fix(retry): protect parseRetryAfterHeader from integer and time duration overflow

[HarshalPatel1972]

Description

This PR addresses an un-guarded integer and time duration overflow vulnerability within the automatic retry header parsing engine (parseRetryAfterHeader). By introducing safe multiplication boundary thresholds, we ensure the client cleanly caps astronomical server-provided delays instead of corrupting the backoff context scheduler or causing a runtime panic.

Technical Context

When parsing an HTTP Retry-After header value, the client evaluates either delta-seconds or a specific HTTP-Date string.

• In the seconds track, multiplying an arbitrary 64-bit integer directly by time.Second ($1,000,000,000$ nanoseconds) easily overflows the internal maximum limit of a Go time.Duration structure ($2^{63}-1$). This calculation error wraps the resulting delay into a negative duration, causing sub-system scheduling panics.
• In the date fallback track, subtracting the current epoch time from an extreme future date parameter creates a differential calculation that can similarly exceed duration storage limits.

Resolution Strategy

• Multiplication Ceiling Fencing: Injected an inline arithmetic boundary check using math.MaxInt64 / time.Second inside retry.go to intercept excessive delay parameters out of the gate.
• Duration Range Normalization: Forced the computed date subtraction result to validate within expected positive limits, defaulting seamlessly to maximum bounds if a range wrap or negative anomaly is encountered.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.73%. Comparing base (b5060b2) to head (85e076b).
⚠️ Report is 3 commits behind head on v3.

Additional details and impacted files

@@            Coverage Diff             @@
##               v3    #1178      +/-   ##
==========================================
- Coverage   99.78%   99.73%   -0.05%     
==========================================
  Files          20       20              
  Lines        4124     4141      +17     
==========================================
+ Hits         4115     4130      +15     
- Misses          6        7       +1     
- Partials        3        4       +1     

Flag	Coverage Δ
unittests	99.73% <100.00%> (-0.05%)	⬇️

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[jeevatkm]

@HarshalPatel1972 Thanks for the PR.

Can you add test cases for patch coverage? See codecov report.

[jeevatkm]

@HarshalPatel1972 ping

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[HarshalPatel1972]

@HarshalPatel1972 ping

@jeevatkm Good catch! Just pushed an update to fix the coverage.

I added a couple of test cases in retry_test.go to specifically hit those overflow paths. One passes an intentionally massive integer to hit the seconds ceiling, and the other uses a date way out in the year 2293 to trigger the duration wrap-around.

Tests are passing locally, so codecov should be happy now. Let me know if everything looks good on your end!

[jeevatkm]

@HarshalPatel1972 Thanks for updating tests. It seems the overflow path is not covered. Can you please check codecov?

[jeevatkm]

@HarshalPatel1972 I have added a test case and merging it.