ktrace: Record detailed ECAPMODE violations

When a Capsicum violation occurs in the kernel, ktrace will now record
detailed information pertaining to the violation.

For example:
- When a namei lookup violation occurs, ktrace will record the path.
- When a signal violation occurs, ktrace will record the signal number.
- When a sendto(2) violation occurs, ktrace will record the recipient
  sockaddr.

For all violations, the syscall and ABI is recorded.

kdump is also modified to display this new information to the user.

Reviewed by:	oshogbo, markj
Approved by:	markj (mentor)
MFC after:	1 month
Differential Revision:	https://reviews.freebsd.org/D40676

sys/kern/kern_ktrace.c

@@ -923,14 +923,17 @@ ktrstructarray(const char *name, enum uio_seg seg, const void *data,
 }
 
 void
-ktrcapfail(enum ktr_cap_fail_type type, const cap_rights_t *needed,
-    const cap_rights_t *held)
+ktrcapfail(enum ktr_cap_violation type, const void *data)
 {
 	struct thread *td = curthread;
 	struct ktr_request *req;
 	struct ktr_cap_fail *kcf;
+	union ktr_cap_data *kcd;
 
-	if (__predict_false(curthread->td_pflags & TDP_INKTRACE))
+	if (__predict_false(td->td_pflags & TDP_INKTRACE))
+		return;
+	if (type != CAPFAIL_SYSCALL &&
+	    (td->td_sa.callp->sy_flags & SYF_CAPENABLED) == 0)
 		return;
 
 	req = ktr_getrequest(KTR_CAPFAIL);
@@ -938,14 +941,32 @@ ktrcapfail(enum ktr_cap_fail_type type, const cap_rights_t *needed,
 		return;
 	kcf = &req->ktr_data.ktr_cap_fail;
 	kcf->cap_type = type;
-	if (needed != NULL)
-		kcf->cap_needed = *needed;
-	else
-		cap_rights_init(&kcf->cap_needed);
-	if (held != NULL)
-		kcf->cap_held = *held;
-	else
-		cap_rights_init(&kcf->cap_held);
+	kcf->cap_code = td->td_sa.code;
+	kcf->cap_svflags = td->td_proc->p_sysent->sv_flags;
+	if (data != NULL) {
+		kcd = &kcf->cap_data;
+		switch (type) {
+		case CAPFAIL_NOTCAPABLE:
+		case CAPFAIL_INCREASE:
+			kcd->cap_needed = *(const cap_rights_t *)data;
+			kcd->cap_held = *((const cap_rights_t *)data + 1);
+			break;
+		case CAPFAIL_SYSCALL:
+		case CAPFAIL_SIGNAL:
+		case CAPFAIL_PROTO:
+			kcd->cap_int = *(const int *)data;
+			break;
+		case CAPFAIL_SOCKADDR:
+			kcd->cap_sockaddr = *(const struct sockaddr *)data;
+			break;
+		case CAPFAIL_NAMEI:
+			strlcpy(kcd->cap_path, data, MAXPATHLEN);
+			break;
+		case CAPFAIL_CPUSET:
+		default:
+			break;
+		}
+	}
 	ktr_enqueuerequest(td, req);
 	ktrace_exit(td);
 }

sys/kern/sys_capability.c

@@ -154,14 +154,13 @@ MALLOC_DECLARE(M_FILECAPS);
 
 static inline int
 _cap_check(const cap_rights_t *havep, const cap_rights_t *needp,
-    enum ktr_cap_fail_type type)
+    enum ktr_cap_violation type)
 {
+	const cap_rights_t rights[] = { *needp, *havep };
 
 	if (!cap_rights_contains(havep, needp)) {
-#ifdef KTRACE
-		if (KTRPOINT(curthread, KTR_CAPFAIL))
-			ktrcapfail(type, needp, havep);
-#endif
+		if (CAP_TRACING(curthread))
+			ktrcapfail(type, rights);
 		return (ENOTCAPABLE);
 	}
 	return (0);
@@ -180,11 +179,10 @@ cap_check(const cap_rights_t *havep, const cap_rights_t *needp)
 int
 cap_check_failed_notcapable(const cap_rights_t *havep, const cap_rights_t *needp)
 {
+	const cap_rights_t rights[] = { *needp, *havep };
 
