Return the actual number of bytes written to through command buffer #287

hslatman · 2023-02-22T15:05:01Z

The Write function returned the number of bytes written to the internal command response buffer. Depending on the type of command executed against the TPM, this would usually result in a different number of bytes being written than the original input.

The fix is useful if one wants to wrap the io.ReadWriterCloser functions with implementations that perform strict checks. An example is using an io.MultiWriter to capture the bytes sent to the TPM for debugging purposes, which will fail if the number of bytes written does not equal the original length of the input bytes.

The `Write` function returned the number of bytes written to the internal command response buffer in the simulator. Depending on the type of command executed against the TPM, this would usually result in a different number of bytes being written than the original input. The fix is useful if one wants to wrap the io.ReadWriterCloser functions with implementations that perform strict checks. An example is using an io.MultiWriter to capture the bytes sent to the TPM for debugging purposes, which will fail if the number of bytes written does not equal the original length of the input bytes.

josephlr

Nice catch, I'm surprised it took so long for us to catch this.

josephlr · 2023-03-09T01:10:53Z

simulator/simulator.go

+	if err != nil {
+		return 0, err
+	}
+	if n != len(resp) {
+		return 0, fmt.Errorf("expected %d bytes to be written to command response buffer, but actual number is %d", len(resp), n)
+	}


We don't need this error checking here, bytes.Buffer will always return a nil error and a length of the input buffer (see https://pkg.go.dev/bytes#Buffer.Write).

Ah, nice 😄 Fixed in 63181f2.

josephlr · 2023-03-09T01:12:14Z

/gcbrun

Use region in spec to create attestation service rest client google#281 Parse EFI App state from the TCG event log google#277 Increase default systemd wait timeout to 900s google#276 Use same env var formatting logic on the launcher as server google#253 Fix image pulling in launcher google#282 Bump version and fix a kernel cmd issue google#291 Return the actual number of bytes written to through command buffer google#287 Fix lint issues after using golangci-lint-1.52.2 google#296 Add image tests and test automation google#275 Update go-sev-guest to v0.4.2 google#278 Update to go-sev-guest v0.4.5 google#279 Add proper debug license and logging to launcher google#280 Upgrade to go-sev-guest v0.5.0 google#283 Import go-sev-guest v0.5.2 google#284 Add override test for workload env vars and cmd google#286 Add test workload code, check OIDC claims, and validate launch policy checks google#288 Bump golang.org/x/net in /launcher google#290 Add RELEASING instructions google#187 https://github.com/google/go-tpm-tools/compare/53cab1a...5dd1056?expand=1

Breaking Changes: New Features: Use region in spec to create attestation service rest client google#281 Parse EFI App state from the TCG event log google#277 Bug Fixes: Increase default systemd wait timeout to 900s google#276 Use same env var formatting logic on the launcher as server google#253 Fix image pulling in launcher google#282 Bump version and fix a kernel cmd issue google#291 Return the actual number of bytes written to through command buffer google#287 Fix lint issues after using golangci-lint-1.52.2 google#296 Other Changes: Add image tests and test automation google#275 Update go-sev-guest to v0.4.2 google#278 Update to go-sev-guest v0.4.5 google#279 Add proper debug license and logging to launcher google#280 Upgrade to go-sev-guest v0.5.0 google#283 Import go-sev-guest v0.5.2 google#284 Add override test for workload env vars and cmd google#286 Add test workload code, check OIDC claims, and validate launch policy checks google#288 Bump golang.org/x/net in /launcher google#290 Add RELEASING instructions google#187 https://github.com/google/go-tpm-tools/compare/53cab1a...5dd1056?expand=1

Breaking Changes: New Features: Use region in spec to create attestation service rest client #281 Parse EFI App state from the TCG event log #277 Bug Fixes: Increase default systemd wait timeout to 900s #276 Use same env var formatting logic on the launcher as server #253 Fix image pulling in launcher #282 Bump version and fix a kernel cmd issue #291 Return the actual number of bytes written to through command buffer #287 Fix lint issues after using golangci-lint-1.52.2 #296 Other Changes: Add image tests and test automation #275 Update go-sev-guest to v0.4.2 #278 Update to go-sev-guest v0.4.5 #279 Add proper debug license and logging to launcher #280 Upgrade to go-sev-guest v0.5.0 #283 Import go-sev-guest v0.5.2 #284 Add override test for workload env vars and cmd #286 Add test workload code, check OIDC claims, and validate launch policy checks #288 Bump golang.org/x/net in /launcher #290 Add RELEASING instructions #187 https://github.com/google/go-tpm-tools/compare/53cab1a...5dd1056?expand=1

