如何使全局環境中的用戶定義函數的源代碼在 R 中無法訪問？ （用於教育目的）

Question

我是一名分子生物學講師，由於學校已經上線，我不得不想辦法繼續進行“實驗”。 我決定在 R 中進行我的“實驗”，因為孩子們已經可以使用它了。

我編寫了一個函數，通過使用某些數字來模擬數據，學生將被要求使用輸出來計算這些數字。

我計划為他們提供作為全局環境對象的功能。 但是，我不希望他們使用getAnywhere()函數跳轉到源代碼，並查看那里的數字並簡單地復制 + 粘貼內容。 有沒有辦法讓我的用戶定義函數的源代碼無法訪問？ 我知道隱藏代碼並不酷，但為了在線教學，我會這樣做。 如果沒有辦法，那么我會嘗試找到另一種解決方案。

Answer 1

我想如果這是出於教育目的，那么合理的遮蔽嘗試就足夠了。 這是一個函數，它將任何其他函數作為參數並返回一個具有相同行為但其代碼不是人類可讀的函數：

obscure <- function(func) {
  f <- as.character(body(func))
  r <- charToRaw(paste(paste(f, collapse = "\n"), "}", sep = "\n"))
  bod <- as.call(list(quote(eval), as.call(list(quote(parse), 
                      text = as.call(list(quote(eval), 
                             as.call(list(quote(rawToChar), r))))))))
  as.function(c(formals(func), bod))
}

因此，假設您想隱藏一個封閉形式的斐波那契生成器：

fib <- function(n) {
  round(((5 + sqrt(5)) / 10) * (( 1 + sqrt(5)) / 2) ** (1:n - 1))
}

fib(10)
#> [1]  1  1  2  3  5  8 13 21 34 55

您需要做的就是：

fib <- obscure(fib)
fib(10)
#> [1]  1  1  2  3  5  8 13 21 34 55

但是如果你看一下函數本身，它現在看起來像這樣：

fib
#> function (n) 
#> eval(parse(text = eval(rawToChar(as.raw(c(0x7b, 0x0a, 0x72, 0x6f, 
#> 0x75, 0x6e, 0x64, 0x28, 0x28, 0x28, 0x35, 0x20, 0x2b, 0x20, 0x73, 
#> 0x71, 0x72, 0x74, 0x28, 0x35, 0x29, 0x29, 0x2f, 0x31, 0x30, 0x29, 
#> 0x20, 0x2a, 0x20, 0x28, 0x28, 0x31, 0x20, 0x2b, 0x20, 0x73, 0x71, 
#> 0x72, 0x74, 0x28, 0x35, 0x29, 0x29, 0x2f, 0x32, 0x29, 0x5e, 0x28, 
#> 0x31, 0x3a, 0x6e, 0x20, 0x2d, 0x20, 0x31, 0x29, 0x29, 0x0a, 0x7d
#> ))))))
#> <environment: 0x0000025b9f7dc068>

當然，高級用戶可能會在幾分鍾內對其進行逆向工程，但是如果您正在教授 R 課程，我猜大多數學生會看到這一點並放棄。

Answer 2

這是一種很難逆轉的方法。 它使用walkast包來混淆函數調用。

本質上，它將f(x)替換為{randomstring <- f; randomNumber randomOperator randomNumber; randomstring(x)} {randomstring <- f; randomNumber randomOperator randomNumber; randomstring(x)}

修改runif(1, min = 0, max = 1)的min和max ，使其在您的秘密數字范圍內。

obfuscate <- function(f) {
  result <- f
  
  body(result) <- walkast::walk_ast(
    body(result),
    walkast::make_visitor(
      hd = function(f) {
        new_name <- as.name(paste0("x", runif(1, 0, 100000000)))
        decoy_f <- as.name(sample(c("+", "-", "*", "/", "%%", "%*%"), 1))
        bquote({
          .(new_name) <- .(f)
          .(decoy_f)(.(runif(1, min = 0, max = 1)), .(runif(1, min = 0, max = 1)))
          .(new_name)
        })
      }
    )
  )
  result
}


fib <- function(n) {
  round(((5 + sqrt(5)) / 10) * (( 1 + sqrt(5)) / 2) ** (1:n - 1))
}

