java.lang.IllegalArgumentException: bad utf-8 byte dc at offset 000000eb

[iBotPeaches]

I frequently am finding dex files like this and previously it was fixed in smali 2.3. Though since in this same application classes13.dex is a completely empty file - I'm partial to believing this is just a corrupted useless file.

➜  3503 java -jar ./smali/baksmali/build/libs/baksmali.jar d classes1.dex                      
Exception in thread "main" java.lang.IllegalArgumentException: bad utf-8 byte dc at offset 000000eb
	at com.android.tools.smali.util.Utf8Utils.throwBadUtf8(Utf8Utils.java:284)
	at com.android.tools.smali.util.Utf8Utils.utf8BytesWithUtf16LengthToString(Utf8Utils.java:220)
	at com.android.tools.smali.dexlib2.dexbacked.DexReader.readString(DexReader.java:610)
	at com.android.tools.smali.dexlib2.dexbacked.DexBackedDexFile$5.get(DexBackedDexFile.java:326)
	at com.android.tools.smali.dexlib2.dexbacked.DexBackedDexFile$5.get(DexBackedDexFile.java:319)
	at com.android.tools.smali.dexlib2.dexbacked.DexBackedDexFile$6.get(DexBackedDexFile.java:362)
	at com.android.tools.smali.dexlib2.dexbacked.DexBackedDexFile$6.get(DexBackedDexFile.java:357)
	at com.android.tools.smali.dexlib2.dexbacked.DexBackedClassDef.getType(DexBackedClassDef.java:107)
	at com.android.tools.smali.dexlib2.util.SyntheticAccessorResolver.<init>(SyntheticAccessorResolver.java:80)
	at com.android.tools.smali.baksmali.DisassembleCommand.getOptions(DisassembleCommand.java:287)
	at com.android.tools.smali.baksmali.DisassembleCommand.run(DisassembleCommand.java:182)
	at com.android.tools.smali.baksmali.Main.main(Main.java:101)

context: iBotPeaches/Apktool#3503
file above: classes1.zip

[sgjesse]

Thank you for including the problematic dex file. It is a very small dex with only 5 strings, and looking at the encoding it is indeed an illegal encoding. Dumping the bytes of the 5 strings gives:

stringIDs.length: 5
Length of 0: 23
4c 61 6e 64 72 6f 69 64 2f 61 70 70 2f 41 63 74 69 76 69 74 79 3b 0
Length of 1: 17
4c 63 6f 6d 2f 6c 69 61 70 70 2f c 2f da dc 3b 0
Length of 2: 2
56 0
Length of 3: 3
da dc 0
Length of 4: 8
da dc 2e 6a 61 76 61 0

The two bytes 0xda and 0xdc of the last string both has the two upper bits set. If the first bytes is 0b110XXXXX then the second must be 0b10XXXXXX for a valid encoding.

I have landed https://r8-review.googlesource.com/c/r8/+/90260 to give a bit more information on the decoding issue.

[iBotPeaches]

thanks! I'll close this out when I see it land in GitHub

[sgjesse]

The R8 source is not in GitHub, but on googlesource.com. Change with better error reporting is in 8.4.21-dev.

[iBotPeaches]

Thanks apologies - I was so used to just watching smali in GitHub and was unaware of parent dependencies and how they played out in Google ecosystem.

[sgjesse]

That said, let's keep this open, and I will extend the error messages in dexlib2/src/main/java/com/android/tools/smali/util/Utf8Utils.java to what I added to R8.

[iBotPeaches]

Thanks for the reference/link to R8 @sgjesse - I had no idea it worked for regular Java projects. I moved Apktool over and it seems to have solved my last remaining issues on the way to making reproducible builds - iBotPeaches/Apktool#3559