[PATCH v8 3/8] pcapng: add length checks to string arguments

[Stephen Hemminger <stephen@networkplumber.org>]

The pcapng file format uses a 16-bit length field in the option
TLV (Type-Length-Value) encoding, limiting strings to UINT16_MAX
bytes.

Add validation for string arguments to prevent silent truncation
or buffer issues when callers pass excessively long strings.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
 doc/guides/rel_notes/release_26_03.rst |  5 ++++
 lib/pcapng/rte_pcapng.c                | 37 ++++++++++++++++++++++----
 lib/pcapng/rte_pcapng.h                |  3 ++-
 3 files changed, 39 insertions(+), 6 deletions(-)

diff --git a/doc/guides/rel_notes/release_26_03.rst b/doc/guides/rel_notes/release_26_03.rst
index 39f381e561..eea01e44e9 100644
--- a/doc/guides/rel_notes/release_26_03.rst
+++ b/doc/guides/rel_notes/release_26_03.rst
@@ -148,6 +148,11 @@ API Changes
   * cfgfile: name must be less than CFG_NAME_LEN
     and value must be less than CFG_VALUE_LEN.
 
+* **Updated the pcapng library.**
+
+  * The length of comment strings is now validated.
+    Maximum allowable length is 2^16-1 because of pcapng file format.
+
 
 ABI Changes
 -----------
diff --git a/lib/pcapng/rte_pcapng.c b/lib/pcapng/rte_pcapng.c
index 5789c2cdca..914d6e7095 100644
--- a/lib/pcapng/rte_pcapng.c
+++ b/lib/pcapng/rte_pcapng.c
@@ -34,6 +34,9 @@
 /* conversion from DPDK speed to PCAPNG */
 #define PCAPNG_MBPS_SPEED 1000000ull
 
+/* upper bound for strings in pcapng option data */
+#define PCAPNG_STR_MAX	UINT16_MAX
+
 /* upper bound for section, stats and interface blocks (in uint32_t) */
 #define PCAPNG_BLKSIZ	(2048 / sizeof(uint32_t))
 
@@ -218,9 +221,11 @@ rte_pcapng_add_interface(rte_pcapng_t *self, uint16_t port, uint16_t link_type,
 	char ifname_buf[IF_NAMESIZE];
 	char ifhw[256];
 	uint64_t speed = 0;
+	int ret;
 
-	if (rte_eth_dev_info_get(port, &dev_info) < 0)
-		return -1;
+	ret = rte_eth_dev_info_get(port, &dev_info);
+	if (ret < 0)
+		return -1;  /* should be ret */
 
 	/* make something like an interface name */
 	if (ifname == NULL) {
@@ -230,8 +235,14 @@ rte_pcapng_add_interface(rte_pcapng_t *self, uint16_t port, uint16_t link_type,
 			snprintf(ifname_buf, IF_NAMESIZE, "dpdk:%u", port);
 			ifname = ifname_buf;
 		}
+	} else if (strlen(ifname) > PCAPNG_STR_MAX) {
+		return -1; /* ENAMETOOLONG */
 	}
 
+	if ((ifdescr && strlen(ifdescr) > PCAPNG_STR_MAX) ||
+	    (filter && strlen(filter) > PCAPNG_STR_MAX))
+		return -1; /* EINVAL */
+
 	/* make a useful device hardware string */
 	dev = dev_info.device;
 	if (dev)
@@ -269,7 +280,7 @@ rte_pcapng_add_interface(rte_pcapng_t *self, uint16_t port, uint16_t link_type,
 	len += sizeof(uint32_t);
 
 	if (len > sizeof(buf))
-		return -1;
+		return -1; /* EINVAL */
 
 	hdr = (struct pcapng_interface_block *)buf;
 	*hdr = (struct pcapng_interface_block) {
@@ -336,6 +347,9 @@ rte_pcapng_write_stats(rte_pcapng_t *self, uint16_t port_id,
 
 	RTE_ETH_VALID_PORTID_OR_ERR_RET(port_id, -EINVAL);
 
+	if (comment && strlen(comment) > PCAPNG_STR_MAX)
+		return -EINVAL;
+
 	optlen = 0;
 
 	if (ifrecv != UINT64_MAX)
@@ -487,6 +501,10 @@ rte_pcapng_copy(uint16_t port_id, uint32_t queue,
 	bool rss_hash;
 
 #ifdef RTE_LIBRTE_ETHDEV_DEBUG
+	/*
+	 * Since this function is used in the fast path for packet capture
+	 * skip argument validation checks unless debug is enabled.
+	 */
 	RTE_ETH_VALID_PORTID_OR_ERR_RET(port_id, NULL);
 #endif
 	orig_len = rte_pktmbuf_pkt_len(md);
@@ -535,8 +553,9 @@ rte_pcapng_copy(uint16_t port_id, uint32_t queue,
 	if (rss_hash)
 		optlen += pcapng_optlen(sizeof(uint8_t) + sizeof(uint32_t));
 
+	/* Comment is silently truncated if necessary */
 	if (comment)
-		optlen += pcapng_optlen(strlen(comment));
+		optlen += pcapng_optlen(strnlen(comment, PCAPNG_STR_MAX));
 
 	/* reserve trailing options and block length */
 	opt = (struct pcapng_option *)
@@ -577,7 +596,7 @@ rte_pcapng_copy(uint16_t port_id, uint32_t queue,
 
 	if (comment)
 		opt = pcapng_add_option(opt, PCAPNG_OPT_COMMENT, comment,
-					strlen(comment));
+					strnlen(comment, PCAPNG_STR_MAX));
 
 	/* Note: END_OPT necessary here. Wireshark doesn't do it. */
 
@@ -692,6 +711,14 @@ rte_pcapng_fdopen(int fd,
 	struct timespec ts;
 	uint64_t cycles;
 
+	if ((osname && strlen(osname) > PCAPNG_STR_MAX) ||
+	    (hardware && strlen(hardware) > PCAPNG_STR_MAX) ||
+	    (appname && strlen(appname) > PCAPNG_STR_MAX) ||
+	    (comment && strlen(comment) > PCAPNG_STR_MAX)) {
+		rte_errno = EINVAL;
+		return NULL;
+	}
+
 	self = malloc(sizeof(*self));
 	if (!self) {
 		rte_errno = ENOMEM;
diff --git a/lib/pcapng/rte_pcapng.h b/lib/pcapng/rte_pcapng.h
index 8d0974c3fd..68e13c67e4 100644
--- a/lib/pcapng/rte_pcapng.h
+++ b/lib/pcapng/rte_pcapng.h
@@ -127,7 +127,8 @@ enum rte_pcapng_direction {
  * @param direction
  *   The direction of the packer: receive, transmit or unknown.
  * @param comment
- *   Packet comment.
+ *   Optional per packet comment.
+ *   Truncated to UINT16_MAX characters.
  *
  * @return
  *   - The pointer to the new mbuf formatted for pcapng_write
-- 
2.51.0