From sacadmin Mon Mar 5 16:24:02 2007 Received: from sfbaymail2sca.sfbay.sun.com (sfbaymail2sca.SFBay.Sun.COM [129.145.155.42]) by sac.sfbay.sun.com (8.13.6+Sun/8.13.6) with ESMTP id l260O2HE022899 for ; Mon, 5 Mar 2007 16:24:02 -0800 (PST) Received: from brmea-mail-4.sun.com (brmea-mail-4.Sun.COM [192.18.98.36]) by sfbaymail2sca.sfbay.sun.com (8.13.6+Sun/8.12.10/ENSMAIL,v2.2) with ESMTP id l260O2sj018659 for ; Mon, 5 Mar 2007 16:24:02 -0800 (PST) Received: from fe-amer-04.sun.com ([192.18.108.178]) by brmea-mail-4.sun.com (8.13.6+Sun/8.12.9) with ESMTP id l260O2Zx029553 for ; Tue, 6 Mar 2007 00:24:02 GMT Received: from conversion-daemon.mail-amer.sun.com by mail-amer.sun.com (Sun Java System Messaging Server 6.2-6.01 (built Apr 3 2006)) id <0JEG00A01GQ6G800@mail-amer.sun.com> (original mail from Ali.Bahrami@Sun.COM) for psarc@sac.sfbay.sun.com; Mon, 05 Mar 2007 17:24:02 -0700 (MST) Received: from [172.20.25.67] by mail-amer.sun.com (Sun Java System Messaging Server 6.2-6.01 (built Apr 3 2006)) with ESMTPSA id <0JEG00KCZH42SDY2@mail-amer.sun.com> for psarc@sac.sfbay.sun.com; Mon, 05 Mar 2007 17:24:02 -0700 (MST) Date: Mon, 05 Mar 2007 17:26:40 -0700 From: Ali Bahrami Subject: 2007/127 Reserved space for editing ELF dynamic sections Sender: Ali.Bahrami@Sun.COM To: psarc@sac.sfbay.sun.com Message-id: <45ECB540.9000905@Sun.COM> MIME-version: 1.0 Content-type: text/plain; format=flowed; charset=ISO-8859-1 Content-transfer-encoding: 7BIT X-Accept-Language: en-us, en User-Agent: Mozilla Thunderbird 1.0.7 (X11/20050930) Status: RO Content-Length: 4871 I am sponsoring the following self approved case for myself. This case qualifies for Architectural self-review, but I wish to record the following information. Timeout 3-7-2007. ----------------------------------------------------------------------- This is a proposal to add a small amount of unused space to the dynamic string table and dynamic section of Solaris objects. This change will significantly improve our ability to edit such files in a safe and backward compatible manner. This work is for: 6516118 Reserved space needed in ELF dynamic section and string table We have long desired a tool that would allow us to modify existing ELF files in minor ways, such as adding or altering the runpath of a dynamic object, without the need to rebuild the file. The problem one encounters in trying to do this is that the various parts of an ELF file refer to each other by their relative offset from each other, and once built, the information required to fix up these interrelationships no longer exists. Therefore, any change that alters the size or relative spacing between the various parts of an ELF file will break it. In contrast, edits that preserve the relative positions of items in an ELF file are possible and can be very useful. For example, to alter the runpath of a sharable object, one might overwrite the existing string with a new one. As long as the new string is smaller or equal in length to the new one, this has an excellent chance of working. However, there are problems with this approach. There may be no existing runpath to overwrite. Or, the runpath may exist, but the compiler and/or linker may have decided to use the same readonly string to satisfy a different unrelated purpose --- changing it to fix the runpath may therefore break something else. Our ability to safely perform such edits can be greatly improved if the linker provides a small amount of extra unused space when producing an object: - A small amount of unused space at the end of the dynamic string table to provide room to add new strings. - A few extra DT_NULL entries at the end of the .dynamic section to