Prevent calling decryption in an encryption context and vice versa

Reviewed-by: Matthias St. Pierre <Matthias.St.Pierre@ncp-e.com>
(Merged from https://github.com/openssl/openssl/pull/7856)

1 files changed, 36 insertions, 4 deletions

diff --git a/crypto/evp/evp_enc.c b/crypto/evp/evp_enc.c
index 0c740d1679..c63fb53ac8 100644
--- a/crypto/evp/evp_enc.c
+++ b/crypto/evp/evp_enc.c
@@ -317,8 +317,9 @@ int EVP_DecryptInit_ex(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *cipher,
     return EVP_CipherInit_ex(ctx, cipher, impl, key, iv, 0);
 }
 
-int EVP_EncryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl,
-                      const unsigned char *in, int inl)
+static int evp_EncryptDecryptUpdate(EVP_CIPHER_CTX *ctx,
+                                    unsigned char *out, int *outl,
+                                    const unsigned char *in, int inl)
 {
     int i, j, bl;
 
@@ -380,6 +381,18 @@ int EVP_EncryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl,
     return 1;
 }
 
+int EVP_EncryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl,
+                      const unsigned char *in, int inl)
+{
+    /* Prevent accidental use of decryption context when encrypting */
+    if (!ctx->encrypt) {
+        EVPerr(EVP_F_EVP_ENCRYPTUPDATE, EVP_R_INVALID_OPERATION);
+        return 0;
+    }
+
+    return evp_EncryptDecryptUpdate(ctx, out, outl, in, inl);
+}
+
 int EVP_EncryptFinal(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl)
 {
     int ret;
@@ -392,6 +405,12 @@ int EVP_EncryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl)
     int n, ret;
     unsigned int i, b, bl;
 
+    /* Prevent accidental use of decryption context when encrypting */
+    if (!ctx->encrypt) {
+        EVPerr(EVP_F_EVP_ENCRYPTFINAL_EX, EVP_R_INVALID_OPERATION);
+        return 0;
+    }
+
     if (ctx->cipher->flags & EVP_CIPH_FLAG_CUSTOM_CIPHER) {
         ret = M_do_cipher(ctx, out, NULL, 0);
         if (ret < 0)
@@ -435,6 +454,12 @@ int EVP_DecryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl,
     int fix_len;
     unsigned int b;
 
+    /* Prevent accidental use of encryption context when decrypting */
+    if (ctx->encrypt) {
+        EVPerr(EVP_F_EVP_DECRYPTUPDATE, EVP_R_INVALID_OPERATION);
+        return 0;
+    }
+
     if (ctx->cipher->flags & EVP_CIPH_FLAG_CUSTOM_CIPHER) {
         fix_len = M_do_cipher(ctx, out, in, inl);
         if (fix_len < 0) {
@@ -451,7 +476,7 @@ int EVP_DecryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl,
     }
 
     if (ctx->flags & EVP_CIPH_NO_PADDING)
-        return EVP_EncryptUpdate(ctx, out, outl, in, inl);
+        return evp_EncryptDecryptUpdate(ctx, out, outl, in, inl);
 
     b = ctx->cipher->block_size;
     OPENSSL_assert(b <= sizeof(ctx->final));
@@ -463,7 +488,7 @@ int EVP_DecryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl,
     } else
         fix_len = 0;
 
-    if (!EVP_EncryptUpdate(ctx, out, outl, in, inl))
+    if (!evp_EncryptDecryptUpdate(ctx, out, outl, in, inl))
         return 0;
 
     /*
@@ -494,6 +519,13 @@ int EVP_DecryptFinal_ex(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl)
 {
     int i, n;
     unsigned int b;
+
+    /* Prevent accidental use of encryption context when decrypting */
+    if (ctx->encrypt) {
+        EVPerr(EVP_F_EVP_DECRYPTFINAL_EX, EVP_R_INVALID_OPERATION);
+        return 0;
+    }
+
     *outl = 0;
 
     if (ctx->cipher->flags & EVP_CIPH_FLAG_CUSTOM_CIPHER) {