今天逆向某app时，发现了最后一步base64编码后后几位不一致。
之前有遇到空格及换行等问题，eg :
在在线工具生成对比后，确实后几位有出入。
回看了代码base64就是调用的标准算法，且也没更换码表。
# hyqBFS+m9jNbmIrG0x0dAYJzG5jiqgwFr+SxV0hRMwGDFcDI+5oJxwtU1mcglidAqD7xOELt1bcUpO1vacWssh487vfpQ98NntxvTIUcVrnHUKNDvwOVKCwp++nRePzSfW3y6f3F/4P0fZrdMLy8S5G9A95UHF2ZC3aZoSOw89+92auduE8fx8CLSEcyqHMNYglPCspJ7U5D6MgHgi9DNG+7e962E/xDDuO2RCjCmL8lznpb/7nHv9gDbg7WfBmAFAEZlwya74RkARDQ+2y6i/no60H1W33ocZb3R96ejQ0kPrzuqWB/hOnoavR7TPyhpEcdFb/1MgyRAatn3p14Lpp8AzT50CXmW5MIfKdUOTggAHm51fRfBL/kfwzmeC2KVCCyYsmj/A8vx9WzL5YwQtGIe2/JCbKgR4h8SW/x8V5RyMJX1OOj0B82TljOarPAxAGUyfKWqWlAWcJuW2maeR78AzL6Q9aW9tiQfho3loewpVfjXW0DQjCF1hpoaHrumId6gxsWet48O+7dTKrkbR+dSQz1a+h4C1BEypYLy+Sy7mYVG6uGJSYqc+HeT2qocf/+FQVqrmYGSEua1Xg5IpJKHz5uV5+6dn4bceDZ3AjWUuB2Rac25h7SHeNDJobYsdxFuwYiG9+AcncZv+1nrSA0aqhqn1oYsl4wkRIsV0UYHA4N9yTuIO730mZQy2NR7jQyemQUZa8MIVf1mAcX8kqrtoQjEfApNUEOblCqPFxp1wWzpAB9YZ0mpwFjqzXLTd4vDhH93LzV0+OL51PamGH0uy63mvK+GrmDjybkVXV2Qc/mp/DeGTFFf0Cz10ul0Be63zR8haMMwD/nRnLgy/JXTfKaAc/LNpkryKtfAiMQ574rCaXKq3+izLPStMl4b3eVnBxzRwru+V1Tkjp229t46fh29ZvfnhH9nZGkWbvoq4bjk49qDJMC264aqkkrVTsxFLf1RWAPtoMdaywUZQ==# 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众所周知，base64是以6位进行便宜，而正常是8个bit位，这样就会缺两位进行==补位。
祥细解说及码表更换base64：https://codeooo.blog.csdn.net/article/details/119810268
经过分析代码：
而我们常规的：
public static final String m54667a(String str, String str2) { String str3 = "(this as java.lang.String).getBytes(charset)"; m73751b(str, "content"); m73751b(str2, "password"); byte[] bArr = null; try { byte[] bytes = str2.getBytes(StandardCharsets.UTF_8); m73745a((Object) bytes, str3); SecretKeySpec secretKeySpec = new SecretKeySpec(bytes, "AES"); Cipher instance = Cipher.getInstance("AES/CBC/PKCS5Padding"); Charset forName = StandardCharsets.UTF_8; m73745a((Object) forName, "Charset.forName(charsetName)"); byte[] bytes2 = str.getBytes(forName); m73745a((Object) bytes2, str3); byte[] bytes3 = str2.getBytes(StandardCharsets.UTF_8); m73745a((Object) bytes3, str3); instance.init(1, secretKeySpec, new IvParameterSpec(bytes3)); String encodeToString = Base64.getEncoder().encodeToString(instance.doFinal(bytes2)); m73745a((Object) encodeToString, "Base64.encodeToString(en…ptResult, Base64.NO_WRAP)"); return encodeToString; } catch (Exception e) { e.printStackTrace(); return ""; } }
故而我们可以使用：
引入一个三方jar包：
com.akdeniz.googleplaycrawler.misc.Base64
import com.akdeniz.googleplaycrawler.misc.Base64; //导入依赖的package包/类public class encryptString { public static String main(String str2Encrypt) throws Exception { byte[] keyByteArray = Base64.decode(GOOGLE_PUBLIC_KEY, Base64.DEFAULT); byte[] header = new byte[5]; byte[] digest = MessageDigest.getInstance("SHA-1").digest(keyByteArray); header[0] = 0; System.arraycopy(digest, 0, header, 1, 4); PublicKey publicKey = createKey(keyByteArray); Cipher cipher = Cipher.getInstance("RSA/ECB/OAEPWITHSHA1ANDMGF1PADDING"); byte[] bytes2Encrypt = str2Encrypt.getBytes("UTF-8"); int len = ((bytes2Encrypt.length - 1) / 86) + 1; byte[] cryptedBytes = new byte[len * 133]; for (int j = 0; j < len; j++) { cipher.init(1, publicKey); byte[] arrayOfByte4 = cipher.doFinal(bytes2Encrypt, j * 86, (bytes2Encrypt.length - j * 86)); System.arraycopy(header, 0, cryptedBytes, j * 133, header.length); System.arraycopy(arrayOfByte4, 0, cryptedBytes, j * 133 + header.length, arrayOfByte4.length); } return Base64.encodeToString(cryptedBytes, 10); }}另一种解决方案：
直接将安卓的base64代码copy进来，就一个文件