allow the addition of a runpath (or other similar items) to a file that does not already have one. There are limits to how much editing can be supported by a small amount of spare space. If enough changes are needed, it will always be necessary to rebuild. However, the 90/10 rule applies in this case --- a very small amount of extra space will allow us to easily handle the vast majority of editing requests, runpath modification being far and away the most common such request. I plan to make the following changes to the linker: - 512 bytes of unused space will be added to the end of the .dynamic string table (.dynstr). This is large enough to handle most cases, and small enough avoid swelling objects unnecessarily. - 10 additional DT_NULL entries will be added to the end of the .dynamic section. These extra slots can be used to add dynamic entries that were not in the original ELF file. The runtime linker stops examining the dynamic section when it encounters the first DT_NULL, so the extra entries will not change its behavior. This is true of older versions of the runtime linker as well, so such a file can be safely moved back to older Solaris versions. - A new dynamic section element, DT_SUNW_STRPAD will record the amount of available space at the end of the dynamic string table. This serves two purposes: (1) The lack of a DT_SUNW_STRPAD entry indicates that have an old ELF file without any extra space, and (2) As extra space is used by editors, the value of DT_SUNW_STRPAD will be reduced by the editor in order to keep track of the use. - A new flag for the DT_FLAGS_1 entry of the dynamic section named DF_1_ELFEDIT, to be set by any editor that alters the elf file. The presence of this flag will therefore advise that the file is not in the original state generated by the linker. A developer who is investigating a problem with such a file will have a way to detect that the file has been manually modified, and may be able to avoid unprofitable debugging as a result. These ELF additions are backward compatible. A file containing them can be safely moved to an older Solaris system. These features represent the result of considered discussion with Rod Evans as to the various approaches we might take to editing ELF files, as well as experimental experience. This case does not include an ELF editor. However, we have an ongoing project underway to eventually supply one. The features described in this case have been successfully used in that project to edit ELF files. ----------------------------------------------------------------------- Release Binding: Patch/Micro DT_SUNW_STRPAD and DF_1_ELFEDIT Committed From sacadmin Tue Mar 6 05:50:52 2007 Received: from sfbaymail1sca.SFBay.Sun.COM (sfbaymail1sca.SFBay.Sun.COM [129.145.154.35]) by sac.sfbay.sun.com (8.13.6+Sun/8.13.6) with ESMTP id l26Dopbu015929 for ; Tue, 6 Mar 2007 05:50:52 -0800 (PST) Received: from gmp-ea-fw-1.sun.com (gmpes-gis-mail-1.UK.Sun.COM [129.156.42.5]) by sfbaymail1sca.SFBay.Sun.COM (8.13.6+Sun/8.13.6/ENSMAIL,v2.2) with ESMTP id l26DopdC010984 for ; Tue, 6 Mar 2007 05:50:51 -0800 (PST) Received: from d1-emea-10.sun.com (d1-emea-10.sun.com [192.18.2.120]) by gmp-ea-fw-1.sun.com (8.13.6+Sun/8.12.9) with ESMTP id l26DojQ6008412 for ; Tue, 6 Mar 2007 13:50:45 GMT Received: from conversion-daemon.d1-emea-10.sun.com by d1-emea-10.sun.com (Sun Java System Messaging Server 6.2-6.01 (built Apr 3 2006)) id <0JEH00B01IAZFG00@d1-emea-10.sun.com> (original mail from Darren.Moffat@Sun.COM) for psarc@sac.sfbay.sun.com; Tue, 06 Mar 2007 13:50:45 +0000 (GMT) Received: from [192.168.73.101] (nessieroo.force9.co.uk [81.174.224.49]) by d1-emea-10.sun.com (Sun Java System