evp enc: cache cipher IV length

Instead of doing a heavy params based query every time a context is asked for
its IV length, this value is cached in the context and only queried if it could
have been modified.

Fixes #17064

Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/17543)

3 files changed, 37 insertions, 17 deletions

diff --git a/crypto/evp/evp_enc.c b/crypto/evp/evp_enc.c
index 1c02cafa16..ff315bd922 100644
--- a/crypto/evp/evp_enc.c
+++ b/crypto/evp/evp_enc.c
@@ -43,6 +43,7 @@ int EVP_CIPHER_CTX_reset(EVP_CIPHER_CTX *ctx)
     if (ctx->fetched_cipher != NULL)
         EVP_CIPHER_free(ctx->fetched_cipher);
     memset(ctx, 0, sizeof(*ctx));
+    ctx->iv_len = -1;
 
     return 1;
 
@@ -61,6 +62,7 @@ int EVP_CIPHER_CTX_reset(EVP_CIPHER_CTX *ctx)
     ENGINE_finish(ctx->engine);
 #endif
     memset(ctx, 0, sizeof(*ctx));
+    ctx->iv_len = -1;
     return 1;
 }
 
@@ -87,6 +89,9 @@ static int evp_cipher_init_internal(EVP_CIPHER_CTX *ctx,
 #if !defined(OPENSSL_NO_ENGINE) && !defined(FIPS_MODULE)
     ENGINE *tmpimpl = NULL;
 #endif
+
+    ctx->iv_len = -1;
+
     /*
      * enc == 1 means we are encrypting.
      * enc == 0 means we are decrypting.
@@ -1079,12 +1084,14 @@ int EVP_CIPHER_CTX_ctrl(EVP_CIPHER_CTX *ctx, int type, int arg, void *ptr)
         if (arg < 0)
             return 0;
         params[0] = OSSL_PARAM_construct_size_t(OSSL_CIPHER_PARAM_IVLEN, &sz);
+        ctx->iv_len = -1;
         break;
     case EVP_CTRL_CCM_SET_L:
         if (arg < 2 || arg > 8)
             return 0;
         sz = 15 - arg;
         params[0] = OSSL_PARAM_construct_size_t(OSSL_CIPHER_PARAM_IVLEN, &sz);
+        ctx->iv_len = -1;
         break;
     case EVP_CTRL_AEAD_SET_IV_FIXED:
         params[0] = OSSL_PARAM_construct_octet_string(
@@ -1248,8 +1255,10 @@ int EVP_CIPHER_get_params(EVP_CIPHER *cipher, OSSL_PARAM params[])
 
 int EVP_CIPHER_CTX_set_params(EVP_CIPHER_CTX *ctx, const OSSL_PARAM params[])
 {
-    if (ctx->cipher != NULL && ctx->cipher->set_ctx_params != NULL)
+    if (ctx->cipher != NULL && ctx->cipher->set_ctx_params != NULL) {
+        ctx->iv_len = -1;
         return ctx->cipher->set_ctx_params(ctx->algctx, params);
+    }
     return 0;
 }
 
diff --git a/crypto/evp/evp_lib.c b/crypto/evp/evp_lib.c
index 3d261c282f..8bac09bba0 100644
--- a/crypto/evp/evp_lib.c
+++ b/crypto/evp/evp_lib.c
@@ -504,23 +504,33 @@ int EVP_CIPHER_get_iv_length(const EVP_CIPHER *cipher)
 
 int EVP_CIPHER_CTX_get_iv_length(const EVP_CIPHER_CTX *ctx)
 {
-    int rv, len = EVP_CIPHER_get_iv_length(ctx->cipher);
-    size_t v = len;
-    OSSL_PARAM params[2] = { OSSL_PARAM_END, OSSL_PARAM_END };
-
-    params[0] = OSSL_PARAM_construct_size_t(OSSL_CIPHER_PARAM_IVLEN, &v);
-    rv = evp_do_ciph_ctx_getparams(ctx->cipher, ctx->algctx, params);
-    if (rv == EVP_CTRL_RET_UNSUPPORTED)
-        goto legacy;
-    return rv != 0 ? (int)v : -1;
-    /* Code below to be removed when legacy support is dropped. */
-legacy:
-    if ((EVP_CIPHER_get_flags(ctx->cipher) & EVP_CIPH_CUSTOM_IV_LENGTH) != 0) {
-        rv = EVP_CIPHER_CTX_ctrl((EVP_CIPHER_CTX *)ctx, EVP_CTRL_GET_IVLEN,
-                                 0, &len);
-        return (rv == 1) ? len : -1;
+    if (ctx->iv_len < 0) {
+        int rv, len = EVP_CIPHER_get_iv_length(ctx->cipher);
+        size_t v = len;
+        OSSL_PARAM params[2] = { OSSL_PARAM_END, OSSL_PARAM_END };
+
+        params[0] = OSSL_PARAM_construct_size_t(OSSL_CIPHER_PARAM_IVLEN, &v);
+        rv = evp_do_ciph_ctx_getparams(ctx->cipher, ctx->algctx, params);
+        if (rv != EVP_CTRL_RET_UNSUPPORTED) {
+            if (rv <= 0)
+                return -1;
+            len = (int)v;
+        }
+        /* Code below to be removed when legacy support is dropped. */
+        else if ((EVP_CIPHER_get_flags(ctx->cipher)
+                  & EVP_CIPH_CUSTOM_IV_LENGTH) != 0) {
+            rv = EVP_CIPHER_CTX_ctrl((EVP_CIPHER_CTX *)ctx, EVP_CTRL_GET_IVLEN,
+                                     0, &len);
+            if (rv <= 0)
+                return -1;
+        }
+        /*-
+         * Casting away the const is annoying but required here.  We need to
+         * cache the result for performance reasons.
+         */
+        ((EVP_CIPHER_CTX *)ctx)->iv_len = len;
     }
-    return len;
+    return ctx->iv_len;
 }
 
 int EVP_CIPHER_CTX_get_tag_length(const EVP_CIPHER_CTX *ctx)
diff --git a/crypto/evp/evp_local.h b/crypto/evp/evp_local.h
index d9e1ca997e..8b114d362d 100644
--- a/crypto/evp/evp_local.h
+++ b/crypto/evp/evp_local.h
@@ -46,6 +46,7 @@ struct evp_cipher_ctx_st {
     /* FIXME: Should this even exist? It appears unused */
     void *app_data;             /* application stuff */
     int key_len;                /* May change for variable length cipher */
+    int iv_len;                 /* IV length */
     unsigned long flags;        /* Various flags */
     void *cipher_data;          /* per EVP data */
     int final_used;