From 47e0a208fb9d91e3f3c86309e752b13a36470ae8 Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Fri, 8 Dec 2017 15:13:28 +0000 Subject: X.509: fix buffer overflow detection in sprint_oid() In sprint_oid(), if the input buffer were to be more than 1 byte too small for the first snprintf(), 'bufsize' would underflow, causing a buffer overflow when printing the remainder of the OID. Fortunately this cannot actually happen currently, because no users pass in a buffer that can be too small for the first snprintf(). Regardless, fix it by checking the snprintf() return value correctly. For consistency also tweak the second snprintf() check to look the same. Fixes: 4f73175d0375 ("X.509: Add utility functions to render OIDs as strings") Cc: Takashi Iwai Signed-off-by: Eric Biggers Signed-off-by: David Howells Reviewed-by: James Morris --- lib/oid_registry.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) (limited to 'lib/oid_registry.c') diff --git a/lib/oid_registry.c b/lib/oid_registry.c index 41b9e50711a7..5a75d127995d 100644 --- a/lib/oid_registry.c +++ b/lib/oid_registry.c @@ -120,10 +120,10 @@ int sprint_oid(const void *data, size_t datasize, char *buffer, size_t bufsize) n = *v++; ret = count = snprintf(buffer, bufsize, "%u.%u", n / 40, n % 40); + if (count >= bufsize) + return -ENOBUFS; buffer += count; bufsize -= count; - if (bufsize == 0) - return -ENOBUFS; while (v < end) { num = 0; @@ -141,9 +141,9 @@ int sprint_oid(const void *data, size_t datasize, char *buffer, size_t bufsize) } while (n & 0x80); } ret += count = snprintf(buffer, bufsize, ".%lu", num); - buffer += count; - if (bufsize <= count) + if (count >= bufsize) return -ENOBUFS; + buffer += count; bufsize -= count; } -- cgit v1.2.3 From 8dfd2f22d3bf3ab7714f7495ad5d897b8845e8c1 Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Fri, 8 Dec 2017 15:13:28 +0000 Subject: 509: fix printing uninitialized stack memory when OID is empty Callers of sprint_oid() do not check its return value before printing the result. In the case where the OID is zero-length, -EBADMSG was being returned without anything being written to the buffer, resulting in uninitialized stack memory being printed. Fix this by writing "(bad)" to the buffer in the cases where -EBADMSG is returned. Fixes: 4f73175d0375 ("X.509: Add utility functions to render OIDs as strings") Signed-off-by: Eric Biggers Signed-off-by: David Howells --- lib/oid_registry.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) (limited to 'lib/oid_registry.c') diff --git a/lib/oid_registry.c b/lib/oid_registry.c index 5a75d127995d..0bcac6ccb1b2 100644 --- a/lib/oid_registry.c +++ b/lib/oid_registry.c @@ -116,7 +116,7 @@ int sprint_oid(const void *data, size_t datasize, char *buffer, size_t bufsize) int count; if (v >= end) - return -EBADMSG; + goto bad; n = *v++; ret = count = snprintf(buffer, bufsize, "%u.%u", n / 40, n % 40); @@ -134,7 +134,7 @@ int sprint_oid(const void *data, size_t datasize, char *buffer, size_t bufsize) num = n & 0x7f; do { if (v >= end) - return -EBADMSG; + goto bad; n = *v++; num <<= 7; num |= n & 0x7f; @@ -148,6 +148,10 @@ int sprint_oid(const void *data, size_t datasize, char *buffer, size_t bufsize) } return ret; + +bad: + snprintf(buffer, bufsize, "(bad)"); + return -EBADMSG; } EXPORT_SYMBOL_GPL(sprint_oid); -- cgit v1.2.3