Breaking Changes: New Features: Use region in spec to create attestation service rest client google#281 Parse EFI App state from the TCG event log google#277 Bug Fixes: Increase default systemd wait timeout to 900s google#276 Use same env var formatting logic on the launcher as server google#253 Fix image pulling in launcher google#282 Bump version and fix a kernel cmd issue google#291 Return the actual number of bytes written to through command buffer google#287 Fix lint issues after using golangci-lint-1.52.2 google#296 Other Changes: Add image tests and test automation google#275 Update go-sev-guest to v0.4.2 google#278 Update to go-sev-guest v0.4.5 google#279 Add proper debug license and logging to launcher google#280 Upgrade to go-sev-guest v0.5.0 google#283 Import go-sev-guest v0.5.2 google#284 Add override test for workload env vars and cmd google#286 Add test workload code, check OIDC claims, and validate launch policy checks google#288 Bump golang.org/x/net in /launcher google#290 Add RELEASING instructions google#187 https://github.com/google/go-tpm-tools/compare/53cab1a...5dd1056?expand=1

Breaking Changes: New Features: Use region in spec to create attestation service rest client #281 Parse EFI App state from the TCG event log #277 Bug Fixes: Increase default systemd wait timeout to 900s #276 Use same env var formatting logic on the launcher as server #253 Fix image pulling in launcher #282 Bump version and fix a kernel cmd issue #291 Return the actual number of bytes written to through command buffer #287 Fix lint issues after using golangci-lint-1.52.2 #296 Other Changes: Add image tests and test automation #275 Update go-sev-guest to v0.4.2 #278 Update to go-sev-guest v0.4.5 #279 Add proper debug license and logging to launcher #280 Upgrade to go-sev-guest v0.5.0 #283 Import go-sev-guest v0.5.2 #284 Add override test for workload env vars and cmd #286 Add test workload code, check OIDC claims, and validate launch policy checks #288 Bump golang.org/x/net in /launcher #290 Add RELEASING instructions #187 https://github.com/google/go-tpm-tools/compare/53cab1a...5dd1056?expand=1

Breaking Changes: New Features: Use region in spec to create attestation service rest client google#281 Parse EFI App state from the TCG event log google#277 Bug Fixes: Increase default systemd wait timeout to 900s google#276 Use same env var formatting logic on the launcher as server google#253 Fix image pulling in launcher google#282 Bump version and fix a kernel cmd issue google#291 Return the actual number of bytes written to through command buffer google#287 Fix lint issues after using golangci-lint-1.52.2 google#296 Other Changes: Add image tests and test automation google#275 Update go-sev-guest to v0.4.2 google#278 Update to go-sev-guest v0.4.5 google#279 Add proper debug license and logging to launcher google#280 Upgrade to go-sev-guest v0.5.0 google#283 Import go-sev-guest v0.5.2 google#284 Add override test for workload env vars and cmd google#286 Add test workload code, check OIDC claims, and validate launch policy checks google#288 Bump golang.org/x/net in /launcher google#290 Add RELEASING instructions google#187 https://github.com/google/go-tpm-tools/compare/53cab1a...5dd1056?expand=1

hslatman force-pushed the fix-write-length branch from d1378dc to d9008ec Compare February 22, 2023 15:07

hslatman force-pushed the fix-write-length branch from d9008ec to 2d2eb44 Compare February 22, 2023 15:11

jkl73 requested a review from josephlr March 9, 2023 01:06

josephlr approved these changes Mar 9, 2023

View reviewed changes

Remove simulator buf.Write error checking

63181f2

hslatman requested a review from josephlr March 13, 2023 11:08

josephlr merged commit 9e791b1 into google:master Mar 14, 2023

alexmwu mentioned this pull request Apr 7, 2023

Release v0.3.11 #298

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Return the actual number of bytes written to through command buffer #287

Return the actual number of bytes written to through command buffer #287

hslatman commented Feb 22, 2023

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josephlr commented Mar 9, 2023

Return the actual number of bytes written to through command buffer #287

Return the actual number of bytes written to through command buffer #287

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