[PATCH v4 4/4] libselinux: check for truncations

["Christian Göttsche" <cgzones@googlemail.com>]

Check for truncations when building or copying strings involving user
input.

Signed-off-by: Christian Göttsche <cgzones@googlemail.com>

---
v4:
   - rebase on top of de285252 ("Revert "libselinux: restorecon: pin
     file to avoid TOCTOU issues"")
v3:
   - free buf in error branch in security_canonicalize_context_raw()
v2:
   - add explicit casts to avoid int <-> size_t comparisons
   - ensure containing functions return -1

Signed-off-by: Christian Göttsche <cgzones@googlemail.com>
---
 libselinux/src/canonicalize_context.c |  6 +++++-
 libselinux/src/compute_av.c           |  8 +++++++-
 libselinux/src/compute_create.c       |  7 +++++++
 libselinux/src/compute_member.c       |  8 +++++++-
 libselinux/src/compute_relabel.c      |  8 +++++++-
 libselinux/src/compute_user.c         |  8 +++++++-
 libselinux/src/selinux_restorecon.c   | 11 ++++++++++-
 libselinux/src/setrans_client.c       |  8 +++++++-
 8 files changed, 57 insertions(+), 7 deletions(-)

diff --git a/libselinux/src/canonicalize_context.c b/libselinux/src/canonicalize_context.c
index faab7305..6af8491d 100644
--- a/libselinux/src/canonicalize_context.c
+++ b/libselinux/src/canonicalize_context.c
@@ -33,7 +33,11 @@ int security_canonicalize_context_raw(const char * con,
 		ret = -1;
 		goto out;
 	}
-	strncpy(buf, con, size);
+	if (strlcpy(buf, con, size) >= size) {
+		errno = EOVERFLOW;
+		ret = -1;
+		goto out2;
+	}
 
 	ret = write(fd, buf, strlen(buf) + 1);
 	if (ret < 0)
diff --git a/libselinux/src/compute_av.c b/libselinux/src/compute_av.c
index 9d17339d..354a19e1 100644
--- a/libselinux/src/compute_av.c
+++ b/libselinux/src/compute_av.c
@@ -40,8 +40,14 @@ int security_compute_av_flags_raw(const char * scon,
 	}
 
 	kclass = unmap_class(tclass);
-	snprintf(buf, len, "%s %s %hu %x", scon, tcon,
+
+	ret = snprintf(buf, len, "%s %s %hu %x", scon, tcon,
 		 kclass, unmap_perm(tclass, requested));
+	if (ret < 0 || (size_t)ret >= len) {
+		errno = EOVERFLOW;
+		ret = -1;
+		goto out2;
+	}
 
 	ret = write(fd, buf, strlen(buf));
 	if (ret < 0)
diff --git a/libselinux/src/compute_create.c b/libselinux/src/compute_create.c
index 1d75714d..e9f3c96a 100644
--- a/libselinux/src/compute_create.c
+++ b/libselinux/src/compute_create.c
@@ -75,8 +75,15 @@ int security_compute_create_name_raw(const char * scon,
 		ret = -1;
 		goto out;
 	}
+
 	len = snprintf(buf, size, "%s %s %hu",
 		       scon, tcon, unmap_class(tclass));
+	if (len < 0 || (size_t)len >= size) {
+		errno = EOVERFLOW;
+		ret = -1;
+		goto out2;
+	}
+
 	if (objname &&
 	    object_name_encode(objname, buf + len, size - len) < 0) {
 		errno = ENAMETOOLONG;
diff --git a/libselinux/src/compute_member.c b/libselinux/src/compute_member.c
index 16234b79..53d2f559 100644
--- a/libselinux/src/compute_member.c
+++ b/libselinux/src/compute_member.c
@@ -36,7 +36,13 @@ int security_compute_member_raw(const char * scon,
 		ret = -1;
 		goto out;
 	}
-	snprintf(buf, size, "%s %s %hu", scon, tcon, unmap_class(tclass));
+
+	ret = snprintf(buf, size, "%s %s %hu", scon, tcon, unmap_class(tclass));
+	if (ret < 0 || (size_t)ret >= size) {
+		errno = EOVERFLOW;
+		ret = -1;
+		goto out2;
+	}
 
