Add support for custom signature parameters

Many signature types define the digest and public key type by a single OID
such as ecdsa_with_sha256.

Some types (RSA-PSS for example) use a single OID to indicate the signature
scheme and additional parameters are encoded in the AlgorithmIdentifier.

Add an X509_SIG_INFO structure to contain details about the signature type:
specifically the digest algorithm, public key algorithm, security bits and
various flags. This supports both existing algorithms and more complex
types.

Add accessors for the structure and a special case that retrieves signature
information from a certificate.

Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/3301)

1 files changed, 77 insertions, 0 deletions

diff --git a/crypto/x509/x509_set.c b/crypto/x509/x509_set.c
index e46174a..08b71ff 100644
--- a/crypto/x509/x509_set.c
+++ b/crypto/x509/x509_set.c
@@ -13,7 +13,10 @@
 #include <openssl/objects.h>
 #include <openssl/evp.h>
 #include <openssl/x509.h>
+#include <openssl/x509v3.h>
+#include "internal/asn1_int.h"
 #include "internal/x509_int.h"
+#include "x509_lcl.h"
 
 int X509_set_version(X509 *x, long version)
 {
@@ -157,3 +160,77 @@ const X509_ALGOR *X509_get0_tbs_sigalg(const X509 *x)
 {
     return &x->cert_info.signature;
 }
+
+int X509_SIG_INFO_get(const X509_SIG_INFO *siginf, int *mdnid, int *pknid,
+                      int *secbits, uint32_t *flags)
+{
+    if (mdnid != NULL)
+        *mdnid = siginf->mdnid;
+    if (pknid != NULL)
+        *pknid = siginf->pknid;
+    if (secbits != NULL)
+        *secbits = siginf->secbits;
+    if (flags != NULL)
+        *flags = siginf->flags;
+    return (siginf->flags & X509_SIG_INFO_VALID) != 0;
+}
+
+void X509_SIG_INFO_set(X509_SIG_INFO *siginf, int mdnid, int pknid,
+                       int secbits, uint32_t flags)
+{
+    siginf->mdnid = mdnid;
+    siginf->pknid = pknid;
+    siginf->secbits = secbits;
+    siginf->flags = flags;
+}
+
+int X509_get_signature_info(X509 *x, int *mdnid, int *pknid, int *secbits,
+                            uint32_t *flags)
+{
+    X509_check_purpose(x, -1, -1);
+    return X509_SIG_INFO_get(&x->siginf, mdnid, pknid, secbits, flags);
+}
+
+static void x509_sig_info_init(X509_SIG_INFO *siginf, const X509_ALGOR *alg,
+                               const ASN1_STRING *sig)
+{
+    int pknid, mdnid;
+    const EVP_MD *md;
+
+    siginf->mdnid = NID_undef;
+    siginf->pknid = NID_undef;
+    siginf->secbits = -1;
+    siginf->flags = 0;
+    if (!OBJ_find_sigid_algs(OBJ_obj2nid(alg->algorithm), &mdnid, &pknid)
+            || pknid == NID_undef)
+        return;
+    siginf->pknid = pknid;
+    if (mdnid == NID_undef) {
+        /* If we have one, use a custom handler for this algorithm */
+        const EVP_PKEY_ASN1_METHOD *ameth = EVP_PKEY_asn1_find(NULL, pknid);
+        if (ameth == NULL || ameth->siginf_set == NULL
+                || ameth->siginf_set(siginf, alg, sig) == 0)
+            return;
+        siginf->flags |= X509_SIG_INFO_VALID;
+        return;
+    }
+    siginf->flags |= X509_SIG_INFO_VALID;
+    siginf->mdnid = mdnid;
+    md = EVP_get_digestbynid(mdnid);
+    if (md == NULL)
+        return;
+    /* Security bits: half number of bits in digest */
+    siginf->secbits = EVP_MD_size(md) * 4;
+    switch (mdnid) {
+        case NID_sha1:
+        case NID_sha256:
+        case NID_sha384:
+        case NID_sha512:
+        siginf->flags |= X509_SIG_INFO_TLS;
+    }
+}
+
+void x509_init_sig_info(X509 *x)
+{
+    x509_sig_info_init(&x->siginf, &x->sig_alg, &x->signature);
+}