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[77.10.118.211]) by smtp.gmail.com with ESMTPSA id b4-20020aa7c904000000b00548a2d1737bsm1632282edt.35.2023.11.20.06.32.10 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 20 Nov 2023 06:32:10 -0800 (PST) From: =?utf-8?q?Christian_G=C3=B6ttsche?= To: selinux@vger.kernel.org Subject: [PATCH 2/2] libsepol: avoid fixed sized format buffer for xperms Date: Mon, 20 Nov 2023 15:31:45 +0100 Message-ID: <20231120143145.28831-2-cgzones@googlemail.com> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20231120143145.28831-1-cgzones@googlemail.com> References: <20231120143145.28831-1-cgzones@googlemail.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: selinux@vger.kernel.org An extended access vector rule can consist of many individual ranges of permissions. Use a dynamically growing sized buffer for formatting such rules instead of a static buffer to avoid write failures due to truncations. Signed-off-by: Christian Göttsche --- checkpolicy/test/dismod.c | 9 +++++- checkpolicy/test/dispol.c | 10 ++++++- libsepol/src/assertion.c | 7 ++++- libsepol/src/kernel_to_conf.c | 9 +++--- libsepol/src/util.c | 54 +++++++++++++++++++++++------------ 5 files changed, 64 insertions(+), 25 deletions(-) diff --git a/checkpolicy/test/dismod.c b/checkpolicy/test/dismod.c index fa7117f5..9f4a669b 100644 --- a/checkpolicy/test/dismod.c +++ b/checkpolicy/test/dismod.c @@ -347,6 +347,7 @@ static int display_avrule(avrule_t * avrule, policydb_t * policy, display_id(policy, fp, SYM_TYPES, avrule->perms->data - 1, ""); } else if (avrule->specified & AVRULE_XPERMS) { avtab_extended_perms_t xperms; + char *perms; int i; if (avrule->xperms->specified == AVRULE_XPERMS_IOCTLFUNCTION) @@ -362,7 +363,13 @@ static int display_avrule(avrule_t * avrule, policydb_t * policy, for (i = 0; i < EXTENDED_PERMS_LEN; i++) xperms.perms[i] = avrule->xperms->perms[i]; - fprintf(fp, "%s", sepol_extended_perms_to_string(&xperms)); + perms = sepol_extended_perms_to_string(&xperms); + if (!perms) { + fprintf(fp, " ERROR: failed to format xperms\n"); + return -1; + } + fprintf(fp, "%s", perms); + free(perms); } fprintf(fp, ";\n"); diff --git a/checkpolicy/test/dispol.c b/checkpolicy/test/dispol.c index b567ce77..944ef7ec 100644 --- a/checkpolicy/test/dispol.c +++ b/checkpolicy/test/dispol.c @@ -196,6 +196,8 @@ static int render_av_rule(avtab_key_t * key, avtab_datum_t * datum, uint32_t wha fprintf(fp, ";\n"); } } else if (key->specified & AVTAB_XPERMS) { + char *perms; + if (key->specified & AVTAB_XPERMS_ALLOWED) fprintf(fp, "allowxperm "); else if (key->specified & AVTAB_XPERMS_AUDITALLOW) @@ -203,7 +205,13 @@ static int render_av_rule(avtab_key_t * key, avtab_datum_t * datum, uint32_t wha else if (key->specified & AVTAB_XPERMS_DONTAUDIT) fprintf(fp, "dontauditxperm "); render_key(key, p, fp); - fprintf(fp, "%s;\n", sepol_extended_perms_to_string(datum->xperms)); + perms = sepol_extended_perms_to_string(datum->xperms); + if (!perms) { + fprintf(fp, " ERROR: failed to format xperms\n"); + return -1; + } + fprintf(fp, "%s;\n", perms); + free(perms); } else { fprintf(fp, " ERROR: no valid rule type specified\n"); return -1; diff --git a/libsepol/src/assertion.c b/libsepol/src/assertion.c index b6ac4cfe..6de7d031 100644 --- a/libsepol/src/assertion.c +++ b/libsepol/src/assertion.c @@ -178,15 +178,20 @@ static int report_assertion_extended_permissions(sepol_handle_t *handle, rc = check_extended_permissions(avrule->xperms, xperms); /* failure on the extended permission check_extended_permissions */ if (rc) { + char *permstring; + extended_permissions_violated(&error, avrule->xperms, xperms); + permstring = sepol_extended_perms_to_string(&error); + ERR(handle, "neverallowxperm on line %lu of %s (or line %lu of %s) violated by\n" "allowxperm %s %s:%s %s;", avrule->source_line, avrule->source_filename, avrule->line, policy_name(p), p->p_type_val_to_name[i], p->p_type_val_to_name[j], p->p_class_val_to_name[curperm->tclass - 1], - sepol_extended_perms_to_string(&error)); + permstring ?: ""); + free(permstring); errors++; } } diff --git a/libsepol/src/kernel_to_conf.c b/libsepol/src/kernel_to_conf.c index b0ae16d9..b5b530d6 100644 --- a/libsepol/src/kernel_to_conf.c +++ b/libsepol/src/kernel_to_conf.c @@ -1683,7 +1683,7 @@ static char *avtab_node_to_str(struct policydb *pdb, avtab_key_t *key, avtab_dat uint32_t data = datum->data; type_datum_t *type; const char *flavor, *src, *tgt, *class, *perms, *new; - char *rule = NULL; + char *rule = NULL, *permstring; switch (0xFFF & key->specified) { case AVTAB_ALLOWED: @@ -1738,13 +1738,14 @@ static char *avtab_node_to_str(struct policydb *pdb, avtab_key_t *key, avtab_dat rule = create_str("%s %s %s:%s { %s };", 5, flavor, src, tgt, class, perms+1); } else if (key->specified & AVTAB_XPERMS) { - perms = sepol_extended_perms_to_string(datum->xperms); - if (perms == NULL) { + permstring = sepol_extended_perms_to_string(datum->xperms); + if (permstring == NULL) { ERR(NULL, "Failed to generate extended permission string"); goto exit; } - rule = create_str("%s %s %s:%s %s;", 5, flavor, src, tgt, class, perms); + rule = create_str("%s %s %s:%s %s;", 5, flavor, src, tgt, class, permstring); + free(permstring); } else { new = pdb->p_type_val_to_name[data - 1]; diff --git a/libsepol/src/util.c b/libsepol/src/util.c index 0a2edc85..25a3ed55 100644 --- a/libsepol/src/util.c +++ b/libsepol/src/util.c @@ -133,19 +133,29 @@ char *sepol_extended_perms_to_string(avtab_extended_perms_t *xperms) uint16_t low_value; unsigned int bit; unsigned int in_range = 0; - static char xpermsbuf[2048]; - char *p; - int len, xpermslen = 0; - xpermsbuf[0] = '\0'; - p = xpermsbuf; + char *buffer = NULL, *p; + int len; + size_t remaining, size = 128; if ((xperms->specified != AVTAB_XPERMS_IOCTLFUNCTION) && (xperms->specified != AVTAB_XPERMS_IOCTLDRIVER)) return NULL; - len = snprintf(p, sizeof(xpermsbuf) - xpermslen, "ioctl { "); +retry: + size *= 2; + if (size == 0) + goto err; + p = realloc(buffer, size); + if (!p) + goto err; + buffer = p; + remaining = size; + + len = snprintf(p, remaining, "ioctl { "); + if (len < 0 || (size_t)len >= remaining) + goto err; p += len; - xpermslen += len; + remaining -= len; for (bit = 0; bit < sizeof(xperms->perms)*8; bit++) { if (!xperm_test(bit, xperms->perms)) @@ -165,35 +175,43 @@ char *sepol_extended_perms_to_string(avtab_extended_perms_t *xperms) value = xperms->driver<<8 | bit; if (in_range) { low_value = xperms->driver<<8 | low_bit; - len = snprintf(p, sizeof(xpermsbuf) - xpermslen, "0x%hx-0x%hx ", low_value, value); + len = snprintf(p, remaining, "0x%hx-0x%hx ", low_value, value); } else { - len = snprintf(p, sizeof(xpermsbuf) - xpermslen, "0x%hx ", value); + len = snprintf(p, remaining, "0x%hx ", value); } } else if (xperms->specified & AVTAB_XPERMS_IOCTLDRIVER) { value = bit << 8; if (in_range) { low_value = low_bit << 8; - len = snprintf(p, sizeof(xpermsbuf) - xpermslen, "0x%hx-0x%hx ", low_value, (uint16_t) (value|0xff)); + len = snprintf(p, remaining, "0x%hx-0x%hx ", low_value, (uint16_t) (value|0xff)); } else { - len = snprintf(p, sizeof(xpermsbuf) - xpermslen, "0x%hx-0x%hx ", value, (uint16_t) (value|0xff)); + len = snprintf(p, remaining, "0x%hx-0x%hx ", value, (uint16_t) (value|0xff)); } } - if (len < 0 || (size_t) len >= (sizeof(xpermsbuf) - xpermslen)) - return NULL; + if (len < 0) + goto err; + if ((size_t) len >= remaining) + goto retry; p += len; - xpermslen += len; + remaining -= len; if (in_range) in_range = 0; } - len = snprintf(p, sizeof(xpermsbuf) - xpermslen, "}"); - if (len < 0 || (size_t) len >= (sizeof(xpermsbuf) - xpermslen)) - return NULL; + len = snprintf(p, remaining, "}"); + if (len < 0) + goto err; + if ((size_t) len >= remaining) + goto retry; + + return buffer; - return xpermsbuf; +err: + free(buffer); + return NULL; } /*