Messaging Server 6.2-6.01 (built Apr 3 2006)) with ESMTPSA id <0JEH003W1IGKSG00@d1-emea-10.sun.com> for psarc@sac.sfbay.sun.com; Tue, 06 Mar 2007 13:50:45 +0000 (GMT) Date: Tue, 06 Mar 2007 13:50:44 +0000 From: Darren J Moffat Subject: Re: 2007/127 Reserved space for editing ELF dynamic sections In-reply-to: <45ECB540.9000905@Sun.COM> Sender: Darren.Moffat@Sun.COM To: Ali Bahrami Cc: psarc@sac.sfbay.sun.com Message-id: <45ED71B4.9020303@Sun.COM> MIME-version: 1.0 Content-type: text/plain; format=flowed; charset=ISO-8859-1 Content-transfer-encoding: 7BIT References: <45ECB540.9000905@Sun.COM> User-Agent: Thunderbird 1.5.0.8 (X11/20061127) Status: RO Content-Length: 354 I assume this case has no impact on elfsign other than if one makes use of the infrastructure this case provides the signature would be invalid until the binary is resigned. Please run the STC2 suites/security/ef test suite before integration as this will test the elfsign functionality to ensure this case has no impact on it. -- Darren J Moffat From sacadmin Tue Mar 6 07:42:14 2007 Received: from sfbaymail2sca.sfbay.sun.com (sfbaymail2sca.SFBay.Sun.COM [129.145.155.42]) by sac.sfbay.sun.com (8.13.6+Sun/8.13.6) with ESMTP id l26FgEVi018970 for ; Tue, 6 Mar 2007 07:42:14 -0800 (PST) Received: from gmp-ea-fw-1.sun.com (gmpes-gis-mail-2.UK.Sun.COM [129.156.42.6]) by sfbaymail2sca.sfbay.sun.com (8.13.6+Sun/8.12.10/ENSMAIL,v2.2) with ESMTP id l26FgD62009812 for ; Tue, 6 Mar 2007 07:42:13 -0800 (PST) Received: from d1-emea-09.sun.com ([192.18.2.119]) by gmp-ea-fw-1.sun.com (8.13.6+Sun/8.12.9) with ESMTP id l26Fg7UG000354 for ; Tue, 6 Mar 2007 15:42:07 GMT Received: from conversion-daemon.d1-emea-09.sun.com by d1-emea-09.sun.com (Sun Java System Messaging Server 6.2-6.01 (built Apr 3 2006)) id <0JEH00101MYWE200@d1-emea-09.sun.com> (original mail from Calum.Mackay@Sun.COM) for psarc@sac.sfbay.sun.com; Tue, 06 Mar 2007 15:42:07 +0000 (GMT) Received: from [192.168.254.1] ([62.24.230.83]) by d1-emea-09.sun.com (Sun Java System Messaging Server 6.2-6.01 (built Apr 3 2006)) with ESMTPSA id <0JEH00HFENM517CC@d1-emea-09.sun.com> for psarc@sac.sfbay.sun.com; Tue, 06 Mar 2007 15:42:06 +0000 (GMT) Date: Tue, 06 Mar 2007 15:42:05 +0000 From: Calum Mackay Subject: Re: 2007/127 Reserved space for editing ELF dynamic sections In-reply-to: <45ECB540.9000905@Sun.COM> Sender: Calum.Mackay@Sun.COM To: Ali Bahrami Cc: psarc@sac.sfbay.sun.com Message-id: <45ED8BCD.8050702@sun.com> Organization: Sun Microsystems MIME-version: 1.0 Content-type: text/plain; format=flowed; charset=ISO-8859-1 Content-transfer-encoding: 7BIT References: <45ECB540.9000905@Sun.COM> User-Agent: Thunderbird 3.0a1 (X11/20070303) Status: RO Content-Length: 754 hi Ali, > In contrast, edits that preserve the relative positions of items in an > ELF file are possible and can be very useful. For example, to alter > the runpath of a sharable object, one might overwrite the existing > string with a new one. As long as the new string is smaller or > equal in length to the new one, this has an excellent chance of > working. However, there are problems with this approach. There may > be no existing runpath to overwrite. Or, the runpath may exist, > but the compiler and/or linker may have decided to use the same readonly > string to satisfy a different unrelated purpose --- changing it to fix > the runpath may therefore break something else. How would this new scheme affect that latter issue? cheers, calum. From sacadmin Tue Mar 6 07:51:57 2007 Received: from sfbaymail2sca.sfbay.sun.com (sfbaymail2sca.SFBay.Sun.COM [129.145.155.42]) by sac.sfbay.sun.com (8.13.6+Sun/8.13.6) with ESMTP id l26FpvKi019049 for ; Tue, 6 Mar 2007 