package android.util;import java.io.UnsupportedEncodingException;public class Base64 { public static final int DEFAULT = 0; public static final int NO_PADDING = 1; public static final int NO_WRAP = 2; public static final int CRLF = 4; public static final int URL_SAFE = 8; public static final int NO_CLOSE = 16; // -------------------------------------------------------- // shared code // -------------------------------------------------------- static abstract class Coder { public byte[] output; public int op; public abstract boolean process(byte[] input, int offset, int len, boolean finish); public abstract int maxOutputSize(int len); } // -------------------------------------------------------- // decoding // -------------------------------------------------------- public static byte[] decode(String str, int flags) { return decode(str.getBytes(), flags); } public static byte[] decode(byte[] input, int flags) { return decode(input, 0, input.length, flags); } public static byte[] decode(byte[] input, int offset, int len, int flags) { // Allocate space for the most data the input could represent. // (It could contain less if it contains whitespace, etc.) Decoder decoder = new Decoder(flags, new byte[len*3/4]); if (!decoder.process(input, offset, len, true)) { throw new IllegalArgumentException("bad base-64"); } // Maybe we got lucky and allocated exactly enough output space. if (decoder.op == decoder.output.length) { return decoder.output; } // Need to shorten the array, so allocate a new one of the // right size and copy. byte[] temp = new byte[decoder.op]; System.arraycopy(decoder.output, 0, temp, 0, decoder.op); return temp; } static class Decoder extends Coder { private static final int DECODE[] = { -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -2, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, }; private static final int DECODE_WEBSAFE[] = { -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -2, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, 63, -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, }; private static final int SKIP = -1; private static final int EQUALS = -2; private int state; // state number (0 to 6) private int value; final private int[] alphabet; public Decoder(int flags, byte[] output) { this.output = output; alphabet = ((flags & URL_SAFE) == 0) ? DECODE : DECODE_WEBSAFE; state = 0; value = 0; } public int maxOutputSize(int len) { return len * 3/4 + 10; } public boolean process(byte[] input, int offset, int len, boolean finish) { if (this.state == 6) return false; int p = offset; len += offset; // Using local variables makes the decoder about 12% // faster than if we manipulate the member variables in // the loop. (Even alphabet makes a measurable // difference, which is somewhat surprising to me since // the member variable is final.) int state = this.state; int value = this.value; int op = 0; final byte[] output = this.output; final int[] alphabet = this.alphabet; while (p < len) { // Try the fast path: we're starting a new tuple and the // next four bytes of the input stream are all data // bytes. This corresponds to going through states // 0-1-2-3-0. We expect to use this method for most of // the data. // // If any of the next four bytes of input are non-data // (whitespace, etc.), value will end up negative. (All // the non-data values in decode are small negative // numbers, so shifting any of them up and or'ing them // together will result in a value with its top bit set.) // // You can remove this whole block and the output should // be the same, just slower. if (state == 0) { while (p+4 <= len && (value = ((alphabet[input[p] & 0xff] << 18) | (alphabet[input[p+1] & 0xff] << 12) | (alphabet[input[p+2] & 0xff] << 6) | (alphabet[input[p+3] & 0xff]))) >= 0) { output[op+2] = (byte) value; output[op+1] = (byte) (value >> 8); output[op] = (byte) (value >> 16); op += 3; p += 4; } if (p >= len) break; } // The fast path isn't available -- either we've read a // partial tuple, or the next four input bytes aren't all // data, or whatever. Fall back to the slower state // machine implementation. int d = alphabet[input[p++] & 0xff]; switch (state) { case 0: if (d >= 