Merge pull request #106 from libtom/fix/106

_base64_decode_internal not compliant with RFC4648

src/headers/tomcrypt_misc.h

@@ -5,14 +5,20 @@ int base64_encode(const unsigned char *in,  unsigned long len,
 
 int base64_decode(const unsigned char *in,  unsigned long len,
                         unsigned char *out, unsigned long *outlen);
+int base64_strict_decode(const unsigned char *in,  unsigned long len,
+                        unsigned char *out, unsigned long *outlen);
 #endif
 
 #ifdef LTC_BASE64_URL
 int base64url_encode(const unsigned char *in,  unsigned long len,
                         unsigned char *out, unsigned long *outlen);
+int base64url_strict_encode(const unsigned char *in,  unsigned long inlen,
+                        unsigned char *out, unsigned long *outlen);
 
 int base64url_decode(const unsigned char *in,  unsigned long len,
                         unsigned char *out, unsigned long *outlen);
+int base64url_strict_decode(const unsigned char *in,  unsigned long len,
+                        unsigned char *out, unsigned long *outlen);
 #endif
 
 /* ===> LTC_HKDF -- RFC5869 HMAC-based Key Derivation Function <=== */

src/misc/base64/base64_decode.c

@@ -71,9 +71,14 @@ static const unsigned char map_base64url[256] = {
 255, 255, 255, 255 };
 #endif /* LTC_BASE64_URL */
 
+enum {
+   relaxed = 0,
+   strict = 1
+};
+
 static int _base64_decode_internal(const unsigned char *in,  unsigned long inlen,
                                  unsigned char *out, unsigned long *outlen,
-                           const unsigned char *map)
+                           const unsigned char *map, int is_strict)
 {
    unsigned long t, x, y, z;
    unsigned char c;
@@ -83,36 +88,42 @@ static int _base64_decode_internal(const unsigned char *in,  unsigned long inlen
    LTC_ARGCHK(out    != NULL);
    LTC_ARGCHK(outlen != NULL);
 
-   g = 3;
+   g = 0; /* '=' counter */
    for (x = y = z = t = 0; x < inlen; x++) {
        c = map[in[x]&0xFF];
-       if (c == 255) continue;
-       /* the final = symbols are read and used to trim the remaining bytes */
        if (c == 254) {
-          c = 0;
+          g++;
-          /* prevent g < 0 which would potentially allow an overflow later */
+          continue;
-          if (--g < 0) {
+       }
-             return CRYPT_INVALID_PACKET;
+       else if (is_strict && g > 0) {
-          }
+          /* we only allow '=' to be at the end */
-       } else if (g != 3) {
-          /* we only allow = to be at the end */
           return CRYPT_INVALID_PACKET;
        }
+       if (c == 255) {
+          if (is_strict)
+             return CRYPT_INVALID_PACKET;
+          else
+             continue;
+       }
 
        t = (t<<6)|c;
 
        if (++y == 4) {
-          if (z + g > *outlen) {
+          if (z + 3 > *outlen) return CRYPT_BUFFER_OVERFLOW;
-             return CRYPT_BUFFER_OVERFLOW;
-          }
           out[z++] = (unsigned char)((t>>16)&255);
-          if (g > 1) out[z++] = (unsigned char)((t>>8)&255);
+          out[z++] = (unsigned char)((t>>8)&255);
-          if (g > 2) out[z++] = (unsigned char)(t&255);
+          out[z++] = (unsigned char)(t&255);
           y = t = 0;
        }
    }
+
    if (y != 0) {
-       return CRYPT_INVALID_PACKET;
+      if (y == 1) return CRYPT_INVALID_PACKET;
+      if ((y + g) != 4 && is_strict && map != map_base64url) return CRYPT_INVALID_PACKET;
+      t = t << (6 * (4 - y));
+      if (z + y - 1 > *outlen) return CRYPT_BUFFER_OVERFLOW;
+      if (y >= 2) out[z++] = (unsigned char) ((t >> 16) & 255);
+      if (y == 3) out[z++] = (unsigned char) ((t >> 8) & 255);
    }
    *outlen = z;
    return CRYPT_OK;
@@ -120,7 +131,7 @@ static int _base64_decode_internal(const unsigned char *in,  unsigned long inlen
 
