeta::blaze::from_json(template_json.value())};
assert(compiled.has_value());
return std::move(compiled.value());
}

} // namespace sourcemeta::one
10 changes: 10 additions & 0 deletions src/actions/include/sourcemeta/one/actions.h
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Original file line number Diff line number Diff line change
@@ -1,6 +1,8 @@
#ifndef SOURCEMETA_ONE_ACTIONS_H
#define SOURCEMETA_ONE_ACTIONS_H

#include <sourcemeta/blaze/compiler.h>
#include <sourcemeta/blaze/evaluator.h>
#include <sourcemeta/core/json.h>
#include <sourcemeta/core/uritemplate.h>

Expand Down Expand Up @@ -80,6 +82,14 @@ class Action {
[[nodiscard]] auto uri_to_relative_path(const std::string_view uri) const
-> std::optional<std::filesystem::path>;

// Loads a precompiled Blaze template from disk for the given
// self-served schema URL (e.g. an `rpcSchema` route argument). The
// mode picks `blaze-fast.metapack` (FastValidation) or
// `blaze-exhaustive.metapack` (Exhaustive). Asserts the file exists.
[[nodiscard]] auto blaze_template(std::string_view schema_uri,
sourcemeta::blaze::Mode mode) const
-> sourcemeta::blaze::Template;

private:
// NOLINTNEXTLINE(cppcoreguidelines-avoid-const-or-ref-data-members)
const std::filesystem::path &base_;
Expand Down
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