Better error messages if there are no encoders/decoders/store loaders

If you don't have the base or default providers loaded and therefore there
are no encoders/decoders or store loaders then the error messages can be
cryptic. We provide better hints about how to fix the problem.

Fixes #13798

Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/15306)

3 files changed, 18 insertions, 0 deletions

diff --git a/crypto/encode_decode/decoder_err.c b/crypto/encode_decode/decoder_err.c
index 1880c8f409..c948d82698 100644
--- a/crypto/encode_decode/decoder_err.c
+++ b/crypto/encode_decode/decoder_err.c
@@ -17,6 +17,8 @@
 static const ERR_STRING_DATA OSSL_DECODER_str_reasons[] = {
     {ERR_PACK(ERR_LIB_OSSL_DECODER, 0, OSSL_DECODER_R_COULD_NOT_DECODE_OBJECT),
     "could not decode object"},
+    {ERR_PACK(ERR_LIB_OSSL_DECODER, 0, OSSL_DECODER_R_DECODER_NOT_FOUND),
+    "decoder not found"},
     {ERR_PACK(ERR_LIB_OSSL_DECODER, 0, OSSL_DECODER_R_MISSING_GET_PARAMS),
     "missing get params"},
     {0, NULL}
diff --git a/crypto/encode_decode/decoder_lib.c b/crypto/encode_decode/decoder_lib.c
index 8a5082c441..c7eac0eddd 100644
--- a/crypto/encode_decode/decoder_lib.c
+++ b/crypto/encode_decode/decoder_lib.c
@@ -48,6 +48,14 @@ int OSSL_DECODER_from_bio(OSSL_DECODER_CTX *ctx, BIO *in)
     int ok = 0;
     BIO *new_bio = NULL;
 
+    if (OSSL_DECODER_CTX_get_num_decoders(ctx) == 0) {
+        ERR_raise_data(ERR_LIB_OSSL_DECODER, OSSL_DECODER_R_DECODER_NOT_FOUND,
+                       "No decoders were found. For standard decoders you need "
+                       "at least one of the default or base providers "
+                       "available. Did you forget to load them?");
+        return 0;
+    }
+
     if (BIO_tell(in) < 0) {
         new_bio = BIO_new(BIO_f_readbuffer());
         if (new_bio == NULL)
diff --git a/crypto/encode_decode/encoder_lib.c b/crypto/encode_decode/encoder_lib.c
index ea0a556e56..f074c9fb60 100644
--- a/crypto/encode_decode/encoder_lib.c
+++ b/crypto/encode_decode/encoder_lib.c
@@ -49,6 +49,14 @@ int OSSL_ENCODER_to_bio(OSSL_ENCODER_CTX *ctx, BIO *out)
     data.bio = out;
     data.current_encoder_inst_index = OSSL_ENCODER_CTX_get_num_encoders(ctx);
 
+    if (data.current_encoder_inst_index == 0) {
+        ERR_raise_data(ERR_LIB_OSSL_ENCODER, OSSL_ENCODER_R_ENCODER_NOT_FOUND,
+                       "No encoders were found. For standard encoders you need "
+                       "at least one of the default or base providers "
+                       "available. Did you forget to load them?");
+        return 0;
+    }
+
     return encoder_process(&data) > 0;
 }