 #if defined(LTC_BASE64)
 /**
-   base64 decode a block of memory
+   Relaxed base64 decode a block of memory
    @param in       The base64 data to decode
    @param inlen    The length of the base64 data
    @param out      [out] The destination of the binary decoded data
@@ -130,13 +141,27 @@ static int _base64_decode_internal(const unsigned char *in,  unsigned long inlen
 int base64_decode(const unsigned char *in,  unsigned long inlen,
                         unsigned char *out, unsigned long *outlen)
 {
-    return _base64_decode_internal(in, inlen, out, outlen, map_base64);
+    return _base64_decode_internal(in, inlen, out, outlen, map_base64, relaxed);
+}
+
+/**
+   Strict base64 decode a block of memory
+   @param in       The base64 data to decode
+   @param inlen    The length of the base64 data
+   @param out      [out] The destination of the binary decoded data
+   @param outlen   [in/out] The max size and resulting size of the decoded data
+   @return CRYPT_OK if successful
+*/
+int base64_strict_decode(const unsigned char *in,  unsigned long inlen,
+                        unsigned char *out, unsigned long *outlen)
+{
+   return _base64_decode_internal(in, inlen, out, outlen, map_base64, strict);
 }
 #endif /* LTC_BASE64 */
 
 #if defined(LTC_BASE64_URL)
 /**
-   base64 (URL Safe, RFC 4648 section 5) decode a block of memory
+   Relaxed base64 (URL Safe, RFC 4648 section 5) decode a block of memory
    @param in       The base64 data to decode
    @param inlen    The length of the base64 data
    @param out      [out] The destination of the binary decoded data
@@ -146,7 +171,21 @@ int base64_decode(const unsigned char *in,  unsigned long inlen,
 int base64url_decode(const unsigned char *in,  unsigned long inlen,
                            unsigned char *out, unsigned long *outlen)
 {
-    return _base64_decode_internal(in, inlen, out, outlen, map_base64url);
+    return _base64_decode_internal(in, inlen, out, outlen, map_base64url, relaxed);
+}
+
+/**
+   Strict base64 (URL Safe, RFC 4648 section 5) decode a block of memory
+   @param in       The base64 data to decode
+   @param inlen    The length of the base64 data
+   @param out      [out] The destination of the binary decoded data
+   @param outlen   [in/out] The max size and resulting size of the decoded data
+   @return CRYPT_OK if successful
+*/
+int base64url_strict_decode(const unsigned char *in,  unsigned long inlen,
+                           unsigned char *out, unsigned long *outlen)
+{
+    return _base64_decode_internal(in, inlen, out, outlen, map_base64url, strict);
 }
 #endif /* LTC_BASE64_URL */
 

src/misc/base64/base64_encode.c

@@ -110,6 +110,12 @@ int base64url_encode(const unsigned char *in,  unsigned long inlen,
 {
     return _base64_encode_internal(in, inlen, out, outlen, codes_base64url, 0);
 }
+
+int base64url_strict_encode(const unsigned char *in,  unsigned long inlen,
+                           unsigned char *out, unsigned long *outlen)
+{
+    return _base64_encode_internal(in, inlen, out, outlen, codes_base64url, 1);
+}
 #endif /* LTC_BASE64_URL */
 
 #endif

testprof/base64_test.c

@@ -5,6 +5,10 @@ int base64_test(void)
 {
    unsigned char in[64], out[256], tmp[64];
    unsigned long x, l1, l2, slen1;
+   const char special_case[] = {
+         0xbe, 0xe8, 0x92, 0x3c, 0xa2, 0x25, 0xf0, 0xf8,
+         0x91, 0xe4, 0xef, 0xab, 0x0b, 0x8c, 0xfd, 0xff,
+         0x14, 0xd0, 0x29, 0x9d, 0x00 };
 
    /*
     TEST CASES SOURCE:
@@ -24,38 +28,87 @@ int base64_test(void)
        {"foo", "Zm9v"       },
        {"foob", "Zm9vYg=="  },
        {"fooba", "Zm9vYmE=" },
-       {"foobar", "Zm9vYmFy"}
+       {"foobar", "Zm9vYmFy"},
+       {special_case,"vuiSPKIl8PiR5O+rC4z9/xTQKZ0="}
+   };
+
+   const struct {
+      const char* s;
+      int is_strict;
+   } url_cases[] = {
+         {"vuiSPKIl8PiR5O-rC4z9_xTQKZ0", 0},
+         {"vuiSPKIl8PiR5O-rC4z9_xTQKZ0=", 1},
+         {"vuiS*PKIl8P*iR5O-rC4*z9_xTQKZ0", 0},
+         {"vuiS*PKIl8P*iR5O-rC4*z9_xTQKZ0=", 0},
+         {"vuiS*PKIl8P*iR5O-rC4*z9_xTQKZ0==", 0},
+         {"vuiS*PKIl8P*iR5O-rC4*z9_xTQKZ0===", 0},
+         {"vuiS*PKIl8P*iR5O-rC4*z9_xTQKZ0====", 0},
+         {"vuiS*=PKIl8P*iR5O-rC4*z9_xTQKZ0=", 0},
+         {"vuiS*==PKIl8P*iR5O-rC4*z9_xTQKZ0=", 0},
+         {"vuiS*===PKIl8P*iR5O-rC4*z9_xTQKZ0=", 0},
    };
 