obfuscate(fib)產生以下函數（這並不難逆轉）。

function (n) 
{
    x67911473.8479257 <- `{`
    0.130855958675966%%0.881266586482525
    x67911473.8479257
}({
    x76250116.8530434 <- round
    0.302100569708273 - 0.405373327899724
    x76250116.8530434
}({
    x82210419.5132852 <- `*`
    0.49425036739558 + 0.228636586572975
    x82210419.5132852
}({
    x15765817.3236996 <- `(`
    0.797338604461402 %*% 0.514307061443105
    x15765817.3236996
}({
    x71525579.597801 <- `/`
    0.909275721525773 %*% 0.446680159773678
    x71525579.597801
}({
    x30879483.6513698 <- `(`
    0.383802859345451%%0.83112145261839
    x30879483.6513698
}({
    x27604046.7899293 <- `+`
    0.876430705189705/0.856748269638047
    x27604046.7899293
}(5, {
    x73314726.5156731 <- sqrt
    0.708666266873479/0.336862851632759
    x73314726.5156731
}(5))), 10)), {
    x70590986.6606817 <- `^`
    0.566703328397125%%0.671325634233654
    x70590986.6606817
}({
    x24871017.2018036 <- `(`
    0.0474121794104576 + 0.763756504980847
    x24871017.2018036
}({
    x88098038.5933071 <- `/`
    0.328246646560729 + 0.514381068525836
    x88098038.5933071
}({
    x36233226.7919555 <- `(`
    0.000577503815293312/0.30069664795883
    x36233226.7919555
}({
    x96489506.5175369 <- `+`
    0.836315712891519%%0.218373921466991
    x96489506.5175369
}(1, {
    x65204835.5899751 <- sqrt
    0.546689067035913/0.838512626476586
    x65204835.5899751
}(5))), 2)), {
    x41097439.0804768 <- `(`
    0.318402596283704 + 0.181835192954168
    x41097439.0804768
}({
    x14225565.2230233 <- `-`
    0.0201902554836124 - 0.763278516940773
    x14225565.2230233
}({
    x67021324.7649372 <- `:`
    0.603728511603549/0.995236924383789
    x67021324.7649372
}(1, n), 1))))))