07:51:57 -0800 (PST) Received: from brmea-mail-1.sun.com (brmea-mail-1.Sun.COM [192.18.98.31]) by sfbaymail2sca.sfbay.sun.com (8.13.6+Sun/8.12.10/ENSMAIL,v2.2) with ESMTP id l26FpvLI014035 for ; Tue, 6 Mar 2007 07:51:57 -0800 (PST) Received: from relay43i.sun.com ([192.5.209.74]) by brmea-mail-1.sun.com (8.13.6+Sun/8.12.9) with ESMTP id l26FmqXD004183 for ; Tue, 6 Mar 2007 15:51:56 GMT Received: from mms48es.sun.com ([160.41.221.231] [160.41.221.231]) by relay43i.sun.com with ESMTP; Tue, 6 Mar 2007 15:51:56 Z Received: from relay41i.sun.com ([192.5.209.70] [192.5.209.70]) by mms48es.sun.com with ESMTP; Tue, 6 Mar 2007 15:51:56 Z Received: from emvision.com ([199.45.162.234] [199.45.162.234]) by relay4i.sun.com with ESMTP; Tue, 6 Mar 2007 15:51:55 Z Received: from [198.182.198.2] (pod.emvision.com [198.182.198.2]) by emvision.com (8.13.6/8.13.6) with ESMTP id l26FpmvY009779; Tue, 6 Mar 2007 08:51:48 -0700 (MST) Message-Id: <45ED8E29.7090906@Sun.COM> Date: Tue, 06 Mar 2007 08:52:09 -0700 From: Ali Bahrami User-Agent: Thunderbird 1.5.0.10 (Macintosh/20070221) MIME-Version: 1.0 To: Darren J Moffat CC: psarc@sac.sfbay.sun.com Subject: Re: 2007/127 Reserved space for editing ELF dynamic sections References: <45ECB540.9000905@Sun.COM> <45ED71B4.9020303@Sun.COM> In-Reply-To: <45ED71B4.9020303@Sun.COM> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-2.0.2 (emvision.com [198.182.198.5]); Tue, 06 Mar 2007 08:51:49 -0700 (MST) Status: RO Content-Length: 610 Darren J Moffat wrote: > I assume this case has no impact on elfsign other than if one makes use > of the infrastructure this case provides the signature would be invalid > until the binary is resigned. > > Please run the STC2 suites/security/ef test suite before integration as > this will test the elfsign functionality to ensure this case has no > impact on it. > You are correct about elfsign. This extra space is part of the standard sections, and a change to them would invalidate the signature, which could then be resigned if appropriate. I will be sure to run STC2 before integration. - Ali From sacadmin Tue Mar 6 08:06:46 2007 Received: from sfbaymail2sca.sfbay.sun.com (sfbaymail2sca.SFBay.Sun.COM [129.145.155.42]) by sac.sfbay.sun.com (8.13.6+Sun/8.13.6) with ESMTP id l26G6kj8020054 for ; Tue, 6 Mar 2007 08:06:46 -0800 (PST) Received: from sca-ea-mail-3.sun.com (sca-ea-mail-3.Sun.COM [192.18.43.21]) by sfbaymail2sca.sfbay.sun.com (8.13.6+Sun/8.12.10/ENSMAIL,v2.2) with ESMTP id l26G6jwJ021387 for ; Tue, 6 Mar 2007 08:06:45 -0800 (PST) Received: from relay2.sun.com (relay2.sun.com [150.143.103.24] (may be forged)) by sca-ea-mail-3.sun.com (8.13.6+Sun/8.12.9) with ESMTP id l26FkkiU014743 for ; Tue, 6 Mar 2007 16:06:45 GMT Received: from mms02es.sun.com ([150.143.104.34] [150.143.104.34]) by relay2.sun.com with ESMTP; Tue, 6 Mar 2007 16:06:17 Z Received: from relay3.sun.com (relay3.sun.com [150.143.103.54]) by mms02es.sun.com with ESMTP id BT-MMP-2704654; Tue, 6 Mar 2007 16:06:17 Z Received: from emvision.com ([199.45.162.234] [199.45.162.234]) by relay3.sun.com with ESMTP; Tue, 6 Mar 2007 16:06:16 Z Received: from [198.182.198.2] (pod.emvision.com [198.182.198.2]) by emvision.com (8.13.6/8.13.6) with ESMTP id l26G6DUO009855; Tue, 6 Mar 2007 09:06:13 -0700 (MST) Message-Id: <45ED9189.8080003@Sun.COM> Date: Tue, 06 Mar 2007 09:06:33 -0700 From: Ali Bahrami User-Agent: Thunderbird 1.5.0.10 (Macintosh/20070221) MIME-Version: 1.0 To: Calum Mackay CC: psarc@sac.sfbay.sun.com Subject: Re: 2007/127 Reserved space for editing ELF dynamic sections References: <45ECB540.9000905@Sun.COM> <45ED8BCD.8050702@sun.com> In-Reply-To: <45ED8BCD.8050702@sun.