Handle PKCS#5 padding in the gcrypt backend.

diff --git a/src/gcrypt/cipher.c b/src/gcrypt/cipher.c
index 518879b..2e8e057 100644 (file)
--- a/src/gcrypt/cipher.c
+++ b/src/gcrypt/cipher.c
@@ -107,11 +107,9 @@ static bool cipher_open(cipher_t *cipher, int algo, int mode) {
        }
 
        cipher->keylen = gcry_cipher_get_algo_keylen(algo);
-       if(mode == GCRY_CIPHER_MODE_ECB || mode == GCRY_CIPHER_MODE_CBC)
-               cipher->blklen = gcry_cipher_get_algo_blklen(algo);
-       else
-               cipher->blklen = 0;
+       cipher->blklen = gcry_cipher_get_algo_blklen(algo);
        cipher->key = xmalloc(cipher->keylen + cipher->blklen);
+       cipher->padding = mode == GCRY_CIPHER_MODE_ECB || mode == GCRY_CIPHER_MODE_CBC;
 
        return true;
 }
@@ -190,62 +188,67 @@ bool cipher_regenerate_key(cipher_t *cipher, bool encrypt) {
        return true;
 }
 
-static bool cipher_add_padding(cipher_t *cipher, void *indata, size_t inlen, size_t *outlen) {
-       size_t reqlen;
-
-       if(cipher->blklen == 1) {
-               *outlen = inlen;
-               return true;
-       }
-
-       reqlen = ((inlen + 1) / cipher->blklen) * cipher->blklen;
-       if(reqlen > *outlen)
-               return false;
-
-       // add padding
+bool cipher_encrypt(cipher_t *cipher, const void *indata, size_t inlen, void *outdata, size_t *outlen, bool oneshot) {
+       gcry_error_t err;
+       uint8_t pad[cipher->blklen];
 
-       *outlen = reqlen;
-       return true;
-}
+       if(cipher->padding) {
+               if(!oneshot)
+                       return false;
 
-static bool cipher_remove_padding(cipher_t *cipher, void *indata, size_t inlen, size_t *outlen) {
-       size_t origlen;
+               size_t reqlen = ((inlen + 1) / cipher->blklen) * cipher->blklen;
+               uint8_t padbyte = reqlen - inlen;
+               inlen = reqlen - cipher->blklen;
 
-       if(cipher->blklen == 1) {
-               *outlen = inlen;
-               return true;
+               for(int i = 0; i < cipher->blklen; i++)
+                       if(i < cipher->blklen - padbyte)
+                               pad[i] = ((uint8_t *)indata)[inlen + i];
+                       else
+                               pad[i] = padbyte;
        }
-
-       if(inlen % cipher->blklen)
+       
+       if((err = gcry_cipher_encrypt(cipher->handle, outdata, *outlen, indata, inlen))) {
+               logger(LOG_ERR, "Error while encrypting: %s", gcry_strerror(err));
                return false;
+       }
+
+       if(cipher->padding) {
+               if((err = gcry_cipher_encrypt(cipher->handle, outdata + inlen, cipher->blklen, pad, cipher->blklen))) {
+                       logger(LOG_ERR, "Error while encrypting: %s", gcry_strerror(err));
+                       return false;
+               }
 
-       // check and remove padding
+               inlen += cipher->blklen;
+       }
 
-       *outlen = origlen;
+       *outlen = inlen;
        return true;
 }
 
-bool cipher_encrypt(cipher_t *cipher, const void *indata, size_t inlen, void *outdata, size_t *outlen, bool oneshot) {
+bool cipher_decrypt(cipher_t *cipher, const void *indata, size_t inlen, void *outdata, size_t *outlen, bool oneshot) {
        gcry_error_t err;
 
-       // To be fixed
-
-       if((err = gcry_cipher_encrypt(cipher->handle, outdata, inlen, indata, inlen))) {
-               logger(LOG_ERR, "Error while encrypting: %s", gcry_strerror(err));
+       if((err = gcry_cipher_decrypt(cipher->handle, outdata, *outlen, indata, inlen))) {
+               logger(LOG_ERR, "Error while decrypting: %s", gcry_strerror(err));
                return false;
        }
 
-       return true;
-}
+       if(cipher->padding) {
+               if(!oneshot)
+                       return false;
 
-bool cipher_decrypt(cipher_t *cipher, const void *indata, size_t inlen, void *outdata, size_t *outlen, bool oneshot) {
-       gcry_error_t err;
+               uint8_t padbyte = ((uint8_t *)outdata)[inlen - 1];
 
-       // To be fixed
+               if(padbyte == 0 || padbyte > cipher->blklen || padbyte > inlen)
+                       return false;
 
-       if((err = gcry_cipher_decrypt(cipher->handle, outdata, inlen, indata, inlen))) {
-               logger(LOG_ERR, "Error while decrypting: %s", gcry_strerror(err));
-               return false;
+               size_t origlen = inlen - padbyte;
+
+               for(int i = inlen - 1; i >= origlen; i--)
+                       if(((uint8_t *)indata)[i] != padbyte)
+                               return false;
+
+               *outlen = origlen;
        }
 
        return true;

diff --git a/src/gcrypt/cipher.h b/src/gcrypt/cipher.h
index 57c8128..8e4a2eb 100644 (file)
--- a/src/gcrypt/cipher.h
+++ b/src/gcrypt/cipher.h
@@ -32,6 +32,7 @@ typedef struct cipher {
        int nid;
        uint16_t keylen;
        uint16_t blklen;
+       bool padding;
 } cipher_t;
 
 extern bool cipher_open_by_name(struct cipher *, const char *);