但是，可以多次調用obfuscate 。 obfuscate(obfuscate(fib))結果如下

function (n) 
{
    x13820952.9686719 <- {
        x14231921.8954071 <- `{`
        0.964784309733659 - 0.318950723856688
        x14231921.8954071
    }({
        x98483844.473958 <- `<-`
        0.499919829424471 %*% 0.25088473292999
        x98483844.473958
    }(x77140931.5057099, `{`), {
        x71807632.4323192 <- `+`
        0.704186083516106 + 0.909325393149629
        x71807632.4323192
    }(0.508911525830626, 0.712898454861715), x77140931.5057099)
    0.915209622122347 + 0.290264912880957
    x13820952.9686719
}({
    x34399270.1265961 <- {
        x98775665.2990356 <- `{`
        0.581808406859636 %*% 0.577146121067926
        x98775665.2990356
    }({
        x72328119.2127615 <- `<-`
        0.989937041886151 %*% 0.646907166577876
        x72328119.2127615
    }(x52481220.1270834, round), {
        x6828759.70378518 <- `%*%`
        0.27078406792134/0.295143382623792
        x6828759.70378518
    }(0.801469809608534, 0.987752696499228), x52481220.1270834)
    0.922306241467595 - 0.56200037105009
    x34399270.1265961
}({
    x94231348.6244529 <- {
        x57375249.103643 <- `{`
        0.72766156680882 * 0.781972301891074
        x57375249.103643
    }({
        x3551404.13157642 <- `<-`
        0.0673318353947252%%0.513684156117961
        x3551404.13157642
    }(x3026251.47160143, `*`), {
        x12980086.7522135 <- `*`
        0.215703511377797 + 0.520233752438799
        x12980086.7522135
    }(0.569129609037191, 0.133742173202336), x3026251.47160143)
    0.510110176866874 - 0.0307286188472062
    x94231348.6244529
}({
    x89750883.4721521 <- {
        x600093.929097056 <- `{`
        0.321572621352971 %*% 0.0427047829143703
        x600093.929097056
    }({
        x71001436.9338751 <- `<-`
        0.771520792506635 %*% 0.772518398938701
        x71001436.9338751
    }(x25210925.8202836, `(`), {
        x68944892.520085 <- `*`
        0.268720921361819 %*% 0.425112737575546
        x68944892.520085
    }(0.52520202845335, 0.656426891451702), x25210925.8202836)
    0.47237404435873 * 0.495256265625358
    x89750883.4721521
}({
    x71292330.3479329 <- {
        x51233950.9557933 <- `{`
        0.357416934100911/0.0655053614173084
        x51233950.9557933
    }({
        x30669082.3053941 <- `<-`
        0.534916127100587 + 0.67862187908031
        x30669082.3053941
    }(x47235390.8233345, `/`), {
        x15582043.2817563 <- `/`
        0.873394214781001 * 0.931123967515305
        x15582043.2817563
    }(0.986741927452385, 0.742083500837907), x47235390.8233345)
    0.15898777008988%%0.68169358978048
    x71292330.3479329
}({
    x32579387.0491907 <- {
        x73828555.5504262 <- `{`
        0.978108135983348 - 0.102359032956883
        x73828555.5504262
    }({
        x49107574.8577714 <- `<-`
        0.7187738600187/0.428680357057601
        x49107574.8577714
    }(x57762583.6245716, `(`), {
        x57358532.4920714 <- `*`
        0.178639843361452 * 0.673680510604754
        x57358532.4920714
    }(0.204503980930895, 0.0359067062381655), x57762583.6245716)
    0.0257267474662513/0.612508951220661
    x32579387.0491907
}({
    x96714596.9159901 <- {
        x11374640.2319521 <- `{`
        0.0720340947154909 + 0.944227180676535
        x11374640.2319521
    }({
        x62696768.6694115 <- `<-`
        0.639268048806116%%0.525764014804736
        x62696768.6694115
    }(x76306633.4184259, `+`), {
        x42795905.0051868 <- `+`
        0.94626947841607 + 0.515851546544582
        x42795905.0051868
    }(0.904065714450553, 0.583518052240834), x76306633.4184259)
    0.604620382655412 * 0.631076122168452
    x96714596.9159901
}(5, {
    x83315562.5732616 <- {
        x83753042.9475009 <- `{`
        0.349399645114318 + 0.651053918525577
        x83753042.9475009
    }({
        x69223746.0520118 <- `<-`
        0.29312734818086 * 0.881964908912778
        x69223746.0520118
    }(x73975120.1821491, sqrt), {
        x67292128.5731718 <- `+`
        0.480338253779337 - 0.482176560908556
        x67292128.5731718
    }(0.601392406970263, 0.380848217988387), x73975120.1821491)
    0.0832952118944377 + 0.0914795149583369
    x83315562.5732616
}(5))), 10)), {
    x98729057.8894317 <- {
        x77170495.1068386 <- `{`
        0.227124285651371/0.278982728952542
        x77170495.1068386
    }({
        x48747039.726004 <- `<-`
        0.782126144738868 * 0.675149171613157
        x48747039.726004
    }(x89894129.1496158, `^`), {
        x96451648.7671062 <- `%%`
