README.md

semgrep-go

This repo holds patterns for finding odd Go code.

The rules engines currently supported:

• semgrep
• ruleguard

I'll accept comby patterns if you can't get them to work with either semgrep or ruleguard.

To run a single semgrep rule:

$ semgrep -f path/to/semgrep-go/rule.yml .

To run all semgrep rules:

$ semgrep -f path/to/semgrep-go/ .

To run all the ruleguard rules:

$ ruleguard -c=0 -rules path/to/semgrep-go/ruleguard.rules.go ./...

Semgrep checks:

• badexponentiation: check for 2^x and 10^x which look like exponentiation
• badnilguard: check for poorly formed nil guards
• errtodo: check for TODOs in error handling code
• hmac-bytes: check for using bytes.Equal() with HMACs
• hostport: check for using fmt.Sprintf() instead of net.JoinHostPort()
• mathbits: check for places you should use math/bits instead
• mail-address: check for using fmt.Sprintf() instead of net/mail.Address.String()
• oddbitwise: check for odd bit-wise expressions
• oddcompare: check for odd comparisons
• oddcompound: check for odd compound += or -= expressions
• oddifsequence: check for an odd sequence of ifs
• oddmathbits: check for odd uses of math/bits
• parseint-downcast: check for places a parsed 64-bit int is downcast to 32-bits
• returnnil: check for odd nil-returns
• sprinterr: check for fmt.Sprint(err) instead of err.Error()
• joinpath: check for using strings.Join() to construct paths
• readfull: check for extra length check for io.ReadFull()
• nilerr: returning a nil err instead of a nil value
• errclosed: check for call strings.Contains() to detect net.ErrClosed
• hmac-hash: check for bad hash.New passed to hmac.New()
• readeof: check for ignoring io.EOF as a successful read
• writestring: check for using io.WriteString(w, string(b))
• wronglock: find incorrect lock/unlock pairs for rwmutex
• contexttodo: find context.TODO() usage and suggest to change it
• close-sql-query-rows: find places database/sql.Rows instance isn't Close()d
• unixnano: check for time.Time comparisons using UnixNano()
• timeafter: leaky use of time.After()
• contextCancelable: checks for cancelable contexts not systematically canceled

Ruleguard checks are in ruleguard.rules.go.

• unconvert: check for unnecessary conversions
• timeeq: check for using == and != with time.Time values
• errnoterror: check for variables called err which are not the error type
• ifbodythenbody: check for if statements with identical if and else bodies
• subtractnoteq: check for x-y==0 instead of x==y
• selfassign: check for variable self-assignments
• oddnestedif: check for odd patterns of nested-ifs.
• oddbitwise: check for odd bitwise expressions
• ifreturn: check for off if/return sequences
• oddifsequence: check for if sequences
• nestedifsequence: check for odd nested if sequences
• identicalassignments: check for x = y ; y = x pairs.
• oddcompoundop: check for odd compound operations
• constswitch: check for switch statements with expressions
• oddcomparisons: check for odd comparisons
• oddmathbits: check for odd uses of math/bits
• floateq: check for exact comparisons of floating point values
• badexponent: check for 2^x and 10^x , which look like exponentiation
• floatloop: check for using floats as loop counters
• urlredacted: check for logging urls without calling url.Redacted()
• sprinterr: check for calling fmt.Sprint(err) instead of err.Error()
• largeloopcopy: check for large value copies in loops
• joinpath: check for using strings.Join() to construct paths
• readfull: check for extra length check for io.ReadFull()
• nilerr: returning an nil error instead of a nil value
• errnetclosed: check for call strings.Contains() to detect net.ErrClosed
• hmac-hash: check for bad hash.New passed to hmac.New()
• readeof: check for ignoring io.EOF as a successful read
• writestring: check for using io.WriteString(w, string(b)) when b is []byte
• badlock: find incorrect lock/unlock pairs for rwmutex
• contexttodo: find context.TODO() usage and suggest to change it _

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