How to sanitize user input?

.NET SDK
1

Just found my application formed

WHERE field = 'bah\'

from user input (by means of Linq2Couchbase) resulting “syntax error: invalid quoted string”. This is a user typo - not a deliberate attempt to inject anything… What would be the best practice to sanitize user input?

PS: Exact Linq2Couchbase error was:
Couchbase.Linq.CouchbaseQueryException: syntax error: invalid quoted string - at '%!b(MISSING)lah\%!'(MISSING)

2

@skaryshev Linq2Couchbase should be escaping user input correctly for you, can you provide some more details showing the code and user input that causes this?

3

I am working on this. Will post when I have more details.

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4

Couchbase server 6.6 Community. Linq2Couchbase 1.4.2

A simple test includes
.Where(obj=>obj.Data == @"data\")

Couchbase log: I did my best to make data\ and data\\ look correct . Do not know how to post raw text.

SELECT RAW META(Extent1).id FROM BUCKET-test as Extent1 WHERE (Extent1.Data =’data\') |Couchbase.Linq.QueryGeneration.QueryPartsAggregator|
Generated query: SELECT RAW META(Extent1).id FROM BUCKET-test as Extent1 WHERE (Extent1.Data = ‘data\’) |Couchbase.Linq.Execution.BucketQueryExecutor|
Gettting Query Uri cid3::0 |Couchbase.N1QL.QueryClient|
Applying creds cid3::0: http://192.168.0.6:8093/query |Couchbase.N1QL.QueryClient|
Removing brackets cid3::0: http://192.168.0.6:8093/query |Couchbase.N1QL.QueryClient|
http://192.168.0.6:8093/query[“statement”:“SELECT RAW META(Extent1).id FROM BUCKET-test as Extent1 WHERE (Extent1.Data = ‘data\\’)”,“timeout”:“75000ms”,“creds”:[REDUCTED] |Couchbase.N1QL.QueryClient|
Buildspan cid3::0: http://192.168.0.6:8093/query |Couchbase.N1QL.QueryClient|
Getting content cid3::4: http://192.168.0.6:8093/query |Couchbase.N1QL.QueryClient|
Sending query cid3::4: http://192.168.0.6:8093/query |Couchbase.N1QL.QueryClient|
Handling response cid3::4: http://192.168.0.6:8093/query |Couchbase.N1QL.QueryClient|
Mapping cid3::4: http://192.168.0.6:8093/query |Couchbase.N1QL.QueryClient|
In GetDatamapper cid3::4 |Couchbase.N1QL.QueryClient|
It is IQueryRequestWithDataMapper cid3::4 |Couchbase.N1QL.QueryClient|

The log stops here

The test outcome:
Message:
Test method Logic.Test.UnitTestDbManager.TestMethodEscape threw exception:
Couchbase.Linq.CouchbaseQueryException: syntax error: invalid quoted string - at 'data\'
Stack Trace:
BucketQueryExecutor.ParseResult[T](IQueryResult1 result) BucketQueryExecutor.ExecuteCollectionAsync[T](LinqQueryRequest queryRequest, CancellationToken cancellationToken) QueryExtensions.ExecuteAsync[T](IQueryable1 source, CancellationToken cancellationToken)
QueryManager.GetKeysAdHoc[T](IEnumerable`1 searchCriteria) line 183
UnitTestDbManager.TestMethodEscape() line 473

5

@skaryshev

This is a bug, I’ve filed it on the Linq2Couchbase project: Backslash is incorrectly escaped in strings · Issue #345 · couchbaselabs/Linq2Couchbase · GitHub

As a workaround, you could do x.Replace("\\", "\\\\"), however the workaround will actually break once you upgrade to receive any fix.

1 Like
6

Thanks, I have already patched it with Replace. Funny thing it is only one user hitting backslash with a long fingernail altogether with Enter key. . :wink:

7

You should always use parameters to avoid sql injection problems.

where field = $1

then set the parameter to whatever the input was. Not only is it safer, it’s more efficient. The server will have the statement already parsed.

8

Right, but I use Linq2Couchbase library with Linq syntax to query data not direct Query API from SDK

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