        0.715406887698919 %*% 0.282268565380946
        x96451648.7671062
    }(0.27587090106681, 0.145314523251727), x89894129.1496158)
    0.381198771763593%%0.307774103712291
    x98729057.8894317
}({
    x97305397.3633796 <- {
        x70868420.926854 <- `{`
        0.277484080987051 + 0.973759955028072
        x70868420.926854
    }({
        x72545721.4051858 <- `<-`
        0.50800796574913 * 0.856975607108325
        x72545721.4051858
    }(x33412416.2793159, `(`), {
        x20543128.5547093 <- `*`
        0.219559877878055%%0.570555842481554
        x20543128.5547093
    }(0.106497411616147, 0.345936729339883), x33412416.2793159)
    0.706679665949196 * 0.461514561669901
    x97305397.3633796
}({
    x92932011.8622854 <- {
        x25150360.353291 <- `{`
        0.945939902681857 + 0.0913955171126872
        x25150360.353291
    }({
        x31840611.0163778 <- `<-`
        0.00124536827206612 * 0.692353655351326
        x31840611.0163778
    }(x61161323.3806565, `/`), {
        x63229239.1266674 <- `%*%`
        0.56810829625465%%0.350754451937973
        x63229239.1266674
    }(0.266102685593069, 0.217837403062731), x61161323.3806565)
    0.544797678478062 * 0.0696846419014037
    x92932011.8622854
}({
    x72556719.5564508 <- {
        x2918882.92413205 <- `{`
        0.382788195740432%%0.233721876982599
        x2918882.92413205
    }({
        x1332410.1222679 <- `<-`
        0.121992226224393 + 0.0637996080331504
        x1332410.1222679
    }(x88590273.0282396, `(`), {
        x84656940.9128278 <- `*`
        0.363471970660612 * 0.967681086389348
        x84656940.9128278
    }(0.47135023586452, 0.495704435743392), x88590273.0282396)
    0.802222049562261 %*% 0.314430670579895
    x72556719.5564508
}({
    x33861630.6427866 <- {
        x7418637.51318306 <- `{`
        0.00906742154620588%%0.331271679606289
        x7418637.51318306
    }({
        x69295283.2672745 <- `<-`
        0.00934437615796924 %*% 0.161317143123597
        x69295283.2672745
    }(x49074813.9331117, `+`), {
        x42538731.6150591 <- `*`
        0.713973646285012/0.187995387706906
        x42538731.6150591
    }(0.276253602933139, 0.325099671958014), x49074813.9331117)
    0.527837971923873 * 0.880572498776019
    x33861630.6427866
}(1, {
    x77607083.4835991 <- {
        x68655005.4699183 <- `{`
        0.858293377095833%%0.16589346411638
        x68655005.4699183
    }({
        x20779904.4670537 <- `<-`
        0.0172271258197725 - 0.85583262424916
        x20779904.4670537
    }(x63671239.4887581, sqrt), {
        x92613451.6252205 <- `%*%`
        0.921735821058974 + 0.557587723247707
        x92613451.6252205
    }(0.53566943667829, 0.865151737350971), x63671239.4887581)
    0.357367471093312 * 0.977310829563066
    x77607083.4835991
}(5))), 2)), {
    x48921614.093706 <- {
        x57634989.1722202 <- `{`
        0.408984839916229 + 0.219921594019979
        x57634989.1722202
    }({
        x20686308.6903468 <- `<-`
        0.87269201874733 * 0.290828781668097
        x20686308.6903468
    }(x31356643.6292604, `(`), {
        x54914335.5572596 <- `/`
        0.42553190421313 * 0.873098325682804
        x54914335.5572596
    }(0.809229557868093, 0.487828205805272), x31356643.6292604)
    0.903046790510416%%0.475023675011471
    x48921614.093706
}({
    x46909810.5793819 <- {
        x71135967.9931775 <- `{`
        0.534440700896084 - 0.723820263287053
        x71135967.9931775
    }({
        x40692157.0654958 <- `<-`
        0.809898991836235 * 0.154304394498467
        x40692157.0654958
    }(x25574955.6235969, `-`), {
        x87320719.3100825 <- `-`
        0.171987064182758 * 0.565342281479388
        x87320719.3100825
    }(0.353071014164016, 0.349617956206203), x25574955.6235969)
    0.145128468051553 + 0.605287740007043
    x46909810.5793819
}({
    x76092396.4902759 <- {
        x33732652.5477692 <- `{`
        0.427568282932043/0.671309909550473
        x33732652.5477692
    }({
        x17347284.3598574 <- `<-`
        0.135752162430435%%0.060178006067872
        x17347284.3598574
    }(x64530064.5381212, `:`), {
        x49644516.8508217 <- `%*%`
        0.75615629600361 * 0.157231835182756
        x49644516.8508217
    }(0.353608228033409, 0.409501505084336), x64530064.5381212)
    0.827440596884117 - 0.0416028220206499
    x76092396.4902759
}(1, n), 1))))))

您可以任意多次調用obfuscate 。 調用它 4 次會產生超過 4k 行代碼

f <- fib
for (i in 1:4) {
  f <- obfuscate(f)
}
length(readLines(textConnection(as.character(body(f)))))
#> 4354