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From 1f63621d098741158b5e1e7158cc570a415d88cd Mon Sep 17 00:00:00 2001
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From: Panu Matilainen <pmatilai@redhat.com>
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Date: Mon, 29 Nov 2021 14:01:39 +0200
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Subject: [PATCH] Fix IMA signature lengths assumed constant (#1833,
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 RhBug:2018937)
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At least ECDSA and RSA signatures can vary in length, but the IMA code
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assumes constant lengths and thus may either place invalid signatures on
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disk from either truncating or overshooting, and segfault if the stars are
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just so.
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Luckily the signatures are stored as strings so we can calculate the
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actual lengths at runtime and ignore the stored constant length info.
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Extend hex2bin() to optionally calculate the lengths and maximum,
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and use these for returning IMA data from the rpmfi(les) API.
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Additionally update the signing code to store the largest IMA signature
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length rather than what happened to be last to be on the safe side.
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We can't rely on this value due to invalid packages being out there,
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but then we need to calculate the lengths on rpmfiles populate so there's
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not a lot to gain anyhow.
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Fixes: #1833
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Backported for 4.16.1.3 and combined with:
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31e9daf823f7052135d1decc0802b6fa775a88c5 (fix-up)
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0c1ad364d65c4144ff71c376e0b49fbc322b686d (python bindings)
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Note that the test case has been removed due to it including a binary
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file (test package) for which we'd have to use -Sgit with %autopatch and
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thus depend on git-core at build time.  Nevertheless, we do have this BZ
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covered in our internal test suite, so no need for it anyway.
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---
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 lib/rpmfi.c          | 59 +++++++++++++++++++++++++++++++++-----------
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 python/rpmfiles-py.c | 18 ++++++++++++++
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 sign/rpmsignfiles.c  |  5 +++-
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 3 files changed, 67 insertions(+), 15 deletions(-)
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diff --git a/lib/rpmfi.c b/lib/rpmfi.c
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index af428468c..ed8927fd5 100644
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--- a/lib/rpmfi.c
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+++ b/lib/rpmfi.c
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@@ -115,7 +115,8 @@ struct rpmfiles_s {
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     struct fingerPrint_s * fps;	/*!< File fingerprint(s). */
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     int digestalgo;		/*!< File digest algorithm */
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-    int signaturelength;	/*!< File signature length */
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+    int *signaturelengths;	/*!< File signature lengths */
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+    int signaturemaxlen;	/*!< Largest file signature length */
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     unsigned char * digests;	/*!< File digests in binary. */
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     unsigned char * signatures; /*!< File signatures in binary. */
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@@ -575,9 +576,9 @@ const unsigned char * rpmfilesFSignature(rpmfiles fi, int ix, size_t *len)
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     if (fi != NULL && ix >= 0 && ix < rpmfilesFC(fi)) {
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 	if (fi->signatures != NULL)
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-	    signature = fi->signatures + (fi->signaturelength * ix);
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+	    signature = fi->signatures + (fi->signaturemaxlen * ix);
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 	if (len)
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-	    *len = fi->signaturelength;
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+	    *len = fi->signaturelengths ? fi->signaturelengths[ix] : 0;
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     }
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     return signature;
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 }
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@@ -1257,6 +1258,7 @@ rpmfiles rpmfilesFree(rpmfiles fi)
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 	fi->flangs = _free(fi->flangs);
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 	fi->digests = _free(fi->digests);
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 	fi->signatures = _free(fi->signatures);
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+	fi->signaturelengths = _free(fi->signaturelengths);
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 	fi->fcaps = _free(fi->fcaps);
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 	fi->cdict = _free(fi->cdict);
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@@ -1486,23 +1488,52 @@ err:
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 }
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 /* Convert a tag of hex strings to binary presentation */
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-static uint8_t *hex2bin(Header h, rpmTagVal tag, rpm_count_t num, size_t len)
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+/* If lengths is non-NULL, assume variable length strings */
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+static uint8_t *hex2bin(Header h, rpmTagVal tag, rpm_count_t num, size_t len,
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+			int **lengths, int *maxlen)
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 {
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     struct rpmtd_s td;
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     uint8_t *bin = NULL;
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     if (headerGet(h, tag, &td, HEADERGET_MINMEM) && rpmtdCount(&td) == num) {
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-	uint8_t *t = bin = xmalloc(num * len);
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 	const char *s;
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+	int maxl = 0;
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+	int *lens = NULL;
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+
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+	/* Figure string sizes + max length for allocation purposes */
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+	if (lengths) {
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+	    int i = 0;
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+	    lens = xmalloc(num * sizeof(*lens));
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+
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+	    while ((s = rpmtdNextString(&td))) {
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+		lens[i] = strlen(s) / 2;
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+		if (lens[i] > maxl)
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+		    maxl = lens[i];
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+		i++;
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+	    }
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+
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+	    *lengths = lens;
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+	    *maxlen = maxl;
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+