-#ifdef KTRACE
-	if (KTRPOINT(curthread, KTR_CAPFAIL))
-		ktrcapfail(CAPFAIL_NOTCAPABLE, needp, havep);
-#endif
+	if (CAP_TRACING(curthread))
+		ktrcapfail(CAPFAIL_NOTCAPABLE, rights);
 	return (ENOTCAPABLE);
 }
 

sys/sys/capsicum.h

@@ -44,6 +44,7 @@
 #include <sys/caprights.h>
 #include <sys/file.h>
 #include <sys/fcntl.h>
+#include <sys/ktrace.h>
 
 #ifndef _KERNEL
 #include <stdbool.h>
@@ -419,6 +420,12 @@ __END_DECLS
 
 #include <sys/systm.h>
 
+#ifdef KTRACE
+#define CAP_TRACING(td) KTRPOINT((td), KTR_CAPFAIL)
+#else
+#define CAP_TRACING(td) 0
+#endif
+
 #define IN_CAPABILITY_MODE(td) (((td)->td_ucred->cr_flags & CRED_FLAG_CAPMODE) != 0)
 
 struct filedesc;

sys/sys/ktrace.h

@@ -32,8 +32,10 @@
 #ifndef _SYS_KTRACE_H_
 #define _SYS_KTRACE_H_
 
+#include <sys/param.h>
 #include <sys/caprights.h>
 #include <sys/signal.h>
+#include <sys/socket.h>
 #include <sys/_uio.h>
 
 /*
@@ -205,16 +207,31 @@ struct ktr_proc_ctor {
  * KTR_CAPFAIL - trace capability check failures
  */
 #define KTR_CAPFAIL	12
-enum ktr_cap_fail_type {
+enum ktr_cap_violation {
 	CAPFAIL_NOTCAPABLE,	/* insufficient capabilities in cap_check() */
-	CAPFAIL_INCREASE,	/* attempt to increase capabilities */
+	CAPFAIL_INCREASE,	/* attempt to increase rights on a capability */
 	CAPFAIL_SYSCALL,	/* disallowed system call */
-	CAPFAIL_LOOKUP,		/* disallowed VFS lookup */
+	CAPFAIL_SIGNAL,		/* sent signal to process other than self */
+	CAPFAIL_PROTO,		/* disallowed protocol */
+	CAPFAIL_SOCKADDR,	/* restricted address lookup */
+	CAPFAIL_NAMEI,		/* restricted namei lookup */
+	CAPFAIL_CPUSET,		/* restricted CPU set modification */
 };
+
+union ktr_cap_data {
+	cap_rights_t	cap_rights[2];
+#define	cap_needed	cap_rights[0]
+#define	cap_held	cap_rights[1]
+	int		cap_int;
+	struct sockaddr	cap_sockaddr;
+	char		cap_path[MAXPATHLEN];
+};
+
 struct ktr_cap_fail {
-	enum ktr_cap_fail_type cap_type;
-	cap_rights_t	cap_needed;
-	cap_rights_t	cap_held;
+	enum ktr_cap_violation cap_type;
+	short	cap_code;
+	u_int	cap_svflags;
+	union ktr_cap_data cap_data;
 };
 
