Securing Department of Homeland Security Firearms Act of 2017 or the Securing DHS Firearms Act of 2017 (Sec. 3) This bill makes the Under Secretary for Management of the Department of Homeland Security (DHS) responsible for the security of DHS firearms and other sensitive assets."Sensitive assets" are defined as any asset, regardless of value, that DHS issues to a DHS employee and that the Under Secretary or a component head determines requires special control and accounting. (Sec. 4) The Under Secretary shall develop and disseminate a directive for achieving adequate security over such assets across DHS, which shall include: (1) descriptions of what equipment is classified as a sensitive asset, (2) requirements for securing such assets, (3) a classification system for all categories of DHS-issued badges and corresponding requirements for safeguarding such assets, and (4) reporting and record keeping requirements for lost assets (defined to include loss by theft). The Under Secretary shall update such directive within one year, including by adding a requirement relating to recording in the inventory systems maintained by each DHS component the acceptance or transfer of a sensitive asset. The Under Secretary shall disseminate a revised version of the Personal Property Asset Management Program Manual that includes: requirements for component heads to develop procedures to safeguard firearms and other sensitive assets during on- and off-duty time; requirements for the issuance of safety locking devices and policies on the use of such assets; requirements for training on safeguarding such assets; instructions for reporting and recording lost sensitive assets and an enforcement mechanism to ensure that supervisors maintain such records; and a requirement that a file on a lost asset contain the DHS report and the corresponding police report. (Sec. 5) DHS components must: comply with federal law, executive branch guidance, and DHS policy regarding the management and oversight of securing sensitive assets; review the need for non-law enforcement badges; require personnel to comply with requirements for safeguarding sensitive assets and reporting on lost assets; and require that lost assets are reported to local law enforcement, the National Crime Information Center, and DHS headquarters and recorded in inventory systems in the time frame established by the security directive. (Sec. 6) The Inspector General of DHS shall, on an ongoing basis, review implementation of this bill and report to Congress on the progress and effectiveness of the directive for safeguarding firearms and sensitive assets.