Re: [PATCH] signature: do not report wrong data for pkc#7 signature

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On 11/15/18 1:29 PM, Yauheni Kaliuta wrote:
when PKC#7 signing method is used the old structure doesn't contain
any useful data, but the data are encoded in the certificate.

The info getting/showing code is not aware of that at the moment and
since 0 is a valid constant, shows, for example, wrong "md4" for the
hash algo.

The patch splits the 2 mothods of gethering the info and reports
"unknown" for the algo.

Signed-off-by: Yauheni Kaliuta <yauheni.kaliuta@xxxxxxxxxx>
---
  libkmod/libkmod-module.c    |  2 +-
  libkmod/libkmod-signature.c | 69 +++++++++++++++++++++++++++----------
  2 files changed, 52 insertions(+), 19 deletions(-)

diff --git a/libkmod/libkmod-module.c b/libkmod/libkmod-module.c
index ee420f4ec2bf..889f26479a98 100644
--- a/libkmod/libkmod-module.c
+++ b/libkmod/libkmod-module.c
@@ -2273,7 +2273,7 @@ KMOD_EXPORT int kmod_module_get_info(const struct kmod_module *mod, struct kmod_
  	struct kmod_elf *elf;
  	char **strings;
  	int i, count, ret = -ENOMEM;
-	struct kmod_signature_info sig_info;
+	struct kmod_signature_info sig_info = {};
if (mod == NULL || list == NULL)
  		return -ENOENT;
diff --git a/libkmod/libkmod-signature.c b/libkmod/libkmod-signature.c
index 1f3e26dea203..2ec2dc1a1a73 100644
--- a/libkmod/libkmod-signature.c
+++ b/libkmod/libkmod-signature.c
@@ -92,6 +92,44 @@ struct module_signature {
  	uint32_t sig_len;    /* Length of signature data (big endian) */
  };
+static bool
+kmod_module_signature_info_default(const char *mem,
+				   off_t size,
+				   const struct module_signature *modsig,
+				   size_t sig_len,
+				   struct kmod_signature_info *sig_info)
+{
+	size -= sig_len;
+	sig_info->sig = mem + size;
+	sig_info->sig_len = sig_len;
+
+	size -= modsig->key_id_len;
+	sig_info->key_id = mem + size;
+	sig_info->key_id_len = modsig->key_id_len;
+
+	size -= modsig->signer_len;
+	sig_info->signer = mem + size;
+	sig_info->signer_len = modsig->signer_len;
+
+	sig_info->algo = pkey_algo[modsig->algo];
+	sig_info->hash_algo = pkey_hash_algo[modsig->hash];
+	sig_info->id_type = pkey_id_type[modsig->id_type];
+
+	return true;
+}
+
+static bool
+kmod_module_signature_info_pkcs7(const char *mem,

I miss a verb in these function names. Those seem more reasonable:

static bool fill_default() { }
static bool fill_unknown() { }


Otherwise looks good.

thanks
Lucas De Marchi

+				 off_t size,
+				 const struct module_signature *modsig,
+				 size_t sig_len,
+				 struct kmod_signature_info *sig_info)
+{
+	sig_info->hash_algo = "unknown";
+	sig_info->id_type = pkey_id_type[modsig->id_type];
+	return true;
+}
+
  #define SIG_MAGIC "~Module signature appended~\n"
/*
@@ -111,7 +149,7 @@ bool kmod_module_signature_info(const struct kmod_file *file, struct kmod_signat
  	off_t size;
  	const struct module_signature *modsig;
  	size_t sig_len;
-
+	bool ret;
size = kmod_file_get_size(file);
  	mem = kmod_file_get_contents(file);
@@ -134,21 +172,16 @@ bool kmod_module_signature_info(const struct kmod_file *file, struct kmod_signat
  	    size < (int64_t)(modsig->signer_len + modsig->key_id_len + sig_len))
  		return false;
- size -= sig_len;
-	sig_info->sig = mem + size;
-	sig_info->sig_len = sig_len;
-
-	size -= modsig->key_id_len;
-	sig_info->key_id = mem + size;
-	sig_info->key_id_len = modsig->key_id_len;
-
-	size -= modsig->signer_len;
-	sig_info->signer = mem + size;
-	sig_info->signer_len = modsig->signer_len;
-
-	sig_info->algo = pkey_algo[modsig->algo];
-	sig_info->hash_algo = pkey_hash_algo[modsig->hash];
-	sig_info->id_type = pkey_id_type[modsig->id_type];
-
-	return true;
+	switch (modsig->id_type) {
+	case PKEY_ID_PKCS7:
+		ret = kmod_module_signature_info_pkcs7(mem, size,
+						       modsig, sig_len,
+						       sig_info);
+		break;
+	default:
+		ret = kmod_module_signature_info_default(mem, size,
+							 modsig, sig_len,
+							 sig_info);
+	}
+	return ret;
  }




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