EVP_DigestSignInit failed, error 0x0000000d?

[noloader@xxxxxxxxx (Jeffrey Walton)]

What does it mean when EVP_DigestSignInit fails with an error code of
0x0000000d?

On failure, the code is being fetched with ERR_get_error().

----------

$ /usr/local/ssl/bin/openssl errstr 0x0d
error:0000000D:lib(0):func(0):ASN1 lib

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I see its declared in evp.h, but I don't see a body anywhere.

$ grep -R EVP_DigestSignInit  *
apps/dgst.c:            r = EVP_DigestSignInit(mctx, &pctx, md, NULL, sigkey);
apps/req.c:    if (!EVP_DigestSignInit(ctx, &pkctx, md, NULL, pkey))
...
crypto/evp/evp.h:int    EVP_DigestSignInit(EVP_MD_CTX *ctx, EVP_PKEY_CTX **pctx,
...