 /*
@@ -317,8 +334,7 @@ void	ktruserret(struct thread *);
 void	ktrstruct(const char *, const void *, size_t);
 void	ktrstruct_error(const char *, const void *, size_t, int);
 void	ktrstructarray(const char *, enum uio_seg, const void *, int, size_t);
-void	ktrcapfail(enum ktr_cap_fail_type, const cap_rights_t *,
-	    const cap_rights_t *);
+void	ktrcapfail(enum ktr_cap_violation, const void *);
 #define ktrcaprights(s) \
 	ktrstruct("caprights", (s), sizeof(cap_rights_t))
 #define	ktritimerval(s) \

usr.bin/kdump/kdump.c

@@ -2125,35 +2125,74 @@ ktrstruct(char *buf, size_t buflen)
 void
 ktrcapfail(struct ktr_cap_fail *ktr)
 {
+	union ktr_cap_data *kcd = &ktr->cap_data;
+
 	switch (ktr->cap_type) {
 	case CAPFAIL_NOTCAPABLE:
 		/* operation on fd with insufficient capabilities */
 		printf("operation requires ");
-		sysdecode_cap_rights(stdout, &ktr->cap_needed);
+		sysdecode_cap_rights(stdout, &kcd->cap_needed);
 		printf(", descriptor holds ");
-		sysdecode_cap_rights(stdout, &ktr->cap_held);
+		sysdecode_cap_rights(stdout, &kcd->cap_held);
 		break;
 	case CAPFAIL_INCREASE:
 		/* requested more capabilities than fd already has */
 		printf("attempt to increase capabilities from ");
-		sysdecode_cap_rights(stdout, &ktr->cap_held);
+		sysdecode_cap_rights(stdout, &kcd->cap_held);
 		printf(" to ");
-		sysdecode_cap_rights(stdout, &ktr->cap_needed);
+		sysdecode_cap_rights(stdout, &kcd->cap_needed);
 		break;
 	case CAPFAIL_SYSCALL:
 		/* called restricted syscall */
-		printf("disallowed system call");
+		printf("system call not allowed: ");
+		syscallname(ktr->cap_code, ktr->cap_svflags);
+		if (syscallabi(ktr->cap_svflags) == SYSDECODE_ABI_FREEBSD) {
+			switch (ktr->cap_code) {
+			case SYS_sysarch:
+				printf(", op: ");
+				print_integer_arg(sysdecode_sysarch_number,
+				    kcd->cap_int);
+				break;
+			case SYS_fcntl:
+				printf(", cmd: ");
+				print_integer_arg(sysdecode_fcntl_cmd,
+				    kcd->cap_int);
+				break;
+			}
+		}
 		break;
-	case CAPFAIL_LOOKUP:
+	case CAPFAIL_SIGNAL:
+		/* sent signal to proc other than self */
+		syscallname(ktr->cap_code, ktr->cap_svflags);
+		printf(": signal delivery not allowed: ");
+		print_integer_arg(sysdecode_signal, kcd->cap_int);
+		break;
+	case CAPFAIL_PROTO:
+		/* created socket with restricted protocol */
+		syscallname(ktr->cap_code, ktr->cap_svflags);
+		printf(": protocol not allowed: ");
+		print_integer_arg(sysdecode_ipproto, kcd->cap_int);
+		break;
+	case CAPFAIL_SOCKADDR:
+		/* unable to look up address */
+		syscallname(ktr->cap_code, ktr->cap_svflags);
+		printf(": restricted address lookup: ");
+		ktrsockaddr(&kcd->cap_sockaddr);
+		return;
+	case CAPFAIL_NAMEI:
 		/* absolute or AT_FDCWD path, ".." path, etc. */
-		printf("restricted VFS lookup");
-		break;
+		syscallname(ktr->cap_code, ktr->cap_svflags);
+		printf(": restricted VFS lookup: %s\n", kcd->cap_path);
+		return;
+	case CAPFAIL_CPUSET:
+		/* modification of an external cpuset */
+		syscallname(ktr->cap_code, ktr->cap_svflags);
+		printf(": restricted cpuset operation\n");
+		return;
 	default:
-		printf("unknown capability failure: ");
-		sysdecode_cap_rights(stdout, &ktr->cap_needed);
-		printf(" ");
-		sysdecode_cap_rights(stdout, &ktr->cap_held);
-		break;
+		syscallname(ktr->cap_code, ktr->cap_svflags);
+		printf(": unknown capability failure\n");
+		return;
 	}
 	printf("\n");
 }