[PATCH 11/14] verification: introduce verify_pgp_signature()

[Roberto Sassu]

Introduce verify_pgp_signature() to verify PGP signatures from detached
data. It will be used by fsverity and by IMA.

Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
---
 certs/system_keyring.c       | 70 ++++++++++++++++++++++++++++++++++++
 include/linux/verification.h | 23 ++++++++++++
 2 files changed, 93 insertions(+)

diff --git a/certs/system_keyring.c b/certs/system_keyring.c
index 692365dee2bd..26a11b1dcd59 100644
--- a/certs/system_keyring.c
+++ b/certs/system_keyring.c
@@ -16,6 +16,7 @@
 #include <keys/asymmetric-type.h>
 #include <keys/system_keyring.h>
 #include <crypto/pkcs7.h>
+#include <crypto/pgp.h>
 #include "common.h"
 
 static struct key *builtin_trusted_keys;
@@ -289,6 +290,75 @@ int verify_pkcs7_signature(const void *data, size_t len,
 }
 EXPORT_SYMBOL_GPL(verify_pkcs7_signature);
 
+#ifdef CONFIG_PGP_KEY_PARSER
+/**
+ * verify_pgp_signature - Verify a PGP-based signature on system data.
+ * @data: The data to be verified (must be provided).
+ * @len: Size of @data.
+ * @raw_pgp: The PGP message that is the signature.
+ * @pgp_len: The size of @raw_pgp.
+ * @trusted_keys: Trusted keys to use (NULL for builtin trusted keys only,
+ *					(void *)1UL for all trusted keys).
+ * @usage: The use to which the key is being put.
+ * @view_content: Callback to gain access to content.
+ * @ctx: Context for callback.
+ */
+int verify_pgp_signature(const void *data, size_t len,
+			 const void *raw_pgp, size_t pgp_len,
+			 struct key *trusted_keys,
+			 enum key_being_used_for usage,
+			 int (*view_content)(void *ctx,
+					     const void *data, size_t len,
+					     size_t asn1hdrlen),
+			 void *ctx)
+{
+	struct pgp_sig_verify *pgp_ctx;
+	int ret;
+
+	if (!data || !len)
+		return -EINVAL;
+
+	pgp_ctx = pgp_sig_parse(raw_pgp, pgp_len);
+	if (IS_ERR(pgp_ctx))
+		return PTR_ERR(pgp_ctx);
+
+	if (!trusted_keys) {
+		trusted_keys = builtin_trusted_keys;
+	} else if (trusted_keys == VERIFY_USE_SECONDARY_KEYRING) {
+#ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
+		trusted_keys = secondary_trusted_keys;
+#else
+		trusted_keys = builtin_trusted_keys;
+#endif
+	} else if (trusted_keys == VERIFY_USE_PLATFORM_KEYRING) {
+#ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
+		trusted_keys = platform_trusted_keys;
+#else
+		trusted_keys = NULL;
+#endif
+		if (!trusted_keys) {
+			ret = -ENOKEY;
+			pr_devel("PGP platform keyring is not available\n");
+			goto error;
+		}
+	}
+
+	/* The data should be detached - so we need to supply it. */
+	if (pgp_sig_add_data(pgp_ctx, data, len)) {
+		pr_err("Failed to supply data for PGP signature\n");
+		ret = -EBADMSG;
+		goto error;
+	}
+
+	ret = pgp_sig_verify(pgp_ctx, trusted_keys);
+error:
+	pgp_sig_verify_cancel(pgp_ctx, false);
+	pr_devel("<==%s() = %d\n", __func__, ret);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(verify_pgp_signature);
+
+#endif /* CONFIG_PGP_KEY_PARSER */
 #endif /* CONFIG_SYSTEM_DATA_VERIFICATION */
 
 #ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
diff --git a/include/linux/verification.h b/include/linux/verification.h
index a655923335ae..c27516d68962 100644
--- a/include/linux/verification.h
+++ b/include/linux/verification.h
@@ -54,6 +54,29 @@ extern int verify_pkcs7_message_sig(const void *data, size_t len,
 							size_t asn1hdrlen),
 				    void *ctx);
 
+#ifdef CONFIG_PGP_KEY_PARSER
+extern int verify_pgp_signature(const void *data, size_t len,
+				const void *raw_pgp, size_t pgp_len,
+				struct key *trusted_keys,
+				enum key_being_used_for usage,
+				int (*view_content)(void *ctx,
+						const void *data, size_t len,
+						size_t asn1hdrlen),
+				void *ctx);
+#else
+static inline int verify_pgp_signature(const void *data, size_t len,
+				const void *raw_pgp, size_t pgp_len,
+				struct key *trusted_keys,
+				enum key_being_used_for usage,
+				int (*view_content)(void *ctx,
+						const void *data, size_t len,
+						size_t asn1hdrlen),
+				void *ctx)
+{
+	return -EOPNOTSUPP;
+}
+#endif /* CONFIG_PGP_KEY_PARSER */
+
 #ifdef CONFIG_SIGNED_PE_FILE_VERIFICATION
 extern int verify_pefile_signature(const void *pebuf, unsigned pelen,
 				   struct key *trusted_keys,
-- 
2.32.0