From 23375b13f98c5464c2b4d15f983cc062940f1f4e Mon Sep 17 00:00:00 2001 From: John Johansen Date: Sun, 26 May 2019 06:42:23 -0700 Subject: [PATCH 1/3] apparmor: fix PROFILE_MEDIATES for untrusted input While commit 11c236b89d7c2 ("apparmor: add a default null dfa") ensure every profile has a policy.dfa it does not resize the policy.start[] to have entries for every possible start value. Which means PROFILE_MEDIATES is not safe to use on untrusted input. Unforunately commit b9590ad4c4f2 ("apparmor: remove POLICY_MEDIATES_SAFE") did not take into account the start value usage. The input string in profile_query_cb() is user controlled and is not properly checked to be within the limited start[] entries, even worse it can't be as userspace policy is allowed to make us of entries types the kernel does not know about. This mean usespace can currently cause the kernel to access memory up to 240 entries beyond the start array bounds. Cc: stable@vger.kernel.org Fixes: b9590ad4c4f2 ("apparmor: remove POLICY_MEDIATES_SAFE") Signed-off-by: John Johansen --- security/apparmor/include/policy.h | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/security/apparmor/include/policy.h b/security/apparmor/include/policy.h index 1ce4e9bdac48..b5b4b8190e65 100644 --- a/security/apparmor/include/policy.h +++ b/security/apparmor/include/policy.h @@ -213,7 +213,16 @@ static inline struct aa_profile *aa_get_newest_profile(struct aa_profile *p) return labels_profile(aa_get_newest_label(&p->label)); } -#define PROFILE_MEDIATES(P, T) ((P)->policy.start[(unsigned char) (T)]) +static inline unsigned int PROFILE_MEDIATES(struct aa_profile *profile, + unsigned char class) +{ + if (class <= AA_CLASS_LAST) + return profile->policy.start[class]; + else + return aa_dfa_match_len(profile->policy.dfa, + profile->policy.start[0], &class, 1); +} + static inline unsigned int PROFILE_MEDIATES_AF(struct aa_profile *profile, u16 AF) { unsigned int state = PROFILE_MEDIATES(profile, AA_CLASS_NET); From 8404d7a674c49278607d19726e0acc0cae299357 Mon Sep 17 00:00:00 2001 From: Jann Horn Date: Tue, 28 May 2019 17:32:26 +0200 Subject: [PATCH 2/3] apparmor: enforce nullbyte at end of tag string A packed AppArmor policy contains null-terminated tag strings that are read by unpack_nameX(). However, unpack_nameX() uses string functions on them without ensuring that they are actually null-terminated, potentially leading to out-of-bounds accesses. Make sure that the tag string is null-terminated before passing it to strcmp(). Cc: stable@vger.kernel.org Fixes: 736ec752d95e ("AppArmor: policy routines for loading and unpacking policy") Signed-off-by: Jann Horn Signed-off-by: John Johansen --- security/apparmor/policy_unpack.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/security/apparmor/policy_unpack.c b/security/apparmor/policy_unpack.c index 01957ce9252b..005a705346f0 100644 --- a/security/apparmor/policy_unpack.c +++ b/security/apparmor/policy_unpack.c @@ -272,7 +272,7 @@ static bool unpack_nameX(struct aa_ext *e, enum aa_code code, const char *name) char *tag = NULL; size_t size = unpack_u16_chunk(e, &tag); /* if a name is specified it must match. otherwise skip tag */ - if (name && (!size || strcmp(name, tag))) + if (name && (!size || tag[size-1] != '\0' || strcmp(name, tag))) goto fail; } else if (name) { /* if a name is specified and there is no name tag fail */ From 156e42996bd84eccb6acf319f19ce0cb140d00e3 Mon Sep 17 00:00:00 2001 From: Mike Salvatore Date: Wed, 12 Jun 2019 14:55:14 -0700 Subject: [PATCH 3/3] apparmor: reset pos on failure to unpack for various functions Each function that manipulates the aa_ext struct should reset it's "pos" member on failure. This ensures that, on failure, no changes are made to the state of the aa_ext struct. There are paths were elements are optional and the error path is used to indicate the optional element is not present. This means instead of just aborting on error the unpack stream can become unsynchronized on optional elements, if using one of the affected functions. Cc: stable@vger.kernel.org Fixes: 736ec752d95e ("AppArmor: policy routines for loading and unpacking policy") Signed-off-by: Mike Salvatore Signed-off-by: John Johansen --- security/apparmor/policy_unpack.c | 47 +++++++++++++++++++++++++------ 1 file changed, 39 insertions(+), 8 deletions(-) diff --git a/security/apparmor/policy_unpack.c b/security/apparmor/policy_unpack.c index 005a705346f0..8cfc9493eefc 100644 --- a/security/apparmor/policy_unpack.c +++ b/security/apparmor/policy_unpack.c @@ -219,16 +219,21 @@ static void *kvmemdup(const void *src, size_t len) static size_t unpack_u16_chunk(struct aa_ext *e, char **chunk) { size_t size = 0; + void *pos = e->pos; if (!inbounds(e, sizeof(u16))) - return 0; + goto fail; size = le16_to_cpu(get_unaligned((__le16 *) e->pos)); e->pos += sizeof(__le16); if (!inbounds(e, size)) - return 0; + goto fail; *chunk = e->pos; e->pos += size; return size; + +fail: + e->pos = pos; + return 0; } /* unpack control byte */ @@ -290,62 +295,84 @@ fail: static bool unpack_u8(struct aa_ext *e, u8 *data, const char *name) { + void *pos = e->pos; + if (unpack_nameX(e, AA_U8, name)) { if (!inbounds(e, sizeof(u8))) - return 0; + goto fail; if (data) *data = get_unaligned((u8 *)e->pos); e->pos += sizeof(u8); return 1; } + +fail: + e->pos = pos; return 0; } static bool unpack_u32(struct aa_ext *e, u32 *data, const char *name) { + void *pos = e->pos; + if (unpack_nameX(e, AA_U32, name)) { if (!inbounds(e, sizeof(u32))) - return 0; + goto fail; if (data) *data = le32_to_cpu(get_unaligned((__le32 *) e->pos)); e->pos += sizeof(u32); return 1; } + +fail: + e->pos = pos; return 0; } static bool unpack_u64(struct aa_ext *e, u64 *data, const char *name) { + void *pos = e->pos; + if (unpack_nameX(e, AA_U64, name)) { if (!inbounds(e, sizeof(u64))) - return 0; + goto fail; if (data) *data = le64_to_cpu(get_unaligned((__le64 *) e->pos)); e->pos += sizeof(u64); return 1; } + +fail: + e->pos = pos; return 0; } static size_t unpack_array(struct aa_ext *e, const char *name) { + void *pos = e->pos; + if (unpack_nameX(e, AA_ARRAY, name)) { int size; if (!inbounds(e, sizeof(u16))) - return 0; + goto fail; size = (int)le16_to_cpu(get_unaligned((__le16 *) e->pos)); e->pos += sizeof(u16); return size; } + +fail: + e->pos = pos; return 0; } static size_t unpack_blob(struct aa_ext *e, char **blob, const char *name) { + void *pos = e->pos; + if (unpack_nameX(e, AA_BLOB, name)) { u32 size; if (!inbounds(e, sizeof(u32))) - return 0; + goto fail; size = le32_to_cpu(get_unaligned((__le32 *) e->pos)); e->pos += sizeof(u32); if (inbounds(e, (size_t) size)) { @@ -354,6 +381,9 @@ static size_t unpack_blob(struct aa_ext *e, char **blob, const char *name) return size; } } + +fail: + e->pos = pos; return 0; } @@ -370,9 +400,10 @@ static int unpack_str(struct aa_ext *e, const char **string, const char *name) if (src_str[size - 1] != 0) goto fail; *string = src_str; + + return size; } } - return size; fail: e->pos = pos;