0) { value = d; ++state; } else if (d != SKIP) { this.state = 6; return false; } break; case 1: if (d >= 0) { value = (value << 6) | d; ++state; } else if (d != SKIP) { this.state = 6; return false; } break; case 2: if (d >= 0) { value = (value << 6) | d; ++state; } else if (d == EQUALS) { // Emit the last (partial) output tuple; // expect exactly one more padding character. output[op++] = (byte) (value >> 4); state = 4; } else if (d != SKIP) { this.state = 6; return false; } break; case 3: if (d >= 0) { // Emit the output triple and return to state 0. value = (value << 6) | d; output[op+2] = (byte) value; output[op+1] = (byte) (value >> 8); output[op] = (byte) (value >> 16); op += 3; state = 0; } else if (d == EQUALS) { // Emit the last (partial) output tuple; // expect no further data or padding characters. output[op+1] = (byte) (value >> 2); output[op] = (byte) (value >> 10); op += 2; state = 5; } else if (d != SKIP) { this.state = 6; return false; } break; case 4: if (d == EQUALS) { ++state; } else if (d != SKIP) { this.state = 6; return false; } break; case 5: if (d != SKIP) { this.state = 6; return false; } break; } } if (!finish) { // We're out of input, but a future call could provide // more. this.state = state; this.value = value; this.op = op; return true; } // Done reading input. Now figure out where we are left in // the state machine and finish up. switch (state) { case 0: // Output length is a multiple of three. Fine. break; case 1: // Read one extra input byte, which isn't enough to // make another output byte. Illegal. this.state = 6; return false; case 2: // Read two extra input bytes, enough to emit 1 more // output byte. Fine. output[op++] = (byte) (value >> 4); break; case 3: // Read three extra input bytes, enough to emit 2 more // output bytes. Fine. output[op++] = (byte) (value >> 10); output[op++] = (byte) (value >> 2); break; case 4: // Read one padding '=' when we expected 2. Illegal. this.state = 6; return false; case 5: // Read all the padding '='s we expected and no more. // Fine. break; } this.state = state; this.op = op; return true; } } // -------------------------------------------------------- // encoding // -------------------------------------------------------- public static String encodeToString(byte[] input, int flags) { try { return new String(encode(input, flags), "US-ASCII"); } catch (UnsupportedEncodingException e) { // US-ASCII is guaranteed to be available. throw new AssertionError(e); } } public static String encodeToString(byte[] input, int offset, int len, int flags) { try { return new String(encode(input, offset, len, flags), "US-ASCII"); } catch (UnsupportedEncodingException e) { // US-ASCII is guaranteed to be available. throw new AssertionError(e); } } public static byte[] encode(byte[] input, int flags) { return encode(input, 0, input.length, flags); } public static byte[] encode(byte[] input, int offset, int len, int flags) { Encoder encoder = new Encoder(flags, null); // Compute the exact length of the array we will produce. int output_len = len / 3 * 4; // Account for the tail of the data and the padding bytes, if any. if (encoder.do_padding) { if (len % 3 > 0) { output_len += 4; } } else { switch (len % 3) { case 0: break; case 1: output_len += 2; break; case 2: output_len += 3; break; } } // Account for the newlines, if any. if (encoder.do_newline && len > 0) { output_len += (((len-1) / (3 * Encoder.LINE_GROUPS)) + 1) * (encoder.do_cr ? 