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+	    /* Reinitialize iterator for next round */
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+	    rpmtdInit(&td);
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+	} else {
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+	    maxl = len;
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+	}
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+	uint8_t *t = bin = xmalloc(num * maxl);
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+	int i = 0;
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 	while ((s = rpmtdNextString(&td))) {
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 	    if (*s == '\0') {
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-		memset(t, 0, len);
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-		t += len;
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-		continue;
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+		memset(t, 0, maxl);
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+	    } else {
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+		if (lens)
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+		    len = lens[i];
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+		for (int j = 0; j < len; j++, s += 2)
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+		    t[j] = (rnibble(s[0]) << 4) | rnibble(s[1]);
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 	    }
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-	    for (int j = 0; j < len; j++, t++, s += 2)
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-		*t = (rnibble(s[0]) << 4) | rnibble(s[1]);
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+	    t += maxl;
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+	    i++;
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 	}
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     }
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     rpmtdFreeData(&td);
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@@ -1570,15 +1601,15 @@ static int rpmfilesPopulate(rpmfiles fi, Header h, rpmfiFlags flags)
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     /* grab hex digests from header and store in binary format */
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     if (!(flags & RPMFI_NOFILEDIGESTS)) {
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 	size_t diglen = rpmDigestLength(fi->digestalgo);
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-	fi->digests = hex2bin(h, RPMTAG_FILEDIGESTS, totalfc, diglen);
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+	fi->digests = hex2bin(h, RPMTAG_FILEDIGESTS, totalfc, diglen,
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+				NULL, NULL);
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     }
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     fi->signatures = NULL;
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     /* grab hex signatures from header and store in binary format */
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     if (!(flags & RPMFI_NOFILESIGNATURES)) {
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-	fi->signaturelength = headerGetNumber(h, RPMTAG_FILESIGNATURELENGTH);
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-	fi->signatures = hex2bin(h, RPMTAG_FILESIGNATURES,
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-				 totalfc, fi->signaturelength);
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+	fi->signatures = hex2bin(h, RPMTAG_FILESIGNATURES, totalfc, 0,
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+				&fi->signaturelengths, &fi->signaturemaxlen);
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     }
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     /* XXX TR_REMOVED doesn;t need fmtimes, frdevs, finodes */
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diff --git a/python/rpmfiles-py.c b/python/rpmfiles-py.c
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index 27666021d..48189a0ac 100644
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--- a/python/rpmfiles-py.c
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+++ b/python/rpmfiles-py.c
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@@ -152,6 +152,22 @@ static PyObject *rpmfile_digest(rpmfileObject *s)
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     Py_RETURN_NONE;
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 }
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+static PyObject *bytebuf(const unsigned char *buf, size_t len)
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+{
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+    if (buf) {
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+	PyObject *o = PyBytes_FromStringAndSize((const char *)buf, len);
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+	return o;
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+    }
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+    Py_RETURN_NONE;
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+}
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+
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+static PyObject *rpmfile_imasig(rpmfileObject *s)
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+{
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+    size_t len = 0;
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+    const unsigned char *sig = rpmfilesFSignature(s->files, s->ix, &len;;
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+    return bytebuf(sig, len);
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+}
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+
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 static PyObject *rpmfile_class(rpmfileObject *s)
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 {
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     return utf8FromString(rpmfilesFClass(s->files, s->ix));
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@@ -278,6 +294,8 @@ static PyGetSetDef rpmfile_getseters[] = {
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       "language the file provides (typically for doc files)" },
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     { "caps",		(getter) rpmfile_caps,		NULL,
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       "file capabilities" },
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+    { "imasig",	(getter) rpmfile_imasig,	NULL,
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+      "IMA signature" },
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     { NULL, NULL, NULL, NULL }
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 };
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diff --git a/sign/rpmsignfiles.c b/sign/rpmsignfiles.c
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index b143c5b9b..6f39db6be 100644
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--- a/sign/rpmsignfiles.c
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+++ b/sign/rpmsignfiles.c
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@@ -98,8 +98,9 @@ rpmRC rpmSignFiles(Header sigh, Header h, const char *key, char *keypass)
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     td.count = 1;
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     while (rpmfiNext(fi) >= 0) {
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+	uint32_t slen;
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 	digest = rpmfiFDigest(fi, NULL, NULL);
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-	signature = signFile(algoname, digest, diglen, key, keypass, &siglen);
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+	signature = signFile(algoname, digest, diglen, key, keypass, &slen);
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 	if (!signature) {
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 	    rpmlog(RPMLOG_ERR, _("signFile failed\n"));
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 	    goto exit;
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@@ -110,6 +111,8 @@ rpmRC rpmSignFiles(Header sigh, Header h, const char *key, char *keypass)
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 	    goto exit;
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 	}
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 	signature = _free(signature);
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+	if (slen > siglen)
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+	    siglen = slen;
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     }
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     if (siglen > 0) {
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-- 
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2.33.1
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