 	ret = write(fd, buf, strlen(buf));
 	if (ret < 0)
diff --git a/libselinux/src/compute_relabel.c b/libselinux/src/compute_relabel.c
index dd20d652..9c0a2304 100644
--- a/libselinux/src/compute_relabel.c
+++ b/libselinux/src/compute_relabel.c
@@ -36,7 +36,13 @@ int security_compute_relabel_raw(const char * scon,
 		ret = -1;
 		goto out;
 	}
-	snprintf(buf, size, "%s %s %hu", scon, tcon, unmap_class(tclass));
+
+	ret = snprintf(buf, size, "%s %s %hu", scon, tcon, unmap_class(tclass));
+	if (ret < 0 || (size_t)ret >= size) {
+		errno = EOVERFLOW;
+		ret = -1;
+		goto out2;
+	}
 
 	ret = write(fd, buf, strlen(buf));
 	if (ret < 0)
diff --git a/libselinux/src/compute_user.c b/libselinux/src/compute_user.c
index ae5e7b4a..f55f945a 100644
--- a/libselinux/src/compute_user.c
+++ b/libselinux/src/compute_user.c
@@ -38,7 +38,13 @@ int security_compute_user_raw(const char * scon,
 		ret = -1;
 		goto out;
 	}
-	snprintf(buf, size, "%s %s", scon, user);
+
+	ret = snprintf(buf, size, "%s %s", scon, user);
+	if (ret < 0 || (size_t)ret >= size) {
+		errno = EOVERFLOW;
+		ret = -1;
+		goto out2;
+	}
 
 	ret = write(fd, buf, strlen(buf));
 	if (ret < 0)
diff --git a/libselinux/src/selinux_restorecon.c b/libselinux/src/selinux_restorecon.c
index 9f5b326c..66e6a4a2 100644
--- a/libselinux/src/selinux_restorecon.c
+++ b/libselinux/src/selinux_restorecon.c
@@ -954,7 +954,16 @@ loop_body:
 			}
 			/* fall through */
 		default:
-			strcpy(ent_path, ftsent->fts_path);
+			if (strlcpy(ent_path, ftsent->fts_path, sizeof(ent_path)) >= sizeof(ent_path)) {
+				selinux_log(SELINUX_ERROR,
+					    "Path name too long on %s.\n",
+					    ftsent->fts_path);
+				errno = ENAMETOOLONG;
+				state->error = -1;
+				state->abort = true;
+				goto finish;
+			}
+
 			ent_st = *ftsent->fts_statp;
 			if (state->parallel)
 				pthread_mutex_unlock(&state->mutex);
diff --git a/libselinux/src/setrans_client.c b/libselinux/src/setrans_client.c
index faa12681..920f9032 100644
--- a/libselinux/src/setrans_client.c
+++ b/libselinux/src/setrans_client.c
@@ -66,7 +66,13 @@ static int setransd_open(void)
 
 	memset(&addr, 0, sizeof(addr));
 	addr.sun_family = AF_UNIX;
-	strncpy(addr.sun_path, SETRANS_UNIX_SOCKET, sizeof(addr.sun_path));
+
+	if (strlcpy(addr.sun_path, SETRANS_UNIX_SOCKET, sizeof(addr.sun_path)) >= sizeof(addr.sun_path)) {
+		close(fd);
+		errno = EOVERFLOW;
+		return -1;
+	}
+
 	if (connect(fd, (struct sockaddr *)&addr, sizeof(addr)) < 0) {
 		close(fd);
 		return -1;
-- 
2.36.1