2 : 1); } encoder.output = new byte[output_len]; encoder.process(input, offset, len, true); assert encoder.op == output_len; return encoder.output; } static class Encoder extends Coder { public static final int LINE_GROUPS = 19; private static final byte ENCODE[] = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/', }; private static final byte ENCODE_WEBSAFE[] = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '-', '_', }; final private byte[] tail; int tailLen; private int count; final public boolean do_padding; final public boolean do_newline; final public boolean do_cr; final private byte[] alphabet; public Encoder(int flags, byte[] output) { this.output = output; do_padding = (flags & NO_PADDING) == 0; do_newline = (flags & NO_WRAP) == 0; do_cr = (flags & CRLF) != 0; alphabet = ((flags & URL_SAFE) == 0) ? ENCODE : ENCODE_WEBSAFE; tail = new byte[2]; tailLen = 0; count = do_newline ? LINE_GROUPS : -1; } public int maxOutputSize(int len) { return len * 8/5 + 10; } public boolean process(byte[] input, int offset, int len, boolean finish) { // Using local variables makes the encoder about 9% faster. final byte[] alphabet = this.alphabet; final byte[] output = this.output; int op = 0; int count = this.count; int p = offset; len += offset; int v = -1; // First we need to concatenate the tail of the previous call // with any input bytes available now and see if we can empty // the tail. switch (tailLen) { case 0: // There was no tail. break; case 1: if (p+2 <= len) { // A 1-byte tail with at least 2 bytes of // input available now. v = ((tail[0] & 0xff) << 16) |((input[p++] & 0xff) << 8) |(input[p++] & 0xff); tailLen = 0; }; break; case 2: if (p+1 <= len) { // A 2-byte tail with at least 1 byte of input. v = ((tail[0] & 0xff) << 16) |((tail[1] & 0xff) << 8) |(input[p++] & 0xff); tailLen = 0; } break; } if (v != -1) { output[op++] = alphabet[(v >> 18) & 0x3f]; output[op++] = alphabet[(v >> 12) & 0x3f]; output[op++] = alphabet[(v >> 6) & 0x3f]; output[op++] = alphabet[v & 0x3f]; if (--count == 0) { if (do_cr) output[op++] = '\r'; output[op++] = '\n'; count = LINE_GROUPS; } } // At this point either there is no tail, or there are fewer // than 3 bytes of input available. // The main loop, turning 3 input bytes into 4 output bytes on // each iteration. while (p+3 <= len) { v = ((input[p] & 0xff) << 16) | ((input[p+1] & 0xff) << 8) | (input[p+2] & 0xff); output[op] = alphabet[(v >> 18) & 0x3f]; output[op+1] = alphabet[(v >> 12) & 0x3f]; output[op+2] = alphabet[(v >> 6) & 0x3f]; output[op+3] = alphabet[v & 0x3f]; p += 3; op += 4; if (--count == 0) { if (do_cr) output[op++] = '\r'; output[op++] = '\n'; count = LINE_GROUPS; } } if (finish) { // Finish up the tail of the input. Note that we need to // consume any bytes in tail before any bytes // remaining in input; there should be at most two bytes // total. if (p-tailLen == len-1) { int t = 0; v = ((tailLen > 0 ? tail[t++] : input[p++]) & 0xff) << 4; tailLen -= t; output[op++] = alphabet[(v >> 6) & 0x3f]; output[op++] = alphabet[v & 0x3f]; if (do_padding) { output[op++] = '='; output[op++] = '='; } if (do_newline) { if (do_cr) output[op++] = '\r'; output[op++] = '\n'; } } else if (p-tailLen == len-2) { int t = 0; v = (((tailLen > 1 ? tail[t++] : input[p++]) & 0xff) << 10) | (((tailLen > 0 ? tail[t++] : input[p++]) & 0xff) << 2); tailLen -= t; output[op++] = alphabet[(v >> 12) & 0x3f]; output[op++] = alphabet[(v >> 6) & 0x3f]; output[op++] = alphabet[v & 0x3f]; if (do_padding) { output[op++] = '='; } if (do_newline) { if (do_cr) output[op++] = '\r'; output[op++] = '\n'; } } else if (do_newline && op > 0 && count != LINE_GROUPS) { if (do_cr) output[op++] = '\r'; output[op++] = '\n'; } assert tailLen == 0; assert p == len; } else { // Save the leftovers in tail to be consumed on the next // call to encodeInternal. if (p == len-1) { tail[tailLen++] = input[p]; } else if (p == len-2) { tail[tailLen++] = input[p]; tail[tailLen++] = input[p+1]; } } this.op = op; this.count = count; return true; } } private Base64() { } // don't instantiate}
完美解决~
来源地址：https://blog.csdn.net/qq_41369057/article/details/131323360
