1 //===- Base64.cpp ---------------------------------------------------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 #define INVALID_BASE64_BYTE 64 10 #include "llvm/Support/Base64.h" 11 12 static char decodeBase64Byte(uint8_t Ch) { 13 constexpr char Inv = INVALID_BASE64_BYTE; 14 static const char DecodeTable[] = { 15 Inv, Inv, Inv, Inv, Inv, Inv, Inv, Inv, // ........ 16 Inv, Inv, Inv, Inv, Inv, Inv, Inv, Inv, // ........ 17 Inv, Inv, Inv, Inv, Inv, Inv, Inv, Inv, // ........ 18 Inv, Inv, Inv, Inv, Inv, Inv, Inv, Inv, // ........ 19 Inv, Inv, Inv, Inv, Inv, Inv, Inv, Inv, // ........ 20 Inv, Inv, Inv, 62, Inv, Inv, Inv, 63, // ...+.../ 21 52, 53, 54, 55, 56, 57, 58, 59, // 01234567 22 60, 61, Inv, Inv, Inv, 0, Inv, Inv, // 89...=.. 23 Inv, 0, 1, 2, 3, 4, 5, 6, // .ABCDEFG 24 7, 8, 9, 10, 11, 12, 13, 14, // HIJKLMNO 25 15, 16, 17, 18, 19, 20, 21, 22, // PQRSTUVW 26 23, 24, 25, Inv, Inv, Inv, Inv, Inv, // XYZ..... 27 Inv, 26, 27, 28, 29, 30, 31, 32, // .abcdefg 28 33, 34, 35, 36, 37, 38, 39, 40, // hijklmno 29 41, 42, 43, 44, 45, 46, 47, 48, // pqrstuvw 30 49, 50, 51 // xyz..... 31 }; 32 if (Ch >= sizeof(DecodeTable)) 33 return Inv; 34 return DecodeTable[Ch]; 35 } 36 37 llvm::Error llvm::decodeBase64(llvm::StringRef Input, 38 std::vector<char> &Output) { 39 constexpr char Base64InvalidByte = INVALID_BASE64_BYTE; 40 // Invalid table value with short name to fit in the table init below. The 41 // invalid value is 64 since valid base64 values are 0 - 63. 42 Output.clear(); 43 const uint64_t InputLength = Input.size(); 44 if (InputLength == 0) 45 return Error::success(); 46 // Make sure we have a valid input string length which must be a multiple 47 // of 4. 48 if ((InputLength % 4) != 0) 49 return createStringError(std::errc::illegal_byte_sequence, 50 "Base64 encoded strings must be a multiple of 4 " 51 "bytes in length"); 52 const uint64_t FirstValidEqualIdx = InputLength - 2; 53 char Hex64Bytes[4]; 54 for (uint64_t Idx = 0; Idx < InputLength; Idx += 4) { 55 for (uint64_t ByteOffset = 0; ByteOffset < 4; ++ByteOffset) { 56 const uint64_t ByteIdx = Idx + ByteOffset; 57 const char Byte = Input[ByteIdx]; 58 const char DecodedByte = decodeBase64Byte(Byte); 59 bool Illegal = DecodedByte == Base64InvalidByte; 60 if (!Illegal && Byte == '=') { 61 if (ByteIdx < FirstValidEqualIdx) { 62 // We have an '=' in the middle of the string which is invalid, only 63 // the last two characters can be '=' characters. 64 Illegal = true; 65 } else if (ByteIdx == FirstValidEqualIdx && Input[ByteIdx + 1] != '=') { 66 // We have an equal second to last from the end and the last character 67 // is not also an equal, so the '=' character is invalid 68 Illegal = true; 69 } 70 } 71 if (Illegal) 72 return createStringError( 73 std::errc::illegal_byte_sequence, 74 "Invalid Base64 character %#2.2x at index %" PRIu64, Byte, ByteIdx); 75 Hex64Bytes[ByteOffset] = DecodedByte; 76 } 77 // Now we have 6 bits of 3 bytes in value in each of the Hex64Bytes bytes. 78 // Extract the right bytes into the Output buffer. 79 Output.push_back((Hex64Bytes[0] << 2) + ((Hex64Bytes[1] >> 4) & 0x03)); 80 Output.push_back((Hex64Bytes[1] << 4) + ((Hex64Bytes[2] >> 2) & 0x0f)); 81 Output.push_back((Hex64Bytes[2] << 6) + (Hex64Bytes[3] & 0x3f)); 82 } 83 // If we had valid trailing '=' characters strip the right number of bytes 84 // from the end of the output buffer. We already know that the Input length 85 // it a multiple of 4 and is not zero, so direct character access is safe. 86 if (Input.back() == '=') { 87 Output.pop_back(); 88 if (Input[InputLength - 2] == '=') 89 Output.pop_back(); 90 } 91 return Error::success(); 92 } 93