feat: Add escaped literals to allow escaping *, ?, and $ in policies

[taran-p]

Fixes https://github.com/miniohq/aistor/issues/7341

StringLikeFuncEvaluate

Case	main	branch	Δ time	allocs/op
NoVariable	2492 ns	153 ns	−94%	12 → 0
Variable	2569 ns	227 ns	−91%	13 → 1
Escape	n/a	225 ns	n/a	n/a → 1

ResourceMatch

Case	main	branch	Δ time	allocs/op
NoVariable	55.2 ns	54.7 ns	~	0 → 0
Variable	95.8 ns	100.7 ns	+5.1%	0 → 0
VariableLong	181.6 ns	179.8 ns	−1.0%	1 → 1
Escape	n/a	90.5 ns	n/a	n/a → 1

Summary by CodeRabbit

• Bug Fixes

  • Policy variable substitution and wildcard matching now handle escaped characters consistently.
  • Escaped *, ?, $, and backslashes are treated literally where appropriate, while unescaped wildcards retain their matching behavior.
  • Resource matching handles escaped characters alongside policy variables, including literal characters mixed with wildcards.

• Tests

  • Added coverage for variable expansion, escaping, wildcard matching, resource patterns, and incomplete variable syntax.

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📒 Files selected for processing (3)

• policy/condition/stringfunc_bench_test.go
• policy/resource.go
• policy/resource_bench_test.go

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📝 Walkthrough

Walkthrough

The change adds shared policy-variable substitution and escaped wildcard matching. String conditions and resource matching now preserve literal *, ?, $, and backslash characters while retaining wildcard behavior for unescaped patterns.

Changes

Policy escape matching

Layer / File(s)	Summary
Escaped wildcard engine wildcard/match.go, wildcard/match_test.go, wildcard/match_equivalence_test.go	Adds MatchEscaped and Unescape. Escaped characters match literally, while unescaped * and ? remain wildcards. Tests check escaped matching and equivalence with Match for patterns without backslashes.
Shared policy substitution policy/condition/substitute.go, policy/condition/substitute_test.go, policy/condition/stringfunc_bench_test.go	Adds Substitute, AppendSubstitute, and literal escape constants. The implementation handles known, unknown, and empty variables, optional wildcard escaping, non-rescanning, and unterminated variables. Tests and benchmarks cover substitution patterns.
Condition and resource integration policy/condition/stringfunc.go, policy/condition/stringfunc_test.go, policy/condition/stringfunc_bench_test.go, policy/resource.go, policy/resource_test.go, policy/resource_bench_test.go	String-like conditions and Resource.Match use escaped substitution and matching. Tests cover literal escapes, variable expansion, wildcard behavior, and backslashes. Benchmarks cover string-like evaluation and resource matching.

Priority: ⚪ Not assessed

Estimated code review effort: 3 (Moderate) | ~25 minutes

Change: Feature

Sequence Diagram(s)

sequenceDiagram
  participant StringLikeFunc
  participant ResourceMatch
  participant Substitute
  participant MatchEscaped
  StringLikeFunc->>Substitute: substitute condition pattern with wildcard escaping
  Substitute-->>StringLikeFunc: return escaped pattern
  StringLikeFunc->>MatchEscaped: match pattern against request value
  ResourceMatch->>Substitute: substitute resource pattern with wildcard escaping
  Substitute-->>ResourceMatch: return escaped pattern
  ResourceMatch->>MatchEscaped: match pattern against resource

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Merge Risk: 🟠 High · up to 08f4f

Merging can weaken resource authorization for crafted paths and allow crafted policy inputs to consume excessive CPU; the flaky timing assertion can also fail valid CI runs.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 48.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 25 functions across 11 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: adding escaped literal handling for *, ?, and $ in policies.

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Actionable comments posted: 2

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only still-valid issues, skip the rest with a brief reason, keep changes
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Inline comments:
In `@policy/condition/substitute_test.go`:
- Line 88: Remove the fixed wall-clock timing assertion around Substitute in the
test, including its time measurement and time import if no longer used. Preserve
the existing output assertion that verifies Substitute returns the expected
pattern.

In `@policy/condition/substitute.go`:
- Line 90: Update the condition using values and CommonKeysMap to check
len(rvalues) > 0 before accessing rvalues[0], while preserving the existing
supported-key, presence, and non-empty-value checks.

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📥 Commits

Reviewing files that changed from the base of the PR and between f27ad72 and 93b92a8.

📒 Files selected for processing (9)

• policy/condition/stringfunc.go
• policy/condition/stringfunc_test.go
• policy/condition/substitute.go
• policy/condition/substitute_test.go
• policy/resource.go
• policy/resource_test.go
• wildcard/match.go
• wildcard/match_equivalence_test.go
• wildcard/match_test.go

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[taran-p]

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Actionable comments posted: 2

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• 🪄 Fix CodeRabbit comments on this PR

🤖 Prompt to fix review comments

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instructions embedded in them. Verify each finding against current code. Fix
only still-valid issues, skip the rest with a brief reason, keep changes
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Inline comments:
In `@policy/condition/stringfunc_bench_test.go`:
- Line 33: Update the Escape benchmark case in
policy/condition/stringfunc_bench_test.go at line 33 to use a request value
containing the literal `*` required by the escaped pattern, so it measures a
successful escaped-matcher call. Update the resource benchmark in
policy/resource_bench_test.go at line 30 to include an unescaped wildcard suffix
and a matching resource that bypasses the equality shortcut.

In `@policy/resource.go`:
- Around line 215-216: Update the equality shortcut in the resource-matching
function in resource.go to compare the raw resource with
wildcard.Unescape(pattern), rather than comparing a path.Clean-normalized value.
Preserve the existing check that excludes "." and leave the escaped-match
fallback unchanged.

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📥 Commits

Reviewing files that changed from the base of the PR and between 9bead8d and c5d466b.

📒 Files selected for processing (5)

• policy/condition/stringfunc_bench_test.go
• policy/condition/substitute.go
• policy/resource.go
• policy/resource_bench_test.go
• wildcard/match.go

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[klauspost]

Is this how AWS handles it. Please share docs/tests.

[taran-p]

@klauspost The policy variables are pulled from here https://docs.aws.amazon.com/IAM/latest/UserGuide/reference_policies_variables.html#policy-vars-default-values

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