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-2.0.2 (emvision.com [198.182.198.5]); Tue, 06 Mar 2007 09:06:15 -0700 (MST) Status: RO Content-Length: 1440 Calum Mackay wrote: > hi Ali, > >> In contrast, edits that preserve the relative positions of items in an >> ELF file are possible and can be very useful. For example, to alter >> the runpath of a sharable object, one might overwrite the existing >> string with a new one. As long as the new string is smaller or >> equal in length to the new one, this has an excellent chance of >> working. However, there are problems with this approach. There may >> be no existing runpath to overwrite. Or, the runpath may exist, >> but the compiler and/or linker may have decided to use the same readonly >> string to satisfy a different unrelated purpose --- changing it to fix >> the runpath may therefore break something else. > > How would this new scheme affect that latter issue? > > cheers, > calum. The new scheme allows you to introduce a new string into the string table. Since it is new, you know by definition that there are no pre-existing uses of it within the ELF file. You then modify the item you wish to change (for instance, the runpath entry in the dynamic section) to reference it. This is safe, because the original string is left where it lies, and is unchanged. Any other reference to it will be OK. It does not break the ELF file, because the relative positions of existing things stay the same. This is because the extra space was built into the ELF file when it was generated, rather than being bolted on later. - Ali From sacadmin Tue Mar 6 09:20:19 2007 Received: from sfbaymail2sca.sfbay.sun.com (sfbaymail2sca.SFBay.Sun.COM [129.145.155.42]) by sac.sfbay.sun.com (8.13.6+Sun/8.13.6) with ESMTP id l26HKJA5022312 for ; Tue, 6 Mar 2007 09:20:19 -0800 (PST) Received: from gmp-ea-fw-1.sun.com (gmpes-gis-mail-1.UK.Sun.COM [129.156.42.5]) by sfbaymail2sca.sfbay.sun.com (8.13.6+Sun/8.12.10/ENSMAIL,v2.2) with ESMTP id l26HKIj8000152 for ; Tue, 6 Mar 2007 09:20:18 -0800 (PST) Received: from d1-emea-10.sun.com (d1-emea-10.sun.com [192.18.2.120]) by gmp-ea-fw-1.sun.com (8.13.6+Sun/8.12.9) with ESMTP id l26HKC1B013493 for ; Tue, 6 Mar 2007 17:20:12 GMT Received: from conversion-daemon.d1-emea-10.sun.com by d1-emea-10.sun.com (Sun Java System Messaging Server 6.2-6.01 (built Apr 3 2006)) id <0JEH00401S4HVU00@d1-emea-10.sun.com> (original mail from Calum.Mackay@Sun.COM) for psarc@sac.sfbay.sun.com; Tue, 06 Mar 2007 17:20:12 +0000 (GMT) Received: from [192.168.254.1] ([62.24.230.83]) by d1-emea-10.sun.com (Sun Java System Messaging Server 6.2-6.01 (built Apr 3 2006)) with ESMTPSA id <0JEH00292S5M5RWJ@d1-emea-10.sun.com> for psarc@sac.sfbay.sun.com; Tue, 06 Mar 2007 17:20:12 +0000 (GMT) Date: Tue, 06 Mar 2007 17:20:09 +0000 From: Calum Mackay Subject: Re: 2007/127 Reserved space for editing ELF dynamic sections In-reply-to: <45ED9189.8080003@Sun.COM> Sender: Calum.Mackay@Sun.COM To: Ali Bahrami Cc: psarc@sac.sfbay.sun.com Message-id: <45EDA2C9.1090001@sun.com> Organization: Sun Microsystems MIME-version: 1.0 Content-type: text/plain; format=flowed; charset=ISO-8859-1 Content-transfer-encoding: 7BIT References: <45ECB540.9000905@Sun.COM> <45ED8BCD.8050702@sun.com> <45ED9189.8080003@Sun.COM> User-Agent: Thunderbird 3.0a1 (X11/20070303) Status: RO Content-Length: 365 Ali Bahrami wrote: > The new scheme allows you to introduce a new string into the string table. > Since it is new, you know by definition that there are no pre-existing uses > of it within the ELF file. You then modify the item you wish to change > (for instance, the runpath entry in the dynamic section) to reference it. Understood, thanks much Ali. cheers, c.