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Diffstat (limited to 'doc')
| -rw-r--r-- | doc/audit/response-202005.tex | 38 |
1 files changed, 26 insertions, 12 deletions
diff --git a/doc/audit/response-202005.tex b/doc/audit/response-202005.tex index 922680eaf..a32a58559 100644 --- a/doc/audit/response-202005.tex +++ b/doc/audit/response-202005.tex @@ -57,12 +57,17 @@ they have all been addressed. \section{General remarks on the code} We understand that writing the code in another programming language may make -certain checks for the auditor less work. However, other programming languages -also have disadvantages (from the complexity of the languages to the -complexity of the compilers to tool support). We believe creating a parallel -implementation in other languages would provide advantages, especially with -respect to avoiding ``the implementation is the specification''-style issues. -However, given limited resources will not make this a priority. +certain checks for the auditor less work to implement. However, our choice of C +is based on the advantages that make it superior to contemporary languages for +our use case: relatively low complexity of the language (compared to C++); +availability of mature compilers, static and dynamic analysis tools; +predictable performance; access to stable and battle-tested libraries; and +future-proofness due to portability to older systems as well as new platforms. + +We believe creating a parallel implementation in other languages would provide +advantages, especially with respect to avoiding ``the implementation is the +specification''-style issues. However, given limited resources will not make +this a priority. We disagree that all modern software development has embraced the idea that memory errors are to be handled in ways other than terminating or restarting @@ -214,11 +219,20 @@ exchange for production. \subsection{Reduce reliance on PostgreSQL} -Using other mechanisms beyond the database as a ``Plan B'' would create -serious availability and cost concerns, as now either mechanism may create -serialization issues and require database rollbacks. Also, any such -append-only logging mechanism would itself have a similar complexity as the -primary database. Thus, we do not believe that the drastic complexity -increase from the combined solution represents a valid security trade-off. +CodeBlau's suggestion to use an append-only transaction logging service in +addition to the PostgreSQL database is a reasonable suggestion for a +production-grade deployment of GNU Taler, as it would allow partial disaster +recovery even in the presence of an attacker that has gained write access to +the exchange's database. + +We are currently still investigating whether the transaction logging should be +implemented directly by the exchange service, or via the database's extensible +replication mechanism. Any implementation of such an append-only logging +mechanism must be carefully designed to ensure it does not negatively impact +the exchange's availability and does not interfere with serializability of +database transactions. As such we believe that transaction logging can only be +provided on a best-effort basis. Fortunately, even a best-effort append-only +transaction log would serve to limit the financial damage incurred by the +exchange in an active database compromise scenario. \end{document} |