    for (x = 0; x < sizeof(cases)/sizeof(cases[0]); ++x) {
+       memset(out, 0, sizeof(out));
+       memset(tmp, 0, sizeof(tmp));
        slen1 = strlen(cases[x].s);
        l1 = sizeof(out);
        DO(base64_encode((unsigned char*)cases[x].s, slen1, out, &l1));
        l2 = sizeof(tmp);
-       DO(base64_decode(out, l1, tmp, &l2));
+       DO(base64_strict_decode(out, l1, tmp, &l2));
-       if (l2 != slen1 || l1 != strlen(cases[x].b64) || memcmp(tmp, cases[x].s, l2) || memcmp(out, cases[x].b64, l1)) {
+       if (compare_testvector(out, l1, cases[x].b64, strlen(cases[x].b64), "base64 encode", x) ||
-           fprintf(stderr, "\nbase64 failed case %lu", x);
+             compare_testvector(tmp, l2, cases[x].s, slen1, "base64 decode", x)) {
-           fprintf(stderr, "\nbase64 should: %s", cases[x].b64);
-           out[sizeof(out)-1] = '\0';
-           fprintf(stderr, "\nbase64 is:     %s", out);
-           fprintf(stderr, "\nplain  should: %s", cases[x].s);
-           tmp[sizeof(tmp)-1] = '\0';
-           fprintf(stderr, "\nplain  is:     %s\n", tmp);
            return 1;
        }
    }
 
+   for (x = 0; x < sizeof(url_cases)/sizeof(url_cases[0]); ++x) {
+       slen1 = strlen(url_cases[x].s);
+       l1 = sizeof(out);
+       if(url_cases[x].is_strict)
+          DO(base64url_strict_decode((unsigned char*)url_cases[x].s, slen1, out, &l1));
+       else
+          DO(base64url_decode((unsigned char*)url_cases[x].s, slen1, out, &l1));
+       if (compare_testvector(out, l1, special_case, strlen(special_case), "base64url decode", x)) {
+           return 1;
+       }
+       if(x < 2) {
+          l2 = sizeof(tmp);
+          if(x == 0)
+             DO(base64url_encode(out, l1, tmp, &l2));
+          else
+             DO(base64url_strict_encode(out, l1, tmp, &l2));
+          if (compare_testvector(tmp, l2, url_cases[x].s, strlen(url_cases[x].s), "base64url encode", x)) {
+              return 1;
+          }
+       }
+   }
+
+   DO(base64url_strict_decode((unsigned char*)url_cases[4].s, slen1, out, &l1) == CRYPT_INVALID_PACKET ? CRYPT_OK : CRYPT_INVALID_PACKET);
+
    for  (x = 0; x < 64; x++) {
        yarrow_read(in, x, &yarrow_prng);
        l1 = sizeof(out);
        DO(base64_encode(in, x, out, &l1));
        l2 = sizeof(tmp);
        DO(base64_decode(out, l1, tmp, &l2));
-       if (l2 != x || memcmp(tmp, in, x)) {
+       if (compare_testvector(tmp, x, in, x, "random base64", x)) {
-           fprintf(stderr, "base64 failed %lu %lu %lu", x, l1, l2);
            return 1;
        }
    }
+
+   x--;
+   memmove(&out[11], &out[10], l1 - 10);
+   out[10] = '=';
+   l1++;
+   l2 = sizeof(tmp);
+   DO(base64_decode(out, l1, tmp, &l2));
+   if (compare_testvector(tmp, l2, in, l2, "relaxed base64 decoding", -1)) {
+       print_hex("input ", out, l1);
+       return 1;
+   }
+   l2 = sizeof(tmp);
+   DO(base64_strict_decode(out, l1, tmp, &l2) == CRYPT_INVALID_PACKET ? CRYPT_OK : CRYPT_INVALID_PACKET);
    return 0;
 }
 #endif